Awesome Java Projects

MapStruct

Code generator that simplifies mappings between different bean types, based on a convention-over-configuration approach.

ModelMapper

Intelligent object mapping library that automatically maps objects to each other.

Orika

JavaBean-mapping framework that recursively copies (among other capabilities) data from one object to another.

JMapper

Uses byte code manipulation for lightning-fast mapping. Supports annotations and API or XML configuration.

Selma

Annotation processor-based bean mapper.

reMap

Lambda and method handle-based mapping which requires code and not annotations if objects have different names.

dOOv

Provides fluent API for typesafe domain model validation and mapping. It uses annotations, code generation and a type safe DSL to make bean validation and mapping fast and easy.

Bazel

Tool from Google that builds code quickly and reliably.

Gradle

Incremental builds programmed via Groovy instead of declaring XML. Works well with Maven's dependency management.

Buck

Encourages the creation of small, reusable modules consisting of code and resources.

Apache Maven

Declarative build and dependency management that favors convention over configuration. It might be preferable to Apache Ant, which uses a rather procedural approach and can be difficult to maintain.

bytecode-viewer

Java 8 Jar & Android APK reverse engineering suite. (GPL-3.0-only)

Byte Buddy

Further simplifies bytecode generation with a fluent API.

Recaf

JVM reverse engineering toolkit, essentially an IDE for Java bytecode.

cglib

Bytecode generation library.

Javassist

Tries to simplify bytecode editing.

Mixin

Manipulate bytecode at runtime using real Java code.

Byteman

Manipulate bytecode at runtime via DSL (rules); mainly for testing/troubleshooting. (LGPL-2.1-or-later)

Perses

Dynamically injects failure/latency at the bytecode level according to principles of chaos engineering.

Maker

Provides low level bytecode generation.

Caffeine

High-performance, near-optimal caching library.

Ehcache

Distributed general-purpose cache.

Infinispan

Highly concurrent key/value datastore used for caching.

cache2k

In-memory high performance caching library.

picocli

ANSI colors and styles in usage help with annotation-based POSIX/GNU/any syntax, subcommands, strong typing for both options and positional args.

Lanterna

Easy console text-GUI library, similar to curses. (LGPL-3.0-only)

JCommander

Command-line argument-parsing framework with custom types and validation via implementing interfaces.

JLine

Includes features from modern shells like completion or history.

Jansi

ANSI escape codes to format console output.

Airline

Annotation-based framework for parsing Git-like command-line arguments.

args4j

Small library to parse command-line arguments.

ASCII Table

Library to draw tables in ASCII.

JOpt Simple

Fluent parser that uses the POSIX#getopt and GNU#getopt_long syntaxes.

Text-IO

Aids the creation of full console-based applications.

Java ASCII Render

Graphical primitives for the console.

jbock

Reflectionless command line parser.

Singularity

Mesos framework that makes deployment and operations easy. It supports web services, background workers, scheduled jobs, and one-off tasks.

Apache Aurora

Mesos framework for long-running services and cron jobs.

p3c

Provides Alibaba's coding guidelines for PMD, IDEA and Eclipse.

Infer

Modern static analysis tool for verifying the correctness of code.

Checkstyle

Static analysis of coding conventions and standards. (LGPL-2.1-or-later)

Error Prone

Catches common programming mistakes as compile-time errors.

PMD

Source code analysis for finding bad coding practices.

NullAway

Eliminates NullPointerExceptions with low build-time overhead.

Spotbugs

Static analysis of bytecode to find potential bugs. (LGPL-2.1-only)

Spoon

Library for analyzing and transforming Java source code.

SonarJava

Static analyzer for SonarQube & SonarLint. (LGPL-3.0-only)

RefactorFirst

Identifies and prioritizes God Classes and Highly Coupled classes.

jQAssistant

Static code analysis with Neo4J-based query language. (GPL-3.0-only)

Error Prone Support

Error Prone extensions: extra bug checkers and a large battery of Refaster templates.

JaCoCo

Framework that enables collection of code coverage metrics, using both offline and runtime bytecode instrumentation.

Cobertura

Relies on offline (or static) bytecode instrumentation and class loading to collect code coverage metrics. (GPL-2.0-only)

Clover

Relies on source-code instrumentation instead of bytecode instrumentation.

JHipster

Yeoman source code generator for Spring Boot and AngularJS.

Lombok

Code generator that aims to reduce verbosity.

JavaPoet

API to generate source files.

Auto

Generates factory, service, and value classes.

Immutables

Annotation processors to generate simple, safe and consistent value objects.

FreeBuilder

Automatically generates the Builder pattern.

Record-Builder

Companion builder class, withers and templates for Java records.

Telosys

Simple and light code generator available as an Eclipse Plugin and also as a CLI.

ADT4J

JSR-269 code generator for algebraic data types.

Joda-Beans

Small framework that adds queryable properties to Java, enhancing JavaBeans.

Geci

Discovers files that need generated code, updates automatically and writes to the source with a convenient API.

Avaje Http Server

Generates Lightweight JAX-RS style http servers using Javalin or Helidon (Nima) SE.

JPA Buddy ![c]

Plugin for IntelliJ IDEA. Provides visual tools for generating JPA entities, Spring Data JPA repositories, Liquibase changelogs and SQL scripts. Offers automatic Liquibase/Flyway script generation by comparing model to DB, and reverse engineering JPA entities from DB tables.

ANTLR

Complex full-featured framework for top-down parsing.

JavaCC

Parser generator that generates top-down parsers. Allows lexical state switching and permits extended BNF specifications.

JFlex

Lexical analyzer generator.

JavaCV

Java interface to OpenCV, FFmpeg, and much more.

BoofCV

Library for image processing, camera calibration, tracking, SFM, MVS, 3D vision, QR Code and much more.

ImageJ

Medical image processing application with an API.

config

Configuration library supporting Java properties, JSON or its human optimized superset HOCON.

Curator Framework

High-level API for Apache ZooKeeper.

owner

Reduces boilerplate of properties.

centraldogma

Highly-available version-controlled service configuration repository based on Git, ZooKeeper and HTTP/2.

cfg4j

Modern configuration library for distributed apps written in Java.

Configurate

Configuration library with support for various configuration formats and transformations.

microconfig

Configuration system designed for microservices which helps to separate configuration from code. The configuration for different services can have common and specific parts and can be dynamically distributed.

KAConf

Annotation-based configuration system for Java and Kotlin.

avaje config

Loads yaml and properties files, supports dynamic configuration, plugins, file-watching and config event listeners.

dotenv

Twelve-factor configuration library which uses environment-specific files.

Externalized Properties

Lightweight yet powerful configuration library which supports resolution of properties from external sources and an extensible post-processing/conversion mechanism.

Timefold

Flexible solver with Spring/Quarkus support and quickstarts for the Vehicle Routing Problem, Maintenance Scheduling, Employee Shift Scheduling and much more.

Choco

Off-the-shelf constraint satisfaction problem solver that uses constraint programming techniques.

JaCoP

Includes an interface for the FlatZinc language, enabling it to execute MiniZinc models. (AGPL-3.0)

OptaPlanner

Business planning and resource scheduling optimization solver.

uniVocity-parsers

One of the fastest and most feature-complete parsers. Also comes with parsers for TSV and fixed-width records.

FastCSV

Performance-optimized, dependency-free and RFC 4180 compliant.

Super CSV

Powerful CSV parser with support for Dozer, Joda-Time and Java 8.

jackson-dataformat-csv

Jackson extension for reading and writing CSV.

Protobuf

Google's data interchange format.

Apache Thrift

Data interchange format that originated at Facebook.

Wire

Clean, lightweight protocol buffers.

RoaringBitmap

Fast and efficient compressed bitmap.

SBE

Simple Binary Encoding, one of the fastest message formats around.

Apache Avro

Data interchange format with dynamic typing, untagged data, and absence of manually assigned IDs.

Tape

Lightning-fast, transactional, file-based FIFO.

Persistent Collection

Persistent and immutable analogue of the Java Collections Framework.

Apache Orc

Fast and efficient columnar storage format for Hadoop-based workloads.

Big Queue

Fast and persistent queue based on memory-mapped files.

HyperMinHash-java

Probabilistic data structure for computing union, intersection, and set cardinality in loglog space.

Apache Parquet

Columnar storage format based on assembly algorithms from Google's paper on Dremel.

Redisson

Allows for distributed and scalable data structures on top of a Redis server.

HikariCP

High-performance JDBC connection pool.

QuestDB

High-performance SQL database for time series. Supports InfluxDB line protocol, PostgreSQL wire protocol, and REST.

druid

High-performance, column-oriented, distributed data store.

Jedis

Small client for interaction with Redis, with methods for commands.

Realm

Mobile database to run directly inside phones, tablets or wearables.

Debezium

Low latency data streaming platform for change data capture.

Trino

Distributed SQL query engine for big data.

Flyway

Simple database migration tool.

Leaf

Distributed ID generate service.

jOOQ

Generates typesafe code based on SQL schema.

MapDB

Embedded database engine that provides concurrent collections backed on disk or in off-heap memory.

Querydsl

Typesafe unified queries.

Liquibase

Database-independent library for tracking, managing and applying database schema changes.

Apache Calcite

Dynamic data management framework. It contains many of the pieces that comprise a typical database management system.

H2

Small SQL database notable for its in-memory functionality.

requery

Modern, lightweight but powerful object mapping and SQL generator. Easily map to or create databases, or perform queries and updates from any Java-using platform.

Chronicle Map

Efficient, in-memory (opt. persisted to disk), off-heap key-value store.

Jest

Client for the Elasticsearch REST API.

Speedment

Database access library that utilizes Java 8's Stream API for querying.

JDBI

Convenient abstraction of JDBC.

Apache Drill

Distributed, schema on-the-fly, ANSI SQL query engine for Big Data exploration.

Xodus

Highly concurrent transactional schema-less and ACID-compliant embedded database.

FlexyPool

Brings metrics and failover strategies to the most common connection pooling solutions.

Apache Phoenix

High-performance relational database layer over HBase for low-latency applications.

Jinq

Typesafe database queries via symbolic execution of Java 8 Lambdas (on top of JPA or jOOQ).

CosId

Universal, flexible, high-performance distributed ID generator.

eXist

NoSQL document database and application platform. (LGPL-2.1-only)

OpenDJ

LDAPv3 compliant directory service, developed for the Java platform, providing a high performance, highly available, and secure store for the identities.

ArangoDB

ArangoDB Java driver.

jetcd

Client library for etcd.

Vibur DBCP

JDBC connection pool library with advanced performance monitoring capabilities.

Spring Data JPA MongoDB Expressions

Allows you to use MongoDB query language to query your relational database.

QueryStream

Build JPA Criteria queries using a Stream-like API.

Modality

Lightweight ORM with database reverse engineering features.

MariaDB4j

Launcher for MariaDB that requires no installation or external dependencies.

Lettuce

Lettuce is a scalable Redis client for building non-blocking Reactive applications.

iCal4j

Parse and build iCalendar [RFC 5545](https://tools.ietf.org/html/rfc5545) data models.

Time4J

Advanced date and time library. (LGPL-2.1-only)

ThreeTen-Extra

Additional date-time classes that complement those in JDK 8.

Jollyday

Determines the holidays for a given year, country/name and eventually state/region.

Dagger

Compile-time injection framework without reflection.

Guice

Lightweight and opinionated framework that completes Dagger.

Governator

Extensions and utilities that enhance Google Guice.

Feather

Ultra-lightweight, JSR-330-compliant dependency injection library.

Avaje Inject

Microservice-focused compile-time injection framework without reflection.

Apache DeltaSpike

CDI extension framework.

HK2

Lightweight and dynamic dependency injection framework.

JayWire

Lightweight dependency injection framework. (LGPL-3.0-only)

JavaParser

Parse, modify and generate Java code.

Manifold

Re-energizes Java with powerful features like type-safe metaprogramming, structural typing and extension methods.

HotswapAgent

Unlimited runtime class and resource redefinition. (GPL-2.0-only)

DCEVM

JVM modification that allows unlimited redefinition of loaded classes at runtime. (GPL-2.0-only)

JavaSymbolSolver

Symbol solver.

AspectJ

Seamless aspect-oriented programming extension.

Faux Pas

Library that simplifies error handling by circumventing the issue that none of the functional interfaces in the Java Runtime is allowed by default to throw checked exceptions.

NoException

Allows checked exceptions in functional interfaces and converts exceptions to Optional return.

SneakyThrow

Ignores checked exceptions without bytecode manipulation. Can also be used inside Java 8 stream operations.

Tail

Enable infinite recursion using tail call optimization.

Zuul

Gateway service that provides dynamic routing, monitoring, resiliency, security, and more.

Apache ZooKeeper

Coordination service with distributed configuration, synchronization, and naming registry for large distributed systems.

resilience4j

Functional fault tolerance library.

Apache Storm

Realtime computation system.

Hazelcast

Highly scalable in-memory datagrid with a free open-source version.

Quasar

Lightweight threads and actors for the JVM.

Failsafe

Simple failure handling with retries and circuit breakers.

Atomix

Fault-tolerant distributed coordination framework.

Apache Geode

In-memory data management system that provides reliable asynchronous event notifications and guaranteed message delivery.

JGroups

Toolkit for reliable messaging and cluster creation.

ScaleCube Services

Embeddable Cluster-Membership library based on SWIM and gossip protocol.

OpenIG

High-performance reverse proxy server with specialized session management and credential replay functionality.

Dropwizard Circuit Breaker

Circuit breaker design pattern for Dropwizard. (GPL-2.0-only)

Atomikos

Provides transactions for REST, SOA and microservices with support for JTA and XA.

Narayana

Provides support for traditional ACID and compensation transactions, also complies with JTA, JTS and other standards. (LGPL-2.1-only)

Bitronix

Simple but complete implementation of the JTA 1.1 API.

Seata

Delivers high performance and easy to use distributed transaction services under a microservices architecture.

packr

Packs JARs, assets and the JVM for native distribution on Windows, Linux and macOS.

Capsule

Simple and powerful packaging and deployment. A fat JAR on steroids, or a "Docker for Java" that supports JVM-optimized containers.

JavaPackager

Maven and Gradle plugin which provides an easy way to package Java applications in native Windows, Mac OS X or GNU/Linux executables, and generate installers for them.

Getdown

A system for deploying Java applications to end-user computers and keeping them up to date. Developed as an alternative to Java Web Start.

Artipie

Binary artifact management toolkit which hosts them on the file system or S3.

Central Repository

Largest binary component repository available as a free service to the open-source community. Default used by Apache Maven, and available in all other build tools.

jDeploy

Deploy desktop apps as native Mac, Windows or Linux bundles.

IzPack

Setup authoring tool for cross-platform deployments.

really-executable-jars-maven-plugin

Maven plugin for making self-executing JARs.

jlink.online

Builds optimized runtimes over HTTP.

docx4j

Create and manipulate Microsoft Open XML files.

Apache POI

Supports OOXML (XLSX, DOCX, PPTX) as well as OLE2 (XLS, DOC or PPT).

fastexcel

High performance library to read and write large Excel (XLSX) worksheets.

documents4j

API for document format conversion using third-party converters such as MS Word.

zerocell

Annotation-based API for reading data from Excel sheets into POJOs with focus on reduced overhead.

ta4j

Library for technical analysis.

Stripe

Integration with the Stripe API.

Cassandre

Trading bot framework.

Parity

Platform for trading venues.

Philadelphia

Low-latency financial information exchange.

Square

Integration with the Square API.

Checker Framework

Pluggable type systems. Includes nullness types, physical units, immutability types and more. (GPL-2.0-only WITH Classpath-exception-2.0)

Java Path Finder (JPF)

JVM formal verification tool containing a model checker and more. Created by NASA.

Daikon

Detects likely program invariants and generates JML specs based on those invariants.

OpenJML

Translates JML specifications into SMT-LIB format and passes the proof problems implied by the program to backend solvers. (GPL-2.0-only)

CATG

Concolic unit testing engine. Automatically generates unit tests using formal methods.

KeY

Formal software development tool that aims to integrate design, implementation, formal specification, and formal verification of object-oriented software as seamlessly as possible. Uses JML for specification and symbolic execution for verification. (GPL-2.0-or-later)

JMLOK 2.0

Detects inconsistencies between code and JML specification through feedback-directed random tests generation, and suggests a likely cause for each nonconformance detected. (GPL-3.0-only)

Vavr

Functional component library that provides persistent data types and functional control structures.

StreamEx

Enhances Java 8 Streams.

jOOλ

Extension to Java 8 that aims to fix gaps in lambda by providing numerous missing types and a rich set of sequential Stream API additions.

Functional Java

Implements numerous basic and advanced programming abstractions that assist composition-oriented development.

Cyclops

Monad and stream utilities, comprehensions, pattern matching, functional extensions for all JDK collections, future streams, trampolines and much more.

derive4j

Java 8 annotation processor and framework for deriving algebraic data types constructors, pattern-matching and morphisms. (GPL-3.0-only)

protonpack

Collection of stream utilities.

libGDX

All-round cross-platform, high-level framework.

LWJGL

Robust framework that abstracts libraries like OpenGL/CL/AL.

FXGL

JavaFX Game Development Framework.

jMonkeyEngine

Game engine for modern 3D development.

JBox2D

Port of the renowned C++ 2D physics engine.

Litiengine

AWT-based, lightweight 2D game engine.

Mini2Dx

Beginner-friendly, master-ready framework for rapidly prototyping and building 2D games.

Void2D

High-level 2D game engine with built-in physics based on Swing.

GraphHopper

Road-routing engine. Used as a Java library or standalone web service.

GeoTools

Library that provides tools for geospatial data. (LGPL-2.1-only)

Mapsforge

Map rendering based on OpenStreetMap data. (LGPL-3.0-only)

Spatial4j

General-purpose spatial/geospatial library.

Geo

GeoHash utilities in Java.

H2GIS

Spatial extension of the H2 database. (LGPL-3.0-only)

Apache SIS

Library for developing geospatial applications.

Jgeohash

Library for using the GeoHash algorithm.

JavaFX

Successor of Swing.

Scene Builder

Visual layout tool for JavaFX applications.

SWT

Graphical widget toolkit.

Disruptor

Inter-thread messaging library.

JCTools

Concurrency tools currently missing from the JDK.

Agrona

Data structures and utility methods that are common in high-performance applications.

Eclipse Collections

Collections framework inspired by Smalltalk.

fastutil

Fast and compact type-specific collections.

Koloboke

Carefully designed extension of the Java Collections Framework with primitive specializations and more.

HPPC

Primitive collections.

Retrofit

Typesafe REST client.

Feign

HTTP client binder inspired by Retrofit, JAXRS-2.0, and WebSocket.

Async Http Client

Asynchronous HTTP and WebSocket client library.

Ribbon

Client-side IPC library that is battle-tested in the cloud.

unirest-java

Simplified, lightweight HTTP client library.

Apache HttpComponents

A toolset of low-level Java components focused on HTTP and associated protocols.

Google HTTP Client

Pluggable HTTP transport abstraction with support for java.net.HttpURLConnection, Apache HTTP Client, Android, Google App Engine, XML, Gson, Jackson and Protobuf.

Riptide

Client-side response routing for Spring's RestTemplate.

methanol

HTTP client extensions library.

Avaje Http Client

A wrapper on JDK 11's HttpClient that adds Feign-like interface among other enhancements.

JSON-LD

JSON-LD implementation.

Siren4J

Library for the Siren specification.

hate

Builds hypermedia-friendly objects according to HAL specification.

Visual Studio Code

Provides Java support for lightweight projects with a simple, modern workflow by using extensions from the internal marketplace.

NetBeans

Provides integration for several Java SE and EE features, from database access to HTML5.

ZXing

Multi-format 1D/2D barcode image processing library.

Thumbnailator

High-quality thumbnail generation library.

TwelveMonkeys

Collection of plugins that extend the number of supported image file formats.

Tess4J

JNA wrapper for Tesseract OCR API.

Imgscalr

Simple, efficient and hardware-accelerated image-scaling library implemented in pure Java 2D.

image-comparison

Library that compares 2 images with the same sizes and shows the differences visually by drawing rectangles. Some parts of the image can be excluded from the comparison.

Reflections

Reflections scans your classpath, indexes the metadata, allows you to query it on runtime and may save and collect that information for many modules within your project.

jOOR

jOOR stands for jOOR Object Oriented Reflection. It is a simple wrapper for the java.lang.reflect package.

ClassGraph

ClassGraph (formerly FastClasspathScanner) is an uber-fast, ultra-lightweight, parallelized classpath scanner and module scanner for Java, Scala, Kotlin and other JVM languages.

ReflectASM

ReflectASM is a very small Java library that provides high performance reflection by using code generation.

Objenesis

Allows dynamic instantiation without default constructor, e.g. constructors which have required arguments, side effects or throw exceptions.

Mirror

Mirror was created to bring light to a simple problem, usually named ReflectionUtil, which is on almost all projects that rely on reflection to do advanced tasks.

Quartz

Feature-rich, open source job scheduling library that can be integrated within virtually any Java application.

shedlock

Makes sure that your scheduled tasks are executed at most once at the same time. If a task is being executed on one node, it acquires a lock which prevents execution of the same task from another node or thread.

JobRunr

Job scheduling library which utilizes lambdas for fire-and-forget, delayed and recurring jobs. Guarantees execution by single scheduler instance using optimistic locking. Has features for persistence, minimal dependencies and is embeddable.

db-scheduler

Persistent and cluster-friendly scheduler.

easy-batch

Set up batch jobs with simple processing pipelines. Records are read in sequence from a data source, processed in pipeline and written in batches to a data sink.

Sundial

Lightweight framework to simply define jobs, define triggers and start the scheduler.

Wisp

Simple library with minimal footprint and straightforward API.

fastjson

Very fast processor with no additional dependencies and full data binding.

Gson

Serializes objects to JSON and vice versa. Good performance with on-the-fly usage.

Moshi

Modern JSON library, less opinionated and uses built-in types like List and Map.

Jackson

Similar to GSON, but offers performance gains if you need to instantiate the library more often.

JsonPath

Extract data from JSON using XPATH-like syntax.

LoganSquare

JSON parsing and serializing library based on Jackson's streaming API. Outperforms GSON & Jackson's library.

Jolt

JSON to JSON transformation tool.

jsoniter

Fast and flexible library with iterator and lazy parsing API.

DSL-JSON

JSON library with advanced compile time databinding.

HikariJSON

High-performance JSON parser, 2x faster than Jackson.

jackson-modules-java8

Set of Jackson modules for Java 8 datatypes and features.

JSON-io

Convert Java to JSON. Convert JSON to Java. Pretty print JSON. Java JSON serializer.

JsonSurfer

Streaming JsonPath processor dedicated to processing big and complicated JSON data.

Jackson-datatype-money

Open-source Jackson module to support JSON serialization and deserialization of JavaMoney data types.

Genson

Powerful and easy-to-use Java-to-JSON conversion library.

Yasson

Binding layer between classes and JSON documents similar to JAXB.

Avaje Jsonb

Reflection-free Json binding via source code generation with Jackson-like annotations.

Graal

Polyglot embeddable JVM. (GPL-2.0-only WITH Classpath-exception-2.0)

Open JDK

Open JDK community home. (GPL-2.0-only WITH Classpath-exception-2.0)

Dragonwell8

Downstream version of OpenJDK optimized for online e-commerce, financial, logistics applications.

OpenJ9

High performance, enterprise-calibre, flexibly licensed, openly-governed cross-platform JVM extending and augmenting the runtime technology components from the Eclipse OMR and OpenJDK project.

Adopt Open JDK

Community-driven OpenJDK builds, including both HotSpot and OpenJ9.

Corretto

No-cost, multiplatform, production-ready distribution of OpenJDK by Amazon. (GPL-2.0-only WITH Classpath-exception-2.0)

ParparVM

VM with non-blocking, concurrent GC for iOS. (GPL-2.0-only WITH Classpath-exception-2.0)

Avian

JVM with JIT, AOT modes and iOS port.

SAP Machine

SAP's no-cost, rigorously tested and JCK-verified OpenJDK friendly fork. (GPL-2.0-only WITH Classpath-exception-2.0)

Liberica JDK

Built from OpenJDK, thoroughly tested and passed the JCK. (GPL-2.0-only WITH Classpath-exception-2.0)

Zulu

OpenJDK builds for Windows, Linux, and macOS. (GPL-2.0-only WITH Classpath-exception-2.0)

Kibana

Analyzes and visualizes log files. Some features require payment.

Logstash

Tool for managing log files.

Graylog

Open-source aggregator suited for extended role and permission management. (GPL-3.0-only)

Apache Log4j 2

Complete rewrite with a powerful plugin and configuration architecture.

Logback

Robust logging library with interesting configuration options via Groovy.

SLF4J

Abstraction layer/simple logging facade.

p6spy

Enables logging for all JDBC transactions without changes to the code.

Logbook

Extensible, open-source library for HTTP request and response logging.

tinylog

Lightweight logging framework with static logger class.

OpenTracing Toolbox

Collection of libraries that build on top of OpenTracing and provide extensions and plugins to existing instrumentations.

Echopraxia

API designed around structured logging, rich context, and conditional logging. There are Logback and Log4J2 implementations, but Echopraxia's API is completely dependency-free, meaning it can be implemented with any logging API.

Apache Flink

Fast, reliable, large-scale data processing engine.

Deeplearning4j

Distributed and multi-threaded deep learning library.

H2O ![c]

Analytics engine for statistics over big data.

Smile

Statistical Machine Intelligence and Learning Engine provides a set of machine learning algorithms and a visualization library.

DJL

High-level and engine-agnostic framework for deep learning.

m2cgen

CLI tool to transpile models into native code.

Apache Mahout

Scalable algorithms focused on collaborative filtering, clustering and classification.

Oryx 2

Framework for building real-time, large-scale machine learning applications. Includes end-to-end applications for collaborative filtering, classification, regression, and clustering.

Siddhi

Cloud native streaming and complex event processing engine.

Tribuo

Provides tools for classification, regression, clustering, model development and interfaces with other libraries such as scikit-learn, pytorch and TensorFlow.

DatumBox

Provides several algorithms and pre-trained models for natural language processing.

JSAT

Algorithms for pre-processing, classification, regression, and clustering with support for multi-threaded execution. (GPL-3.0-only)

oj! Algorithms

High-performance mathematics, linear algebra and optimisation needed for data science, machine learning and scientific computing.

Weka

Collection of algorithms for data mining tasks ranging from pre-processing to visualization. (GPL-3.0-only)

Intelligent java

Seamlessly integrate with remote deep learning and language models programmatically.

Apache Kafka

High-throughput distributed messaging system.

EventBus

Simple publish/subscribe event bus.

Apache RocketMQ

Fast, reliable, and scalable distributed messaging platform.

Apache Pulsar

Distributed pub/sub-messaging system.

Aeron

Efficient, reliable, unicast and multicast message transport.

Apache Camel

Glues together different transport APIs via Enterprise Integration Patterns.

Smack

Cross-platform XMPP client library.

JeroMQ

Implementation of ZeroMQ.

Apache ActiveMQ

Message broker that implements JMS and converts synchronous to asynchronous communication.

RabbitMQ Java client

RabbitMQ client.

Nakadi

Provides a RESTful API on top of Kafka.

Hermes

Fast and reliable message broker built on top of Kafka.

NATS client

NATS client.

Apache Qpid

Apache Qpid makes messaging tools that speak AMQP and support many languages and platforms.

Deezpatch

Simple, lightweight, and performant dispatch library for decoupling messages (requests and events) and message handlers.

Nacos

Dynamic service discovery, configuration and service management platform for building cloud native applications.

Sentinel

Flow control component enabling reliability, resilience and monitoring for microservices.

Quarkus

Kubernetes stack tailored for the HotSpot and Graal VM.

Eureka

REST-based service registry for resilient load balancing and failover.

Micronaut

Modern full-stack framework with focus on modularity, minimal memory footprint and startup time.

Armeria

Asynchronous RPC/REST client/server library built on top of Java 8, Netty, HTTP/2, Thrift and gRPC.

OpenAI-Java

Java libraries for using OpenAI's GPT-3 API.

JDA

Wrapping of the Discord REST API and its WebSocket events.

Helidon

Two-style approach for writing microservices: Functional-reactive and as an implementation of MicroProfile.

kubernetes-client

Client provides access to the full Kubernetes & OpenShift REST APIs via a fluent DSL.

Apollo

Libraries for writing composable microservices.

ActiveRPC

Lightweight and fast library for complex high-load distributed applications and Memcached-like solutions.

consul-api

Client for the Consul API: a distributed, highly available and datacenter-aware registry/discovery service.

Design Patterns

Implementation and explanation of the most common design patterns.

FizzBuzz Enterprise Edition

No-nonsense implementation of FizzBuzz made by serious businessmen for serious business purposes. (No explicit license)

Modern Java - A Guide to Java 8

Popular Java 8 guide.

OpenRefine

Tool for working with messy data: cleaning, transforming, extending it with web services and linking it to databases.

J2ObjC

Java-to-Objective-C translator for porting Android libraries to iOS.

OctoLinker

Browser extension which allows to navigate through code on GitHub more efficiently.

Jimfs

In-memory file system.

Svix

Library for the Svix API to send webhooks and verify signatures.

AWS SDK for Java 2.0

Wrapper around AWS' API.

LittleProxy

High performance HTTP proxy atop Netty's event-based networking library.

CQEngine

Ultra-fast, SQL-like queries on Java collections.

Maven Wrapper

Analogue of Gradle Wrapper for Maven, allows building projects without installing maven.

jsweet

Source transpiler to TypeScript/JavaScript.

FF4J

Feature Flags for Java.

Simple Java Mail

Mailing with a clean and fluent API.

JBot

Framework for building chatbots. (GPL-3.0-only)

JBake

Static website generator.

Togglz

Implementation of the Feature Toggles pattern.

Polyglot for Maven

Extensions for Maven 3.3.1+ that allows writing the POM model in dialects other than XML.

Joda-Money

Basic currency and money classes and algorithms not provided by the JDK.

TypeTools

Tools for resolving generic types.

jOOX

Simple wrapper for the org.w3c.dom package, to allow for fluent XML document creation and manipulation with an API inspired by jQuery.

Membrane Service Proxy

Open-source, reverse-proxy framework.

PipelinR

Small utility library for using handlers and commands with pipelines.

Smooks

Framework for fragment-based message processing. (Apache-2.0 OR LGPL-3.0-or-later)

Modernizer

Detect uses of legacy Java APIs.

yGuard

Obfuscation via renaming and shrinking.

JCuda

JCuda offers Java bindings for CUDA and CUDA-related libraries.

MinimalFTP

Lightweight, small and customizable FTP server.

XMLBeam

Processes XML by using annotations or XPath within code.

JObfuscator![c]

Source code obfuscator.

RR4J

RR4J is a tool that records java bytecode execution and later allows developers to replay locally.

Codename One

Cross-platform solution for writing native mobile apps. (GPL-2.0-only WITH Classpath-exception-2.0)

Multi-OS Engine

Open-source, cross-platform engine to develop native mobile (iOS, Android, etc.) apps.

zipkin

Distributed tracing system which gathers timing data needed to troubleshoot latency problems in microservice architectures.

Pinpoint

Open-source APM tool.

Metrics

Expose metrics via JMX or HTTP and send them to a database.

hippo4j

Dynamic and observable thread pool framework.

JavaMelody

Performance monitoring and profiling.

Prometheus

Provides a multi-dimensional data model, DSL, autonomous server nodes and much more.

Stagemonitor

Open-source performance monitoring and transaction tracing for JVM apps.

jmxtrans

Connect to multiple JVMs and query them for their attributes via JMX. Its query language is based on JSON, which allows non-Java programmers to access the JVM attributes. Supports different output writes, including Graphite, Ganglia, and StatsD.

Glowroot

Open-source Java APM.

Sentry ![c]

Integration with [Sentry](https://github.com/getsentry/sentry), an application error tracking and performance analysis platform.

Jolokia

JMX over REST.

Automon

Combines the power of AOP with monitoring and/or logging tools.

Datadog ![c]

Modern monitoring & analytics.

inspectIT

Captures detailed run-time information via hooks that can be changed on the fly. It supports tracing over multiple systems via the OpenTracing API and can correlate the data with end user monitoring.

Jaeger client

Jaeger client.

nudge4j

Remote developer console from the browser for Java 8 via bytecode injection.

Sysmon

Lightweight platform monitoring tool for Java VMs.

Failsafe Actuator

Out of the box monitoring of Failsafe Circuit Breaker in Spring-Boot environment.

SPM ![c]

Performance monitor with distributing transaction tracing for JVM apps.

HertzBeat

Real-time monitoring system with custom-monitor and agentless.

JNA

Work with native libraries without writing JNI. Also provides interfaces to common system libraries.

JavaCPP

Provides efficient and easy access to native C++.

JNR

Work with native libraries without writing JNI. Also provides interfaces to common system libraries. Same goals as JNA, but faster, and serves as the basis for the upcoming [Project Panama](http://openjdk.java.net/projects/panama).

Aparapi

Converts bytecode to OpenCL which allows execution on GPUs.

CoreNLP

Provides a set of fundamental tools for tasks like tagging, named entity recognition, and sentiment analysis. (GPL-3.0-or-later)

CogCompNLP

Provides common annotators for plain text input. (Research and Academic Use License)

DKPro

Collection of reusable NLP tools for linguistic pre-processing, machine learning, lexical resources, etc.

Dubbo

High-performance RPC framework.

Netty

Framework for building high-performance network applications.

gRPC

RPC framework based on protobuf and HTTP/2.

Undertow

Web server providing both blocking and non-blocking APIs based on NIO. Used as a network layer in WildFly. (LGPL-2.1-only)

sshj

Programmatically use SSH, SCP or SFTP.

KryoNet

Provides a clean and simple API for efficient TCP and UDP client/server network communication using NIO and Kryo.

ServiceTalk

Framework built on Netty with APIs tailored to specific protocols and support for multiple programming paradigms.

MINA

Abstract, event-driven async I/O API for network operations over TCP/IP and UDP/IP via Java NIO.

Comsat

Integrates standard Java web-related APIs with Quasar fibers and actors.

Drift

Easy-to-use, annotation-based library for creating Thrift clients and serializable types.

TLS Channel

Implements a ByteChannel interface over SSLEngine, enabling easy-to-use (socket-like) TLS.

Fluency

High throughput data ingestion logger to Fluentd and Fluent Bit.

Grizzly

NIO framework. Used as a network layer in Glassfish.

urnlib

Represent, parse and encode URNs, as in RFC 2141. (GPL-3.0-only)

Commons-networking

Client for server-sent events (SSE).

MyBatis

Couples objects with stored procedures or SQL statements.

Hibernate

Robust and widely used, with an active community. (LGPL-2.1-only)

Ebean

Provides simple and fast data access.

ObjectiveSql

ActiveRecord ORM for rapid development and convention over configuration.

SimpleFlatMapper

Simple database and CSV mapper.

Doma

Database access framework that verifies and generates source code at compile time using annotation processing as well as native SQL templates called two-way SQL.

Permazen

Language-natural persistence layer.

Apache Cayenne

Provides a clean, static API for data access. Also includes a GUI Modeler for working with database mappings, and DB reverse engineering and generation.

EclipseLink

Supports a number of persistence standards: JPA, JAXB, JCA and SDO.

OpenPDF

Open-source iText fork. (LGPL-3.0-only & MPL-2.0)

Apache PDFBox

Toolbox for creating and manipulating PDFs.

flyingsaucer

XML/XHTML and CSS 2.1 renderer. (LGPL-2.1-or-later)

Open HTML to PDF

Properly supports modern PDF standards based on flyingsaucer and Apache PDFBox.

Tabula

Extracts tables from PDF files.

iText ![c]

Creates PDF files programmatically.

JasperReports

Complex reporting engine. (LGPL-3.0-only)

Eclipse BIRT

Report engine for creating PDF and other formats (DOCX, XLSX, HTML, etc) using Eclipse-based visual editor.

Dynamic Jasper

Abstraction layer to JasperReports. (LGPL-3.0-only)

DynamicReports

Simplifies JasperReports. (LGPL-3.0-only)

Apache FOP

Creates PDFs from XSL-FO.

JITWatch

Analyze the JIT compiler optimisations made by the HotSpot JVM.

JMH

Harness for building, running, and analysing nano/micro/milli/macro benchmarks written in Java and other languages targeting the JVM. (GPL-2.0 only WITH Classpath-exception-2.0)

honest-profiler

Low-overhead, bias-free sampling profiler.

jHiccup

Logs and records platform JVM stalls.

LatencyUtils

Utilities for latency measurement and reporting.

Lang

Provides extra functionality for classes in java.lang.

IO

Collection of I/O utilities.

Collections

Extends or augments the Java Collections Framework.

Math

Lightweight, self-contained mathematics and statistics components.

Pool

Generic object pooling component.

Codec

General encoding/decoding algorithms, e.g. phonetic, base64 or URL.

Imaging

Image library.

CSV

Component for reading and writing comma separated value files.

DbUtils

JDBC helper library.

CLI

Command-line arguments parser.

DBCP

Database connection pooling services.

Compress

Defines an API for working with tar, zip and bzip2 files.

BeanUtils

Easy-to-use wrappers around the Java reflection and introspection APIs.

Net

Collection of network utilities and protocol implementations.

BCEL

Byte Code Engineering Library - analyze, create, and manipulate Java class files.

FileUpload

File upload capability for your servlets and web applications.

VFS

Virtual File System component for treating files, FTP, SMB, ZIP and such like as a single logical file system.

Validator

Framework to define validators and validation rules in an xml file.

Configuration

Reading of configuration/preferences files in various formats.

Jexl

Expression language which extends the Expression Language of the JSTL.

Email

Library for sending e-mail from Java.

Logging

Wrapper around a variety of logging API implementations.

Exec

API for dealing with external process execution and environment management in Java.

Daemon

Alternative invocation mechanism for unix-daemon-like java code.

JCS

Java Caching System.

OGNL

Object-graph navigation language.

Chain

Chain of Responsibility pattern implementation.

Digester

XML-to-Java-object mapping utility.

RNG

Commons Rng provides implementations of pseudo-random numbers generators.

SCXML

Implementation of the State Chart XML specification aimed at creating and maintaining a Java SCXML engine.

RDF

Common implementation of RDF 1.1 that could be implemented by systems on the JVM.

JXPath

Utilities for manipulating Java Beans using the XPath syntax.

Graph

General purpose graph APIs and algorithms.

Proxy

Library for creating dynamic proxies.

BSF

Bean Scripting Framework - interface to scripting languages, including JSR-223.

Functor

Function that can be manipulated as an object, or an object representing a single, generic function.

Weaver

Provides an easy way to enhance (weave) compiled bytecode.

Jelly

XML based scripting and processing engine.

JCI

Java Compiler Interface.

Light-4J

Fast, lightweight and productive microservices framework with built-in [security](https://github.com/networknt/light-oauth2/).

CUBA Platform

High-level framework for developing enterprise applications with a rich web interface, based on Spring, EclipseLink and Vaadin.

Orienteer

Open-source business application platform for rapid configuration/development of CRM, ERP, LMS and other applications.

zt-exec

Provides a unified API to Apache Commons Exec and ProcessBuilder.

zt-process-killer

Stops processes started from Java or the system processes via PID.

ch.vorburger.exec

Convenient API around Apache Commons Exec.

RxJava

Allows for composing asynchronous and event-based programs using observable sequences.

vert.x

Polyglot event-driven application framework.

Akka

Toolkit and runtime for building concurrent, distributed, fault-tolerant and event-driven applications.

Reactor

Library for building reactive fast-data applications.

Reactive Streams

Provides a standard for asynchronous stream processing with non-blocking backpressure.

Spark

Sinatra inspired framework.

Dropwizard

Opinionated framework for setting up modern web applications with Jetty, Jackson, Jersey and Metrics.

springdoc-openapi

Automates the generation of API documentation using Spring Boot projects.

rest.li

Framework for building robust, scalable RESTful architectures using typesafe bindings and asynchronous, non-blocking IO with an end-to-end developer workflow that promotes clean practices, uniform interface design and consistent data modeling.

Rapidoid

Simple, secure and extremely fast framework consisting of an embedded HTTP server, GUI components and dependency injection.

RESTEasy

Fully certified and portable implementation of the JAX-RS specification.

Elide

Opinionated framework for JSON- or GraphQL-APIs based on a JPA data model.

Microserver

Convenient, extensible microservices plugin system for Spring & Spring Boot. With more than 30 plugins and growing, it supports both micro-monolith and pure microservices styles.

RestExpress

Thin wrapper on the JBoss Netty HTTP stack that provides scaling and performance.

Jersey

JAX-RS reference implementation.

Restlet Framework

Pioneering framework with powerful routing and filtering capabilities, and a unified client and server API.

Crnk

Implementation of the JSON API specification to build resource-oriented REST endpoints with sorting, filtering, paging, linking, object graphs, type-safety, bulk updates, integrations and more.

Tablesaw

Includes a data-frame, an embedded column store, and hundreds of methods to transform, summarize, or filter data.

JGraphT

Graph library that provides mathematical graph-theory objects and algorithms.

XChart

Light-weight library for plotting data. Many customizable chart types are available.

JFreeChart

2D chart library for Swing, JavaFX and server-side applications. (LGPL-2.1-only)

JGraphX

Library for visualizing (mainly Swing) and interacting with node-edge graphs.

BioJava

Facilitates processing biological data by providing algorithms, file format parsers, sequencing and 3D visualization commonly used in bioinformatics.

Chart-FX

Scientific charting library with focus on performance optimised real-time data visualisation at 25 Hz update rates for large data sets.

GraphStream

Library for modeling and analyzing dynamic graphs.

Morpheus

Provides a versatile two-dimensional memory efficient tabular data structure called a DataFrame to enable efficient in-memory analytics for scientific computing on the JVM.

LogicNG

Library for creating, manipulating and solving Boolean and Pseudo-Boolean formulas.

Erdos

Modular, light and easy graph framework for theoretic algorithms.

Orson-Charts

Generates a wide variety of 3D charts that can be displayed with Swing and JavaFX or exported to PDF, SVG, PNG and JPEG. (GPL-3.0-only)

Mines Java Toolkit

Library for geophysical scientific computation, visualization and digital signal analysis.

Elasticsearch

Distributed, multitenant-capable, full-text search engine with a RESTful web interface and schema-free JSON documents.

Apache Lucene

High-performance, full-featured, cross-platform, text search engine library.

Apache Solr

Enterprise search engine optimized for high-volume traffic.

Indexer4j

Simple and light full text indexing and searching library.

Keycloak

Integrated SSO and IDM for browser apps and RESTful web services.

Cryptomator

Multiplatform, transparent, client-side encryption of files in the cloud. (GPL-3.0-only)

jjwt

JSON web token for Java and Android.

DependencyCheck

Detects publicly disclosed vulnerabilities contained within a project's dependencies.

Apache Shiro

Performs authentication, authorization, cryptography and session management.

Keywhiz

System for distributing and managing secrets.

pac4j

Security engine.

Bouncy Castle

All-purpose cryptographic library and JCA provider offering a wide range of functions, from basic helpers to PGP/SMIME operations.

Themis

Multi-platform high-level cryptographic library provides easy-to-use encryption for protecting sensitive data: secure messaging with forward secrecy, secure data storage (AES256GCM); suits for building end-to-end encrypted applications.

Topaz

Fine-grained authorization for applications with support for RBAC, ABAC, and ReBAC.

OpenAM

Access management solution that includes authentication, SSO, authorization, federation, entitlements and web services security.

SSLContext-Kickstart

High-level SSL context builder for configuring HTTP clients with SSL/TLS.

Password4j

User-friendly cryptographic library that supports Argon2, Bcrypt, Scrypt, PBKDF2 and various other cryptographic hash functions.

Nbvcxz

Advanced password strength estimation.

Passay

Enforce password policy by validating candidate passwords against a configurable rule set.

Hdiv

Runtime application that repels application security risks included in the OWASP Top 10, including SQL injection, cross-site scripting, cross-site request forgery, data tampering, and brute force attacks.

Kalium

Binding for the Networking and Cryptography (NaCl) library.

Jwks RSA

JSON Web Key Set parser.

OTP-Java

One-time password generator library according to RFC 4226 (HOTP) and RFC 6238 (TOTP).

OACC

Provides permission-based authorization services.

SecurityBuilder

Fluent Builder API for JCA and JSSE classes and especially X.509 certificates.

jwt-java

Easily create and parse JSON Web Tokens and create customized JWT validators using a fluent API.

Tink

Provides a simple and misuse-proof API for common cryptographic tasks.

FlatBuffers

Memory-efficient serialization library that can access serialized data without unpacking and parsing it.

Kryo

Fast and efficient object graph serialization framework.

FST

JDK-compatible, high-performance object graph serialization.

MessagePack

Efficient binary serialization format.

PHP Serializer

Serializing objects in the PHP serialization format.

Fury

A blazing fast multi-language serialization framework powered by jit and zero-copy.

Apache Tomcat

Robust, all-round server for Servlet and JSP.

nanohttpd

Tiny, easily embeddable HTTP server.

Jetty

Provides a Web server and javax.servlet container, plus support for HTTP/2, WebSocket, OSGi, JMX, JNDI, JAAS and many other integrations.

WildFly

Formerly known as JBoss and developed by Red Hat with extensive Java EE support. (LGPL-2.1-only)

Apache TomEE

Tomcat plus Java EE.

Thymeleaf

Aims to be a substitute for JSP and works for XML files.

Handlebars.java

Logicless and semantic Mustache templates.

Pebble

Inspired by Twig and separates itself with its inheritance feature and its easy-to-read syntax. It ships with built-in autoescaping for security and it includes integrated support for internationalization.

Freemarker

Library to generate text output (HTML web pages, e-mails, configuration files, source code, etc.) based on templates and changing data.

StringTemplate

Template engine for generating source code, web pages, emails, or any other formatted text output.

jte

Compiles to classes, and uses an easy syntax, several features to make development easier and provides fast execution and a small footprint.

Rocker

Optimized, memory efficient and speedy template engine producing statically typed, plain objects.

Jade4J

Implementation of Pug (formerly known as Jade).

Jtwig

Modular, configurable and fully tested template engine.

jstachio

Typesafe Mustache templating engine.

Jamal

Extendable template engine embedded into Maven/JavaDoc, supporting multiple extensions (Groovy, Ruby, JavaScript, JShell, PlantUml) with support for snippet handling.

Cucumber

Provides a way to describe features in a plain language which customers can understand.

Serenity BDD

Automated Acceptance testing and reporting library that works with Cucumber, JBehave and JUnit to make it easier to write high quality executable specifications.

JGiven

Provides a fluent API which allows for simpler composition.

Lamdba Behave

Aims to provide a fluent API to write tests in long and descriptive sentences that read like plain English.

JBehave

Extensively configurable framework that describes stories.

Cukes-REST

Collection of Gherkin steps for REST-service testing using Cucumber.

J8Spec

Follows a Jasmine-like syntax.

Java Faker

Port of Ruby's fake data generator.

Instancio

Automates data setup in unit tests by generating fully-populated, reproducible objects. Includes JUnit 5 extension.

jFairy

Fake data generator.

Mockneat

Another fake data generator.

Fixture Factory

Generates fake objects from a template.

Randomized Testing

JUnit test runner and plugins for running JUnit tests with pseudo-randomness.

Beanmother

Sets up beans from YAML fixtures.

Apache JMeter

Functional testing and performance measurements.

Gatling

Load testing tool designed for ease of use, maintainability and high performance.

JUnit

Common testing framework.

ArchUnit

Test library for specifying and asserting architecture rules.

PIT

Fast mutation-testing framework for evaluating fault-detection abilities of existing JUnit or TestNG test suites.

Pact JVM

Consumer-driven contract testing.

jqwik

Engine for property-based testing built on JUnit 5.

Citrus

Integration testing framework that focuses on both client- and server-side messaging.

Arquillian

Integration and functional testing platform for Java EE containers.

Truth

Google's fluent assertion and proposition framework.

AssertJ

Fluent assertions that improve readability.

Hamcrest

Matchers that can be combined to create flexible expressions of intent.

JSONAssert

Simplifies testing JSON strings.

JsonUnit

Library that simplifies JSON comparison in tests.

XMLUnit

Simplifies testing for XML output.

TestContainers

Provides throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.

LogCaptor

Captures log entries for unit testing purposes.

junit-dataprovider

TestNG-like data provider/runner for JUnit.

Mutability Detector

Reports whether instances of a given class are immutable.

raml-tester

Tests if a request/response matches a given RAML definition.

pojo-tester

Automatically performs tests on basic POJO methods. (LGPL-3.0-only)

ConsoleCaptor

Captures console output for unit testing purposes.

log-capture

Captures log entries and provides assertions for unit and integration testing.

Mockito

Mocking framework that lets you write tests with a clean and simple API.

WireMock

Stubs and mocks web services.

MockServer

Allows mocking of systems integrated with HTTPS.

Moco

Concise web services for stubs and mocks.

PowerMock

Mocks static methods, constructors, final classes and methods, private methods, and removal of static initializers.

JMockit

Integration testing, API mocking and faking, and code coverage.

Guava

Collections, caching, primitives support, concurrency libraries, common annotations, string processing, I/O, and more.

Arthas

Allows to troubleshoot production issues for applications without modifying code or restarting servers.

Gephi

Cross-platform for visualizing and manipulating large graph networks. (GPL-3.0-only)

JavaVerbalExpressions

Library that helps with constructing difficult regular expressions.

bucket4j

Rate limiting library based on token-bucket algorithm.

Embulk

Bulk data loader that helps data transfer between various databases, storages, file formats, and cloud services.

Dex

Java/JavaFX tool capable of powerful ETL and data visualization.

Java Diff Utils

Utilities for text or data comparison and patching.

minio-java

Provides simple APIs to access any Amazon S3-compatible object storage server.

Protégé

Provides an ontology editor and a framework to build knowledge-based systems.

CRaSH

Provides a shell into a JVM that's running CRaSH. Used by Spring Boot and others. (LGPL-2.1-or-later)

cactoos

Collection of object-oriented primitives.

Underscore-java

Port of Underscore.js functions.

JGit

Lightweight, pure Java library implementing the Git version control system.

Chocotea

Generates postman collection, environment and integration tests from java code.

fswatch

Micro library to watch for directory file system changes, simplifying java.nio.file.WatchService.

SDKMan

Java Version Manager inspired by RVM and rbenv. Supports UNIX-based platforms.

jenv

Java Version Manager inspired by rbenv. Can configure globally or per project. Tested on Debian and macOS.

jabba

Java Version Manager inspired by nvm. Supports macOS, Linux and Windows.

webmagic

Scalable crawler with downloading, url management, content extraction and persistent.

jsoup

Scrapes, parses, manipulates and cleans HTML.

Crawler4j

Simple and lightweight web crawler.

Apache Nutch

Highly extensible, highly scalable web crawler for production environments.

StormCrawler

SDK for building low-latency and scalable web crawlers.

Play

Built on Akka, it provides predictable and minimal resource consumption (CPU, memory, threads) for highly-scalable applications in Java and Scala.

Javalin

Microframework for web applications.

Blade

Lightweight, modular framework that aims to be elegant and simple.

Ratpack

Set of libraries that facilitate fast, efficient, evolvable and well-tested HTTP applications.

Ninja

Full-stack web framework.

Vaadin

Event-driven framework that uses standard web components. Server-side architecture with Ajax on the client side.

PrimeFaces

JSF framework with both free and commercial/support versions and frontend components.

Jooby

Scalable, fast and modular micro-framework that offers multiple programming models.

Bootique

Minimally opinionated framework for runnable apps.

ActiveJ

Lightweight asynchronous framework built from the ground up for developing high-performance web applications.

Takes

Opinionated web framework which is built around the concepts of True Object-Oriented Programming and immutability.

Pippo

Small, highly modularized, Sinatra-like framework.

Apache Wicket

Component-based web application framework similar to Tapestry, with a stateful GUI.

Firefly

Asynchronous framework for rapid development of high-performance web application.

Apache Tapestry

Component-oriented framework for creating dynamic, robust, highly scalable web applications.