Awesome Java

A curated list of awesome Java frameworks, libraries and software.

• Awesome Java
  • Ancients
  • Bean Mapping
  • Build
  • Bytecode Manipulation
  • Caching
  • Cluster Management
  • Code Analysis
  • Code Coverage
  • Code Generators
  • Command-line Argument Parsers
  • Compiler-compiler
  • Configuration
  • Constraint Satisfaction Problem Solver
  • Continuous Integration
  • CSV
  • Data structures
  • Database
  • Date and Time
  • Dependency Injection
  • Development
  • Distributed Applications
  • Distributed Databases
  • Distribution
  • Document Processing
  • Formal Verification
  • Functional Programming
  • Game Development
  • Geospatial
  • GUI
  • High Performance
  • Hypermedia Types
  • IDE
  • Imagery
  • JSON Processing
  • JSON
  • JVM and JDK
  • Logging
  • Machine Learning
  • Messaging
  • Microservice
  • Miscellaneous
  • Monitoring
  • Native
  • Natural Language Processing
  • Networking
  • ORM
  • PaaS
  • PDF
  • Performance analysis
  • Platform
  • Reactive libraries
  • REST Frameworks
  • Science
  • Search
  • Security
  • Serialization
  • Server
  • Template Engine
  • Testing
  • Utility
  • Web Crawling
  • Web Frameworks
• Resources
  • Communities
  • Frontends
  • Influential Books
  • Podcasts
  • Twitter
  • Websites
• Contributing

Ancients

In existence since the beginning of time and which will continue being used long after the hype has waned.

• Apache Ant - Build process management with XML.
• Apache Hadoop - Storage and large-scale processing of data-sets on clusters of commodity hardware.
• Apache OpenNLP - Toolkit for common tasks like tokenization.
• Apache Velocity - Templates for HTML pages, emails or source code generation in general.
• FreeMarker - General templating engine without any heavyweight or opinionated dependencies.
• GlassFish - Application server and reference implementation for Java EE sponsored by Oracle.
• GWT - Toolbox which includes a Java-to-JavaScript compiler for client-side code, XML parser, API for RPC, JUnit integration, internationalization support and widgets for the GUI.
• Hamcrest - Matchers that can be combined to create flexible expressions of intent.
• HornetQ - Clear, concise, modular and made to be embedded.
• Hudson - Continuous integration server still in active development.
• Java Modeling Language (JML) - Behavioral interface specification language that can be used to specify the behavior of code modules. It combines the design by contract approach of Eiffel and the model-based specification approach of the Larch family of interface specification languages, with some elements of the refinement calculus. Used by several other verification tools.
• JavaCC - More specific and slightly easier to learn. Has syntactic lookahead.
• JavaServer Faces - Oracle's open-source implementation of the JSF standard, Mojarra.
• JavaServer Pages - Common templating for websites with custom tag libraries.
• JUnit - Common testing framework.
• Launch4j - Wraps JARs in lightweight and native Windows executables.
• Quartz - Open-source job scheduler library with Apache 2.0 license.
• TestNG - Testing framework.
• Trove - Primitive collections.

Bean Mapping

Frameworks that ease bean mapping.

• Dozer - Mapper that copies data from one object to another, using annotations, API or XML configuration.
• JMapper - Using byte code manipulation for lightning fast mapping. Supporting annotations, API or XML configuration.
• MapStruct - Code generator which simplifies mappings between different bean types, based on a convention over configuration approach.
• ModelMapper - ModelMapper is an intelligent object mapping library that automatically maps objects to each other.
• Orika - Orika is a Java Bean mapping framework that recursively copies (among other capabilities) data from one object to another.
• Selma - Stupid Simple Statically Linked Mapper. Selma is an Annotation Processor Based bean mapper.

Build

Tools which handle the build cycle and dependencies of an application.

• Apache Maven - Declarative build and dependency management which favors convention over configuration. It might be preferable to Apache Ant which uses a rather procedural approach and can be difficult to maintain.
• Bazel - Build tool from Google that builds code quickly and reliably.
• Gradle - Incremental builds which are programmed via Groovy instead of declaring XML. Works well with Maven's dependency management.

Bytecode Manipulation

Libraries to manipulate bytecode programmatically.

• ASM - All purpose, low level, bytecode manipulation and analysis.
• Byte Buddy - Further simplifies bytecode generation with a fluent API.
• Byteman - Manipulate bytecode at runtime via DSL (rules) mainly for testing/troubleshooting.
• cglib - Bytecode generation library.
• Javassist - Tries to simplify the editing of bytecode.

Caching

Libraries which provide caching facilities.

• Caffeine - High performance, near optimal caching library.
• Ehcache - Distributed general purpose cache.

Cluster Management

Frameworks which can dynamically manage applications inside of a cluster.

• Apache Aurora - Apache Aurora is a Mesos framework for long-running services and cron jobs.
• Apache Mesos - Abstracts CPU, memory, storage, and other compute resources away from machines.
• Singularity - Singularity is a Mesos framework that makes deployment and operations easy. It supports web services, background workers, scheduled jobs, and one-off tasks.

Code Analysis

Tools that provide metrics and quality measurements.

• Checkstyle - Static analysis of coding conventions and standards.
• Codacy - Continuous static analysis, code coverage, and software metrics to automate code reviews.
• Error Prone - Catches common programming mistakes as compile-time errors.
• FindBugs - Static analysis of bytecode to find potential bugs.
• Infer - Tool to produce a list of potential bugs.
• jQAssistant - Static code analysis with Neo4J-based query language.
• PMD - Source code analysis for finding bad coding practices.
• SonarQube - Integrates other analysis components via plugins and provides an overview of the metrics over time.
• Spoon - Library for analyzing and transforming Java source code.

Code Coverage

Frameworks and tools that enable collection of code coverage metrics for test suites.

• Clover - Proprietary code coverage tool by Atlassian that relies on source-code instrumentation, instead of bytecode instrumentation.
• Cobertura - Relies on offline (or static) bytecode instrumentation and class loading to collect code coverage metrics; GPLv2 licensed.
• JaCoCo - Framework that enables collection of code coverage metrics, using both offline and runtime bytecode instrumentation; prominently used by EclEmma, the Eclipse code-coverage plugin.

Code Generators

Tools that generate patterns for repetitive code in order to reduce verbosity and error-proneness.

• ADT4J - JSR-269 code generator for algebraic data types.
• Auto - Generates factory, service, and value classes.
• FreeBuilder - Automatic generation of the Builder pattern.
• Immutables - Annotation processors to generate simple, safe and consistent value objects.
• JHipster - Yeoman source code generator for Spring Boot and AngularJS.
• Joda-Beans - Small framework that adds queryable properties to Java, enhancing JavaBeans.
• Lombok - Code generator which aims to reduce verbosity.

Command-line Argument Parsers

Libraries that make it easy to parse command line options, arguments, etc.

• Airline - Annotation-based framework for parsing Git like command line arguments.
• args4j - Small library to parse command like arguments similar to javac.
• JCommander - Command line arguments parsing framework with custom types and validation via implementing interfaces.
• JOpt Simple - Simple parser that uses the POSIX getopt() and GNU getopt_long() syntaxes. Does not use annotations, uses a fluent API instead.

Compiler-compiler

Frameworks that help to create parsers, interpreters or compilers.

• ANTLR - Complex full-featured framework for top-down parsing.
• JFlex - A lexical analyzer generator.

Configuration

Libraries that provide external configuration.

• config - Configuration library for JVM languages.
• ini4j - Provides an API for handling Windows' INI files.
• owner - Reduces boilerplate of properties.

• KAConf - Annotation-based configuration system for Java and Kotlin.

Constraint Satisfaction Problem Solver

Libraries that help on implementing optimization and satisfiability problems.

• Choco - Off-the-shelf constraint satisfaction problem solver, which uses constraint programming techniques.
• JaCoP - Includes an interface for the FlatZinc language, enabling it to execute MiniZinc models.
• OptaPlanner - Business planning and resource scheduling optimization solver.

Continuous Integration

Tools which support continuously building, testing and releasing applications.

• Bamboo - Atlassian's solution with good integration of their other products. You can either apply for an open-source license or buy it.
• Concourse - Provides dockerized pipeline with configuration that can be saved in version control.
• fabric8 - Integration platform for containers.
• Go - ThoughtWork's open-source solution.
• Jenkins - Provides server-based deployment services.
• Semaphore - Hosted CI/CD service, free for open-source and 100 private builds with native Docker support.
• TeamCity - JetBrain's CI solution with a free version.
• Travis - Hosted service often used for open-source projects.

CSV

Frameworks and libraries that simplify reading/writing CSV data.

• jackson-dataformat-csv - Jackson extension for reading and writing CSV.
• opencsv - Simple CSV parser.
• Super CSV - Powerful CSV parser with support for Dozer, Joda-Time and Java 8.
• uniVocity-parsers - One of the fastest and most feature-complete CSV. Also comes with parsers for TSV and fixed width records.

Database

Everything which simplifies interactions with the database.

• Apache Hive - Data warehouse infrastructure built on top of Hadoop.
• Apache Phoenix - High performance relational database layer over HBase for low latency applications.
• Chronicle Map - Efficient in-memory (opt. persisted to disk) off-heap key-value store.
• eXist - A NoSQL document database and application platform.
• FlexyPool - Brings metrics and failover strategies to the most common connection pooling solutions.
• Flyway - Simple database migration tool.
• H2 - Small SQL Database notable for its in-memory functionality.
• HikariCP - High performance JDBC connection pool.
• JDBI - Convenient abstraction of JDBC.
• Jedis - A small client for interaction with redis, with methods for commands.
• jetcd - A client library for etcd.
• jOOQ - Generates typesafe code based on SQL schema.
• Liquibase - Database-independent library for tracking, managing and applying database schema changes.
• MapDB - Embedded database engine that provides concurrent collections backed on disk or in off-heap memory.
• MariaDB4j - Launcher for MariaDB which requires no installation or external dependencies.
• Presto - Distributed SQL query engine for big data.
• Querydsl - Typesafe unified queries.
• Realm - Mobile database to run directly inside phones, tablets or wearables.
• Redisson - Allows for distributed and scalable data structures on top of a Redis server.
• Speedment - Database access library that utilizes the Java 8 Stream API for querying.
• sql2o - Thin JDBC wrapper that simplifies database access and provides simple mapping of ResultSets to POJOs.
• Vibur DBCP - JDBC connection pool library which offers advanced performance monitoring capabilities.

Data structures

Efficient and specific data structures.

• Apache Avro - Data interchange format featuring among others: dynamic typing, untagged data, absence of manually assigned IDs.
• Apache Orc - Fast and efficient columnar storage format for hadoop based workloads.
• Apache Parquet - Columnar storage format based on assembly algorithms from the Dremel paper by Google.
• Apache Thrift - Data interchange format that originated at Facebook.
• Persistent Collection - Persistent and immutable analogue of the Java Collections Framework.
• Protobuf - Google's data interchange format.
• SBE - Simple Binary Encoding, one of the fastest message formats around.
• Wire - Clean, lightweight protocol buffers.

Date and Time

Libraries related to handling date and time.

• Almanac Converter - Simple conversion between different calendar systems.
• iCal4j - Parsing and building iCalendar RFC 5545 data models.
• Joda-Time - De facto standard date/time-library before Java 8.
• ThreeTenBP - Port of JSR 310 (java.time package) by the author of Joda-Time.
• Time4J - Advanced date and time library.

Dependency Injection

Libraries that help to realize the Inversion of Control paradigm.

• Apache DeltaSpike - CDI extension framework.
• Dagger2 - Compile-time injection framework without reflection.
• Guice - Lightweight but powerful framework that completes Dagger.
• HK2 - Light-weight and dynamic dependency injection framework.

Development

Augmentation of the development process at a fundamental level.

• AspectJ - Seamless aspect-oriented programming extension.
• DCEVM - Modification of the JVM that allows unlimited redefinition of loaded classes at runtime.
• 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.
• HotswapAgent - Unlimited runtime class and resource redefinition.
• JavaParser - Parse, modify and generate Java code.
• JavaSymbolSolver - A symbol solver for Java.
• JRebel - Instantly reloads code and configuration changes without redeploys.
• Spring Loaded - Class reloading agent.

Distributed Applications

Libraries and frameworks for writing distributed and fault-tolerant applications.

• Akka - Toolkit and runtime for building concurrent, distributed, and fault tolerant event-driven applications.
• Apache Storm - Realtime computation system.
• Apache ZooKeeper - Coordination service with distributed configuration, synchronization, and naming registry for large distributed systems.
• Atomix - Fault-tolerant distributed coordination framework.
• Axon Framework - Framework for creating CQRS applications.
• Copycat - Fault-tolerant state machine replication framework.
• Hazelcast - Highly scalable in-memory datagrid with a free open-source version.
• Hystrix - Provides latency and fault tolerance.
• JGroups - Toolkit for reliable messaging and creating clusters.
• Orbit - Virtual Actors, adding another level of abstraction to traditional actors.
• Quasar - Lightweight threads and actors for the JVM.

Distributed Databases

Databases in a distributed system that appear to applications as a single data source.

• Apache Cassandra - Column-oriented and providing high availability with no single point of failure.
• Apache HBase - Hadoop database for big data.
• Druid - Real-time and historical OLAP data store that excel at aggregation and approximation queries.
• Infinispan - Highly concurrent key/value datastore used for caching.
• OpenTSDB - Scalable and distributed time series database written on top of Apache HBase.
• OrientDB - Embeddable distributed database written on top of Hazelcast.

Distribution

Tools which handle the distribution of applications in native formats.

• Bintray - Version control for binaries which handles the publishing. Can also be used with Maven or Gradle and has a free plan for open-source software or several business plans.
• Boxfuse - Deployment of JVM application to AWS using the principles of Immutable Infrastructure.
• Capsule - Simple and powerful packaging and deployment. A fat JAR on steroids or a "Docker for Java" that supports JVM-optimized containers.
• 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.
• IzPack - Setup authoring tool for cross-platform deployments.
• JitPack - Easy to use package repository for GitHub. Builds Maven/Gradle projects on demand and publishes ready-to-use packages.
• Nexus - Binary management with proxy and caching capabilities.
• packr - Packs JARs, assets and the JVM for native distribution on Windows, Linux and Mac OS X.
• really-executable-jars-maven-plugin - Maven plugin for making self-executing JARs.

Document Processing

Libraries that assist with processing office document formats.

• Apache POI - Supports OOXML (XLSX, DOCX, PPTX) as well as OLE2 (XLS, DOC or PPT).
• documents4j - API for document format conversion using third-party converters such as MS Word.
• docx4j - Creating and manipulating Microsoft Open XML files.

Formal Verification

Formal-methods tools: proof assistants, model checking, symbolic execution etc.

• CATG - Concolic unit testing engine. Automatically generates unit tests using formal methods.
• Checker Framework - Pluggable type systems. Includes nullness types, physical units, immutability types and more.
• Daikon - Daikon detects likely program invariants and can generate JML specs based on those invariats.
• Java Path Finder (JPF) - JVM formal verification tool containing a model checker and more. Created by NASA.
• JMLOK 2.0 - Detects nonconformances between code and JML specification through the feedback-directed random tests generation, and suggests a likely cause for each nonconformance detected.
• KeY - The KeY System is a 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.
• OpenJML - Translates JML specifications into SMT-LIB format and passes the proof problems implied by the program to backend solvers.

Functional Programming

Libraries that facilitate functional programming.

• cyclops-react - 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, morphisms.
• Fugue - Functional extensions to Guava.
• Functional Java - Implements numerous basic and advanced programming abstractions that assist composition-oriented development.
• Javaslang - Functional component library that provides persistent data types and functional control structures.
• jOOλ - Extension to Java 8 which aims to fix gaps in lambda, providing numerous missing types and a rich set of sequential Stream API additions.
• protonpack - Collection of stream utilities.
• StreamEx - Enhancing Java 8 Streams.

Game Development

Frameworks that support the development of games.

• jMonkeyEngine - Game engine for modern 3D development.
• libGDX - All-round cross-platform, high-level framework.
• LWJGL - Robust framework that abstracts libraries like OpenGL/CL/AL.

Geospatial

Libraries for working with geospatial data and algorithms.

• Apache SIS - Library for developing geospatial applications.
• Geo - GeoHash utilities in Java.
• Geotoolkit.org - Library for developing geospatial applications. Built on top of the Apache SIS project.
• GeoTools - Library that provides tools for geospatial data.
• GraphHopper - Road routing engine. Used as Java library or standalone web service.
• H2GIS - A spatial extension of the H2 database.
• Jgeohash - Library that can assist Java developers in using the GeoHash algorithm.
• Mapsforge - Software for the rendering of maps based on OpenStreetMap data.
• Spatial4j - General purpose spatial/geospatial ASL licensed open-source Java library.

GUI

Libraries to create modern graphical user interfaces.

• JavaFX - The successor of Swing.
• Scene Builder - Visual layout tool for JavaFX applications.
• SWT - The Standard Widget Toolkit (SWT) is a graphical widget toolkit for use with the Java platform.

High Performance

Everything about high performance computation, from collections to specific libraries.

• Agrona - Data structures and utility methods that are common in high-performance applications.
• Disruptor - Inter-thread messaging library.
• Eclipse Collections - Collections framework inspired by Smalltalk.
• fastutil - Fast and compact type-specific collections.
• HPPC - Primitive collections.
• JCTools - Concurrency tools currently missing from the JDK.
• Koloboke - Hash sets and hash maps.

Hypermedia Types

Libraries that handle serialization to hypermedia types.

• JSON-LD - JSON-LD implementation.
• Siren4J - Library for the Siren specification.

IDE

Integrated development environments that try to simplify several aspects of development.

• Eclipse - Established, open-souce project with support for lots of plugins and languages.
• IntelliJ IDEA - Supports a lot of JVM languages and provides good options for Android development. The commercial edition targets the enterprise sector.
• NetBeans - Provides integration for several Java SE and EE features from database access to HTML5.

Imagery

Libraries that assist with the creation, evaluation or manipulation of graphical images.

• Imgscalr - Simple and efficient hardware-accelerated image-scaling library implemented in pure Java 2D.
• Tess4J - A JNA wrapper for Tesseract OCR API.
• Thumbnailator - Thumbnailator is a high-quality thumbnail generation library for Java.
• TwelveMonkeys - Collection of plugins which extend the number of supported image file formats.
• ZXing - Multi-format 1D/2D barcode image processing library.

JSON

Libraries for serializing and deserializing JSON to and from Java objects.

• Genson - Powerful and easy to use Java to JSON conversion library.
• Gson - Serializes objects to JSON and vice versa. Good performance with on-the-fly usage.
• Jackson-datatype-money - Open-source Jackson module to support JSON serialization and deserialization of JavaMoney data types.
• Jackson - Similar to GSON but has performance gains if you need to instantiate the library more often.
• JSON-io - Convert Java to JSON. Convert JSON to Java. Pretty print JSON. Java JSON serializer.
• jsoniter - Fast and flexible library with iterator and lazy parsing API.
• LoganSquare - JSON parsing and serializing library based on Jackson's streaming API. Outperforms GSON & Jackson's library.

JSON Processing

Libraries for processing data in JSON format.

• fastjson - Very fast processor with no additional dependencies and full data binding.
• Jolt - JSON to JSON transformation tool.
• JsonPath - Extract data from JSON using XPATH like syntax.
• JsonSurfer - Streaming JsonPath processor dedicated to processing big and complicated JSON data.

JVM and JDK

Current implementations of the JVM/JDK.

• Avian - JVM with both a JIT & AOT modes. Includes an iOS port.
• JDK 9 - Early access releases of JDK 9.
• OpenJDK - Open-source implementation for Linux.
• ParparVM - VM with non-blocking concurrent GC for iOS.
• Zulu OpenJDK 9 - Early access OpenJDK 9 builds for Windows, Linux, and Mac OS X.
• Zulu OpenJDK - OpenJDK builds for Windows, Linux, and Mac OS X through Java 8.

Logging

Libraries that log the behavior of an application.

• Apache Log4j 2 - Complete rewrite with a powerful plugin and configuration architecture.
• Graylog - Open-source aggregator suited for extended role and permission management.
• Kibana - Analyzes and visualizes log files. Some features require payment.
• Logback - Robust logging library with interesting configuration options via Groovy.
• Logbook - Extensible, open-source library for HTTP request and response logging.
• Logstash - Tool for managing log files.
• SLF4J - Abstraction layer which is to be used with an implementation.
• tinylog - Lightweight logging framework with static logger class.
• Tracer - Call tracing and log correlation in distributed systems.

Machine Learning

Tools that provide specific statistical algorithms which allow learning from data.

• Apache Flink - Fast and reliable large-scale data processing engine.
• Apache Mahout - Scalable algorithms focused on collaborative filtering, clustering and classification.
• Apache Spark - Data analytics cluster computing framework.
• DatumBox - Provides several algorithms and pre-trained models for natural language processing.
• DeepDive - Creates structured information from unstructured data and integrates it into an existing database.
• Deeplearning4j - Distributed and multi-threaded deep learning library.
• H2O - Analytics engine for statistics over big data.
• JSAT - Algorithms for pre-processing, classification, regression, and clustering with support for multi-threaded execution.
• Oryx 2 - A framework for building real-time large scale machine learning applications, which also includes end-to-end applications for collaborative filtering, classification, regression, and clustering.
• Smile - The Statistical Machine Intelligence and Learning Engine provides a set of machine learning algorithms and a visualization library.
• Weka - Collection of algorithms for data mining tasks ranging from pre-processing to visualization.

Messaging

Tools that help to send messages between clients in order to ensure protocol independency.

• Aeron - Efficient reliable unicast and multicast message transport.
• Apache ActiveMQ - Message broker that implements JMS and converts synchronous to asynchronous communication.
• Apache Camel - Glues together different transport APIs via Enterprise Integration Patterns.
• Apache Kafka - High-throughput distributed messaging system.
• Hermes - Fast and reliable message broker built on top of Kafka.
• JeroMQ - Implementation of ZeroMQ.
• Nakadi - Provides a RESTful API on top of Kafka.
• RocketMQ - A fast, reliable, and scalable distributed messaging platform.
• Smack - Cross-platform XMPP client library.

Miscellaneous

Everything else.

• Codename One - Cross platform solution for writing native mobile (iOS, Android, etc.)
• CQEngine - Ultra-fast SQL-like queries on Java collections.
• Design Patterns - Implementation and explanation of the most common design patterns.
• Failsafe - Simple failure handling with retries and circuit breakers.
• J2ObjC - Java to Objective-C translator for porting Android libraries to iOS.
• jabba - Java Version Manager inspired by nvm.
• javaslang-circuitbreaker - Functional fault tolerance library.
• JavaX - Reinventing and extending Java with a focus on simplicity.
• JBake - Static website generator.
• Jimfs - In-memory file system.
• Joda-Money - Basic currency and money classes and algorithms not provided by the JDK.
• JPad - Snippet runner.
• Lanterna - Easy console text GUI library similar to curses.
• LightAdmin - Pluggable CRUD UI library for rapid application development.
• Membrane Service Proxy - An open source, reverse proxy framework written in Java.
• Modern Java - A Guide to Java 8 - Popular Java 8 guide.
• Modernizer - Detect uses of legacy Java APIs.
• OpenRefine - Tool for working with messy data: cleaning, transforming, extending it with web services and linking it to databases.
• TypeTools - Tools for resolving generic types.

Microservice

Tools for managing microservices, i.e. creation, coordination or discovery.

• Apollo - Libraries for writing composable microservices.
• consul-api - Client for the Consul API a distributed, highly available and datacenter-aware registry/discovery service.
• Eureka - REST based service registry for resilient load balancing and failover.
• Lagom - Framework for creating microservice-based systems.
• SnopEE - Discovery service for Java EE microservices.
• restQL-core - Microservice query language that fetches information from multiple services.

Monitoring

Tools that monitor applications in production.

• AppDynamics - Performance monitor.
• Glowroot - Open source Java APM.
• JavaMelody - Performance monitoring and profiling.
• jmxtrans - Tool to connect to multiple JVMs and to query them for their attributes via JMX. Its query language is based on JSON, which allows non-Java programmers to access the JVMs attributes. Likewise, this tool supports different output writes, including Graphite, Ganglia, StatsD, among others.
• Jolokia - JMX over REST.
• Kamon - Tool for monitoring applications running on the JVM.
• Metrics - Expose metrics via JMX or HTTP and can send them to a database.
• New Relic - Performance monitor.
• nudge4j - Remote developer console from the browser for Java 8 via bytecode injection.
• OverOps - In-Production error monitoring and debugging.
• Pinpoint - Open source APM tool.
• Prometheus - Provides a multi-dimensional data model, DSL, autonomous server nodes and much more.
• SPM - Performance monitor with distributing transaction tracing for JVM apps.
• Stagemonitor - Open source performance monitoring and transaction tracing for JVM apps.

Native

For working with platform-specific native libraries.

• JNA - Work with native libraries without writing JNI. Also provides interfaces to common system libraries.
• 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.
• JavaCPP - Provides efficient and easy access to native C++.

Natural Language Processing

Libraries that specialize on processing text.

• CoreNLP - Stanford's CoreNLP provides a set of fundamental tools for tasks like tagging, named entity recognition, sentiment analysis and many more.
• DKPro - A collection of re-usable NLP tools for linguistic pre-processing, machine learning, lexical resources, etc.
• LingPipe - Toolkit for a variety of tasks ranging from POS tagging to sentiment analysis.

Networking

Libraries for network programming.

• Async Http Client - Asynchronous HTTP and WebSocket client library.
• Comsat - Integrates standard Java web-related APIs with Quasar fibers and actors.
• Finagle - Extensible RPC system used to construct high-concurrency servers. It implements uniform client and server APIs for several protocols, and is protocol agnostic, which simplifies the implementation of new protocols.
• Grizzly - NIO framework. Used as a network layer in Glassfish.
• gRPC - RPC framework based on protobuf and HTTP/2.
• MINA - Abstract event-driven async I/O API for network operations over TCP/IP and UDP/IP via Java NIO.
• Netty - Framework for building high performance network applications.
• Nifty - Implementation of Thrift clients and servers on Netty.
• OkHttp - HTTP+SPDY client.
• Riptide - Client-side response routing for Spring's RestTemplate.
• Undertow - Web server providing both blocking and non-blocking API’s based on NIO. Used as a network layer in WildFly.
• urnlib - Java library for representing, parsing and encoding URNs as in RFC 2141.

ORM

APIs which handle the persistence of objects.

• Apache Cayenne - Provides clean, static API for data access. Also includes GUI Modeler for working with database mappings, DB reverse engineering and generation.
• Ebean - Provides simple and fast data access.
• EclipseLink - Supports a number of persistence standards: JPA, JAXB, JCA and SDO.
• Hibernate - Robust and widely used with an active community.
• MyBatis - Couples objects with stored procedures or SQL statements.

PaaS

Java platform as a service.

• AWS Elastic Beanstalk - AWS-based with support for Tomcat and Jetty.
• AWS Lambda - Serverless computation.
• Google App Engine - PaaS on Google's infrastructure.
• Heroku - Abstract computing environments.
• Jelastic - Supports Tomcat, Jetty, GlassFish, JBoss, TomEE and WildFly.
• OpenShift Enterprise - On premise solution.

PDF

Everything that helps with the creation of PDF files.

• Apache FOP - Creates PDF from XSL-FO.
• Apache PDFBox - Toolbox for creating and manipulating PDF.
• Dynamic Jasper - Abstraction layer to JasperReports.
• DynamicReports - Simplifies JasperReports.
• flyingsaucer - XML/XHTML and CSS 2.1 renderer.
• iText - Creates PDF files programmatically but requires a license for commercial purposes.
• JasperReports - Complex reporting engine.

Performance analysis

Tools for performance analysis, profiling and benchmarking.

• fastThread - Analyze and visualize thread dumps with a free cloud-based upload interface.
• GCeasy - Tool to analyze and visualize GC logs. It provides a free cloud-based upload interface.
• honest-profiler - An low-overhead, bias-free sampling profiler.
• jHiccup - Logs and records platform JVM stalls.
• JITWatch - Analyze the JIT compiler optimisations made by the HotSpot JVM.
• JMH - JMH is a Java harness for building, running, and analysing nano/micro/milli/macro benchmarks written in Java and other languages targeting the JVM.
• JProfiler - Profiler.
• LatencyUtils - Utilities for latency measurement and reporting.
• XRebel - Profiler for web applications.
• YourKit Java Profiler - Profiler.

Platform

Frameworks that are suites of multiple libraries encompassing several categories.

• CUBA Platform - High level framework for development of enterprise applications with rich web interface, based on Spring, EclipseLink and Vaadin.
• Light-Java - A fast, lightweight and productive microservices framework with security built in.
• Orienteer - Open source business application platform for rapid configuration/development of CRM, ERP, LMS and other applications.
• Spring - Provides many packages ranging from dependency injection to aspect-oriented programming to security.

Reactive libraries

Libraries for developing reactive applications.

• Reactive Streams - Provide a standard for asynchronous stream processing with non-blocking backpressure.
• Reactor - Library for building reactive fast-data applications.
• RxJava - Library for composing asynchronous and event-based programs using observable sequences from the JVM.
• vert.x - Polyglot event-driven application framework.

REST Frameworks

Frameworks specifically for creating RESTful services.

• Dropwizard - Opinionated framework for setting up modern web applications with Jetty, Jackson, Jersey and Metrics.
• Feign - HTTP client binder inspired by Retrofit, JAXRS-2.0, and WebSocket.
• Jersey - JAX-RS reference implementation.
• Microserver — A convenient extensible Microservices plugin system for Spring & Spring Boot, with over 30 plugins and growing, that supports both micro-monolith and pure microservices styles.
• RAML - Modeling language to generate REST APIs with contract first.
• Rapidoid - A simple, secure and extremely fast framework consisting of embedded HTTP server, GUI components and dependency injection.
• rest.li - Framework for building robust, scalable RESTful architectures using type-safe bindings and asynchronous, non-blocking IO with an end-to-end developer workflow that promotes clean practices, uniform interface design and consistent data modeling.
• RESTEasy - Fully certified and portable implementation of the JAX-RS specification.
• RestExpress - Thin wrapper on the JBoss Netty HTTP stack to provide scaling and performance.
• Restlet Framework - Pioneering framework with powerful routing and filtering capabilities, unified client and server API.
• Retrofit - Type-safe REST client.
• Spark - Sinatra inspired framework.
• Swagger - Swagger is a specification and complete framework implementation for describing, producing, consuming, and visualizing RESTful web services.

Science

Libraries for scientific computing, analysis and visualization.

• DataMelt - Environment for scientific computation, data analysis and data visualization.
• GraphStream - Library for modeling and analysis of dynamic graphs.
• JGraphT - Graph library that provides mathematical graph-theory objects and algorithms.
• JGraphX - Library for visualisation (mainly Swing) and interaction with node-edge graphs.
• Erdos - Modular, light and easy graph theoretic framework.

Search

Engines which index documents for search and analysis.

• Apache Lucene - High-performance, full-featured cross-platform text search engine library.
• Apache Solr - Enterprise search engine optimized for high volume traffic.
• Elasticsearch - Distributed, multitenant-capable full-text search engine with a RESTful web interface and schema-free JSON documents.

Security

Libraries that handle security, authentication, authorization or session management.

• Apache Shiro - Performs authentication, authorization, cryptography and session management.
• Bouncy Castle - All-purpose cryptographic library. JCA provider, wide range of functions from basic helpers to PGP/SMIME operations.
• Cryptomator - Multiplatform transparent client-side encryption of files in the cloud.
• Hdiv - Runtime application self-protection against OWASP Top 10 security risks such us Insecure Direct Object References, SQL injection, Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF) and much more.
• jjwt - Java JWT: JSON Web Token for Java and Android.
• Keycloak - Integrated SSO and IDM for browser apps and RESTful web services.
• Keyczar - Easy to use, yet safe encryption framework with key versioning.
• Nbvcxz - Advanced password strength estimation.
• OACC - Provides permission-based authorization services.
• pac4j - Security engine.
• PicketLink - Umbrella project for security and identity management.

Serialization

Libraries that handle serialization with high efficiency.

• FlatBuffers - Memory efficient serialization library that can access serialized data without unpacking and parsing it.
• FST - JDK compatible high performance object graph serialization.
• Kryo - Fast and efficient object graph serialization framework.
• MessagePack - Efficient binary serialization format.

Server

Servers which are specifically used to deploy applications.

• Apache Tomcat - Robust all-round server for Servlet and JSP.
• Apache TomEE - Tomcat plus Java EE.
• Jetty - Lightweight, small server, often embedded in projects.
• nanohttpd - Tiny, easily embeddable HTTP server.
• WebSphere Liberty - Lightweight, modular server developed by IBM.
• WildFly - Formerly known as JBoss and developed by Red Hat with extensive Java EE support.

Template Engine

Tools which substitute expressions in a template.

• Handlebars.java - Logic-less and semantic Mustache templates.
• Jtwig - Modular, configurable and fully tested template engine.
• Thymeleaf - Aims to be a substitute for JSP and works for XML files in general.

Testing

Tools that test from model to the view.

• Apache JMeter - Functional testing and performance measurements.
• Arquillian - Integration and functional testing platform for Java EE containers.
• AssertJ - Fluent assertions that improve readability.
• Awaitility - DSL for synchronizing asynchronous operations.
• Citrus - Integration testing framework with focus on client- and serverside messaging.
• ConcurrentUnit - Toolkit for testing multi-threaded and asynchronous applications.
• Cucumber - BDD testing framework.
• Cukes-REST - A collection of Gherkin steps for REST-service testing using Cucumber.
• Gatling - Load testing tool designed for ease of use, maintainability and high performance.
• GreenMail - In-memory email server for integration testing. Supports SMTP, POP3 and IMAP including SSL.
• J8Spec - J8Spec is a library that allows tests written in Java to follow the BDD style introduced by RSpec and Jasmine.
• JSONAssert - Simplifies testing of JSON strings.
• JBehave - Framework for Behavioural Driven Development.
• [JFairy] (https://github.com/Codearte/jfairy) - Fake data generator.
• JGiven - Developer-friendly BDD testing framework compatible with JUnit and TestNG.
• JMockit - Mocks static, final methods and more.
• junit-dataprovider - A TestNG like dataprovider runner for JUnit.
• JUnitParams - Creation of readable and maintainable parametrised tests.
• Lamdba Behave - Descriptive behavioural specification framework.
• Mockito - Creation of test double objects in automated unit tests for the purpose of TDD or BDD.
• MockServer - Allows mocking of systems that are integrated with HTTP/S.
• Moco - Concise web services for stubs and mocks, Duke's Choice Award 2013.
• PIT - Fast mutation-testing framework for evaluating fault-detection abilities of existing JUnit or TestNG test-suites.
• pojo-tester - Automatically performs tests on basic POJO-methods.
• PowerMock - Enables mocking of static methods, constructors, final classes and methods, private methods and removal of static initializers.
• raml-tester - Tests if a request/response matches a given RAML definition.
• REST Assured - Java DSL for easy testing for REST/HTTP services.
• Selenide - Concise API around Selenium to write stable and readable UI tests.
• Selenium - Portable software testing framework for web applications.
• Spock - JUnit-compatible framework featuring an expressive Groovy-derived specification language.
• TestContainers - Provides throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.
• Truth - Google's assertion and proposition framework.
• WireMock - Stubs and mocks web services.

Utility

Libraries which provide general utility functions.

• Apache Commons - Provides different general purpose functions like configuration, validation, collections, file upload or XML processing.
• CRaSH - Provides a shell into a JVM that's running CRaSH. Used by Spring Boot and others.
• Dex - Java/JavaFX tool capable of powerful ETL and data visualization.
• Embulk - Bulk data loader that helps data transfer between various databases, storages, file formats, and cloud services.
• Gephi - Cross-platform for visualizing and manipulating large graph networks.
• Guava - Collections, caching, primitives support, concurrency libraries, common annotations, string processing, I/O, and so forth.
• JADE - Framework and environment for building and to debugging multi-agent systems.
• JavaVerbalExpressions - A library that helps to construct difficult regular expressions.
• 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.
• Underscore-java - Port of Underscore.js functions.
• JGit - A lightweight pure Java library implementing the Git version control system.

Web Crawling

Libraries that analyze the content of websites.

• Apache Nutch - Highly extensible, highly scalable web crawler for production environment.
• Crawler4j - Simple and lightweight web crawler.
• JSoup - Scrapes, parses, manipulates and cleans HTML.

Web Frameworks

Frameworks that handle the communication between the layers of an web application.

• Apache Tapestry - Component-oriented framework for creating dynamic, robust, highly scalable web applications.
• Apache Wicket - Component-based web application framework similar to Tapestry with a stateful GUI.
• Baratine - Toolkit for building distributed and reactive applications for multiple environments, either standalone or embedded.
• Blade - Lightweight, modular framework which aims to be elegant and simple.
• Bootique - Minimally opinionated framework for runnable apps.
• Grails - Groovy framework with the aim to provide a highly productive environment by favoring convention over configuration, no XML and support for mixins.
• Jooby - Scalable, fast and modular micro framework which offers multiple programming models.
• Ninja - Full stack web framework.
• Pippo - Small, highly modularized Sinatra-like framework.
• Play - Uses convention over configuration, hot code reloading and display of errors in the browser.
• PrimeFaces - JSF framework which has a free and a commercial version with support. Provides several frontend components.
• Ratpack - Set of libraries that facilitate fast, efficient, evolvable and well tested HTTP applications.
• Spring Boot - Microframework which simplifies the development of new Spring applications.
• Vaadin - Event-driven framework build on top of GWT. Uses server-side architecture with Ajax on the client-side.

Resources

Communities

Active discussions.

• r/java - Subreddit for the Java community.
• stackoverflow - Question/answer platform.
• vJUG - Virtual Java User Group.

Frontends

Websites that provide a frontend for this list. Please note, there won't be an official website. We don't associate with a particular website and everybody is allowed to create one.

• java.libhunt.com

Influential Books

Books that had a high impact and are still worth reading.

• Core Java Volume I--Fundamentals
• Core Java, Volume II--Advanced Features
• Effective Java (2nd Edition)
• Java 8 in Action
• Java Concurrency in Practice
• Thinking in Java

Podcasts

Something to listen to while programming.

• Java Off Heap
• The Java Council
• The Java Posse - Discontinued as of 02/2015.

Twitter

Active accounts to follow. Descriptions from Twitter.

• Adam Bien - Freelancer: Author, JavaONE Rockstar Speaker, Consultant, Java Champion.
• Aleksey Shipilëv - Performance Geek, Benchmarking Tzar, Concurrency Bug Hunter.
• Antonio Goncalves - Java Champion, JUG Leader, Devoxx France, Java EE 6/7, JCP, Author.
• Arun Gupta - Java Champion, JavaOne Rockstar, JUG Leader, Devoxx4Kids-er, VP of Developer Advocacy at Couchbase.
• Brian Goetz - Java Language Architect at Oracle.
• Bruno Borges - Product Manager/Java Jock at Oracle.
• Ed Burns - Consulting Member of the Technical Staff at Oracle.
• Eugen Paraschiv - Author of the Spring Security Course.
• James Weaver - Java/JavaFX/IoT developer, author and speaker.
• Java EE - Official Java EE Twitter account.
• Java Magazine - Official Java Magazine account.
• Java - Official Java Twitter account.
• Javin Paul - Well-known Java blogger.
• Lukas Eder - Java Champion, speaker, JUG.ch co-leader, Founder and CEO Data Geekery (jOOQ).
• Mario Fusco - RedHatter, JUG coordinator, frequent speaker and author.
• Mark Reinhold - Chief Architect, Java Platform Group, Oracle.
• Markus Eisele - Java EE evangelist, Red Hat.
• Martijn Verburg - London JUG co-leader, speaker, author, Java Champion and much more.
• Martin Thompson - Pasty faced performance gangster.
• OpenJDK - Official OpenJDK account.
• Peter Lawrey - Peter Lawrey, Java performance expert.
• Reza Rahman - Java EE/GlassFish/WebLogic evangelist, author, speaker, open source hacker.
• Simon Maple - Java Champion, virtualJUG founder, LJC leader, RebelLabs author.
• Stephen Colebourne - Java Champion, speaker.
• Trisha Gee - Java Champion and speaker.

Websites

Sites to read.

• Google Java Style
• InfoQ
• Java Algorithms and Clients
• Java, SQL, and jOOQ
• Java.net
• Javalobby
• JavaWorld
• JAXenter
• RebelLabs
• The Takipi Blog
• TheServerSide.com
• Vanilla Java
• Voxxed

Contributing

Contributions are very welcome!

Please have a look at CONTRIBUTING for guidelines.