Awesome Java

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

Bean Mapping

Frameworks that ease bean mapping.

Dozer391 173 - Mapper that copies data from one object to another using annotations and API or XML configuration.
JMapper - Uses byte code manipulation for lightning-fast mapping. Supports annotations and API or XML configuration.
MapStruct868 199 - Code generator that simplifies mappings between different bean types, based on a convention-over-configuration approach.
ModelMapper540 128 - Intelligent object mapping library that automatically maps objects to each other.
Orika429 126 - JavaBean-mapping framework that recursively copies (among other capabilities) data from one object to another.
Selma100 26 - Annotation processor-based bean mapper.

Build

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

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.
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.

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.
cglib1k 441 - Bytecode generation library.
Javassist - Tries to simplify bytecode editing.

Caching

Libraries that provide caching facilities.

Caffeine4k 366 - High-performance, near-optimal caching library.
Ehcache - Distributed general-purpose cache.
Infinispan - Highly concurrent key/value datastore used for caching.

Cluster Management

Frameworks that can dynamically manage applications inside of a cluster.

Apache Aurora - Mesos framework for long-running services and cron jobs.
Apache Mesos - Abstracts CPU, memory, storage, and other compute resources away from machines.
Singularity - 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.

Checkstyle3k 2k - Static analysis of coding conventions and standards.
Error Prone4k 496 - Catches common programming mistakes as compile-time errors.
Infer8k 1k - Modern static analysis tool for verifying the correctness of code.
jQAssistant - Static code analysis with Neo4J-based query language.
NullAway2k 98 - Eliminates NullPointerExceptions with low build-time overhead.
PMD1k 497 - Source code analysis for finding bad coding practices.
SonarJava305 290 - Static analyzer for SonarQube & SonarLint.
Sourcetrail - Visual source code navigator.
Spoon439 106 - Library for analyzing and transforming Java source code.
Spotbugs575 94 - Static analysis of bytecode to find potential bugs.

Code Coverage

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

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

Code Generators

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

ADT4J98 7 - JSR-269 code generator for algebraic data types.
Auto7k 838 - Generates factory, service, and value classes.
FreeBuilder699 122 - Automatically generates the Builder pattern.
Immutables - Annotation processors to generate simple, safe and consistent value objects.
JavaPoet4k 512 - API to generate source files.
JHipster11k 3k - Yeoman source code generator for Spring Boot and AngularJS.
Joda-Beans - Small framework that adds queryable properties to Java, enhancing JavaBeans.
Lombok - Code generator that aims to reduce verbosity.

Command-line Argument Parsers

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

Airline260 33 - Annotation-based framework for parsing Git-like command-line arguments.
args4j - Small library to parse command-line arguments.
JCommander - Command-line argument-parsing framework with custom types and validation via implementing interfaces.
JOpt Simple - Simple parser that uses the POSIX getopt() and GNU getopt_long() syntaxes. Uses a fluent API instead of annotations.
picocli - ANSI colors and styles in usage help. Can be included as source to avoid dependency. Annotation-based, POSIX/GNU/any syntax, subcommands, strong typing for both options and positional args.

Compiler-compiler

Frameworks that help to create parsers, interpreters or compilers.

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 - A lexical analyzer generator.

Configuration

Libraries that provide external configuration.

centraldogma52 17 - Highly-available version-controlled service configuration repository based on Git, ZooKeeper and HTTP/2.
cfg4j271 64 - Modern configuration library for distributed apps written in Java.
config3k 509 - Configuration library for JVM languages.
dotenv - A twelve-factor configuration library for Java.
ini4j - Provides an API for handling Windows' INI files.
KAConf - Annotation-based configuration system for Java and Kotlin.
owner569 139 - Reduces boilerplate of properties.

Constraint Satisfaction Problem Solver

Libraries that help with implementing optimization and satisfiability problems.

Choco - Off-the-shelf constraint satisfaction problem solver that uses constraint programming techniques.
JaCoP103 48 - Includes an interface for the FlatZinc language, enabling it to execute MiniZinc models.
OptaPlanner - Business planning and resource scheduling optimization solver.

CSV

Frameworks and libraries that simplify reading/writing CSV data.

jackson-dataformat-csv196 87 - 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-parsers457 133 - One of the fastest and most feature-complete parsers. Also comes with parsers for TSV and fixed-width records.

Database

Everything that simplifies interactions with the database.

Apache Phoenix - High-performance relational database layer over HBase for low-latency applications.
Chronicle Map1k 260 - Efficient, in-memory (opt. persisted to disk), off-heap key-value store.
eXist209 154 - A NoSQL document database and application platform.
FlexyPool462 67 - 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.
HikariCP6k 1k - High-performance JDBC connection pool.
JDBI - Convenient abstraction of JDBC.
Jedis6k 3k - Small client for interaction with Redis, with methods for commands.
Jest934 507 - Client for the Elasticsearch REST API.
jetcd81 26 - Client library for etcd.
Jinq472 76 - Typesafe database queries via symbolic execution of Java 8 Lambdas (on top of JPA or jOOQ).
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.
MariaDB4j195 59 - Launcher for MariaDB that requires no installation or external dependencies.
OrientDB - Embeddable distributed database written on top of Hazelcast.
Presto3k 1k - Distributed SQL query engine for big data.
Querydsl - Typesafe unified queries.
Realm10k 2k - Mobile database to run directly inside phones, tablets or wearables.
Redisson2k 561 - Allows for distributed and scalable data structures on top of a Redis server.
requery2k 211 - A 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.
Speedment1k 170 - Database access library that utilizes Java 8's 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 with advanced performance monitoring capabilities.
Xodus - Highly concurrent transactional schema-less and ACID-compliant embedded database.

Data Structures

Efficient and specific data structures.

Apache Avro - Data interchange format with dynamic typing, untagged data, and 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 Google's paper on Dremel.
Apache Thrift - Data interchange format that originated at Facebook.
Big Queue98 26 - A big, fast and persistent queue based on memory-mapped files.
Persistent Collection - Persistent and immutable analogue of the Java Collections Framework.
Protobuf26k 8k - Google's data interchange format.
SBE1k 264 - Simple Binary Encoding, one of the fastest message formats around.
Tape2k 298 - A lightning-fast, transactional, file-based FIFO.
Wire2k 354 - Clean, lightweight protocol buffers.

Date and Time

Libraries related to handling date and time.

Almanac Converter - Simple conversion between different calendar systems.
iCal4j266 102 - Parse and build iCalendar RFC 5545 data models.
ThreeTen-Extra131 34 - Additional date-time classes that complement those in JDK 8.
Time4J169 35 - 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.
Feather243 33 - Ultra-lightweight, JSR-330-compliant dependency injection library.
Governator578 154 - Extensions and utilities that enhance Google Guice.
Guice6k 1k - Lightweight and opinionated framework that completes Dagger.
HK2 - Lightweight and dynamic dependency injection framework.

Development

Augmentation of the development process at a fundamental level.

AspectJ - Seamless aspect-oriented programming extension.
DCEVM - JVM modification that allows unlimited redefinition of loaded classes at runtime.
Faux Pas13 1 - 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.
HotswapAgent1k 347 - Unlimited runtime class and resource redefinition.
JavaParser2k 420 - Parse, modify and generate Java code.
JavaSymbolSolver175 50 - A symbol solver for Java.
JRebel - Instantly reloads code and configuration changes without redeploys.
NoException - Allows checked exceptions in functional interfaces and converts exceptions to Optional return.

Distributed Applications

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

Apache Geode - In-memory data management system that provides reliable asynchronous event notifications and guaranteed message delivery.
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.
Dropwizard Circuit Breaker15 1 - Circuit breaker design pattern for Dropwizard.
Failsafe2k 117 - Simple failure handling with retries and circuit breakers.
Hazelcast - Highly scalable in-memory datagrid with a free open-source version.
Hystrix11k 2k - Provides latency and fault tolerance.
JGroups - Toolkit for reliable messaging and cluster creation.
Orbit - Virtual actors; adds another level of abstraction to traditional actors.
Quasar - Lightweight threads and actors for the JVM.
resilience4j326 35 - Functional fault tolerance library.
ScaleCube108 33 - Embeddable Cluster-Membership library based on SWIM and gossip protocol.
Zuul3k 785 - A gateway service that provides dynamic routing, monitoring, resiliency, security, and more.

Distributed Transactions

Distributed transactions provide a mechanism for ensuring consistency of data updates in the presence of concurrent access and partial failures.

Atomikos - Provides transactions for REST, SOA and microservices with support for JTA and XA.
Bitronix39 20 - A simple but complete implementation of the JTA 1.1 API.
Narayana - Provides support for traditional ACID and compensation transactions, also complies with JTA, JTS and other standards.

Distribution

Tools that handle the distribution of applications in native formats.

Bintray - Version control for binaries that handle publishing. Compatible with Maven or Gradle, with a free plan for open-source software as well as several business plans.
Boxfuse - Deployment of JVM applications 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.
packr2k 93 - Packs JARs, assets and the JVM for native distribution on Windows, Linux and Mac OS X.
really-executable-jars-maven-plugin87 18 - 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 - Create and manipulate Microsoft Open XML files.

Formal Verification

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

CATG53 21 - 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 - Detects likely program invariants and generates JML specs based on those invariants.
Java Path Finder (JPF) - JVM formal verification tool containing a model checker and more. Created by NASA.
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.
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.
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-react390 54 - Monad and stream utilities, comprehensions, pattern matching, functional extensions for all JDK collections, future streams, trampolines and much more.
derive4j273 33 - Java 8 annotation processor and framework for deriving algebraic data types constructors, pattern-matching and morphisms.
Fugue - Functional extensions to Guava.
Functional Java - Implements numerous basic and advanced programming abstractions that assist composition-oriented development.
jOOλ1k 104 - 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.
protonpack297 36 - Collection of stream utilities.
StreamEx660 80 - Enhances Java 8 Streams.
Vavr - Functional component library that provides persistent data types and functional control structures.

Game Development

Frameworks that support the development of games.

FXGL - JavaFX Game Development Framework.
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.
Geo197 57 - 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.
GraphHopper2k 752 - Road-routing engine. Used as a Java library or standalone web service.
H2GIS - A spatial extension of the H2 database.
Jgeohash - Library for using the GeoHash algorithm.
Mapsforge574 312 - Map rendering based on OpenStreetMap data.
Spatial4j197 57 - General-purpose spatial/geospatial 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, a graphical widget toolkit.

High Performance

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

Agrona866 143 - Data structures and utility methods that are common in high-performance applications.
Disruptor - Inter-thread messaging library.
Eclipse Collections433 129 - Collections framework inspired by Smalltalk.
fastutil - Fast and compact type-specific collections.
HPPC - Primitive collections.
JCTools1k 205 - Concurrency tools currently missing from the JDK.
Koloboke500 64 - Hash sets and hash maps.

HTTP Clients

Libraries that assist with creating HTTP requests and/or binding responses.

Async Http Client5k 1k - Asynchronous HTTP and WebSocket client library.
Feign2k 473 - HTTP client binder inspired by Retrofit, JAXRS-2.0, and WebSocket.
OkHttp - HTTP+SPDY client.
restQL-core11 1 - Microservice query language that fetches information from multiple services.
Retrofit - Typesafe REST client.
Ribbon1k 381 - Client-side IPC library that is battle-tested in cloud.
Riptide40 12 - Client-side response routing for Spring's RestTemplate.

Hypermedia Types

Libraries that handle serialization to hypermedia types.

JSON-LD216 119 - JSON-LD implementation.
Siren4J11 12 - Library for the Siren specification.

IDE

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

Eclipse - Established open-source project with support for lots of plugins and languages.
IntelliJ IDEA - Supports many 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.
Visual Studio Code - Provides Java support for lightweight projects with a simple, modern workflow by using extensions from the internal marketplace.

Imagery

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

Imgscalr381 82 - Simple, efficient and hardware-accelerated image-scaling library implemented in pure Java 2D.
Tess4J313 140 - A JNA wrapper for Tesseract OCR API.
Thumbnailator762 223 - High-quality thumbnail generation library.
TwelveMonkeys538 147 - Collection of plugins that extend the number of supported image file formats.
ZXing15k 8k - 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.
Gson10k 3k - Serializes objects to JSON and vice versa. Good performance with on-the-fly usage.
HikariJSON89 15 - High-performance JSON parser, 2x faster than Jackson.
jackson-modules-java896 24 - Set of Jackson modules for Java 8 datatypes and features.
Jackson-datatype-money59 19 - Open-source Jackson module to support JSON serialization and deserialization of JavaMoney data types.
Jackson725 311 - Similar to GSON, but offers performance gains if you need to instantiate the library more often.
JSON-io211 86 - 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.
LoganSquare3k 354 - JSON parsing and serializing library based on Jackson's streaming API. Outperforms GSON & Jackson's library.
Moshi4k 322 - Modern JSON library, less opinionated and uses built-in types like List and Map.
Yasson62 14 - Binding layer between classes and JSON documents similar to JAXB.

JSON Processing

Libraries for processing data in JSON format.

fastjson16k 5k - Very fast processor with no additional dependencies and full data binding.
Jolt435 98 - JSON to JSON transformation tool.
JsonPath2k 415 - Extract data from JSON using XPATH-like syntax.
JsonSurfer83 21 - Streaming JsonPath processor dedicated to processing big and complicated JSON data.

JVM and JDK

Current implementations of the JVM/JDK.

Avian981 153 - JVM with both JIT and AOT modes. Includes an iOS port.
OpenJ91k 181 - High performance, enterprise calibre, flexibly licensed, openly governed cross platform Java Virtual Machine extending and augmenting the runtime technology components from the Eclipse OMR and OpenJDK project.
OpenJDK - Open-source implementation for Linux.
ParparVM671 223 - 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.
Logbook132 28 - Extensible, open-source library for HTTP request and response logging.
Logstash - Tool for managing log files.
SLF4J - Abstraction layer/simple logging facade.
tinylog - Lightweight logging framework with static logger class.
Tracer48 17 - Call tracing and log correlation in distributed systems.

Machine Learning

Tools that provide specific statistical algorithms for learning from data.

Apache Flink - Fast, 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.
JSAT327 146 - Algorithms for pre-processing, classification, regression, and clustering with support for multi-threaded execution.
Oryx 21k 360 - Framework for building real-time, large-scale machine learning applications. 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 send messages between clients to ensure protocol independency.

Aeron3k 372 - 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.
Apache Pulsar - Distributed pub/sub-messaging system.
Hermes - Fast and reliable message broker built on top of Kafka.
JeroMQ1k 411 - Implementation of ZeroMQ.
Nakadi253 90 - Provides a RESTful API on top of Kafka.
RocketMQ4k 2k - A fast, reliable, and scalable distributed messaging platform.
Smack1k 751 - Cross-platform XMPP client library.

Miscellaneous

Everything else.

Codename One - Cross-platform solution for writing native mobile apps.
CQEngine586 94 - Ultra-fast, SQL-like queries on Java collections.
Design Patterns24k 8k - Implementation and explanation of the most common design patterns.
Failsafe2k 117 - Simple failure handling with retries and circuit breakers.
FF4J - Feature Flags for Java.
J2ObjC5k 804 - Java-to-Objective-C translator for porting Android libraries to iOS.
JavaX - Reinventing and extending Java with a focus on simplicity.
JBake - Static website generator.
JBot202 88 - Framework for building chatbots.
Jimfs1k 205 - In-memory file system.
Joda-Money - Basic currency and money classes and algorithms not provided by the JDK.
JPad - Snippet runner.
Lanterna588 115 - Easy console text-GUI library, similar to curses.
LightAdmin - Pluggable CRUD UI library for rapid application development.
Maven Wrapper434 66 - Analogue of Gradle Wrapper for Maven, allows building projects without installing maven.
Membrane Service Proxy173 80 - An open-source, reverse-proxy framework written in Java.
MinimalFTP4 1 - Lightweight, small and customizable FTP server.
Modern Java - A Guide to Java 8170 110 - Popular Java 8 guide.
Modernizer158 32 - Detect uses of legacy Java APIs.
Multi-OS Engine - An open-source, cross-platform engine to develop native mobile (iOS, Android, etc.) apps.
OpenRefine - Tool for working with messy data: cleaning, transforming, extending it with web services and linking it to databases.
Polyglot for Maven312 51 - Extensions for Maven 3.3.1+ that allows writing the POM model in dialects other than XML.
Smooks174 219 - Extensible framework for building applications that process data which means bindings, transformations, message processing and enrichment.
Togglz - Implementation of the Feature Toggles pattern.
TypeTools285 45 - Tools for resolving generic types.
XMLBeam40 5 - Processes XML by using annotations or XPath within code.
OctoLinker1k 123 - Browser extension which allows to navigate through code on GitHub more efficiently.

Microservice

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

Apollo - Libraries for writing composable microservices.
consul-api14 6 - Client for the Consul API: a distributed, highly available and datacenter-aware registry/discovery service.
Eureka4k 1k - REST-based service registry for resilient load balancing and failover.
Lagom - Framework for creating microservice-based systems.

Monitoring

Tools that monitor applications in production.

AppDynamics - Performance monitor.
Automon396 89 - Combines the power of AOP with monitoring and/or logging tools.
BugSnag - Exception and error monitoring with an integration of several third party tools for a better workflow and a free hobbyist tier.
Failsafe Actuator22 12 - Out of the box monitoring of Failsafe Circuit Breaker in Spring-Boot environment.
Glowroot - Open-source Java APM.
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.
Instrumental - Real-time Java application performance monitoring. A commercial service with free development accounts.
JavaMelody1k 421 - Performance monitoring and profiling.
jmxtrans1k 461 - 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.
Jolokia - JMX over REST.
Kamon - Tool for monitoring applications running on the JVM.
Metrics - Expose metrics via JMX or HTTP and send them to a database.
New Relic - Performance monitor.
nudge4j82 7 - Remote developer console from the browser for Java 8 via bytecode injection.
OverOps - In-production error monitoring and debugging.
Pinpoint5k 2k - 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.
Stagemonitor1k 227 - Open-source performance monitoring and transaction tracing for JVM apps.
Sysmon146 28 - Lightweight platform monitoring tool for Java VMs.

Native

For working with platform-specific native libraries.

JavaCPP2k 314 - Provides efficient and easy access to native C++.
JNA2k 483 - Work with native libraries without writing JNI. Also provides interfaces to common system libraries.
JNR445 70 - 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.

Natural Language Processing

Libraries that specialize in processing text.

CogCompNLP61 12 - Provides common annotators for plain text input.
CoreNLP - Provides a set of fundamental tools for tasks like tagging, named entity recognition, and sentiment analysis.
DKPro - Collection of reusable NLP tools for linguistic pre-processing, machine learning, lexical resources, etc.
LingPipe - Toolkit for tasks ranging from POS tagging to sentiment analysis.

Networking

Libraries for building network servers.

Comsat432 59 - Integrates standard Java web-related APIs with Quasar fibers and actors.
Dubbo16k 10k - High-performance RPC framework.
Finagle7k 1k - Extensible RPC system for constructing high-concurrency servers. It implements uniform client and server APIs for several protocols, and is protocol-agnostic to simplify implementation of new protocols.
Grizzly - NIO framework. Used as a network layer in Glassfish.
gRPC4k 1k - RPC framework based on protobuf and HTTP/2.
KryoNet386 108 - Provides a clean and simple API for efficient TCP and UDP client/server network communication using NIO and Kryo.
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.
Nifty728 286 - Implementation of Thrift clients and servers on Netty.
sshj1k 315 - Programatically use SSH, SCP or SFTP.
Undertow - Web server providing both blocking and non-blocking APIs based on NIO. Used as a network layer in WildFly.
urnlib5 2 - Represent, parse and encode URNs, as in RFC 2141.

ORM

APIs that handle the persistence of objects.

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.
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.
SimpleFlatMapper169 34 - Simple database and CSV mapper.

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

Tools to help with PDF file creation.

Apache FOP - Creates PDFs from XSL-FO.
Apache PDFBox - Toolbox for creating and manipulating PDFs.
Dynamic Jasper - Abstraction layer to JasperReports.
DynamicReports - Simplifies JasperReports.
flyingsaucer948 389 - XML/XHTML and CSS 2.1 renderer.
iText - Creates PDF files programmatically.
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-profiler148 17 - A low-overhead, bias-free sampling profiler.
jHiccup361 62 - Logs and records platform JVM stalls.
JITWatch1k 206 - Analyze the JIT compiler optimisations made by the HotSpot JVM.
JMH - a Java harness for building, running, and analysing nano/micro/milli/macro benchmarks written in Java and other languages targeting the JVM.
JProfiler - Database profiling for JDBC, JPA and NoSQL, with JEE support.
LatencyUtils279 31 - Utilities for latency measurement and reporting.
XRebel - Real-time profiling for web applications, with an in-browser widget.
YourKit Java Profiler - Profiler for any application running on the JVM.

Platform

Frameworks that are suites of multiple libraries encompassing several categories.

Apache Commons

Pool - Generic object pooling component.
BCEL - Byte Code Engineering Library - analyze, create, and manipulate Java class files.
Codec - General encoding/decoding algorithms (for example phonetic, base64, URL).
Compress - Defines an API for working with tar, zip and bzip2 files.
IO - Collection of I/O utilities.
Configuration - Reading of configuration/preferences files in various formats.
VFS - Virtual File System component for treating files, FTP, SMB, ZIP and such like as a single logical file system.
Jelly - XML based scripting and processing engine.
CSV - Component for reading and writing comma separated value files.
JCS - Java Caching System.
Email - Library for sending e-mail from Java.
DbUtils - JDBC helper library.
FileUpload - File upload capability for your servlets and web applications.
Lang - Provides extra functionality for classes in java.lang.
Jexl - Expression language which extends the Expression Language of the JSTL.
CLI - Command Line arguments parser.
Validator - Framework to define validators and validation rules in an xml file.
Net - Collection of network utilities and protocol implementations.
RNG - Commons Rng provides implementations of pseudo-random numbers generators.
RDF - Common implementation of RDF 1.1 that could be implemented by systems on the JVM.
Weaver - Provides an easy way to enhance (weave) compiled bytecode.
BeanUtils - Easy-to-use wrappers around the Java reflection and introspection APIs.
Collections - Extends or augments the Java Collections Framework.
DBCP - Database connection pooling services.
Math - Lightweight, self-contained mathematics and statistics components.
Exec - API for dealing with external process execution and environment management in Java.
Logging Wrapper around a variety of logging API implementations.
OGNL - An Object-Graph Navigation Language.
JCI - Java Compiler Interface.
Daemon - Alternative invocation mechanism for unix-daemon-like java code.
Functor - A functor is a function that can be manipulated as an object, or an object representing a single, generic function.
Digester - XML-to-Java-object mapping utility.
BSF - Bean Scripting Framework - interface to scripting languages, including JSR-223.
Imaging - A pure-Java image library.
SCXML - An implementation of the State Chart XML specification aimed at creating and maintaining a Java SCXML engine.
JXPath - Utilities for manipulating Java Beans using the XPath syntax.
Chain - Chain of Responsibility pattern implementation.
Proxy - Library for creating dynamic proxies.
BeanUtils2 - Redesign of Commons BeanUtils.
ClassScan - Find Class interfaces, methods, fields, and annotations without loading.
CLI2 Redesign of Commons CLI.
Convert - Commons-Convert aims to provide a single library dedicated to the task of converting an object of one type to another.
Finder - Java library inspired by the UNIX find command.
Flatfile - Java library for working with flat data structures.
Graph - A general purpose Graph APIs and algorithms.
I18n - Adds the feature of localized message bundles that consist of one or many localized texts that belong together.
Id - Id is a component used to generate identifiers.
Javaflow - Continuation implementation to capture the state of the application.
JNet - JNet allows to use dynamically register url stream handlers through the java.net API.
Monitoring - Monitoring aims to provide a simple but extensible monitoring solution for Java applications.
Nabla - Nabla provides automatic differentiation classes that can generate derivative of any function implemented in the Java language.
OpenPGP - Interface to signing and verifying data using OpenPGP.
Performance - A small framework for microbenchmark clients, with implementations for Commons DBCP and Pool.
Pipeline - Provides a set of pipeline utilities designed around work queues that run in parallel to sequentially process data objects.

Other

CUBA Platform - High-level framework for developing enterprise applications with a rich web interface, based on Spring, EclipseLink and Vaadin.
Light-Java299 65 - A fast, lightweight and productive microservices framework with built-in security67 31 .
Orienteer29 18 - Open-source business application platform for rapid configuration/development of CRM, ERP, LMS and other applications.
Spring - Provides many packages for dependency injection, aspect-oriented programming, security, etc.

Reactive libraries

Libraries for developing reactive applications.

Akka - Toolkit and runtime for building concurrent, distributed, fault-tolerant and event-driven applications.
Reactive Streams2k 187 - Provides a standard for asynchronous stream processing with non-blocking backpressure.
Reactor - Library for building reactive fast-data applications.
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.
Jersey - JAX-RS reference implementation.
Microserver846 216 — A 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.
Rapidoid - A simple, secure and extremely fast framework consisting of an embedded HTTP server, GUI components and dependency injection.
rest.li2k 340 - 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.
RESTEasy - Fully certified and portable implementation of the JAX-RS specification.
RestExpress796 277 - Thin wrapper on the JBoss Netty HTTP stack that provides scaling and performance.
Restlet Framework583 282 - Pioneering framework with powerful routing and filtering capabilities, and a unified client and server API.
Spark - Sinatra inspired framework.
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.

Science

Libraries for scientific computing, analysis and visualization.

DataMelt - Environment for scientific computation, data analysis and data visualization.
Erdos55 2 - Modular, light and easy graph framework for theoretic algorithms.
GraphStream - Library for modeling and analyzing dynamic graphs.
JGraphT990 439 - Graph library that provides mathematical graph-theory objects and algorithms.
JGraphX450 311 - Library for visualizing (mainly Swing) and interacting with node-edge graphs.
Mines Java Toolkit8 5 - Library for geophysical scientific computation, visualization and digital signal analysis.
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.
Tablesaw566 157 - Includes a data-frame, an embedded column store, and hundreds of methods to transform, summarize, or filter data.

Search

Engines that 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 and JCA provider offering a wide range of functions, from basic helpers to PGP/SMIME operations.
Cryptomator - Multiplatform, transparent, client-side encryption of files in the cloud.
Hdiv130 44 - 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.
jjwt2k 403 - JSON web token for Java and Android.
Keycloak - Integrated SSO and IDM for browser apps and RESTful web services.
Keyczar946 147 - Easy-to-use, safe encryption framework with key versioning.
Keywhiz2k 186 - System for distributing and managing secrets.
Nbvcxz82 14 - Advanced password strength estimation.
OACC - Provides permission-based authorization services.
pac4j1k 396 - Security engine.
PicketLink - Umbrella project for security and identity management.
Vault - Secures, stores, and tightly controls access to tokens, passwords, certificates, API keys, and other secrets. It handles leasing, key revocation, key rolling, and auditing. Through a unified API, users can access an encrypted Key/Value store and network encryption-as-a-service, or generate AWS IAM/STS credentials, SQL/NoSQL databases, X.509 certificates, SSH credentials, and more.

Serialization

Libraries that handle serialization with high efficiency.

FlatBuffers9k 1k - Memory-efficient serialization library that can access serialized data without unpacking and parsing it.
FST926 191 - JDK-compatible, high-performance object graph serialization.
Kryo3k 556 - Fast and efficient object graph serialization framework.
MessagePack875 237 - Efficient binary serialization format.
PHP Serializer - Serializing objects in the PHP serialization format.

Server

Servers specifically used to deploy applications.

Apache Tomcat - Robust, all-round server for Servlet and JSP.
Apache TomEE - Tomcat plus Java EE.
Jetty - Provides a Web server and javax.servlet container, plus support for HTTP/2, WebSocket, OSGi, JMX, JNDI, JAAS and many other integrations.
nanohttpd3k 1k - 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 that substitute expressions in a template.

Handlebars.java - Logicless and semantic Mustache templates.
Jade4J600 131 - Implementation of Pug (formerly known as Jade).
Jtwig - Modular, configurable and fully tested template engine.
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.
Thymeleaf - Aims to be a substitute for JSP and works for XML files.

Testing

Tools that test from model to the view.

Asynchronous

Tools that simplify testing asynchronous services.

Awaitility349 45 - DSL for synchronizing asynchronous operations.
ConcurrentUnit187 29 - Toolkit for testing multi-threaded and asynchronous applications.
GreenMail - In-memory email server for integration testing. Supports SMTP, POP3 and IMAP including SSL.
Hoverfly Java33 15 - Native bindings for Hoverfly, a proxy which allows you to simulate HTTP services.
REST Assured1k 343 - DSL for easy testing of REST/HTTP services.

BDD

Testing for the software development process that emerged from TDD and was heavily influenced by DDD and OOAD.

Cucumber2k 2k - Provides a way to describe features in a plain language which customers can understand.
Cukes-REST39 34 - A collection of Gherkin steps for REST-service testing using Cucumber.
J8Spec37 2 - Follows a Jasmine-like syntax.
JBehave - Extensively configurable framework that describes stories.
JGiven - Provides a fluent API which allows for simpler composition.
Lamdba Behave200 39 - Aims to provide a fluent API to write tests in long and descriptive sentences that read like plain English.

Fixtures

Everything related to the creation and handling of random data.

Beanmother29 9 - Sets up beans from YAML fixtures.
Fixture Factory207 70 - Generates fake objects from a template.
JFairy328 83 - Fake data generator.
Randomized Testing37 10 - JUnit test runner and plugins for running JUnit tests with pseudo-randomness.

Frameworks

Provide environments to run tests for a specific use case.

ArchUnit223 16 - Test library for specifying and asserting architecture rules.
Apache JMeter - Functional testing and performance measurements.
Arquillian - Integration and functional testing platform for Java EE containers.
Citrus - Integration testing framework that focuses on both client- and server-side messaging.
Gatling - Load testing tool designed for ease of use, maintainability and high performance.
JUnit - Common testing framework.
Pact JVM510 270 - Consumer-driven contract testing.
PIT - Fast mutation-testing framework for evaluating fault-detection abilities of existing JUnit or TestNG test suites.

Matchers

Libraries that provide custom matchers.

AssertJ - Fluent assertions that improve readability.
JSONAssert - Simplifies testing JSON strings.
Truth1k 189 - Google's assertion and proposition framework.

Miscellaneous

Other stuff related to testing.

Mutability Detector138 58 - Reports whether instances of a given class are immutable.
raml-tester72 17 - Tests if a request/response matches a given RAML definition.
TestContainers941 179 - Provides throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.
pojo-tester - Automatically performs tests on basic POJO methods.

Mocking

Tools which mock collaborators to help testing single, isolated units.

JMockit - Integration testing, API mocking and faking, and code coverage.
Mockito7k 1k - Mocking framework that lets you write tests with a clean and simple API.
MockServer - Allows mocking of systems integrated with HTTPS.
Moco2k 542 - Concise web services for stubs and mocks.
PowerMock1k 292 - Mocks static methods, constructors, final classes and methods, private methods, and removal of static initializers.
WireMock - Stubs and mocks web services.

Parameterization

Simplifies the writing of parameterized tests.

Burst429 21 - A unit testing library for varying test data.
junit-dataprovider132 27 - A TestNG-like data provider/runner for JUnit.
JUnitParams - Creates readable and maintainable parametrised tests.

Utility

Libraries which provide general utility functions.

cactoos - Collection of object-oriented primitives.
CRaSH - Provides a shell into a JVM that's running CRaSH. Used by Spring Boot and others.
Dex774 212 - 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.
fswatch - Micro library to watch for directory file system changes, simplifying java.nio.file.WatchService
Gephi2k 1k - Cross-platform for visualizing and manipulating large graph networks.
Guava24k 6k - Collections, caching, primitives support, concurrency libraries, common annotations, string processing, I/O, and more.
JADE - Framework and environment for building and debugging multi-agent systems.
JavaVerbalExpressions2k 193 - Library that helps with constructing difficult regular expressions.
JGit - A lightweight, pure Java library implementing the Git version control system.
minio-java80 78 - 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-java164 37 - Port of Underscore.js functions.

Version Managers

Utilities that help create the development shell environment and switch between different Java versions.

jabba289 26 - Java Version Manager inspired by nvm. Supports Mac OS X, Linux and Windows.
jenv1k 146 - Java Version Manager inspired by rbenv. Can configure globally or per project. Tested on Debian and Mac OS X.
SDKMan1k 190 - Java Version Manager inspired by RVM and rbenv. Supports UNIX-based platforms and Windows.

Web Crawling

Libraries that analyze the content of websites.

Apache Nutch - Highly extensible, highly scalable web crawler for production environments.
Crawler4j2k 1k - Simple and lightweight web crawler.
jsoup - Scrapes, parses, manipulates and cleans HTML.
StormCrawler - SDK for building low-latency and scalable web crawlers.

Web Frameworks

Frameworks that handle the communication between the layers of a 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.
Blade3k 808 - Lightweight, modular framework that aims to be elegant and simple.
Bootique - Minimally opinionated framework for runnable apps.
Firefly - Asynchronous framework for rapid development of high-performance web application.
Grails - Groovy framework that provides a highly productive environment by favoring convention over configuration, no XML and support for mixins.
Jooby - Scalable, fast and modular micro-framework that offers multiple programming models.
Ninja - Full-stack web framework.
Pippo - Small, highly modularized, Sinatra-like framework.
Play - Built on Akka, it provides predictable and minimal resource consumption (CPU, memory, threads) for highly-scalable applications in Java and Scala.
PrimeFaces - JSF framework with both free and commercial/support versions and frontend components.
Ratpack - Set of libraries that facilitate fast, efficient, evolvable and well-tested HTTP applications.
Takes380 168 - Opinionated web framework which is built around the concepts of True Object-Oriented Programming and immutability.
Vaadin - Event-driven framework built on top of GWT. Uses server-side architecture with Ajax on the client side.

Resources

Awesome Lists

Awesome lists related to the Java & JVM ecosystem.

Communities

Active discussions.

r/java - Subreddit for the Java community.
stackoverflow - Question/answer platform.
VirtualJUG - 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 made a big impact and are still worth reading.

Podcasts and Screencasts

Something to look at or listen to while programming.

Java Off Heap
Marco Behler's Screencasts - Screencasts about modern Java development.
The Java Council
The Java Posse - Discontinued as of 02/2015.

Twitter

Active accounts to follow. Descriptions from Twitter.

Adam Bien - Freelance author, JavaOne Rockstar speaker, consultant, Java Champion.
Aleksey Shipilëv - Performance geek, benchmarking czar, 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.
Chris Richardson - Software architect, consultant, and serial entrepreneur, Java Champion, JavaOne Rock Star, POJOs in Action author.
Ed Burns - Consulting Member of the Technical Staff at Oracle.
Eugen Paraschiv - Author of the Spring Security Course.
Heinz Kabutz - Java Champion, speaker, author of The Java Specialists' Newsletter, concurrency performance expert.
Holly Cummins - Technical Lead of IBM London's Bluemix Garage, Java Champion, developer, author, JavaOne rockstar.
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.
Josh Long - Spring Advocate at Pivotal, author of O'Reilly's Cloud Native Java and Building Microservices with Spring Boot, JavaOne Rock Star.
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 Heckler - Pivotal Principal Technologist and Developer Advocate, conference speaker, published author, and Java Champion, focusing on Internet of Things and the cloud.
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.
Monica Beckwith - Performance consultant, JavaOne Rock Star.
OpenJDK - Official OpenJDK account.
Peter Lawrey - Peter Lawrey, Java performance expert.
Randy Shoup - Stitch Fix VP Engineering, speaker, JavaOne Rock Star.
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.
Venkat Subramaniam - Author, University of Houston professor, MicroSoft MVP award recipient, JavaOne Rock Star, Java Champion.

Websites

Sites to read.

Contributing

Contributions are very welcome!

Please have a look at the CONTRIBUTING guidelines.