Java bytecode manipulation framework
AspectWerkz - Dynamic AOP for Java
Axis - an implementation of the SOAP (Simple Object Access Protocol) submission to W3C
Batik SVG Toolkit - Toolkit using images in the Scalable Vector Graphics (SVG) format
Byte Code Engineering Library - Analyze, create and manipulate Java class files
BeanUtils - Utilities for working with JavaBeans
Catalina - Servlet and JSP based web server
Professional Object Relational Mapping
CGLIB - Dynamic byte code generatorhttp://andyluo.blogjava.net
Chain - Implementation of the GoF "Chain of Responsibility" pattern
Checkstyle - Development tool to help writing Java code that adheres to a coding standard
Command Line Library - Simple API for working with the command line arguments and options
Commons Codec - Encoders and decoders like Base64, Hex, phonetic encodings and URLs
Collections - Filling the holes left in Sun's Collections API
Commons Configuration - Generic API enabling configuration from a variety of sources
DBCP - Connection pooling implementations
DbUtils - Set of classes designed to make working with JDBC easier
Struts Digester - Configure an XML/Java mapping with actions when patterns are recognized
Discovery - Discovering, or finding, implementations for pluggable interfaces
DNS in Java - Supporting common record types, queries, zone transfers and dynamic updates
JavaDoc Doclet - Custom output from the types methods and fields in a source tree.
DOM4J - XML, XPath and XSLT library
DTDParse DTD Library - You can use this library to parse a DTD
EL - The JSP 2.0 Expression Language Interpreter from Apache
FastUtil - Type-specific maps sets and lists with a small memory footprint and fast access
HTTP File Upload Library - Add robust, fast file upload capability to your web applications
Giant Java Tree - Java library consisting entirely of open source components
GNU Regular Expressions - Implementation of a traditional (non-POSIX) NFA regex engine
Groovy - Scripting Language
an oo app server implements JavaEE 5
Hibernate - Relational Persistence For Idiomatic Java
HiveMind - A services and configuration microkernel
HSQLDB - The Java SQL relational database
HTML Parser - Java library used to parse HTML
HTTP Client - Fills holes left by the java.net package, including most recent HTTP standards
Informa - News aggregation library --- LGPL协议
Commons-IO - Utility classes, stream implementations, file filters and endian classes for IO
iText - Generates PDF on the fly
Java 2 Platform, Enterprise Edition
Java2 Standard Edition v5
Java Advanced Imaging - Network-enabled, scalable, platform-independent image processing
Jalopy Source Formatter - Formats Java source code according to widely configurable rules
JasperReports - Free Java reporting library
Java3D - Object-oriented interfaces that support a simple, high-level programming mode
Java Communications - API for technologies such as voice mail, fax and smartcards
JavaGroups - Reliable multicast communication enable processes to send messages to each other
Jaxen XPath Processor - Object model walker; evaluate XPath expressions in dom4j and JDOM
JaxMe 2 - Open source implementation of JAXB
JClassLib - Library for reading, modifing and writing Java class files and bytecode
JCommon - Collection of useful classes used by JFreeChart, JFreeReport and other projects
JCronTab - Scheduler written in Java, provide a fully functional schedules for Java projects
JDIC - JDesktop Integration Components
JDNC - JDesktop Network Components
Java Data Objects - Direct storage of Java domain model instances into a database
JDOM XML Library - For accessing, manipulating and outputting XML data from Java code.
JetSpeed - Java Portal Server
Java Expression Language - is an embedable expression language engine
JFreeChart - Free library for generating charts, including pie, bar, line and areas charts
JGroups - Multicast communication toolkit
JMeter - Load testing applcation
Java Media Framework - Library for audio, video and other time-based media
JMock - Testing library
JavaServer Faces - Web Framework
JSword - Bible software in Java, compatible with the Sword project for C/C++
JTidy - HTML syntax checker
JUnit - Regression testing framework used by the developer who implements unit tests in Java
JXPath Library - Simple interpreter of an expression language called XPath
Lang - Utilities including Enums, String manipulation, reflection, serialization and more
Log4J - Fast logging API that lets you configure logging at runtime
Commons Logging - Simple wrapper API around multiple logging APIs
Lucene - high-performance, full-featured text search engine written entirely in Java
Math - Library of lightweight, self-contained mathematics and statistics components
Network Library - Support for Finger, Whois, TFTP, Telnet, FTP, NNTP, etc developed by ORO
OJB - O/R tool that allows transparent persistence
Open source JMS server
ORO - Text processing library
OSCache - A high performance J2EE caching framework
Pure Java AWT - Toolkit for drawing graphics without any native graphics resources
PMD - Scans Java source code for potential problems
POI - Java OLE 2 Manipulator
Commons Pooling - provides an generic, configurable Object-pooling API
Primitives - Collection of types and utilities optimized for working with Java primitives
Java connection pool
Quartz - J2EE open source job scheduler
Jakarta Regular Expressions - Java RegEx library under BSD style license
Mozilla JavaScript - open-source implementation of JavaScript written entirely in Java
Seraph - Atlassian Security Framework
A web-page layout and decoration framework
Slide - Content repository, can serve as a basis for CMS
Apache Soap - implementation of the SOAP submission to W3C
Server Side alternative to J2EE APIs
Jakarta Struts - open source framework for building web applications
Tapestry - Web Framework
Turbine - Servlet based framework allowing developers to quickly build secure web applications
UDDI4J - Library that provides an API to interact with a UDDI registry
Validtator - Validate data from user input
Velocity - Support for clean, quick MVC web development and support for the Struts framework
Village - API that sits on top of the JDBC to make it easier to interact with a JDBC
Next generation of WebWork
Xalan - XSLT processor for transforming XML documents into HTML, text, or XML
XDoclet - Code generation engine
Xerces2 - The next generation of high performance, XML parsers in the Apache Xerces family
XMLPull - Defines a simple pull parsing API that does pull XML parsing from J2ME to J2EE
XML-RPC - Implementation of XML-RPC, using XML over HTTP to implement remote procedure calls
Xerces Native Interface - Framework for streaming a document and constructing generic parsers
XML Object Model - Tree-based API for processing XML that strives for correctness and simplicity.
XML serialization