Java Open Application Server. JOnAS is an open source software server, developed within the ObjectWeb consortium. ObjectWeb is an open source initiative which can be compared to Apache or Linux, but in the area of middleware. The aim of ObjectWeb is to develop and promote open source middleware software.

JOnAS Features:
JOnAS is a pure Java, open source, software server. Its high modularity allows to it to be used as
1. a J2EE server, for deploying and running EAR applications (i.e. applications composed of both web and ejb components),
2. an EJB container, for deploying and running EJB components (e.g. for applications without web interfaces or when using JSP/Servlet engines that are not integrated as a JOnAS container),
3. a Web container, for deploying and running JSPs and Servlets (e.g. for applications without EJB components).

System Requirements
JOnAS is available for JDK 1.4 and JDK 5. It has been used on many operating systems (Linux, AIX, Windows, Solaris, HP-UX, etc.), and with different Databases (Oracle, PostgreSQL, MySQL, SQL server, Access, DB2, Versant, Informix, Interbase, etc.).

JOnAS supports the deployment of applications conforming to J2EE 1.4 specification. Its current integration of Tomcat or Jetty as a Web container ensures conformity to Servlet 2.4 and JSP 2.0 specifications. The JOnAS server relies on or implements the following Java APIs: EJB 2.1, JTA 1.0.1, JDBC 3.0, J2EE CA 1.5, JMX 1.2, JNDI 1.2.1, JMS 1.1, JavaMail 1.3, Servlet 2.4, JSP 2.0, JAAS 1.0, JACC 1.0, Web Services 1.1, JAX-RPC 1.1, SAAJ 1.2, JAXR 1.0, J2EE Management 1.0, JAF 1.0, JAXP 1.2 specifications. JOnAS is architectured in terms of services.

JOnAS provides the following important advanced features:
1. Management: JOnAS server management uses JMX and provides a JSP/Struts-based management console.
2. Services: JOnAS's service-based architecture provides for high modularity and configurability of the server.
3. Scalability: JOnAS integrates several optimization mechanisms for increasing server scalability.
4. Clustering: JOnAS clustering solutions, both at the WEB and EJB levels, provide load balancing, high availability, and failover support.
5. Distribution: JOnAS works with several distributed processing environments, due to the integration of the CAROL (Common Architecture for RMI ObjectWeb Layer) ObjectWeb project, which allows simultaneous support of several communication protocols:
* RMI using the Sun proprietary protocol JRMP
* RMI on IIOP
* CMI, the "Cluster aware" distribution protocol of JOnAS
* IRMI, an open source RMI protocol implementation

6. Support of "Web Services:" Due to the integration of AXIS, JOnAS allows J2EE components to access "Web services" (i.e., to be "Web Services" clients), and allows J2EE components to be deployed as "Web Services" endpoints.
7. Support of JDO: By integrating the ObjectWeb implementation of JDO, SPEEDO, and its associated J2EE CA Resource Adapter, JOnAS provides the ability of using JDO within J2EE components.
8. Early support of EJB3: Even before the EJB3 specification (part of Java EE 5, the new J2EE specification) is finalized, JOnAS already provides an EJB3 container.

Three critical J2EE aspects were implemented early on in the JOnAS server:
1. J2EECA: Enterprise Information Systems (EIS) can be easily accessed from JOnAS applications.
2. JMS: JMS implementations can be easily plugged into JOnAS.
3. JTA: The JOnAS platform supports distributed transactions that involve multiple components and transactional resources.

JOnAS offers several services that can be turned on or off according to your needs.
1. ejb: this is the EJB container service.
2. jtm: this is the distributed Transaction Manager.
3. dbm: the DataBase Manager provides database access through JDBC.
4. jms: the Java Messaging Service must be started if you use message-driven beans.
5. security: this is the security service.
6. jmx: this service allows to manage and monitor JOnAS through a Web interface using JAdmin
7. resource: the resource service is an optional service that must be started as soon as EJB components have to access an external Enterprise Information System.

The license of this software is Freeware, you can free download and free use this server utility software.