Adobe 38000382 Getting Started Guide - Page 34
JRun servers, Using JRun servers
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− EJB JRun provides a runtime environment for EJB components. The EJB specification defines a software component model whereby you can deploy server-side application logic (enterprise beans) using EJB-compliant application servers. The JRun EJB container provides automation of services, including component lifecycle, naming, transaction management, messaging, resource management, security, distribution, state management, and persistence. • Web services JRun lets you publish and consume web services, which are distributed software components that provide platform- and location-independent computing, using XML and standard Internet protocols such as HTTP. Using JRun, you can reuse existing Java code as a web service or write new code specifically to publish as a web service. You also can create object- and tag-based clients that can invoke methods on remote web services, even when those services reside on non-Java platforms, such as Microsoft .NET. The following sections contain detailed descriptions of these components. JRun servers A JRun server provides the services necessary for a web server to process J2EE applications containing servlets, JSPs, and EJBs. The JRun server runs in its own process outside any web server process. Running the JRun server in a separate process offers the following advantages: • Increased stability of the web server • The ability to start and stop a web server independently of JRun • The ability to modify an application without restarting the web server • The ability for a single JRun server to communicate with multiple web servers A single installation of JRun supports multiple JRun servers. One reason to create multiple JRun servers is to isolate applications within the processes of separate computers. For example, each JRun server has associated with it a single Java Virtual Machine (JVM) that executes all servlets, JSP pages, and EJBs for that server. The JVM, also known as a JRE, is the software implementation of a CPU. It contains everything necessary to run programs written for the Java platform. By deploying applications on multiple JRun servers, and therefore, in their own JVMs, you can prevent one application from adversely affecting another. Additionally, you can define classpaths, data sources, EJBs, and other resources for each application at the server level. Another reason to execute applications on different JRun servers is that each JRun server can implement its own user-authentication mechanism or set of user-authentication rules. Thus, you can take advantage of a particular server's authentication settings. For more information on authentication, see JRun Administrator's Guide. Using JRun servers JRun provides utilities to start, stop, and perform other functions on the JRun servers. This section describes these utilities for the different JRun platforms. 20 Chapter 2 JRun Programming Model