Eric Lerognon's blog: Business Integration - In the field

Introduction

Java CAPS 6 includes the Glassfish Application server. It is easy to migrate existing web applications from Tomcat to Glassfish. By doing so, we eliminate the installation of Tomcat. We can consolidate integration projects built with Java CAPS 6 and Web applications on the same runtimes. The migration is easy for most of the Java code. In my experience, the only issues are for a few specific configuration items.

Class Loader delegation model

The Servlet specification recommends that the Web class loader look in the local class loader before delegating to its parent. This is what Tomcat does by default whereas Glassfish does the reverse by default. This feature is comonly used with the log4j library and its configuration file log4j.properties. We store this configuration file in the WEB-INF/classes directory so that each web application has its own logging configuration. With the default Glassfish configuration, if there is a configuration file in the main classloader, this file takes precedence other the configuration files inside each web application. You can have a file in the main classloader if one JAR library file which contains a log4j.properties is located in appserver/lib or domains/domain1/lib.

The solution is to configure the web application with the delegate="false" in the class-loader element of the sun-web.xml file. This makes the Web class loader follow the delegation model in the Servlet specification.

Reference information:

ClassLoaders in GlassFish - a FAQ

Class Loader Delegation in Sun Java System Application Server 9.1 Developer's Guide

Default Servlet for serving static content

Web application often contains static web files like HTML, CSS, JS in addition to dynamic content like JSP. To deliver this content from a Web Application it is very easy to use the Apache Tomcat Default Servlet. As a matter of fact this default servlet is integrated in Glassfish but not declared by default.

The solution to use the default serlvet for static content is to declare it in the "web.xml" file, as shown below:

    <servlet>
        <servlet-name>DefaultServlet</servlet-name>
        <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>DefaultServlet</servlet-name>
        <url-pattern>*.html</url-pattern>
    </servlet-mapping>

Additional migration tips

Migration Guide for GlassFish

GlassFish equivalent to WebSphere's "shared libraries"