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Spring Context Loader Servlet

                         

In this section we will learn about Spring's Context loader servlet and then see how to add the required configuration in the web.xml file to load the Spring Context.

Spring ContextLoaderServlet (org.springframework.web.context.ContextLoaderServlet)

Context Loader Servlet start up Spring's root WebApplicationContext when web application is loaded.

This class has been deprecated for containers implementing Servlet API 2.4 or higher, in favor of ContextLoaderListener. According to Servlet 2.4, listeners must be initialized before load-on-startup servlets. Many Servlet 2.3 containers already enforce this behavior. If you use such a container, this servlet can be replaced with ContextLoaderListener. Else or if working with a Servlet 2.2 container, stick with this servlet.

Servlet 2.3 containers known to work with bootstrap listeners are:

  • Apache Tomcat 4.x+
  • Jetty 4.x+
  • Resin 2.1.8+
  • Orion 2.0.2+
  • BEA WebLogic 8.1 SP3
For working with any of them, ContextLoaderListener is recommended.

Servlet 2.3 containers known not to work with bootstrap listeners are:

  • BEA WebLogic up to 8.1 SP2
  • IBM WebSphere 5.x
  • Oracle OC4J 9.0.3

Modification in the web.xml file

Following code needs to be added to the web.xml file to register the ContextLoaderServlet.

<servlet>
	  <servlet-name>context</servlet-name>
	  <servlet-class>
	org.springframework.web.context.ContextLoaderServlet
	  </servlet-class>
	<load-on-startup>1</load-on-startup>
</servlet>

Following code specifies the the path of applicationContext-hibernate.xml file, where the contextConfigLocation parameter has been defined..
<context-param>
	<param-name>contextConfigLocation</param-name>
	<param-value>/WEB-INF/applicationContext-hibernate.x
ml</param-value>
</context-param>

Here is the full content of our web.xml file:
<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app
  PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
  "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">

<web-app>
  <display-name>Struts Blank Application</display-name>
  

	<!-- Spring context Configuration Begins-->
    <context-param>
		<param-name>log4jConfigLocation</param-name>
		<param-value>/WEB-INF/log4j.properties
</param-value>
	</context-param>

	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-valu
e>/WEB-INF/applicationContext-hibernate.xml</param-value>
	</context-param>

<servlet>
 <servlet-name>context</servlet-name>
   <servlet-class>
     org.springframework.web.context.ContextLoaderServlet
	</servlet-class>
	<load-on-startup>1</load-on-startup>
	</servlet>
    <!-- Spring context loading ends-->

  <!-- Standard Action Servlet Configuration (with debugging) -->
  <servlet>
    <servlet-name>action</servlet-name>
    <servlet-class>org.apache.struts.action.ActionServlet
</servlet-class>
    <init-param>
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>debug</param-name>
      <param-value>2</param-value>
    </init-param>
    <init-param>
      <param-name>detail</param-name>
      <param-value>2</param-value>
    </init-param>
    <load-on-startup>2</load-on-startup>
  </servlet>


  <!-- Standard Action Servlet Mapping -->
  <servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>


  <!-- The Usual Welcome File List -->
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
	
  </welcome-file-list>


  <!-- Struts Tag Library Descriptors -->
  <taglib>
    <taglib-uri>/tags/struts-bean</taglib-uri>
    <taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/tags/struts-html</taglib-uri>
    <taglib-location>/WEB-INF/struts-html.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/tags/struts-logic</taglib-uri>
    <taglib-location>/WEB-INF/struts-logic.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/tags/struts-nested</taglib-uri>
    <taglib-location>/WEB-INF/struts-nested.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/tags/struts-tiles</taglib-uri>
    <taglib-location>/WEB-INF/struts-tiles.tld</taglib-location>
  </taglib>

 

</web-app>


If you don't add the above code the Spring context won't initialized and you will get the following error:

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.IllegalStateException: No WebApplicationContext found: no 
        ContextLoaderListener registered?
	org.springframework.web.context.support.WebApplicationContext
        Utils.getRequiredWebApplicationContext(WebApplicationContextUtils.java:84)
	roseindia.tutorial.services.ServiceFinder.getContext(Unknown Source)
	org.apache.jsp.test_jsp._jspService(org.apache.jsp.test_jsp:51)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.12 logs.

                         

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