Webapplicationcontext: org. springframework. Web. Context. contextloaderlistener

You can also use Org. springframework. web. context. contextloaderlistener, for example, in the web. use the <listener> label to define in XML:

...
<Listener>
<Listener-class>
Org. springframework. Web. Context. contextloaderlistener
</Listener-class>
</Listener>
...

Contextloaderlistener reads applicationcontext. xml by default. You can specify your own definition file by specifying the "contextconfiglocation" parameter in <context-param>. For example:

...
<Context-param>
<Param-Name> contextconfiglocation </param-Name>
<Param-value>/WEB-INF/beans-config.xml,
→/WEB-INF/demo-service.xml </param-value>
</Context-param>
...

Then you can use org. springframework. Web. Context. Support. webapplicationcontextutils in the Custom servlet to obtain org. springframework. Web. Context. webapplicationcontext from servletcontext, for example:

Webapplicationcontext CTX =
Webapplicationcontextutils.
Getrequiredwebapplicationcontext (
This. getservletcontext ());

Webapplicationcontext implements the applicationcontext interface. It is the applicationcontext implementation class designed by spring for servlet web applications. After obtaining the webapplicationcontext, you can use it to obtain the bean instance defined in the bean definition file. For example:
Date = (date) CTX. getbean ("datebean ");

On containers that do not support listener settings (for example, Servlet 2.2 is earlier), you can use org. springframework. Web. Context. contextloaderservlet to replace the preceding contextloaderlistener settings. For example:

...
<Servlet>
<Servlet-Name> contextloader </servlet-Name>
<Servlet-class>
Org. springframework. Web. Context. contextloaderservlet
</Servlet-class>
<Load-on-startup> 1 </load-on-startup>
</Servlet>
...

Based on the above description, write a simple example to demonstrate the complete configuration method. Assume that you have written a simple servlet program to provide a simple reporting function, as shown below:

• Timeservlet. Java

package onlyfun.caterpillar;

import java.io.*; 
import javax.servlet.*; 
import javax.servlet.http.*; 
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.
                                support.WebApplicationContextUtils;

public class TimeServlet extends HttpServlet { 
    public void doGet(HttpServletRequest req, 
                    HttpServletResponse res) 
                  throws ServletException, IOException { 
        WebApplicationContext ctx = 
                WebApplicationContextUtils.
                    getRequiredWebApplicationContext(
                        this.getServletContext());

        PrintWriter out = res.getWriter(); 
        out.println(ctx.getBean("dateBean")); 
    } 
}

This servlet uses webapplicationcontext to try to obtain datebean. You can define the position of the contextloaderlistener and bean definition file in Web. XML, for example:

• Web. xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
    → http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
  version="2.4">
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>    

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/beans-config.xml</param-value>
    </context-param>     

    <listener>
        <listener-class>
         org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>

    <servlet>
        <servlet-name>time</servlet-name>
        <servlet-class>
            onlyfun.caterpillar.TimeServlet
        </servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>time</servlet-name>
        <url-pattern>/time.do</url-pattern>
    </servlet-mapping>      
</web-app>

In the "contextconfiglocation" attribute of <context-param>, the location and name of the bean definition file are set. The content of the bean definition file is as follows:

• Beans-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC 
 "-//SPRING/DTD BEAN/EN" 
 "http://www.springframework.org/dtd/spring-beans.dtd"> 

<beans>   
    <bean id="dateBean" class="java.util.Date" singleton="false"/>
</beans>

You can connect to timeservlet. The result shows the connection time.