Basic use of filters and listeners in Servlets

One: Filter filters

1. Simple to use

Public Classsimplefilter extends HttpServlet implements Filter {

public void init (Filterconfig config) throws servletexception {

String Initparm=config.getinitparameter ("ref");

System.out.println ("Initialize filter:" +initparm);

}

public void DoFilter (ServletRequest arg0,servletresponse arg1,

Filterchain chain) Throwsioexception, servletexception {

SYSTEM.OUT.PRINTLN ("* * * * * Dofilter () method before * * *)");

Chain.dofilter (arg0, arg1);

SYSTEM.OUT.PRINTLN ("* * * * * * Dofilter () method)";

}

@Override

public void Destroy () {

System.out.println ("Destroy Filter");

}

}

Config filter under Web. xml

<filter>

<filter-name>SimpleFilter</filter-name>

<filter-class>com.cloud.day1.SimpleFilter</filter-class>

<init-param>

<param-name>ref</param-name>

<param-value>Spring</param-value>

</init-param>

</filter>

<filter-mapping>

<filter-name>SimpleFilter</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

2. Filter code

http://blog.csdn.net/dzy21/article/details/47042891

This article uses filters to solve coding problems in detail.

Two: Listener

public class Demo2implements Servletcontextlistener {

public void contextinitialized (servletcontexteventevent) {

SYSTEM.OUT.PRINTLN ("Initialize:" +event.getservletcontext (). Getcontextpath ());

}

Public voidcontextdestroyed (Servletcontextevent event) {

System.out.println ("Destroy:" +event.getservletcontext (). Getcontextpath ());

}

}

Config listener under Web. xml

<!--configuration Listener--

<listener>

<listener-class>

Com.cloud.day1.Demo2

</listener-class>

</listener>

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Basic use of filters and listeners in Servlets