[Java Web] Filter

First, brief

A filter is a middle-tier component of the request and response of the server and the client, and the primary user filters the browser's requests and forwards them to the next resource.

The client's request passes through Filterchain before being handed over to the servlet, and the response returned by the server is Filterchain. The filterchain contains multiple filter.

Second, use

Filterconfig is the configuration object of the filter, and the main function is to get the configuration information in the filter.

//Myfilter.java Packagefilter;Importjavax.servlet.*;Importjava.io.IOException;ImportJava.io.PrintWriter; Public classMyfilterImplementsFilter {Privatefilterconfig config; PrivateString addr; @Override Public voidDoFilter (ServletRequest servletrequest, Servletresponse servletresponse, Filterchain filterchain)throwsIOException, servletexception {String remote=servletrequest.getremoteaddr (); Servletresponse.setcharacterencoding ("GB2312"); PrintWriter out=Servletresponse.getwriter (); if(remote.equals (addr)) {Out.println ("Request rejected:" +remote); } Else{out.println ("Request accepted:" +remote);        Filterchain.dofilter (ServletRequest, servletresponse); }} @Override Public voidInit (filterconfig filterconfig) {config=Filterconfig; Addr= Config.getinitparameter ("addr"); }}//Web. XML<?xml version= "1.0" encoding= "UTF-8"?><web-app> <filter> <filter-name>myfilter</filte R-name> <filter-class>filter. myfilter</filter-class> <init-param> <param-name>addr</param-name> <param-value>127.0.0. 1</param-value> </init-param> </filter> <filter-mapping> <filter-name>my Filter</filter-name> <url-pattern>/*</url-pattern> <!--filter all requests --</filter-mapping></web-app>

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Converts character encodings using filters.

//Myfilter.java Packagefilter;Importjavax.servlet.*;Importjava.io.IOException; Public classMyfilterImplementsFilter {Private Booleanenable; PrivateString encoding; @Override Public voidDoFilter (ServletRequest servletrequest, Servletresponse servletresponse, Filterchain filterchain)throwsIOException, servletexception {if(enable) {servletrequest.setcharacterencoding (encoding);        servletresponse.setcharacterencoding (encoding);    } filterchain.dofilter (ServletRequest, servletresponse); } @Override Public voidInit (Filterconfig filterconfig) {Enable= Boolean.valueof (Filterconfig.getinitparameter ("Enable")); Encoding= Filterconfig.getinitparameter ("Encoding"); }}//Web. XML<?xml version= "1.0" encoding= "UTF-8"?><web-app> <filter> <filter-name>myfilter</filte R-name> <filter-class>filter. myfilter</filter-class> <init-param> <param-name>enable</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>encoding</param- name> <param-value>GB2312</param-value> </init-param> </filter> <fil Ter-mapping> <filter-name>MyFilter</filter-name> <url-pattern>/*</url-pattern> <!--filter all requests --</filter-mapping></web-app>

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[Java Web] Filter