java web中过滤器的配置

 首先在项目中新建个类 public class FirstFilter implements Filter 要实现Filter接口

代码如下

package jia;


import java.io.IOException;


import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;


public class FirstFilter implements Filter {


FilterConfig config;
private String targetEncoding=null;
public void destroy() {
      this.config=null;
      this.targetEncoding=null;


}


@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
arg0.setCharacterEncoding(targetEncoding);
arg2.doFilter(arg0, arg1);


}


@Override
public void init(FilterConfig arg0) throws ServletException {
this.config=arg0;
this.targetEncoding=config.getInitParameter("encoding");//这里的encoding就是web.xml中的utf-8


}


}

在web.xml中配置

<filter>
        <filter-name>FirstFilter</filter-name>
        <filter-class>jia.FirstFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>FirstFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher>
        <dispatcher>FORWARD</dispatcher>
    </filter-mapping>
</web-app>