package filter;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 CharacterEncodingFilter implements Filter {private String    characterEncoding;private boolean enabled;@Overridepublic void init(FilterConfig arg0) throws ServletException {　　//web程序启动时初始化Filter，通过FilterConfig对象从web.xml文件获取初始化参数值characterEncoding=arg0.getInitParameter("characterEncoding");enabled="true".equalsIgnoreCase(arg0.getInitParameter("enabled".trim()));}@Overridepublic void doFilter(ServletRequest arg0, ServletResponse arg1,FilterChain arg2) throws IOException, ServletException {//当初始化的参数为启用状态时，对request对象和response对象进行编码设置if(enabled||characterEncoding!=null){arg0.setCharacterEncoding(characterEncoding);arg1.setCharacterEncoding(characterEncoding);}arg2.doFilter(arg0, arg1);}@Overridepublic void destroy() {　　　　//web程序关闭时，销毁Filter时将资源对象置为空characterEncoding=null;}
}

<filter><filter-name>characterEncodingFilter</filter-name><filter-class>filter.CharacterEncodingFilter</filter-class><init-param><param-name>characterEncoding</param-name><param-value>UTF-8</param-value></init-param><init-param><param-name>enabled</param-name><param-value>true</param-value></init-param>
</filter>
<filter-mapping><filter-name>characterEncodingFilter</filter-name><url-pattern>/*</url-pattern>//所有页面访问前都要进行过滤
</filter-mapping>