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 SetCharacterEncodingFilter implements Filter {


protected String encoding = null;
protected FilterConfig filterConfig = null;
protected boolean ignore = true;

//destroy方法
public void destroy() {

   this.encoding = null;
   this.filterConfig = null;

}

//选择设置使用的字符编码
public void doFilter(ServletRequest request, ServletResponse response,
    FilterChain chain) throws IOException, ServletException {

   // Conditionally select and set the character encoding to be used
   if (ignore || (request.getCharacterEncoding() == null)) {
    String encoding = selectEncoding(request);
    if (encoding != null)
     request.setCharacterEncoding(encoding);
   }

   // Pass control on to the next filter
   chain.doFilter(request, response);

}

//将这个filter放置在服务器中
public void init(FilterConfig filterConfig) throws ServletException {
   this.filterConfig = filterConfig;
   this.encoding = filterConfig.getInitParameter("encoding");
   String value = filterConfig.getInitParameter("ignore");
   if (value == null)
    this.ignore = true;
   else if (value.equalsIgnoreCase("true"))
    this.ignore = true;
   else if (value.equalsIgnoreCase("yes"))
    this.ignore = true;
   else
    this.ignore = false;

}


//选择适当的字符编码
protected String selectEncoding(ServletRequest request) {
 
   return (this.encoding);

}

}


配置这个Filter，只需在web.xml文件中添加如下代码：

<filter>
   <filter-name>Set Character Encoding</filter-name>
   <filter-class>com.wanglei.SetCharacterEncodingFilter</filter-class>
   <init-param>
    <param-name>encoding</param-name>
    <param-value>UTF-8</param-value>
   </init-param>
</filter>
   <filter-mapping>
   <filter-name>Set Character Encoding</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>