html：

        <form action="/WEB24/EnCoding" method="get">
		<input type="text" name="username">
		<input type="submit" value="提交">
	</form>

 filter：

package web.filter;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class EncodingFilter implements Filter{

	
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		
		
		//被增強的物件
		final HttpServletRequest req = (HttpServletRequest) request;

		HttpServletRequest newProxyInstance = (HttpServletRequest) Proxy.newProxyInstance(req.getClass().getClassLoader(),
								req.getClass().getInterfaces(), 
								new InvocationHandler() {
									
									@Override
									public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
										String mothodName = method.getName();
										if("getParameter".equals(mothodName)) {
											String invoke = (String) method.invoke(req, args);
											System.out.println("亂碼"+invoke);
											invoke = new String(invoke.getBytes("iso8859-1"),"UTF-8");
											return invoke;
										}
										return method.invoke(req, args);
									}
								});
		
		chain.doFilter(newProxyInstance, response);
		
	}

	@Override
	public void destroy() {
		
	}
	
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		
	}

}

 

servlet：

            String parameter = request.getParameter("username");
		System.out.println(parameter);
		response.setContentType("text/html;charset=UTF-8"); 
		response.getWriter().write(parameter);

web.xml

​
  <filter>
    <filter-name>EncodingFilter</filter-name>
    <filter-class>web.filter.EncodingFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>EncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

​