package www.test.web.filter;

import java.io.IOException;
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;

public class EncodingFilter implements Filter{

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

    @Override
    public
 
 void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        final HttpServletRequest req = (HttpServletRequest) request;
        //使用動態代碼解決全局亂碼問題
        HttpServletRequest enhanceRequset = (HttpServletRequest) Proxy.newProxyInstance(
            
 
//loader ,和目標類相同的類加載器
            request.getClass().getClassLoader(),
            // interfaces  :代表與目標對象實現的所有接口字節碼對象數組
            request.getClass().getInterfaces(),
            
            // h : 具體的操作，InvocationHandler接口
            new InvocationHandler() {
                
                @Override
                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                    //對 getParameter 方法進行增強
                    String name = method.getName();//獲得目標對象的方法名稱
                    if("getParameter".equals(name)){
                        String invoke = (String) method.invoke(req, args);//亂碼
                        //轉碼
                        invoke = new String(invoke.getBytes("iso8859-1"),"UTF-8");
                        return invoke;
                        } 
                    return method.invoke(req, args);
                }
            });
        chain.doFilter(enhanceRequset, response);
    }

    @Override
    public void destroy() {
    }
    
}

動態代理：實際開發中一般用於攔截。判斷不同的角色，決定是否可以調用這個方法。

使用動態代理解決全局亂碼問題