package filter;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

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;

import javax.servlet.http.HttpServletResponse;

public class CharacterFilter implements Filter {

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest) req;

HttpServletResponse response = (HttpServletResponse) res;

//POST的乱码解决方案

request.setCharacterEncoding("utf-8");

//返回数据的乱码解决方案

response.setCharacterEncoding("utf-8");

response.setContentType("text/html;charset=utf-8");

//将增强后的对象放行

MyRequest myRequest = new MyRequest(request);

chain.doFilter(myRequest, response); //这样一来,后面所有的操作都是基于这个增强后的对象进行的

}

/**创建一个request对象的包装类:

1.编写一个类,实现与被增强对象相同的接口

2.在类中定义一个变量,记住被增强对象

3.在类中定义一个构造方法,接收被增强对象

4.覆写想要增强的方法

5.对于不想增强的方法,直接调用被增强对象(目标对象)的方法

包装设计模式"五步曲"

*/

class MyRequest extends HttpServletRequestWrapper{

private HttpServletRequest request;

public MyRequest(HttpServletRequest request) {

super(request);

this.request = request;

}

public String getParameter(String name) {

//如果请求方式是POST,则不用增强,直接调用目标对象的方法

if(this.request.getMethod().equalsIgnoreCase("POST")){

return this.request.getParameter(name);

}

/*程序运行到此,请求方式必然为GET

先获取值,再进行手动转换*/

String value = this.request.getParameter(name);

try {

value = new String(value.getBytes("iso8859-1"),"utf-8");

} catch (UnsupportedEncodingException e) {

throw new RuntimeException(e);

}

return value; //返回

}

}

public void destroy() {

// TODO Auto-generated method stub

}

public void init(FilterConfig fConfig) throws ServletException {

// TODO Auto-generated method stub

}

}