Servlet——使用Filter设置全局的字符编码

使用包装设计模式对request进行增强

Servlet API 中提供了一个request对象的Decorator设计模式的默认实现类++HttpServletRequestWrapper++，以避免用户在对request对象进行增强时需要实现request接口中的所有方法。

package com.kexin.web.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 CharacterEncodingFilter1 implements Filter {
    private FilterConfig config;
    private String defaultCharset = "utf-8";
    @Override
    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain chain)
            throws IOException, ServletException {
        String charset = this.config.getInitParameter("charset");
        if(charset==null){
            charset = defaultCharset;
        }
        HttpServletRequest request = (HttpServletRequest) arg0;
        HttpServletResponse response = (HttpServletResponse) arg1;
        request.setCharacterEncoding(charset);
        response.setCharacterEncoding(charset);
        response.setContentType("text/html;charset="+charset);
        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        this.config = arg0;
    }

}
class MyRequest extends HttpServletRequestWrapper{
    private HttpServletRequest request;
    public MyRequest(HttpServletRequest request) {
        super(request);
        this.request = request;
    }
    @Override
    public String getParameter(String name) {
        String value = this.request.getParameter(name);
        if(!request.getMethod().equalsIgnoreCase("get")){
            return value;
        }
        if(value==null){
            return null;
        }
        try {
            return value = new String(value.getBytes("iso8859-1"),request.getCharacterEncoding());
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }

    }

}