案例13-利用装饰者模式解决全局乱码

package www.test.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;

public class EncodingFilter implements Filter{
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        
        //request.setCharacterEncoding("UTF-8");
        
        //在传递request之前对request的getParameter方法进行增强
        /*
         * 装饰者模式(包装)
         * 
         * 1、增强类与被增强的类要实现统一接口
         * 2、在增强类中传入被增强的类
         * 3、需要增强的方法重写 不需要增强的方法调用被增强对象的
         * 
         */
        
        //被增强的对象
        HttpServletRequest req = (HttpServletRequest) request;
        //增强对象
        EnhanceRequest enhanceRequest = new EnhanceRequest(req);
        
        
        chain.doFilter(enhanceRequest, response);
        
    }

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

}

class EnhanceRequest extends HttpServletRequestWrapper{
    
    private HttpServletRequest request;

    public EnhanceRequest(HttpServletRequest request) {
        super(request);
        this.request = request;
    }
    
    //对getParaameter增强
    @Override
    public String getParameter(String name) {
        String parameter = request.getParameter(name);//乱码
        try {
            parameter = new String(parameter.getBytes("iso8859-1"),"UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return parameter;
    }
    
}