package com.jspdev.ch8;

import javax.servlet.FilterChain;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import javax.servlet.FilterConfig;

public class EncodingFilter implements Filter
{
    protected FilterConfig filterConfig;
    private String targetEncoding = "gb2312";
    
    /**
     *初始化過濾器,和一般的Servlet一樣，它也可以獲得初始參數。
     */
    public void init(FilterConfig config) throws ServletException {
        this.filterConfig = config;
        this.targetEncoding = config.getInitParameter("encoding");
    }
    
    /**
      *進行過濾處理，這個方法最重要，所有過濾處理的代碼都在此實現。
      */
     public  void doFilter(ServletRequest srequest, ServletResponse  sresponse, FilterChain chain)
        throws IOException, ServletException {
        // System.out.println("使用以下方法對請求進行編碼：encoding="+targetEncoding);
            
        HttpServletRequest request = (HttpServletRequest)srequest;
        request.setCharacterEncoding(targetEncoding);
        // 把處理權發送到下一個
       chain.doFilter(srequest,sresponse);  
    }   

	public void setFilterConfig(final FilterConfig filterConfig)
	{
		this.filterConfig=filterConfig;
	}
    
    //銷毀過濾器
	public void destroy()
	{
		this.filterConfig=null;
	}
}