使用Filter 设置编码简化Servlet的开发

1. 核心代码

package com.mscncn.jsd1404;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 EncodingFilter implements Filter {		private static String encoding;	private static final String DEFAULT_CHARSET="UTF-8";	@Override	public void destroy() {		System.out.println("--------destroy---------");	}	@Override	public void doFilter(ServletRequest request, ServletResponse response,			FilterChain chain) throws IOException, ServletException {		System.out.println("--------doFilter---------");		HttpServletRequest httpRequest = (HttpServletRequest) request;  		HttpServletResponse httpResponse=(HttpServletResponse)response;		if("GET".equals(httpRequest.getMethod())){			EncodingHttpServletRequest wrapper = new EncodingHttpServletRequest(httpRequest, encoding);               chain.doFilter(wrapper, response);  		}else{			httpRequest.setCharacterEncoding(encoding);			httpResponse.setContentType("text/html;charset="+encoding);			chain.doFilter(request, response);  		}	}	private static class  EncodingHttpServletRequest extends HttpServletRequestWrapper{		 private HttpServletRequest request;		 public EncodingHttpServletRequest(HttpServletRequest request,String encoding) {		   super(request);		   this.request = request;		 }		 @Override		public String getParameter(String name) {			   String value = request.getParameter(name);			   try {			    value = new String(value.getBytes("iso8859-1"), encoding);			   } catch (UnsupportedEncodingException e) {			    e.printStackTrace();			   }			   return super.getParameter(name);		}	}	@Override	public void init(FilterConfig config) throws ServletException {		 System.out.println("--------init---------");  		 encoding = config.getInitParameter("encoding");		 if(encoding==null||"".equals(encoding))			 encoding=DEFAULT_CHARSET;	}}

 2. web.xml 中得配置

      
    
       	
     
      characterFilter
       	
     
      com.mscncn.jsd1404.EncodingFilter
       	
     
        		
      
       encoding
        		
      
       UTF-8
        	
       
      
    
       	
     
      characterFilter
       	
       	
     
      /*
       
    

3. filter 的执行流程

测试代码如下:

    servlet

public class MyFilterTestServlet extends HttpServlet {	private static final long serialVersionUID = 1L;	@Override	protected void service(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		System.out.println(" 执行servlet 中的 service()方法 \t\t\t\t\t"+" 33333333");	}}

第一个拦截器:

package com.mscncn.jsd1404;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class ServletFilter1 implements Filter {	@Override	public void destroy() {			}	@Override	public void doFilter(ServletRequest request, ServletResponse response,			FilterChain chain) throws IOException, ServletException {		System.out.println("第一个拦截器的chain.doFilter()之前 \t\t\t\t\t"+" 111111111");		chain.doFilter(request, response);		System.out.println("第一个拦截器的chain.doFilter()之后 \t\t\t\t\t"+" 5555555");	}	@Override	public void init(FilterConfig arg0) throws ServletException {	}}

第二个拦截器:

package com.mscncn.jsd1404;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class ServletFilter2 implements Filter {	@Override	public void destroy() {			}	@Override	public void doFilter(ServletRequest request, ServletResponse response,			FilterChain chain) throws IOException, ServletException {		System.out.println("第二个拦截器的chain.doFilter()之前 \t\t\t\t\t"+" 2222222");		chain.doFilter(request, response);		System.out.println("第二个拦截器的chain.doFilter()之后 \t\t\t\t\t"+" 4444444");	}	@Override	public void init(FilterConfig arg0) throws ServletException {	}}

web.xml中的配置:

    
    
       
     
      1D
       
     
          
      
       index.html
          
      
       index.htm
          
      
       index.jsp
          
      
       default.html
          
      
       default.htm
          
      
       default.jsp
        
         
       
     
        	
      
       characterFilter
        	
      
       com.mscncn.jsd1404.EncodingFilter
        	
      
         		
       
        encoding
         		
       
        UTF-8
         	
        
         
     
        	
      
       filter1
        	
      
       com.mscncn.jsd1404.ServletFilter1
        
       
     
        	
      
       filter2
        	
      
       com.mscncn.jsd1404.ServletFilter2
        
         
     
        	
      
       characterFilter
        	
        	
      
       /*
        
       
     
        	
      
       filter1
        	
        	
      
       /test
        
         
     
        	
      
       filter2
        	
        	
      
       /test
        
       
     
        	
      
       test
        	
      
       com.mscncn.jsd1404.MyFilterTestServlet
        
       
     
        	
      
       test
        	
      
       /test
        
     
    

执行结果: