拦截器与过滤器的区别以及如何自定义一个过滤器和拦截器

拦截器与过滤器的区别 ：

     1. 拦截器是基于java的反射机制的，而过滤器是基于函数回调。
     2. 拦截器不依赖与servlet容器，过滤器依赖与servlet容器。
     3. 拦截器只能对action请求起作用，而过滤器则可以对几乎所有的请求起作用。
     4. 拦截器可以访问action上下文、值栈里的对象，而过滤器不能访问。

     5. 在action的生命周期中，拦截器可以多次被调用，而过滤器只能在容器初始化时被调用一次.

自定义一个拦截器(SpringMVC):

Spring MVC也可以使用拦截器对请求进行拦截处理，用户可以自定义拦截器来实现特定的功能，自定义的拦截器必须实现HandlerInterceptor接口。

代码如下:

      
    import java.io.UnsupportedEncodingException;  
    import java.net.URLDecoder;  
    import java.util.Iterator;  
    import java.util.Map;  
      
    import javax.servlet.http.HttpServletRequest;  
      
    import org.apache.commons.logging.Log;  
    import org.apache.commons.logging.LogFactory;  
    import org.apache.struts2.ServletActionContext;  
      
    import com.opensymphony.xwork2.ActionInvocation;  
    import com.opensymphony.xwork2.interceptor.AbstractInterceptor;  
       
    public class UrlDecodeFilterInterceptor extends AbstractInterceptor {  
        private static final long serialVersionUID = -2335290125344040914L;  
        private static final Log LOG = LogFactory.getLog(UrlDecodeFilterInterceptor.class);  
      
        public String intercept(ActionInvocation invocation) throws Exception {  
            Map parameters = invocation.getInvocationContext().getParameters();  
            HttpServletRequest request = ServletActionContext. getRequest();   
              
            if("get".equalsIgnoreCase(request.getMethod())){  
                for (Iterator i = parameters.keySet().iterator(); i.hasNext();) {  
                    String param = (String) i.next();  
                    String[] values = (String[])parameters.get(param);  
                    if(values != null && values.length > 0){  
                        for (int j = 0; j < values.length; j++) {  
                            if(values[j] != null && !"".equals(values[j])){  
                                try {  
                                    values[j] = new String(values[j].getBytes("iso8859-1"),"UTF-8");  
                                    parameters.put(param, values[j]);  
                                } catch (UnsupportedEncodingException e1) {  
                                    e1.printStackTrace();  
                                }   
                            }  
                        }  
                    }  
                }  
            }  
              
            if("application/x-www-form-urlencoded;charset=UTF-8".equals(request.getContentType())){  
                for (Iterator i = parameters.keySet().iterator(); i.hasNext();) {  
                    String param = (String) i.next();  
                    String[] values = (String[])parameters.get(param);  
                    if(values != null && values.length > 0){  
                        for (int j = 0; j < values.length; j++) {  
                            if(values[j] != null && !"".equals(values[j])){  
                                try {  
                                    values[j] = URLDecoder.decode(values[j], "UTF-8");  
                                    parameters.put(param, values[j]);  
                                } catch (UnsupportedEncodingException e1) {  
                                    e1.printStackTrace();  
                                }   
                            }  
                        }  
                    }  
                }  
            }         
      
            return invocation.invoke();  
        }  
    } 
配置文件如
  
              
              
              
              
                  
                  
              
              
        

当然,处理编码集可以通过springmvc自带的过滤器进行拦截,只需要在web.xml中配置即

    encodingFilter
    org.springframework.web.filter.CharacterEncodingFilter
    
      encoding
      UTF-8
    
  
  
    encodingFilter
    /*
  

自定义一个过滤器:
定义一个类去实现Filter.
代码实现

public class JspExportFilter implements Filter {
	@Override
	public void destroy() {
		
	}
	
	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
		FilterChain chain) throws IOException, ServletException {
		//判断导出格式
		String type= request.getParameter("t");
		
		//文件名称（解码）
		String exportName = URLDecoder.decode(request.getParameter("n"),"UTF-8");
		
		//编码
		exportName = URLEncoder.encode(exportName, "UTF-8");
		
		if(exportName == null || exportName.isEmpty()){
			exportName = "export";
		}
	
		if(type==null){
			//null
			chain.doFilter(request, response);
			return;
		}
		//使用我们自定义的响应包装器来包装原始的ServletResponse
		ResponseWrapper wrapper = new ResponseWrapper((HttpServletResponse)response);
		//这句话非常重要，注意看到第二个参数是我们的包装器而不是response
		chain.doFilter(request, wrapper);
		String result = wrapper.getResult();
		HttpServletResponse httpResp = (HttpServletResponse) response;
		httpResp.reset();
		response.setCharacterEncoding("UTF-8");
		httpResp.setContentType("application/download");
	
		ServletOutputStream sos = response.getOutputStream();
		try{
			if("xls".equals(type)){
				//xls
				String place="";
				result = result.replace("", place);
				httpResp.addHeader("Content-Disposition", "attachment;filename="+exportName+".xls");
				sos.write(result.getBytes("UTF-8"));
			}else if("doc".equals(type)){
				//doc
				String place="";
				result = result.replace("", place);
				httpResp.addHeader("Content-Disposition", "attachment;filename="+exportName+".doc");
				sos.write(result.getBytes("UTF-8"));
			}else if("pdf".equals(type)){
				//pdf
				httpResp.addHeader("Content-Disposition", "attachment;filename="+exportName+".pdf");
				try {
					this.htmlCodeComeString(result, response.getOutputStream());
				} catch (Exception e) {
					BeanLog.getLogger().fatal("pdf export", e);
					throw new IOException("pdf export", e);
				}
			}
		}finally{
			sos.close();
			response.flushBuffer();
		}
	}
	
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		
	}
	
	private void htmlCodeComeString(String htmlCode, OutputStream outstream) throws Exception {
		Document doc = new Document(PageSize.A4.rotate());
		try {
			PdfWriter writer =PdfWriter.getInstance(doc, outstream);
			ByteArrayInputStream bis = new ByteArrayInputStream(htmlCode.getBytes("UTF-8"));
			// 解决中文问题：需要在导出jsp的样式中设置font-family: SimSun。例如：
			/*
			body{
				font-size:12.0px; font-family: SimSun;
			}
			*/
			//jsp必须是xhtml，而且头必须引入
			//
			doc.open();
			XMLWorkerHelper.getInstance().parseXHtml(writer,
					doc, bis, Charset.forName("UTF-8"));
			doc.close();
			bis.close();
		}catch(Exception e) {
			BeanLog.getLogger().fatal("pdf export", e);
			throw e;
		}
	}

            在web.xml中配置

    jspExport
    com.jbns.easymaster.web.sysmgr.filter.JspExportFilter
  
  
    jspExport
    /export/*