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基于Filter Dispatcher的Model2

虽然Servlet是Model2应用程序最常用的Controller，但也可以使用Filter作为Controller。

但是Filter无权充当欢迎页面。Structs2用Filter作为Controller。

JSP页面与Servlet Controller中一样；但它不是使用Servlet作为Controller，而是用了一个名为DispatcherFilter的类：

package com.gof.test.filter;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.gof.test.action.SaveProductAction;import com.gof.test.bean.Product;import com.gof.test.bean.ProductForm;public class DispatcherFilter implements Filter {	public void init(FilterConfig filterConfig) throws ServletException {		// TODO Auto-generated method stub	}	public void doFilter(ServletRequest req, ServletResponse resp,			FilterChain chain) throws IOException, ServletException {		String uri = ((HttpServletRequest)req).getRequestURI();		int lastIndex = uri.lastIndexOf("/");		String action = uri.substring(lastIndex + 1);		String dispatchUrlString = null;				if (action.equals("product_input")){			dispatchUrlString = "/jsp/controller/ProductForm.jsp";		}else 		if (action.equals("product_save")){			ProductForm productForm = new ProductForm();						productForm.setName(req.getParameter("name"));			productForm.setDescription(req.getParameter("description"));			productForm.setPrice(req.getParameter("price"));						Product product = new Product();			product.setName(productForm.getName());			product.setDescription(productForm.getDescription());			try{				product.setPrice(Float.parseFloat(productForm.getPrice()));			}catch (NumberFormatException e){				e.printStackTrace();			}						SaveProductAction saveProductAction = new SaveProductAction();			saveProductAction.save(product);						req.setAttribute("product", product);			dispatchUrlString = "/jsp/controller/ProductDetails.jsp";		}        		if (dispatchUrlString != null){			RequestDispatcher rDispatcher = req.getRequestDispatcher(dispatchUrlString);			rDispatcher.forward(req, resp);		}else{			chain.doFilter(req, resp);		}	}	public void destroy() {		// TODO Auto-generated method stub	}}

在web.xml中注册这个Filter：

       
           
    
     dispatcherfilter
            
    
     com.gof.test.filter.DispatcherFilter
        
       
           
    
     dispatcherfilter
            
    
     /*
        
   

对于不是 product_input 和 product_save 的action，需要调用filterChain.doFilter()方法继续进行下面的流程。

在浏览器中访问之前的URL：

http://localhost:8080/base-webapp/product_input

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