【Java.Web】MVC —— 基于Filter Dispatcher的Model2 —— 示例

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：

<!--  Filter -->
    <filter>
        <filter-name>dispatcherfilter</filter-name>
        <filter-class>com.gof.test.filter.DispatcherFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>dispatcherfilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

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