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1.MVC 设计模式概览：
实现 MVC(Model、View、Controller) 模式的应用程序由 3 大部分构成：
1）模型：封装应用程序的数据和业务逻辑：POJO(Plain Old Java Object)
2）视图：实现应用程序的信息显示功能：JSP
3）控制器：接收来自用户的输入，调用模型层，响应对应的视图组件：Servlet，Filter
2. 使用 Filter 作为控制器的好处 使用一个过滤器来作为控制器, 可以方便地在应用程序里对所有资源(包括静态资源)进行控制访问.:<url-pattern>*.action</url-pattern>
Servlet VS Filter
Servlet 能做的 Filter 是否都可以完成 ? 嗯。 Filter 能做的 Servlet 都可以完成吗 ? 拦截资源却不是 Servlet 所擅长的! Filter 中有一个 FilterChain，这个 API 在 Servlet 中没有！
3.demo
代码
index.jsp
1 <%@ page language="java" contentType="text/html; charset=UTF-8"
2 pageEncoding="UTF-8"%>
3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
4 <html>
5 <head>
6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
7 <title>Insert title here</title>
8 </head>
9 <body>
10
11
12 <a href="product-input.action">Product Input</a>
13 </body>
14 </html>
input.jsp
1 <%@ page language="java" contentType="text/html; charset=UTF-8"
2 pageEncoding="UTF-8"%>
3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
4 <html>
5 <head>
6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
7 <title>input page</title>
8 </head>
9 <body>
10
11 <form action="product-save.action" method="post">
12 ProductName:<input type="text" name="productName"/>
13 <br><br>
14
15 ProductDesc:<input type="text" name="productDesc"/>
16 <br><br>
17
18 ProductPrice:<input type="text" name="productPrice"/>
19 <br><br>
20
21 <input type="submit" value="submit" />
22 </form>
23 </body>
24 </html>
detial.jsp
1 <%@ page language="java" contentType="text/html; charset=UTF-8"
2 pageEncoding="UTF-8"%>
3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
4 <html>
5 <head>
6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
7 <title>detail page</title>
8 </head>
9 <body>
10
11 ProductId:${requestScope.product.productId }
12 <br><br>
13 ProductName:${requestScope.product.productName }
14 <br><br>
15 ProductDesc:${requestScope.product.productDesc }
16 <br><br>
17 ProductPrice:${requestScope.product.productPrice }
18 <br><br>
19
20
21 </body>
22 </html>
product.java
1 package com.jason.struts.helloword;
2
3 public class Product {
4
5 private Integer productId;
6 private String productName;
7 private String productDesc;
8
9 private double productPrice;
10
11
12
13
14
15 public Product() {
16 super();
17 }
18
19 public Product(Integer productId, String productName, String productDesc,
20 double productPrice) {
21 super();
22 this.productId = productId;
23 this.productName = productName;
24 this.productDesc = productDesc;
25 this.productPrice = productPrice;
26 }
27
28 @Override
29 public String toString() {
30 return "Product [productId=" + productId + ", productName="
31 + productName + ", productDesc=" + productDesc
32 + ", productPrice=" + productPrice + "]";
33 }
34
35 public Integer getProductId() {
36 return productId;
37 }
38
39 public void setProductId(Integer productId) {
40 this.productId = productId;
41 }
42
43 public String getProductName() {
44 return productName;
45 }
46
47 public void setProductName(String productName) {
48 this.productName = productName;
49 }
50
51 public String getProductDesc() {
52 return productDesc;
53 }
54
55 public void setProductDesc(String productDesc) {
56 this.productDesc = productDesc;
57 }
58
59 public double getProductPrice() {
60 return productPrice;
61 }
62
63 public void setProductPrice(double productPrice) {
64 this.productPrice = productPrice;
65 }
66
67
68
69 }
FilterDispatcher.java
1 package com.jason.struts.helloword;
2
3 import java.io.IOException;
4
5 import javax.servlet.Filter;
6 import javax.servlet.FilterChain;
7 import javax.servlet.FilterConfig;
8 import javax.servlet.ServletException;
9 import javax.servlet.ServletRequest;
10 import javax.servlet.ServletResponse;
11 import javax.servlet.annotation.WebFilter;
12 import javax.servlet.http.HttpServletRequest;
13 import javax.servlet.http.HttpServletResponse;
14
15 /**
16 * Servlet Filter implementation class FilterDispatcher
17 */
18 @WebFilter("*.action")
19 public class FilterDispatcher implements Filter {
20
21
22
23 public void destroy() {
24
25 }
26
27
28 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
29
30 HttpServletRequest req = (HttpServletRequest)request;
31 //1.获取servletPath
32 String servletPath = req.getServletPath();
33 System.out.println(servletPath);
34 String path = null;
35 //2.判断 servletPath，若其等于 "/product-input.action", 则转发到WEB-INF/struts/input.jsp
36 if("/struts2/product-input.action".equals(servletPath)){
37 path = "/struts2/input.jsp";
38
39 }
40 //3.若servletPath，为"/product-save.action",则
41 if("/struts2/product-save.action".equals(servletPath)){
42
43 //1) 获取请求参数
44 String productName = request.getParameter("productName");
45 String productDesc = request.getParameter("productDesc");
46 String productPrice = request.getParameter("productPrice");
47
48 //2) 把请求信息封装我一个Product 对象
49 Product product = new Product(null, productName, productDesc, Double.parseDouble(productPrice));
50 //3) 执行保存操作
51 System.out.println("save Product" + product + "" );
52
53 product.setProductId(1001);
54 request.setAttribute("product", product);
55
56 path = "/struts2/details.jsp";
57
58
59
60
61 }
62 //4.把Product 对象保存到request 中。
63
64 if(path != null){
65 req.getRequestDispatcher(path).forward(request, response);
66 return;
67 }
68
69 chain.doFilter(request, response);
70 }
71
72 public void init(FilterConfig fConfig) throws ServletException {
73
74 }
75
76
77
78
79
80 }