（01）Struts2_使用 Filter 作为控制器的 MVC 应用

阳光穿透心脏的1/2处 2021-10-06 14:02 196阅读 0赞

### **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： ####

*  模型：封装应用程序的数据和业务逻辑
 *  视图：实现应用程序的信息显示功能
 *  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）

### **需求：** ###

![这里写图片描述][20160831213740951]

### **编码：** ###

![这里写图片描述][20160831213938187]

#### **index.jsp** ####

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
    <head>
    </head>
    <body>
        <a href="czy_input.action">进入Input.jsp页面</a>
    </body>
    </html>

#### **Input.jsp** ####

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
      </head>
      <body>
      <form action="czy_save.action" method="post">
           编号：<input type="text" name="dlh"/><br>
           姓名：<input type="text" name="name"/><br>
           部门：<input type="text" name="bmmc"/><br>
           <input type="submit" value="保存"/>
       </form>
      </body>
    </html>

#### **Show.jsp** ####

<%@ page language="java" import="java.util.*" pageEncoding="utf-8" contentType="text/html; charset=UTF-8"%>
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
      </head>
      <body>
           ID：${requestScope.czy.id}<br>
           编号：${ requestScope.czy.dlh}<br>
           姓名：${ requestScope.czy.name}<br>
           部门：${ requestScope.czy.bmmc}<br>
      </body>
    </html>

#### **FilterDispatcher.java** ####

package com.qbz.struts2_01;
    
    import java.io.IOException;
    import java.util.UUID;
    
    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.HttpServletResponse;
    
    public class FilterDispatcher implements Filter { 
    
        @Override
        public void destroy() {
    
        }
    
        @SuppressWarnings("unused")
        @Override
        public void doFilter(ServletRequest arg0, ServletResponse arg1,
                FilterChain arg2) throws IOException, ServletException {
    
            HttpServletRequest request = (HttpServletRequest) arg0;
            HttpServletResponse response = (HttpServletResponse) arg1;
    
            request.setCharacterEncoding("UTF-8");
            response.setContentType("text/html;charset=UTF-8");
    
            String servletPath = request.getServletPath();
            String path = null;
    
            if("/czy_input.action".equals(servletPath)){
                path="/WEB-INF/page/Input.jsp";
            }else if("/czy_save.action".equals(servletPath)){
                String dlh = request.getParameter("dlh");
                String name = request.getParameter("name");
                String bmmc = request.getParameter("bmmc");
    
                String id = UUID.randomUUID().toString().replace("-", "");
                GG_CZY czy = new GG_CZY(id,dlh, name, bmmc);
    
                request.setAttribute("czy", czy);
    
                path = "/WEB-INF/page/Show.jsp";
            }
    
            if(path!=null){
                request.getRequestDispatcher(path).forward(request, response);
                return;
            }
            arg2.doFilter(request, response);
        }
    
        @Override
        public void init(FilterConfig arg0) throws ServletException {
    
        }
    
    }

#### **GG\_CZY.java** ####

package com.qbz.struts2_01;
    
    public class GG_CZY { 
        private String id;
        private String dlh;
        private String name;
        private String bmmc;
    
        public String getId() {
            return id;
        }
    
        public void setId(String id) {
            this.id = id;
        }
    
        public String getDlh() {
            return dlh;
        }
    
        public void setDlh(String dlh) {
            this.dlh = dlh;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getBmmc() {
            return bmmc;
        }
    
        public void setBmmc(String bmmc) {
            this.bmmc = bmmc;
        }
    
        public GG_CZY(String id, String dlh, String name, String bmmc) {
            super();
            this.id = id;
            this.dlh = dlh;
            this.name = name;
            this.bmmc = bmmc;
        }
    
        public GG_CZY() {
            super();
        }
    
        @Override
        public String toString() {
            return "GG_CZY [id=" + id + ", dlh=" + dlh + ", name=" + name
                    + ", bmmc=" + bmmc + "]";
        }
    
    }

#### **web.xml** ####

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
        <display-name>struts2-01</display-name>
        <welcome-file-list>
            <welcome-file>index.jsp</welcome-file>
        </welcome-file-list>
        
        <filter>
            <filter-name>filterDispatcher</filter-name>
            <filter-class>com.qbz.struts2_01.FilterDispatcher</filter-class>
        </filter>
        <filter-mapping>
            <filter-name>filterDispatcher</filter-name>
            <url-pattern>*.action</url-pattern>
        </filter-mapping>
    </web-app>

### **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. ####

### **Servlet VS Filter** ###

*  Servlet可以做到的，Filter都可以完成。
 *  拦截资源却不是Servlet所擅长的。
 *  Filter 中有一个FilterChain，Servlet中没有这个API。

[20160831213740951]: /images/20211006/d2bec71f1ea749e79c957ebbf05e409d.png
[20160831213938187]: /images/20211006/d2c01112c3d34442a28cddf8f9bdce83.png