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（01）Struts2_使用 Filter 作为控制器的 MVC 应用
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：
编码：
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>
<!-- 拦截所有后缀为.action的请求 -->
<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。
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