Struts2 学习笔记 09 访问Web元素
我们想要访问Map类型request，session，application。真实类型HttpServletRequest，HttpSession，ServletContext的引用，并对它们进行操作。
这是我们的主页文件。
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
取得Map类型request，session，application。真实类型HttpServletRequest，HttpSession，ServletContext的引用 <br>
<ol>
<li>前三者依赖于容器</li>
<li>前三者，IOC</li>
<li>后三者，依赖于容器</li>
<li>后三者，IOC</li>
</ol>
<form action="" name="f" method="post">
用户名：<input type="text" name="name"/>
密码：<input type="text" name="password"/>
<br>
<input type="button" value="submit1" onclick="javascript:document.f.action='login/login1';document:f.submit();">
<input type="button" value="submit2" onclick="javascript:document.f.action='login/login2';document:f.submit();">
<input type="button" value="submit3" onclick="javascript:document.f.action='login/login3';document:f.submit();">
<input type="button" value="submit4" onclick="javascript:document.f.action='login/login4';document:f.submit();">
</form>
</body>
</html>
页面有四个按钮，单击后动态调用login/login*，然后提交。submit1 会调用Login1Action.java.
Login1Action.java
package com.tfj.struts2.action;
import java.util.Map;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class Login1Action extends ActionSupport{
private Map request;
private Map session;
private Map application;
public Login1Action() {
request = (Map)ActionContext.getContext().get("request");
session = ActionContext.getContext().getSession();
application = ActionContext.getContext().getApplication();
}
public String execute() {
request.put("r1", "r1");
session.put("s1", "s1");
application.put("a1", "a1");
return SUCCESS;
}
}
在这个文件中，自己定义了Map类型的request，session，和application，通过ActionContext取得Action的上下文，在拿到request。在execute（）方法对request赋值。在显示的页面loginsuccess.jsp显示出来。
loginsuccess.jsp
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@taglib uri="/struts-tags" prefix="s"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'loginsuccess.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<s:property value="#request.r1"/> | <%=request.getAttribute("r1") %><br />
<s:property value="#session.s1"/> | <%=session.getAttribute("s1") %><br />
<s:property value="#application.a1"/> | <%=application.getAttribute("a1") %><br/>
<br>
</body>
</html>
这里有两种调用方式<s:property value="#request.r1"/> 因为request是stack context里的内容 需要加#符号来调用里里面的内容（通过debug标签可以自己看），<%=request.getAttribute("r1") %>则是用javascript代码来调用。结果如图
接下来讲一种更为常用的，应该说最常用的方法，叫做DI（Dependeny Injection）依赖注入，也叫IoC（InversionofControl）控制反转。
单击submit2，调用Login2Action.java
Login2Action.java
package com.tfj.struts2.action;
import java.util.Map;
import org.apache.struts2.interceptor.ApplicationAware;
import org.apache.struts2.interceptor.RequestAware;
import org.apache.struts2.interceptor.SessionAware;
import com.opensymphony.xwork2.ActionSupport;
public class Login2Action extends ActionSupport implements RequestAware,SessionAware,ApplicationAware{
private Map<String, Object> request;
private Map<String,Object> session;
private Map<String,Object> application;
@Override
public String execute() throws Exception {
request.put("r1", "r1");
session.put("s1", "s1");
application.put("a1", "a1");
return SUCCESS;
}
@Override
public void setApplication(Map<String, Object> application) {
this.application=application;
}
@Override
public void setSession(Map<String, Object> session) {
// TODO Auto-generated method stub
this.session=session;
}
@Override
public void setRequest(Map<String, Object> request) {
// TODO Auto-generated method stub
this.request=request;
}
}
实现 RequestAware,SessionAware,ApplicationAware接口，实现对应的方法setRequest(Map<String, Object> request)，setSession(Map<String, Object> session)，setApplication(Map<String, Object> application)。为什么这种方法叫DI或IoC呢？
因为这种方法并不是request去取得一个值，而是询问request是否存在（requestAware接口），如果存在就调用setRequest（）方法来给request初始化，叫做依赖注入。IoC反转控制也很好理解，本来的控制端被反转了。
这种方法最常用，要好好理解。
这是取得Map类型request，session，application。要取得真实类型HttpServletRequest，HttpSession，ServletContext的引用道理类似。submi3，是依赖容器的方法，submit4，是IoC，简单了解即可。
Login3Action.java
package com.tfj.struts2.action;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class Login3Action extends ActionSupport{
private HttpServletRequest request;
private HttpSession session;
private ServletContext application;
public Login3Action() {
request=ServletActionContext.getRequest();
session=request.getSession();
application=session.getServletContext();
}
@Override
public String execute() {
request.setAttribute("r1", "r1");
session.setAttribute("s1", "s1");
application.setAttribute("r1", "r1");
return SUCCESS;
}
}
实现ServletRequestAware接口即可。
Login4Action.java
package com.tfj.struts2.action;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.commons.fileupload.servlet.ServletRequestContext;
import org.apache.struts2.ServletActionContext;
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.util.ServletContextAware;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class Login4Action extends ActionSupport implements ServletRequestAware{
private HttpServletRequest request;
private HttpSession session;
private ServletContext application;
@Override
public void setServletRequest(HttpServletRequest request) {
this.request=ServletActionContext.getRequest();
this.session=request.getSession();
this.application=session.getServletContext();
}
@Override
public String execute() {
request.setAttribute("r1", "r1");
session.setAttribute("s1", "s1");
application.setAttribute("r1", "r1");
return SUCCESS;
}