Struts2 学习笔记 09 访问Web元素

2023-07-18 16:50:52

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;

	}

码农公寓

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