Struts2.0之Action详解(二)
例5 classes/tutorial/LoginX.java
package tutorial;
import com.opensymphony.xwork2.ActionSupport;
publicclass LoginX extends ActionSupport {
private User user;
private String message;
publicvoid setUser(User user) {
this.user = user;
}
public User getUser() {
return user;
}
public String getMessage() {
return message;
}
@Override
public String execute() {
if("max".equals(user.getName()) &&"secret".equals(user.getPassword())) {
message ="Welcome, "+ user.getName();
}else{
message ="Invalid user or password";
}
return SUCCESS;
}
}
例5 LoginX.jsp
<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title>Login</title>
</head>
<body>
<s:form action="LoginX" method="POST">
<s:textfield name="user.name" label="User name"/>
<s:password name="user.password" label="Password"/>
<s:submit value="Submit"/>
</s:form>
</body>
</html>
例5 classes/struts.xml中的LoginX Action配置
<action name="LoginX" class="tutorial.LoginX">
<result>/HelloWorld.jsp</result>
</action>
很多时候我的同事会问我：“如果我要取得Servlet API中的一些对象，如request、response或session等，应该怎么做？这里的execute不像Struts 1.x的那样在参数中引入。”开发Web应用程序当然免不了跟这些对象打交道。在Strutx 2.0你可以有两种方式获得这些对象：非IoC（控制反转Inversion of Control）方式和IoC方式。
非IoC方式
要获得上述对象，关键Struts 2.0中com.opensymphony.xwork2.ActionContext类。我们可以通过它的静态方法getContext()获取当前Action的上下文对象。 另外，org.apache.struts2.ServletActionContext作为辅助类（Helper Class），可以帮助您快捷地获得这几个对象。
HttpServletRequest request = ServletActionContext.getRequest();
HttpServletResponse response = ServletActionContext.getResponse();
HttpSession session = request.getSession();
如果你只是想访问session的属性（Attribute），你也可以通过ActionContext.getContext().getSession()获取或添加session范围（Scoped）的对象。
IoC方式
要使用IoC方式，我们首先要告诉IoC容器（Container）想取得某个对象的意愿，通过实现相应的接口做到这点。具体实现，请参考例6 IocServlet.java。
例6 classes/tutorial/NonIoCServlet.java
package tutorial;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
publicclass NonIoCServlet extends ActionSupport {
private String message;
public String getMessage() {
return message;
}
@Override
public String execute() {
ActionContext.getContext().getSession().put("msg", "Hello World from Session!");
HttpServletRequest request = ServletActionContext.getRequest();
HttpServletResponse response = ServletActionContext.getResponse();
HttpSession session = request.getSession();
StringBuffer sb =new StringBuffer("Message from request: ");
sb.append(request.getParameter("msg"));
sb.append("<br>Response Buffer Size: ");
sb.append(response.getBufferSize());
sb.append("<br>Session ID: ");
sb.append(session.getId());
message = sb.toString();
return SUCCESS;
}
}
例6 classes/tutorial/IoCServlet.java
package tutorial;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;
import org.apache.struts2.interceptor.SessionAware;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
publicclass IoCServlet extends ActionSupport implements SessionAware, ServletRequestAware, ServletResponseAware {
private String message;
private Map att;
private HttpServletRequest request;
private HttpServletResponse response;
public String getMessage() {
return message;
}
publicvoid setSession(Map att) {
this.att = att;
}
publicvoid setServletRequest(HttpServletRequest request) {
this.request = request;
}
publicvoid setServletResponse(HttpServletResponse response) {
this.response = response;
}
@Override
public String execute() {
att.put("msg", "Hello World from Session!");
HttpSession session = request.getSession();
StringBuffer sb =new StringBuffer("Message from request: ");
sb.append(request.getParameter("msg"));
sb.append("<br>Response Buffer Size: ");
sb.append(response.getBufferSize());
sb.append("<br>Session ID: ");
sb.append(session.getId());
message = sb.toString();
return SUCCESS;
}
}
例6 Servlet.jsp
<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title>Hello World!</title>
</head>
<body>
<h2>
<s:property value="message" escape="false"/>
<br>Message from session: <s:property value="#session.msg"/>
</h2>
</body>
</html>
例6 classes/struts.xml中NonIocServlet和IoCServlet Action的配置
<action name="NonIoCServlet" class="tutorial.NonIoCServlet">
<result>/Servlet.jsp</result>
</action>
<action name="IoCServlet" class="tutorial.IoCServlet">
<result>/Servlet.jsp</result>
</action>
运行Tomcat，在浏览器地址栏中键入http://localhost:8080/Struts2_Action/NonIoCServlet.action?msg=Hello%20World! 或http://localhost:8080/Struts2_Action/IoCServlet.action?msg=Hello%20World!，出现如图7所示页面。
在Servlet.jsp中，我用了两次property标志，第一次将escape设为false为了在JSP中输出<br>转行，第二次的value中的OGNL为“#session.msg”，它的作用与session.getAttribute("msg")等同。