Struts2.0之Action详解(二)

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Struts IOC Servlet JSP Apache

Struts 2.0更厉害的是支持更高级的POJO访问，如user.getPassword()。我们可以用另一写法实现例4。首先，将name和password从Login类中分离出来，到新建类User中。这样对我们开发多层系统尤其有用。它可以使系统结构更清晰。

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>