Struts2中Action对象的set方法和get方法调用规则

    Struts的Action是采用的是多实例多线程设计，而不是像Servlet那样采用单实例多线程设计，因此在struts中，一个请求就对应一个Action对象，个对象之间的数据相互之间互不干扰。没接到一个新的请求，就产生一个新的Action对象，并对Action对象的各属性赋予默认初始值。之后再根据一定的规则调用set方法给各属性赋值，并根据一定规则调用get方法。也就是说，Action对象不是一开始就必须调用set方法的。本文重点讲Action对象调用set和get方法的规则：

1.get方法的调用规则

    Action对象get方法的调用规则相对简单，因此先说get方法的调用规则。调用get方法方法是为了获取属性值，这一点不仅仅在struts中是这样，在任何java程序中，都是这样的。那么什么时候才需要一个Action对象的属性值呢？就目前本人探索和总结的结果来看，分为以下三种情况：

（一）、在Action请求转发到下一个Action时（即result的type属性为chain时），下一个Action有对应属性的set方法；

    这种情况是为了传递数据，让数据跟着Action流程的流转而进入到下一个Action对象，因此是非常重要的。但是呢，这种传递不一定能达到想要的目的，意外出现在如果最初的http请求本身就有了对应的查询参数值，则目标Action会在获得了源Action的get值之后，再次去过的请求的查询参数值，并用这个值作为set方法的传入参数，在这种情况下，目标Filed的值还是http请求的查询参数值。

（二）、在struts.xml配置文件中引用了相应的Action属性；

    这种情况其实是显式调用了get方法，所以一定会被调用，也没什么好说的。

（三）有对应的request.getAttribute()，且之前没有用过相应的request.setAttribute()。

   这里说的request.getAttribute()一般出现在视图中，比如jsp的requestScope.filedName，或者显示的request.getAttribute() java 代码。

  Action对象get方法调用的具体规则流程如下：

需要强调的是，只有在真正需要数据的时候，才会调用get方法，而不是在离开Action的时候。所以，在下一个Action的拦截器之后，到达Action时，上一个Action的get方法才被调用（因为这时需要给目标Action赋值了，而赋值需要值的来源，所以就要调用上一个Action的get方法以获得赋值的来源）。

还有需要强调的是，需要get方法时，总是调用最近Action对象的get方法，如果最近的Action没有get方法，则调用次近的，知道最开始的那个Action。

2.set方法的调用规则

    Action对象set方法的调用规则相对于get方法来说比较复杂。同样，在任何java程序中，set方法都是为了给对象的属性赋值，因此，set方法的调用规则关乎到Action对象的数据是怎么获取的，因此显得尤为重要。

    因为set方法是给Action对象数据赋值的，所以，要知道set方法的调用规则，首先要清楚Action对象的属性数据的来源有哪些。就本人目前探索和总结来看，Action对象的属性数据的来源有以下两类：（1）上一个Action的get方法、（2）http请求参数。这两类数据来源也就对应了set方法的调用规则。

（一）从源Action的get方法中获得

    这种情况对应于get方法调用规则中的第一种情况，也是在Action转发时发生的，而且和get方法的第一种情况总是同时发生的，也就是说，这两张情况要么都发生，要么都不发生。两种情况共同完成Action对象的数据传递。

（二）从请求参数中来

    如果有对应的请求参数值，则这种情况一定会发生，及时上一种情况已经发生过了。这样，如果源Action有对应的get方法，请求中也有对应的请求参数值（注意是getParameter到的值，而不是getAttribute到的值，Action是不能从request的Attribute中得到属性值的），则一个get方法会被调用两次，后面一次获取的是请求参数中的值，最终的属性值和请求参数一致。

    set方法调用规则的流程如下：

测试用的代码如下：LoginAction是源Action，LoginAction2是目标Action。

import com.opensymphony.xwork2.ActionSupport;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.struts2.ServletActionContext;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginAction2 extends ActionSupport{
    private final Logger log = LogManager.getLogger(getClass());
    private String username;
    private String password;
    private String usernameAndPassword;
    private int age;

    public String getUsername() {
        log.trace("getUsername is in invoked");

        return username;
    }

    public void setUsername(String username) {
        log.trace("setUsername is in invoked");

        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUsernameAndPassword() {
        log.trace("getUsernameAndPassword is in invoked");

        return usernameAndPassword;
    }

    public void setUsernameAndPassword(String usernameAndPassword) {
        log.trace("setUsernameAndPassword is in invoked");

        this.usernameAndPassword = usernameAndPassword;
    }

    @Override
    public void validate() {
        log.trace("validate is invoked");
        HttpServletRequest request = ServletActionContext.getRequest();
        HttpServletResponse response = ServletActionContext.getResponse();
        System.out.println( request.getAttribute("age"));
    }

    public int getAge() {
        log.trace("getAge is invoked");
        System.out.println("getAge:  "+age);

        return 70;
    }

//    public void setAge(int age) {
//        log.trace("setAge is invoked");
//        System.out.println("setAge:  "+age);
//        this.age = age;
//    }
}

package edu.whu.swe.learnstruts2;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import edu.whu.swe.learnstruts2.service.LoginService;
import edu.whu.swe.learnstruts2.service.impl.LoginServiceImpl;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.struts2.ServletActionContext;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class LoginAction extends ActionSupport {
    private final Logger log = LogManager.getLogger(getClass());
    private String username;
    private String password;
    private String alianname;
    private String othertest;
    private int age;

    private final LoginService loginService = new LoginServiceImpl();


    public String execute() throws Exception {


        if (!loginService.isLogin(username, password)) {

            return INPUT;

        }
        HttpServletRequest request = ServletActionContext.getRequest();
        HttpServletResponse response = ServletActionContext.getResponse();
//        request.setAttribute("age", 22);
//        this.age=22;

/** 因为是使用的框架，所以重定向语句之后的代码依旧会执行，但是业务逻辑已经转到定向后的地方了 */
//        ServletContext context =request.getSession().getServletContext();
//        RequestDispatcher dispatcher=context.getRequestDispatcher("/usernameInvalide.jsp");
//        System.out.println("print this before dispatcher");
//        dispatcher.forward(request,response);
//        System.out.println("print this after dispatcher");
//        age+=1000;


        //
        System.out.println("LoginAction is executed");
        return SUCCESS;

    }

    public String getUsernameAndPassword() {
        log.trace("getUsernameAndPassword is in invoked");
        return username + password;
    }

    public void setUsernameAndPassword(String usernameAndPassword) {
        log.trace("setUsernameAndPassword is in invoked");

    }


    public String getUsername() {
        log.trace("getUsername is in invoked");
        return username;
    }

    public void setUsername(String username) {
        log.trace("setUsername is in invoked");
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }


    public String getAlianame() {
        log.trace("getAlianame is in invoked");

        return alianname;
    }

    public void setAlianame(String alianname) {
        log.trace("setAlianame is in invoked");

        this.alianname = alianname;
    }

    public String getOthertest() {
        return othertest;
    }

    public void setOthertest(String othertest) {
        this.othertest = othertest;
    }


    @Override
    public void validate() {
        log.trace("validate is invoked");
    }

    public void setAge(int age) {
        log.trace("setAge is invoked");
        this.age = age + 33;
    }

    public int getAge() {
        log.trace("setAge is invoked");
        return 55;
    }
}

关键的struts.xml配置如下：

<action name="login1" class="edu.whu.swe.learnstruts2.LoginAction2">
            <result name="success">/welcome.jsp</result>
</action>


<action name="login" class="edu.whu.swe.learnstruts2.LoginAction">
            <result name="success" type="chain">
                <param name="actionName">login1</param>
                <param name="namespace">/</param>
            </result>
</action>

 测试结果如下：

不输入age
2018-01-12 16:34:58.876 TRACE edu.whu.swe.learnstruts2.LoginAction setUsername - " setUsername is in invoked " 
2018-01-12 16:34:58.877 TRACE edu.whu.swe.learnstruts2.LoginAction validate - " validate is invoked " 
LoginAction is executed
2018-01-12 16:34:58.877 TRACE edu.whu.swe.learnstruts2.LoginAction getAge - " setAge is invoked " 
2018-01-12 16:34:58.878 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
2018-01-12 16:34:58.878 TRACE edu.whu.swe.learnstruts2.LoginAction getUsername - " getUsername is in invoked " 
2018-01-12 16:34:58.878 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:34:58.878 TRACE edu.whu.swe.learnstruts2.LoginAction getUsernameAndPassword - " getUsernameAndPassword is in invoked " 
2018-01-12 16:34:58.879 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsernameAndPassword - " setUsernameAndPassword is in invoked " 
2018-01-12 16:34:58.879 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:34:58.880 TRACE edu.whu.swe.learnstruts2.LoginAction2 validate - " validate is invoked " 
2018-01-12 16:34:58.883 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsername - " getUsername is in invoked " 
2018-01-12 16:34:58.883 TRACE edu.whu.swe.learnstruts2.LoginAction2 getAge - " getAge is invoked " 
2018-01-12 16:34:58.884 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsernameAndPassword - " getUsernameAndPassword is in invoked " 

输入了age
2018-01-12 16:35:36.356 TRACE edu.whu.swe.learnstruts2.LoginAction setAge - " setAge is invoked " 
2018-01-12 16:35:36.356 TRACE edu.whu.swe.learnstruts2.LoginAction setUsername - " setUsername is in invoked " 
2018-01-12 16:35:36.357 TRACE edu.whu.swe.learnstruts2.LoginAction validate - " validate is invoked " 
LoginAction is executed
2018-01-12 16:35:36.358 TRACE edu.whu.swe.learnstruts2.LoginAction getAge - " setAge is invoked " 
2018-01-12 16:35:36.358 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
2018-01-12 16:35:36.358 TRACE edu.whu.swe.learnstruts2.LoginAction getUsername - " getUsername is in invoked " 
2018-01-12 16:35:36.359 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:35:36.359 TRACE edu.whu.swe.learnstruts2.LoginAction getUsernameAndPassword - " getUsernameAndPassword is in invoked " 
2018-01-12 16:35:36.359 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsernameAndPassword - " setUsernameAndPassword is in invoked " 
2018-01-12 16:35:36.360 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
2018-01-12 16:35:36.360 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:35:36.360 TRACE edu.whu.swe.learnstruts2.LoginAction2 validate - " validate is invoked " 
2018-01-12 16:35:36.363 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsername - " getUsername is in invoked " 
2018-01-12 16:35:36.363 TRACE edu.whu.swe.learnstruts2.LoginAction2 getAge - " getAge is invoked " 
2018-01-12 16:35:36.363 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsernameAndPassword - " getUsernameAndPassword is in invoked " 


没有age表单
2018-01-12 16:37:41.549 TRACE edu.whu.swe.learnstruts2.LoginAction setUsername - " setUsername is in invoked " 
2018-01-12 16:37:41.591 TRACE edu.whu.swe.learnstruts2.LoginAction validate - " validate is invoked " 
LoginAction is executed
2018-01-12 16:37:41.610 TRACE edu.whu.swe.learnstruts2.LoginAction getAge - " setAge is invoked " 
2018-01-12 16:37:41.611 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
2018-01-12 16:37:41.611 TRACE edu.whu.swe.learnstruts2.LoginAction getUsername - " getUsername is in invoked " 
2018-01-12 16:37:41.611 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:37:41.612 TRACE edu.whu.swe.learnstruts2.LoginAction getUsernameAndPassword - " getUsernameAndPassword is in invoked " 
2018-01-12 16:37:41.612 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsernameAndPassword - " setUsernameAndPassword is in invoked " 
2018-01-12 16:37:41.615 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:37:41.622 TRACE edu.whu.swe.learnstruts2.LoginAction2 validate - " validate is invoked " 
2018-01-12 16:37:41.741 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsername - " getUsername is in invoked " 
2018-01-12 16:37:41.741 TRACE edu.whu.swe.learnstruts2.LoginAction2 getAge - " getAge is invoked " 
2018-01-12 16:37:41.742 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsernameAndPassword - " getUsernameAndPassword is in invoked " 

没有age表单，在源Action有getAge{return age+55}和setAge{this.age=age+33},返回页面结果是：age:55
2018-01-12 16:47:33.884 TRACE edu.whu.swe.learnstruts2.LoginAction setUsername - " setUsername is in invoked " 
2018-01-12 16:47:33.933 TRACE edu.whu.swe.learnstruts2.LoginAction validate - " validate is invoked " 
LoginAction is executed
2018-01-12 16:47:33.955 TRACE edu.whu.swe.learnstruts2.LoginAction getAge - " setAge is invoked " 
2018-01-12 16:47:33.955 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
2018-01-12 16:47:33.956 TRACE edu.whu.swe.learnstruts2.LoginAction getUsername - " getUsername is in invoked " 
2018-01-12 16:47:33.956 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:47:33.956 TRACE edu.whu.swe.learnstruts2.LoginAction getUsernameAndPassword - " getUsernameAndPassword is in invoked " 
2018-01-12 16:47:33.957 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsernameAndPassword - " setUsernameAndPassword is in invoked " 
2018-01-12 16:47:33.960 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:47:33.971 TRACE edu.whu.swe.learnstruts2.LoginAction2 validate - " validate is invoked " 
2018-01-12 16:47:34.132 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsername - " getUsername is in invoked " 
2018-01-12 16:47:34.133 TRACE edu.whu.swe.learnstruts2.LoginAction2 getAge - " getAge is invoked " 
2018-01-12 16:47:34.134 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsernameAndPassword - " getUsernameAndPassword is in invoked " 


输入age表单值为666，在源Action有getAge{return age+55}和setAge{this.age=age+33},在目标Action中打印相应的Filed。返回页面结果是：age:22
2018-01-12 17:19:51.730 TRACE edu.whu.swe.learnstruts2.LoginAction setAge - " setAge is invoked " 
2018-01-12 17:19:51.731 TRACE edu.whu.swe.learnstruts2.LoginAction setUsername - " setUsername is in invoked " 
2018-01-12 17:19:51.731 TRACE edu.whu.swe.learnstruts2.LoginAction validate - " validate is invoked " 
LoginAction is executed
2018-01-12 17:19:51.734 TRACE edu.whu.swe.learnstruts2.LoginAction getAge - " setAge is invoked " 
2018-01-12 17:19:51.734 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
setAge:  754
2018-01-12 17:19:51.735 TRACE edu.whu.swe.learnstruts2.LoginAction getUsername - " getUsername is in invoked " 
2018-01-12 17:19:51.736 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 17:19:51.736 TRACE edu.whu.swe.learnstruts2.LoginAction getUsernameAndPassword - " getUsernameAndPassword is in invoked " 
2018-01-12 17:19:51.736 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsernameAndPassword - " setUsernameAndPassword is in invoked " 
2018-01-12 17:19:51.737 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
setAge:  666
2018-01-12 17:19:51.737 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 17:19:51.738 TRACE edu.whu.swe.learnstruts2.LoginAction2 validate - " validate is invoked " 
2018-01-12 17:19:51.741 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsername - " getUsername is in invoked " 
2018-01-12 17:19:51.741 TRACE edu.whu.swe.learnstruts2.LoginAction2 getAge - " getAge is invoked " 
getAge:  666
2018-01-12 17:19:51.742 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsernameAndPassword - " getUsernameAndPassword is in invoked " 



输入age表单值为666，在源Action有getAge{return age+55}和setAge{this.age=age+33},设置setAttribute("age",22);在目标Action中打印相应的Filed。返回页面结果是：age:22
2018-01-12 16:56:50.179 TRACE edu.whu.swe.learnstruts2.LoginAction setAge - " setAge is invoked " 
2018-01-12 16:56:50.195 TRACE edu.whu.swe.learnstruts2.LoginAction setUsername - " setUsername is in invoked " 
2018-01-12 16:56:50.229 TRACE edu.whu.swe.learnstruts2.LoginAction validate - " validate is invoked " 
LoginAction is executed
2018-01-12 16:56:50.249 TRACE edu.whu.swe.learnstruts2.LoginAction getAge - " setAge is invoked " 
2018-01-12 16:56:50.250 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
setAge:  754
2018-01-12 16:56:50.250 TRACE edu.whu.swe.learnstruts2.LoginAction getUsername - " getUsername is in invoked " 
2018-01-12 16:56:50.250 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:56:50.251 TRACE edu.whu.swe.learnstruts2.LoginAction getUsernameAndPassword - " getUsernameAndPassword is in invoked " 
2018-01-12 16:56:50.251 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsernameAndPassword - " setUsernameAndPassword is in invoked " 
2018-01-12 16:56:50.253 TRACE edu.whu.swe.learnstruts2.LoginAction2 setAge - " setAge is invoked " 
setAge:  666
2018-01-12 16:56:50.255 TRACE edu.whu.swe.learnstruts2.LoginAction2 setUsername - " setUsername is in invoked " 
2018-01-12 16:56:50.263 TRACE edu.whu.swe.learnstruts2.LoginAction2 validate - " validate is invoked " 
2018-01-12 16:56:50.414 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsername - " getUsername is in invoked " 
2018-01-12 16:56:50.415 TRACE edu.whu.swe.learnstruts2.LoginAction2 getUsernameAndPassword - " getUsernameAndPassword is in invoked "