struts 2 简单笔记

struts 2是对MVC模式的封装：

一.其基本特性例子如下：

1. 配置struts.xml

<package name = "struts" namespace="" extends="struts-default">
    <action name = "login" class="com.LoginAction">
        <result name = "LOG">/index.jsp</result>
    </action>
</package>

2.实现com.LoginAction

public class LoginAction extends ActionSupport {
    private String name;
    private String mail;
    public String execute()throws Exception{
        
        System.out.println(name);
        System.out.println(mail);
        
        return "LOG";
    }

3. 前端调用jsp如下：

       <s:form action = "login">
       <s:textfield label = "id" name = "id"></s:textfield>
       <s:textfield label = "name" name = "name"></s:textfield>
       <s:submit value = "submit"/>
       </s:form>

二.同时struts 2也支持领域模型驱动，类似于将前端界面封装成VO的POJO类，此时需要实现Action类如下：

public class LoginAction extends ActionSupport implements ModelDriven<User> {

    private final User usr = new User();
        
    public String execute()throws Exception{
            
        
        System.out.println(getModel().getId());
        System.out.println(getModel().getName());
        return "LOG";
    }
    
    public User getModel() {
        return usr;
    }

其中必须继承并实现ModelDriven<User>接口
三. 通过action中方法的跳转，可以实现类似business业务流的封装。典型的应用就是功能向导，此时struts 2设置如下：

    <action name = "step1" class = "com.StepAction" method = "stepMethod1">    
         <result name = "step2">step2.jsp</result>
         <interceptor-ref name = "testinter"></interceptor-ref>
     </action>
    <action name = "step2" class = "com.StepAction" method = "stepMethod2">
         <result name = "step3">step3.jsp</result>
     </action>    
     <action name = "step3" class = "com.StepAction" method = "stepMethod3">
         <result name = "index">index.jsp</result>
     </action>

public class StepAction extends ActionSupport {
    private String step1Value;
    private String step2Value;
    private String step3Value;
    
    public String stepMethod1(){
        ActionContext.getContext().getSession().put("stepvalue1", step1Value);
        return "step2";
    }
    
    public String stepMethod2(){
        ActionContext.getContext().getSession().put("stepvalue2", step2Value);
        return "step3";
    }
    
    public String stepMethod3(){
        ActionContext.getContext().getSession().put("stepvalue3", step3Value);
        return "index";
    }

四. struts 2的拦截器也是比较典型的应用，类似于servlet的过滤器，实现是struts 2配置如下：

      <interceptors>
     <interceptor name = "testinter" class  ="com.MyIntercept"/>
   </interceptors>
     <action name = "step1" class = "com.StepAction" method = "stepMethod1">    
         <result name = "step2">step2.jsp</result>
         <interceptor-ref name = "testinter"></interceptor-ref>
     </action>

实现interceptor类如下：

public class MyIntercept extends AbstractInterceptor {

    @Override
    public String intercept(ActionInvocation arg0) throws Exception {
        // TODO Auto-generated method stub
        Object action = arg0.getAction();
        
        System.out.println("intercept");
        String result = arg0.invoke();
        return result;
    }
}

五.struts 2的内部机制整理如下：

1. 接收到客户请求后，FilterDispatcher调用ActionMapper看是否存在调用的Action
2. 若存在，FilterDispater调用其方法serviceAction；
3. 在serviceAction方法中首先调用createContextMap，把application,session,request的keyvalue拷贝到map中；
4. 通过StrutsObjectFactory创建代理类actionProxy,执行ActionProxy的invoke方法；
5. 在invoke方法中创建defaultActionInvocation，该类的init函数中createAction创建action；
6. 然后defalutActionInvocation的invode函数中，会首先遍历执行interceptor，然后执行invokeActionOnly; 注：action中的属性是在拦截器执行完后才赋值的，防止拦截器对属性值有修改，没看到这段代码。
7. 在此函数中正真的action方法被通过反射的手段调用；
8. 执行完毕后会由defaultActionInvocation调用executeResult，返回需要的视图；