Struts2把session、request这些web对象封装起来

想要寻摸个自己惯用的、比较完善的框架出来。Struts2把session、request这些web对象封装起来，固然带来了很多便利，但有时也是个麻烦。用这个方法可以在自己的Action里获取到这些对象，并进行操作。

from：http://blog.csdn.net/puffCN/archive/2010/05/19/5607557.aspx

Struts2 的Action中若希望访问Session对象，可采用两种方式：

1、从ActionContext中获取；

2、实现SessionAware接口。

1、从ActionContext中获取：

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import java.util.Map;  
import com.opensymphony.xwork2.ActionContext;  
import com.opensymphony.xwork2.ActionSupport;  
public class SessionTestAction extends ActionSupport {  
    public String execute() {  
     ActionContext actionContext = ActionContext.getContext();  
       Map session = actionContext.getSession();  
       session.put("USER_NAME", "Test User");  
       return SUCCESS;  
    }  
}
import java.util.Map;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class SessionTestAction extends ActionSupport {
    public String execute() {
     ActionContext actionContext = ActionContext.getContext();
       Map session = actionContext.getSession();
       session.put("USER_NAME", "Test User");
       return SUCCESS;
    }
}

2、实现SessionAware接口：

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import java.util.Map;  
import org.apache.struts2.interceptor.SessionAware;  
import com.opensymphony.xwork2.ActionSupport;  
public class SessionTest1Action extends ActionSupport implements SessionAware {  
    private Map session;  
    public void setSession(Map session) {  
       this.session = session;  
    }  
    public String execute() {  
       this.session.put("USER_NAME", "Test User 1");  
       return SUCCESS;  
    }  
}
import java.util.Map;
import org.apache.struts2.interceptor.SessionAware;
import com.opensymphony.xwork2.ActionSupport;
public class SessionTest1Action extends ActionSupport implements SessionAware {
    private Map session;
    public void setSession(Map session) {
       this.session = session;
    }
    public String execute() {
       this.session.put("USER_NAME", "Test User 1");
       return SUCCESS;
    }
}

进一步阅读Struts2.1.8.1源码，SessionAware接口的实现方式如下：

struts-default.xml配置：

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<interceptors>
...  
<interceptor name="servletConfig" class="org.apache.struts2.interceptor.ServletConfigInterceptor"/>
...  
</interceptors>
<interceptor-stack name="defaultStack">
...  
<interceptor-ref name="servletConfig"/>
...  
</interceptor-stack>
<interceptors>
...
<interceptor name="servletConfig" class="org.apache.struts2.interceptor.ServletConfigInterceptor"/>
...
</interceptors>
<interceptor-stack name="defaultStack">
...
<interceptor-ref name="servletConfig"/>
...
</interceptor-stack>

打开ServletConfigInterceptor.java源码：

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public String intercept(ActionInvocation invocation) throws Exception {  
    final Object action = invocation.getAction();  
    final ActionContext context = invocation.getInvocationContext();  
      
    ...  
    if (action instanceof SessionAware) {  
        ((SessionAware) action).setSession(context.getSession());  
    }  
    ...  
    return invocation.invoke();  
}
public String intercept(ActionInvocation invocation) throws Exception {
    final Object action = invocation.getAction();
    final ActionContext context = invocation.getInvocationContext();
   
    ...
    if (action instanceof SessionAware) {
        ((SessionAware) action).setSession(context.getSession());
    }
    ...
    return invocation.invoke();
}

即在拦截器处理过程中发现目标Action实现了SessionAware接口，便会调用Action中已经实现的setSession(...)方法，将ActionContext中包装的Session注入目标Action中。目标Action也就可以进一步对Session进行操作了。