java如何从struts2运行线程

Question

我正在开发一个sturts2 Web应用程序，我有一个带有用户名和密码字段的登录页面。一旦用户提交了带有值的表单，我将验证登录，如果用户提供了有效的用户名和密码，它将重定向到主页。在重定向主页时，我必须调用一个线程，在该线程中我在会话中设置了一些数据以备将来使用。如何做到这一点

我所做的是

import com.opensymphony.xwork2.ActionContext;

if( loginSuccess(userInfo) ) {
    initializeDatas(); // calling thread after userInfo bean validated
    // redirecting to home page
    return HOME_PAGE;
}

我添加了一个实现runnable的新类

class intilalizer implements Runnable {
    @Override
    public void run() {
        try {
            System.out.println("Started to set values ");
            List<String> iphoneSdks = new ArrayList<String>();
            List<String> iphoneOSSdks = IosSdkUtil.getMacSdks(MacSdkType.iphoneos);
            List<String> simSdks = IosSdkUtil.getMacSdks(MacSdkType.iphonesimulator);
            List<String> macSdks = IosSdkUtil.getMacSdks(MacSdkType.macosx);
            iphoneSdks.addAll(iphoneOSSdks);
            iphoneSdks.addAll(simSdks);
            iphoneSdks.addAll(macSdks);

            ActionContext context = ActionContext.getContext();
            System.out.println("context ===> " + context); // here i am getting null value
            String httpRequest = ServletActionContext.HTTP_REQUEST;
            System.out.println("httpRequest =====> " + httpRequest);
            Object object = context.get(httpRequest);
            System.out.println(object);
            HttpServletRequest req = (HttpServletRequest) object;

            req.setAttribute(REQ_IPHONE_SDKS, iphoneSdks);
            req.setAttribute(REQ_IPHONE_SIMULATOR_SDKS, simSdks);
            System.out.println("Value initialized@@@@");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

我越来越

java.lang.NullPointerException
    at com.photon.phresco.framework.actions.intilalizer.run(Login.java:286)
    at java.lang.Thread.run(Thread.java:680)

我在网上发现了这个错误

ActionContext context = ActionContext.getContext();
System.out.println("context ===> " + context); // here i am getting null value

Answer 1

我只是想知道为什么需要启动一个新线程来将一些数据放入session

（你说你想做的事情，但实际上你没有在发布的代码中做，而是把东西放在request）

您只需通过您的操作implement SessionAware Interface

Actions that want access to the user's HTTP session attributes should implement this interface.

This will give them access to a Map where they can put objects that can be made available to subsequent requests.

Typical uses may be cached user data such as name, or a shopping cart.

它不是强制性的，但是it is a best practice用于从操作中访问会话，而不是请求操作上下文：

You can obtain the session attributes by asking the ActionContext or implementing SessionAware. Implementing SessionAware is preferred.

如果需要，这里有一个小的用法示例：http://www.splinter.com.au/how-to-use-sessions-with-struts-2/

Answer 2

if( loginSuccess(userInfo) ) {
    // redirecting to home page
    return HOME_PAGE;
    initializeDatas(); // calling thread after userInfo bean validated
}

那不行。该方法将在返回调用后结束。尝试先调用创建新线程的方法

if( loginSuccess(userInfo) ) {
    // redirecting to home page
    initializeDatas(); // calling thread after userInfo bean validated
    return HOME_PAGE;

}

Answer 3

来自Struts2Javadoc

The ActionContext is thread local which means that values stored in the ActionContext are unique per thread

您只需创建一个新线程，这样您的ThreadLocal变量在那里就不可用了。你应该这样做：

import com.opensymphony.xwork2.ActionContext;

if( loginSuccess(userInfo) ) {
   ActionContext context = ActionContext.getContext(); 
   initializeDatas(context); // calling thread after userInfo bean validated
   // redirecting to home page
   return HOME_PAGE;
}

最好的方法是将上下文传递给线程构造函数。但我不确定上下文是否是线程安全的