gwt - HttpServletRequest 请求 = this.getThreadLocalRequest() 返回 null？

Question

我想在 GWT 应用程序中获取 session 的属性。我得到这样的 session

HttpServletRequest request = this.getThreadLocalRequest();
System.out.println("Check HttpServletRequest");       
HttpSession session = request.getSession();

但是 this.getThreadLocalRequest()总是 null .

代码 :

客户:

@RemoteServiceRelativePath("service.s3gwt")
public interface getAttributeSession extends RemoteService 
{
    String getSessionAttribute(String name);
}

public interface getAttributeSessionAsync 
{
    void getSessionAttribute(String name, AsyncCallback<String> callback);
}

服务器:

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;
import daTotNghiep.client.service.getAttributeSession;

public class getAttributeSessionImpl extends RemoteServiceServlet implements getAttributeSession 
{
    private static final long serialVersionUID = 1L;

    public String getSessionAttribute(String name) 
    {
    // TODO Auto-generated method stub

    HttpServletRequest request = this.getThreadLocalRequest();
    System.out.println("Check HttpServletRequest");
    if(request == null) System.out.println("SO BAD");

   //   HttpSession session = request.getSession();
   // System.out.println("ID session "+session.getId());

     return "";
    }
}

调用方法时 getSessionAttribute()我看到了 this.getThreadLocalRequest()总是返回 null .所以为什么？以及如何修复它？

Answer 1

方法getThreadLocalRequest()在类 AbstractRemoteServiceServlet 中实现，由 RemoteServiceServlet 继承.实现设置字段 perThreadRequest (由 getThreadLocalRequest() 使用)仅用于方法 doPost() .这意味着，getThreadLocalRequest()只有在 POST 请求中调用时才会返回该请求，并且仅当您没有覆盖 doPost() 时才返回该请求。无需调用 super 方法。

所以要确保getThreadLocalRequest()不返回 null

确保您在 POST 请求中调用它(而不是 GET 或其他一些 HTTP 请求类型)。

确保您没有覆盖 doPost()无需调用 super.doPost()