Google AppEngine会话示例

我刚刚在我的Google AppEngine/Java + GWT应用程序中启用了Session.我该如何使用它？如何从中获取会话ID和播放所有好处？是否有任何简单登录页面的真实示例,我只是输入LoginName和Password,然后通过RPC调用进入服务器,对数据库进行身份验证并将会话ID发送回客户端.

我已经有以下代码,但不知道下一步该做什么:

GWT登录表格:

public class LoginForm {
    private final LoginServiceAsync loginService = GWT.create(LoginService.class);

    VerticalPanel loginVp = new VerticalPanel();
    TextBox loginTxt = new TextBox();
    TextBox passTxt = new TextBox();

    Button loginBtn = new Button("Login");

    public Widget getLoginWidget(){

        loginBtn.addClickHandler(new ClickHandler(){

            public void onClick(ClickEvent arg0) {

                loginService.authenticateUser(loginTxt.getText(), passTxt.getText(), 
                        new AsyncCallback(){

                            public void onFailure(Throwable caught) {
                                InfoPanel.show(InfoPanelType.HUMANIZED_MESSAGE, "No Connetion", "Problem conneting to the server.");
                            }

                            public void onSuccess(String result) {
                                InfoPanel.show(InfoPanelType.HUMANIZED_MESSAGE, "Session ID", "Your session id is: " + result);

                                GWT.log("Setting up session", null);
                                String sessionID = result;
                                final long DURATION = 1000 * 60 * 60 * 24 * 14; //duration remembering login. 2 weeks
                                Date expires = new Date(System.currentTimeMillis() + DURATION);
                                Cookies.setCookie("sid", sessionID, expires, null, "/", false);
                            }
                        }
                );  
            }   
        });

        loginVp.add(loginTxt);
        loginVp.add(passTxt);
        loginVp.add(loginBtn);

        return loginVp;
    }
}

RPC Servlet:

public class LoginServiceImpl extends RemoteServiceServlet implements LoginService{ 
    //Sends back to the client session id
    public String authenticateUser(String login, String password){
        String sessionId = new String();

        // TODO: figure out how to work with session id in GAE/J
        sessionId = "How to get session id?";

        return sessionId;
    }

    public Boolean checkIfSessionIsValid(String sessionId){

        //TODO: figure out how to check user's credentials  
        return true;
    }
}

任何正确方向的提示都会有所帮助.谢谢.

启用会话支持为您提供标准的Servlet HttpSession.

这将通过cookie(称为JSESSONID)进行跟踪,该cookie由封面下的servlet容器管理.您无需关心会话ID.

然后,您可以设置将与会话关联的属性(服务器端)(以便以后可以检索它们).

HttpServletRequest request = this.getThreadLocalRequest();

HttpSession session = request.getSession();

// in your authentication method
if(isCorrectPassword)
   session.setAttribute("authenticatedUserName", "name");

// later
 if (session.getAttribute("authenticatedUserName") != null)

这也适用于GWT的Ajax请求.有关更多详细信息,请参阅任何Servlet教程.

GAE上的会话(与其他servlet引擎相比)的缺点是它们每次都被序列化并从数据库加载,这可能很昂贵,特别是如果你在那里放了大量数据.

以下是如何在GAE中进行会话的方法:

this.getThreadLocalRequest().getSession();