Go语言视频零基础入门到精通

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　　在做游戏开发的时候，很多游戏都会提供一个全球分数排名的的功能，这就需要使用服务器了，当然，你可以选择搭建自己的服务器，但从成本，稳定性和开发周期上看，我认为Google AppEngine是个很不错的选择.

java代码：
import java.util.Date;

import javax.jdo.annotations.IdGeneratorStrategy;

import javax.jdo.annotations.IdentityType;

import javax.jdo.annotations.PersistenceCapable;

import javax.jdo.annotations.Persistent;

import javax.jdo.annotations.PrimaryKey;





//标记对象可以持久化

@PersistenceCapable(identityType = IdentityType.APPLICATION)

public class Employee {

//标记主键，作以后查询之用

@PrimaryKey

@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)

private String firstName;





@Persistent

private String lastName;





@Persistent

private Date birthDate;





public Employee(String firstName, String lastName, Date birthDate) {

this.firstName = firstName;

this.lastName = lastName;

this.birthDate = birthDate;

}





public String getFirstName() {

return firstName;

}

}
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       步骤2.存取Bean(可以写在Servlet的doGet()或者doPost()里面):

java代码：
import java.io.IOException;

import java.util.Date;

import javax.jdo.PersistenceManager;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;





@SuppressWarnings("serial")

public class HelloServlet extends HttpServlet {

public void doGet(HttpServletRequest req,

HttpServletResponse resp)throws IOException {





resp.setContentType("text/plain");





Employee e = new Employee("Alfred", "Smith", new Date());

//获取用以存取对象的PersistenceManager

PersistenceManager pm = PMF.get().getPersistenceManager();

try {

//存储对象

resp.getWriter().println("saving object!");

pm.makePersistent(e);

}catch(Exception ex){

resp.getWriter().println("cannot persistent!");

ex.printStackTrace();

}

finally {

pm.close();

}





try{

//再次获取用以存取对象的PersistenceManager

pm = PMF.get().getPersistenceManager();

//由主键检索对象，Alfred之前被定义为主键的

Employee newE = pm.getObjectById(Employee.class, "Alfred");

//读取新对象的信息检测对象检索是否成功

resp.getWriter().println("Employee:"+newE.getFirstName());

}catch(Exception ex){

ex.printStackTrace();

resp.getWriter().println("cannot get data!");

pm.close();

}

}





@Override

protected void doPost(HttpServletRequest req,

HttpServletResponse resp)throws ServletException, IOException {

this.doGet(req, resp);

}

}
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       其中PMF类的代码如下，没看错应该是个单例模式：

java代码：
import javax.jdo.JDOHelper;

import javax.jdo.PersistenceManagerFactory;





public final class PMF {

private static final PersistenceManagerFactory pmfInstance =

JDOHelper.getPersistenceManagerFactory("transactions-optional");





private PMF() {}





public static PersistenceManagerFactory get() {

return pmfInstance;

}

}
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        使用Google 账户认证服务：

java代码：
import java.io.IOException;





import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;





import com.google.appengine.api.users.UserService;

import com.google.appengine.api.users.UserServiceFactory;





public class GoogleAccount extends HttpServlet{





@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

//创建用户服务

UserService userService = UserServiceFactory.getUserService();





String thisURL = req.getRequestURI();

//通过请求对象的 getUserPrincipal() 方法测试用户是否使用 Google 帐户登录

if (req.getUserPrincipal() != null) {

//如果有登录，则创建Login地址

resp.getWriter().println("<p>Hello, " +

req.getUserPrincipal().getName() +

"! You can <a href=\"" +

userService.createLogoutURL(thisURL) +

"\">sign out</a>.</p>");

} else {

//如果没有登录，则创建Login地址

resp.getWriter().println("<p&gtlease <a href=\"" +

userService.createLoginURL(thisURL) +

"\">sign in</a>.</p>");

}

}





@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

doGet(req, resp);

}

}
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