外幣機器人Android: Google App Engine

1.jdoconfig.xml(用eclipse產生Web Application Project時會自動產生，在src/META-INF/)
2.PMF.java用來跟App Engine datastore溝通


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;
}
}

3.利用JDO Class自訂資料欄位


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

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Greeting {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Long id;

@Persistent
private User author;

@Persistent
private String content;

@Persistent
private Date date;

public Greeting(User author, String content, Date date) {
  this.author = author;
  this.content = content;
  this.date = date;
}

public Long getId() {
  return id;
}

public User getAuthor() {
  return author;
}

public String getContent() {
  return content;
}

public Date getDate() {
  return date;
}

public void setAuthor(User author) {
  this.author = author;
}

public void setContent(String content) {
  this.content = content;
}

public void setDate(Date date) {
  this.date = date;
}
}

4.用servlet新增一筆紀錄


package guestbook;

import java.io.IOException;
import java.util.Date;
import java.util.logging.Logger;
import javax.jdo.PersistenceManager;
import javax.servlet.http.*;
import com.google.appengine.api.users.User;
import com.google.appengine.api.users.UserService;
import com.google.appengine.api.users.UserServiceFactory;

import guestbook.Greeting;
import guestbook.PMF;

public class SignGuestbookServlet extends HttpServlet {
private static final Logger log = Logger.getLogger(SignGuestbookServlet.class.getName());

public void doPost(HttpServletRequest req, HttpServletResponse resp)
          throws IOException {
  UserService userService = UserServiceFactory.getUserService();
  User user = userService.getCurrentUser();//取得登入gmail的用戶名稱

  String content = req.getParameter("content");//要存入的字串
  Date date = new Date();//產生目前日期時間
  Greeting greeting = new Greeting(user, content, date);//將資料存入JDO物件

  PersistenceManager pm = PMF.get().getPersistenceManager();//建立一個新的實例PersistenceManager
  try {
      pm.makePersistent(greeting);//JDO物件的資料寫入App Engine datastore
  } finally {
      pm.close();
  }

  resp.sendRedirect("/guestbook.jsp");
}
}

5.用JSP讀取資料


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="java.util.List" %>
<%@ page import="javax.jdo.PersistenceManager" %>
<%@ page import="com.google.appengine.api.users.User" %>
<%@ page import="com.google.appengine.api.users.UserService" %>
<%@ page import="com.google.appengine.api.users.UserServiceFactory" %>
<%@ page import="guestbook.Greeting" %>
<%@ page import="guestbook.PMF" %>

<html>
<head>
  <link type="text/css" rel="stylesheet" href="/stylesheets/main.css" />
</head>

<body>

<%
  UserService userService = UserServiceFactory.getUserService();
  User user = userService.getCurrentUser();
  if (user != null) {
%>
<p>Hello, <%= user.getNickname() %>! (You can
<a href="<%= userService.createLogoutURL(request.getRequestURI()) %>">sign out</a>.)</p>
<%
  } else {
%>
<p>Hello!
<a href="<%= userService.createLoginURL(request.getRequestURI()) %>">Sign in</a>
to include your name with greetings you post.</p>
<%
  }
%>

<%
  PersistenceManager pm = PMF.get().getPersistenceManager();
  String query = "select from " + Greeting.class.getName() + " order by date desc range 0,5";
  List<Greeting> greetings = (List<Greeting>) pm.newQuery(query).execute();
  if (greetings.isEmpty()) {
%>
<p>The guestbook has no messages.</p>
<%
  } else {
      for (Greeting g : greetings) {
          if (g.getAuthor() == null) {
%>
<p>An anonymous person wrote:</p>
<%
          } else {
%>
<p><b><%= g.getAuthor().getNickname() %></b> wrote:</p>
<%
          }
%>
<blockquote><%= g.getContent() %></blockquote>
<%
      }
  }
  pm.close();
%>

  <form action="/sign" method="post">
    <div><textarea name="content" rows="3" cols="60"></textarea></div>
    <div><input type="submit" value="Post Greeting" /></div>
  </form>

</body>
</html>

資料來源http://code.google.com/intl/en/appengine/docs/java/gettingstarted/usingdatastore.html

--web.xml


<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
 PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<!-- Servlets -->
<servlet>
 <servlet-name>hello</servlet-name>
 <servlet-class>org.example.HelloAppEngineServlet</servlet-class>
</servlet>

<servlet-mapping>
 <servlet-name>hello</servlet-name>
 <url-pattern>/helloappengine</url-pattern>
</servlet-mapping>

<!-- Default page to serve -->
<welcome-file-list>
 <welcome-file>index.html</welcome-file>
</welcome-file-list>

</web-app>

---Servlet


package org.example;

import java.io.IOException;
import javax.servlet.http.*;

public class HelloAppEngineServlet extends HttpServlet {
 public void doGet(HttpServletRequest req, HttpServletResponse resp)
         throws IOException {
     resp.setContentType("text/plain");
     resp.setCharacterEncoding("UTF-8");
//resp.setContentType("text/html; charset=UTF-8");

     resp.getWriter().println("Hello, world
");
     resp.getWriter().println("Hello, 黃金甲一號");
 }
}

---
result

http://localhost:8080/helloappengine

check the page source
---------------
Hello, world
Hello, 黃金甲一號

外幣機器人Android

2009年7月26日星期日

Using the Datastore with JDO #2

2009年7月19日星期日

Using the Datastore with JDO

2009年7月17日星期五

Use Servlet to write a hello world class

2009年6月10日星期三

Google App Engine

2009年7月26日 星期日