GAE for Java 的留言版範例

GAE 雲端程式

簡介

環境安裝

管理介面

資料庫

中文編碼

程式範例

Hello

Guestbook

WikiBox

TxtDBase

訊息

相關網站

參考文獻

最新修改

簡體版

English

專案下載：guestbook.zip

最後成果

  1. http://ccckmittest.appspot.com/guestbook.jsp

操作方法

請按照下列入門指南建立一個 GAE for Java 的留言版程式。

  1. Google 應用服務引擎:入門指南：Java — http://code.google.com/intl/zh-TW/appengine/docs/java/gettingstarted/

問題

  1. 我遇到了 Your Web Application Project must be configured to use a JDK in order to use JSPs. 這個錯誤訊息
  2. 該指南的中文版有一個錯誤 (英文版是對的)，就是在最後 SignGuestbookServlet 當中，會轉到 /intl/zh-TW/guestbook.jsp 裡面，這樣就會找不到我們的應用，應該改為 /guestbook.jsp 就可以了。
package guestbook;

import java.io.IOException;
import java.util.logging.Logger;
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;

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();

        String content = req.getParameter("content");
        if (content == null) {
            content = "(No greeting)";
        }
        if (user != null) {
            log.info("Greeting posted by user " + user.getNickname() + ": " + content);
        } else {
            log.info("Greeting posted anonymously: " + content);
        }
        resp.sendRedirect("/intl/zh-TW/guestbook.jsp"); // 錯誤：改為 /guestbook.jsp
    }
}

程式範例

檔案：guestbook.jsp

<%@ 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();
    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>

檔案：Web.xml

<?xml version="1.0" encoding="utf-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
    <servlet>
        <servlet-name>Guestbook</servlet-name>
        <servlet-class>guestbook.GuestbookServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Guestbook</servlet-name>
        <url-pattern>/guestbook</url-pattern>
    </servlet-mapping>
    <welcome-file-list>
        <welcome-file>guestbook.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>sign</servlet-name>
        <servlet-class>guestbook.SignGuestbookServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>sign</servlet-name>
        <url-pattern>/sign</url-pattern>
    </servlet-mapping>    
</web-app>

檔案：Greeting.java

package guestbook;
 
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;
    }
}

檔案：GuestbookServlet

package guestbook;
 
import java.io.IOException;
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;
 
public class GuestbookServlet extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
              throws IOException {
        UserService userService = UserServiceFactory.getUserService();
        User user = userService.getCurrentUser();
 
        if (user != null) {
            resp.setContentType("text/plain");
            resp.getWriter().println("Hello, " + user.getNickname());
        } else {
            resp.sendRedirect(userService.createLoginURL(req.getRequestURI()));
        }
    }
}

檔案：PMF.java

package guestbook;
 
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;
    }
}

檔案：SignGuestbookServlet

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();
 
        String content = req.getParameter("content");
        Date date = new Date();
        Greeting greeting = new Greeting(user, content, date);
 
        PersistenceManager pm = PMF.get().getPersistenceManager();
        try {
            pm.makePersistent(greeting);
        } finally {
            pm.close();
        }
        resp.sendRedirect("/guestbook.jsp");
    }
}

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page revision: 7, last edited: 03 Oct 2010 05:18
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