使用 Java 開發 Facebook Web App - 3 - Programming Design Notes

上一回: 使用 Java 開發 Facebook Web App - 2

今次我們將 IndexServlet 修改一下，不再顯示 Hello World，改為顯示用戶朋友的資料，這個功能應該是非常常用的。

首先將 IndexServlet 的 doGet 清空，並加入以下程式碼:

protected void doGet(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    HttpSession session = request.getSession();
    FacebookXmlRestClient xmlClient = FacebookFilter.getUserClient(session);
}

首先先取得用戶的 FacebookXmlRestClient，利用 FacebookXmlRestClient 提供的方法去存取用戶資料。而我比較喜歡用 FacebookJaxbRestClient，FacebookJaxbRestClient 可以將 Facebook 回傳的 XML 自動轉為 Java Object。

對這種技術有興趣的朋友可以參考以下網址。
Java Architecture for XML Binding (JAXB): http://java.sun.com/developer/technicalArticles/WebServices/jaxb/

那怎麼將 FacebookXmlRestClient 轉為使用 FacebookJaxbRestClient? 轉換方法非常簡單，加入以下程式碼:

FacebookJaxbRestClient jaxbClient = new FacebookJaxbRestClient(
        xmlClient.getApiKey(), xmlClient.getSecret(), xmlClient
                .getCacheSessionKey());

設定好 Rest Client 後可以開始進入正題，存取朋友資料前要先知道朋友的 ID 才行，以下程式碼是拿取用戶所有朋友 ID 後再將 ID 放到 List 內。

try {

    // Get user friend list
    FriendsGetResponse friendResponse = (FriendsGetResponse) jaxbClient
            .friends_get(jaxbClient.getCacheUserId());
    List<Long> friends = friendResponse.getUid();
} catch (FacebookException e) {
    e.printStackTrace();
}

現在有一個 List 裝了所有的 ID，那便可以批次地拿到相對應 ID 的用戶資料。在這裡我只選擇拿取用戶 ID，名稱，性別和生日日期。

// Get friend info
UsersGetInfoResponse userResponse = jaxbClient.users_getInfo(
        friends, EnumSet.of(ProfileField.UID, ProfileField.NAME, ProfileField.SEX,
                ProfileField.BIRTHDAY));
List<User> friendsInfo = userResponse.getUser();

ProfileField API: ProfileField

現在我們已經拿到用戶資料了。再來便是將資料傳給 JSP，讓 JSP 顯示出來。

Map<String, Object> model = new HashMap<String, Object>();
model.put("friendsInfo", friendsInfo);
request.setAttribute("model", model);

RequestDispatcher dispatcher = request
        .getRequestDispatcher("/WEB-INF/pages/index.jsp");

dispatcher.forward(request, response);

完整的 IndexServlet:

package com.blogspot.lawpronotes.servlet;

import java.io.IOException;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.blogspot.lawpronotes.filter.FacebookFilter;
import com.google.code.facebookapi.FacebookException;
import com.google.code.facebookapi.FacebookJaxbRestClient;
import com.google.code.facebookapi.FacebookXmlRestClient;
import com.google.code.facebookapi.ProfileField;
import com.google.code.facebookapi.schema.FriendsGetResponse;
import com.google.code.facebookapi.schema.User;
import com.google.code.facebookapi.schema.UsersGetInfoResponse;

/**
 * Servlet implementation class IndexServlet
 */
public class IndexServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public IndexServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        FacebookXmlRestClient xmlClient = FacebookFilter.getUserClient(session);
        FacebookJaxbRestClient jaxbClient = new FacebookJaxbRestClient(
                xmlClient.getApiKey(), xmlClient.getSecret(), xmlClient
                        .getCacheSessionKey());
        try {

            // Get user friend list
            FriendsGetResponse friendResponse = (FriendsGetResponse) jaxbClient
                    .friends_get(jaxbClient.getCacheUserId());
            List<Long> friends = friendResponse.getUid();

            // Get friend info
            UsersGetInfoResponse userResponse = jaxbClient.users_getInfo(
                    friends, EnumSet.of(ProfileField.UID, ProfileField.NAME,
                            ProfileField.SEX, ProfileField.BIRTHDAY));
            List<User> friendsInfo = userResponse.getUser();

            Map<String, Object> model = new HashMap<String, Object>();
            model.put("friendsInfo", friendsInfo);
            request.setAttribute("model", model);

            RequestDispatcher dispatcher = request
                    .getRequestDispatcher("/WEB-INF/pages/index.jsp");
            dispatcher.forward(request, response);

        } catch (FacebookException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

在 JSP 我選擇用 foreach 將所有朋友資料也列印出來，記得要加上:

<%@taglib uri="http://java.sun.com/jsp/jstl/core" 
prefix="c" %>

完整的 JSP:

<?xml version="1.0" encoding="UTF-8"?>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" isELIgnored="false" %>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:fb="http://www.facebook.com/2008/fbml">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
        <title>Index</title>
    </head>
    <body>
        <table style="text-align:center;">
            <thead>
                <tr>
                    <th>
                        Image
                    </th>
                    <th>
                        Name
                    </th>
     <th>
                        Sex
                    </th>
     <th>
                        Birthday
                    </th>
                </tr>
            </thead>
            <c:forEach var="info" items="${model['friendsInfo']}">
                <tr>
                    <td>
                        <img src="http://graph.facebook.com/${info['uid']}/picture/" alt="profile image" />
                    </td>
                    <td>
                        ${info['name']}
                    </td>
                    <td>
                        ${info['sex']}
                    </td>
                    <td>
                        ${info['birthday']}
                    </td>
                </tr>
            </c:forEach>
        </table>
    </body>
</html>