Google base的介绍、原理分析与应用实例
这几天使用Google base发布了一些东西，感觉用起来很方便而且很有用，关于这方面的博客现在基本还没有，这里就给大家介绍一下Gbase的原理与使用。
Gbase是一个帮助你发表虚拟类型的任何信息的免费服务，用户把信息发布到Gbase上，然后可以在google网站上搜索。这个服务就很有用，我们知道google 的搜索能力很强大，如果我们把我们的产品或者服务发布到Gbase上，就有可能让全世界的人看到我们发布的信息。
发布一个项目很简单，前提是必须得有一个google帐户，有账户的用户步骤如下：
1.进入google base网站首页：http://www.google.com/base/
2.点击“One at a time”，就进入了添加item页面，或者直接登录进去自己的Gbase首页，点击左下角“Add a item”按钮就可以添加item。
3.填完信息后，点击“Publish”即可。
这里添加的信息包括item类别（你可以选择已有的类别，或者自定义一个类别），然后填写可能包含的数量、金额和描述信息等等。上述方法是一次添加一个item的方式，如果你想批量添加，可以添加一个本地的xml文件，该文件符合google base规定的格式。
下面介绍如何使用Google base API编写Gbase应用，主要是给程序开发等编程人员提供参考。
Data item：在Google base 中描述一个单独的entry,他包含一组属性。
Attribute：描述内容的name/pair对，如![]()
Gbase是一个帮助你发表虚拟类型的任何信息的免费服务，用户把信息发布到Gbase上，然后可以在google网站上搜索。这个服务就很有用，我们知道google 的搜索能力很强大，如果我们把我们的产品或者服务发布到Gbase上，就有可能让全世界的人看到我们发布的信息。
发布一个项目很简单，前提是必须得有一个google帐户，有账户的用户步骤如下：
1.进入google base网站首页：http://www.google.com/base/
2.点击“One at a time”，就进入了添加item页面，或者直接登录进去自己的Gbase首页，点击左下角“Add a item”按钮就可以添加item。
3.填完信息后，点击“Publish”即可。
这里添加的信息包括item类别（你可以选择已有的类别，或者自定义一个类别），然后填写可能包含的数量、金额和描述信息等等。上述方法是一次添加一个item的方式，如果你想批量添加，可以添加一个本地的xml文件，该文件符合google base规定的格式。
下面介绍如何使用Google base API编写Gbase应用，主要是给程序开发等编程人员提供参考。
Data item：在Google base 中描述一个单独的entry,他包含一组属性。
Attribute：描述内容的name/pair对，如
<g:label>kung pao chicken</g:label>
一个entry的信息如下所示：
<? xml version ='1.0' ?>
< entry xmlns ='http://www.w3.org/2005/Atom'
xmlns:g ='http://base.google.com/ns/1.0' >
< author >
< name >Jane Doe </ name >
< email >[email protected] </ email >
</ author >
< category scheme ='http://www.google.com/type' term ='googlebase.item' />
< title type ='text' >He Jingxian's chicken </ title >
< content type ='xhtml' >
< div xmlns ='http://www.w3.org/1999/xhtml' >Delectable Sichuan specialty </ div >
</ content >
< link rel ='alternate' type ='text/html' href ='http://www.host.com/123456jsh9' />
< g:item_type >Recipes </ g:item_type >
< g:cooking_time >30 </ g:cooking_time >
< g:main_ingredient >chicken </ g:main_ingredient >
< g:main_ingredient >chili peppers </ g:main_ingredient >
< g:main_ingredient >peanuts </ g:main_ingredient >
< g:spices_used >Szechuan peppercorn </ g:spices_used >
< g:cook_technique >blackened </ g:cook_technique >
</ entry >
每一个item都有一个URL，或者说一个唯一的ID，用于标识这个item或者说entry，比我添加的一条记录的URL如下所示：
http://base.google.com/base/feeds/items/2139682888944988653
item ID是
2139682888944988653。
这个URL一般是程序代码中使用的，item自己生成的URL是http://base.google.com/base/a/6380400/D2139682888944988653，他们的实质都是一样的。
每一个Googel base API操作跟HTTP方法相同，你可以使用HTTP GET、POST、PUT和DELETE方法来操作。
一个查询的例子如下所示：
发送的HTTP请求是：
GET /base/feeds/snippets?bq=digital+camera
Content-Type: application/atom+xml
Authorization: AuthSub token=""
X-Google-Key: key=ABQIAAAA7VerLsOcLuBYXR7vZI2NjhTRERdeAiwZ9EeJWta3L_JZVS0bOBRIFbhTrQjhHE52fqjZvfabYYyn6A
由于响应信息比较多，这里就不显示了。
使用API添加item的代码如下所示。
InsertExample.java代码：
/* Copyright (c) 2006 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cn.edu.xidian;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.StringTokenizer;
/**
* Add a new item to Google Base using the Google Base data API server.
*/
public class InsertExample {
/**
* URL of the authenticated customer feed.
*/
private static final String ITEMS_FEED = "http://base.google.com/base/feeds/items";
/**
* The data item we are going to insert, in XML/Atom format.
*/
private static final String DATA_ITEM =
"<?xml version='1.0'?>\n" +
"<entry xmlns='http://www.w3.org/2005/Atom'\n" +
" xmlns:g='http://base.google.com/ns/1.0'>\n" +
" <g:item_type type='text'>repaceService</g:item_type>\n" +
" <title type='text'>EchoService_ID</title>\n" +
" <content type='xhtml'>08d8440b82554bad9a7a5ad9a1487</content>\n" +
"</entry>";
/**
* URL used for authenticating and obtaining an authentication token.
* More details about how it works:
* <code>http://code.google.com/apis/accounts/AuthForInstalledApps.html<code>
*/
private static final String AUTHENTICATION_URL = "https://www.google.com/accounts/ClientLogin";
/**
* Fill in your Google Account email here.
*/
private static final String EMAIL = "[email protected]";
/**
* Fill in your Google Account password here.
*/
private static final String PASSWORD = "yourpassword";
/**
* The main method constructs a <code>InsertExample</code> instance, obtains an
* authorization token and posts a new item to Google Base.
*/
public static void main(String[] args) throws MalformedURLException, IOException {
InsertExample insertExample = new InsertExample();
String token = insertExample.authenticate();
System.out.println("Obtained authorization token: " + token);
insertExample.postItem(token);
}
/**
* Inserts <code>DATA_ITEM</code> by making a POST request to
* <code>ITEMS_URL<code>.
* @param token authentication token obtained using <code>authenticate</code>
* @throws IOException if an I/O exception occurs while creating/writing/
* reading the request
*/
public void postItem(String token) throws IOException {
HttpURLConnection connection = (HttpURLConnection)(new URL(ITEMS_FEED)).openConnection();
connection.setDoInput(true);
connection.setDoOutput(true);
// Set the properties of the connection: the Http method, the content type
// of the POST request and the authorization header
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "application/atom+xml");
connection.setRequestProperty("Authorization", "GoogleLogin auth=" + token);
// Post the data item
OutputStream outputStream = connection.getOutputStream();
outputStream.write(DATA_ITEM.getBytes());
outputStream.close();
// Retrieve the output
int responseCode = connection.getResponseCode();
InputStream inputStream;
if (responseCode == HttpURLConnection.HTTP_CREATED) {
inputStream = connection.getInputStream();
} else {
inputStream = connection.getErrorStream();
}
// write the output to the console
System.out.println(toString(inputStream));
}
/**
* Retrieves the authentication token for the provided set of credentials.
* @return the authorization token that can be used to access authenticated
* Google Base data API feeds
*/
public String authenticate() {
// create the login request
String postOutput = null;
try {
URL url = new URL(AUTHENTICATION_URL);
postOutput = makeLoginRequest(url);
} catch (IOException e) {
System.out.println("Could not connect to authentication server: "
+ e.toString());
System.exit(1);
}
// Parse the result of the login request. If everything went fine, the
// response will look like
// HTTP/1.0 200 OK
// Server: GFE/1.3
// Content-Type: text/plain
// SID=DQAAAGgA...7Zg8CTN
// LSID=DQAAAGsA...lk8BBbG
// Auth=DQAAAGgA...dk3fA5N
// so all we need to do is look for "Auth" and get the token that comes after it
StringTokenizer tokenizer = new StringTokenizer(postOutput, "=\n ");
String token = null;
while (tokenizer.hasMoreElements()) {
if (tokenizer.nextToken().equals("Auth")) {
if (tokenizer.hasMoreElements()) {
token = tokenizer.nextToken();
}
break;
}
}
if (token == null) {
System.out.println("Authentication error. Response from server:\n" + postOutput);
System.exit(1);
}
return token;
}
/**
* Makes a HTTP POST request to the provided {@code url} given the provided
* {@code parameters}. It returns the output from the POST handler as a
* String object.
*
* @param url the URL to post the request
* @return the output from the handler
* @throws IOException if an I/O exception occurs while
* creating/writing/reading the request
*/
private String makeLoginRequest(URL url)
throws IOException {
// Create a login request. A login request is a POST request that looks like
// POST /accounts/ClientLogin HTTP/1.0
// Content-type: application/x-www-form-urlencoded
// [email protected]&Passwd=north23AZ&service=gbase&source=Insert Example
// Open connection
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Set properties of the connection
urlConnection.setRequestMethod("POST");
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);
urlConnection.setUseCaches(false);
urlConnection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
// Form the POST parameters
StringBuilder content = new StringBuilder();
content.append("Email=").append(URLEncoder.encode(EMAIL, "UTF-8"));
content.append("&Passwd=").append(URLEncoder.encode(PASSWORD, "UTF-8"));
content.append("&source=").append(URLEncoder.encode("Repace service example", "UTF-8"));
content.append("&service=").append(URLEncoder.encode("gbase", "UTF-8"));
OutputStream outputStream = urlConnection.getOutputStream();
outputStream.write(content.toString().getBytes("UTF-8"));
outputStream.close();
// Retrieve the output
int responseCode = urlConnection.getResponseCode();
InputStream inputStream;
if (responseCode == HttpURLConnection.HTTP_OK) {
inputStream = urlConnection.getInputStream();
} else {
inputStream = urlConnection.getErrorStream();
}
return toString(inputStream);
}
/**
* Writes the content of the input stream to a <code>String<code>.
*/
private String toString(InputStream inputStream) throws IOException {
String string;
StringBuilder outputBuilder = new StringBuilder();
if (inputStream != null) {
BufferedReader reader =
new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
while (null != (string = reader.readLine())) {
outputBuilder.append(string).append('\n');
}
}
return outputBuilder.toString();
}
}
如果email和密码正确，验证通过，则在你的email帐号下的Gbase下添加了一条item，这个item需要大概1天的时间能够通过google搜索。
QueryExample3.java代码：
/* Copyright (c) 2006 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cn.edu.xidian;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.StringTokenizer;
/**
* Display all items of a specific customer.
*/
public class QueryExample3 {
/**
* URL of the authenticated customer feed.
*/
private static final String ITEMS_FEED = "http://base.google.com/base/feeds/items/2139682888944988653";
/**
* URL used for authenticating and obtaining an authentication token.
* More details about how it works:
* <code>http://code.google.com/apis/accounts/AuthForInstalledApps.html<code>
*/
private static final String AUTHENTICATION_URL = "https://www.google.com/accounts/ClientLogin";
/**
* Fill in your Google Account email here.
*/
private static final String EMAIL = "[email protected]";
/**
* Fill in your Google Account password here.
*/
private static final String PASSWORD = "yourpassword";
/**
* Create a <code>QueryExample3</code> instance and call
* <code>displayMyItems</code>, which displays all items that belong to the
* currently authenticated user.
*/
public static void main(String[] args) throws IOException {
QueryExample3 queryExample = new QueryExample3();
String token = queryExample.authenticate();
queryExample.displayMyItems(token);
}
/**
* Retrieves the authentication token for the provided set of credentials.
* @return the authorization token that can be used to access authenticated
* Google Base data API feeds
*/
public String authenticate() {
// create the login request
String postOutput = null;
try {
URL url = new URL(AUTHENTICATION_URL);
postOutput = makeLoginRequest(url);
} catch (IOException e) {
System.out.println("Could not connect to authentication server: "
+ e.toString());
System.exit(1);
}
// Parse the result of the login request. If everything went fine, the
// response will look like
// HTTP/1.0 200 OK
// Server: GFE/1.3
// Content-Type: text/plain
// SID=DQAAAGgA...7Zg8CTN
// LSID=DQAAAGsA...lk8BBbG
// Auth=DQAAAGgA...dk3fA5N
// so all we need to do is look for "Auth" and get the token that comes after it
StringTokenizer tokenizer = new StringTokenizer(postOutput, "=\n ");
String token = null;
while (tokenizer.hasMoreElements()) {
if (tokenizer.nextToken().equals("Auth")) {
if (tokenizer.hasMoreElements()) {
token = tokenizer.nextToken();
}
break;
}
}
if (token == null) {
System.out.println("Authentication error. Response from server:\n" + postOutput);
System.exit(1);
}
return token;
}
/**
* Displays the "items" feed, that is the feed that contains the items that
* belong to the currently authenticated user.
*
* @param token the authorization token, as returned by
* <code>authenticate<code>
* @throws IOException if an IOException occurs while creating/reading the
* request
*/
public void displayMyItems(String token) throws MalformedURLException, IOException {
HttpURLConnection connection = (HttpURLConnection)(new URL(ITEMS_FEED)).openConnection() ;
// Set properties of the connection
connection.setRequestMethod("GET");
connection.setRequestProperty("Authorization", "GoogleLogin auth=" + token);
int responseCode = connection.getResponseCode();
InputStream inputStream;
if (responseCode == HttpURLConnection.HTTP_OK) {
inputStream = connection.getInputStream();
} else {
inputStream = connection.getErrorStream();
}
System.out.println(toString(inputStream));
}
/**
* Makes a HTTP POST request to the provided {@code url} given the provided
* {@code parameters}. It returns the output from the POST handler as a
* String object.
*
* @param url the URL to post the request
* @return the output from the Google Accounts server, as string
* @throws IOException if an I/O exception occurs while
* creating/writing/reading the request
*/
private String makeLoginRequest(URL url)
throws IOException {
// Create a login request. A login request is a POST request that looks like
// POST /accounts/ClientLogin HTTP/1.0
// Content-type: application/x-www-form-urlencoded
// [email protected]&Passwd=north23AZ&service=gbase&source=Insert Example
// Open connection
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Set properties of the connection
urlConnection.setRequestMethod("POST");
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);
urlConnection.setUseCaches(false);
urlConnection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
// Form the POST parameters
StringBuilder content = new StringBuilder();
content.append("Email=").append(URLEncoder.encode(EMAIL, "UTF-8"));
content.append("&Passwd=").append(URLEncoder.encode(PASSWORD, "UTF-8"));
content.append("&service=").append(URLEncoder.encode("gbase", "UTF-8"));
content.append("&source=").append(URLEncoder.encode("Repace service example", "UTF-8"));
OutputStream outputStream = urlConnection.getOutputStream();
outputStream.write(content.toString().getBytes("UTF-8"));
outputStream.close();
// Retrieve the output
int responseCode = urlConnection.getResponseCode();
InputStream inputStream;
if (responseCode == HttpURLConnection.HTTP_OK) {
inputStream = urlConnection.getInputStream();
} else {
inputStream = urlConnection.getErrorStream();
}
return toString(inputStream);
}
/**
* Writes the content of the input stream to a <code>String<code>.
*/
private String toString(InputStream inputStream) throws IOException {
String string;
StringBuilder outputBuilder = new StringBuilder();
if (inputStream != null) {
BufferedReader reader =
new BufferedReader(new InputStreamReader(inputStream));
while (null != (string = reader.readLine())) {
outputBuilder.append(string).append('\n');
}
}
return outputBuilder.toString();
}
}
改代码的执行结果如下：
<? xml version ='1.0' encoding ='UTF-8' ?> < entry xmlns ='http://www.w3.org/2005/Atom' xmlns:gm ='http://base.google.com/ns-metadata/1.0' xmlns:g ='http://base.google.com/ns/1.0' xmlns:batch ='http://schemas.google.com/gdata/batch' > < id >http://www.google.com/base/feeds/items/2139682888944988653 </ id > < published >2009-08-01T12:55:09.000Z </ published > < updated >2009-08-01T12:55:09.000Z </ updated > < category scheme ='http://base.google.com/categories/itemtypes' term ='repaceService' /> < title type ='text' >EchoService_ID </ title > < content type ='html' >08d8440b82554bad9a7a5ad9a1487 </ content > < link rel ='alternate' type ='text/html' href ='http://base.google.com/base/a/6380400/D2139682888944988653' /> < link rel ='self' type ='application/atom+xml' href ='http://www.google.com/base/feeds/items/2139682888944988653' /> < link rel ='edit' type ='application/atom+xml' href ='http://www.google.com/base/feeds/items/2139682888944988653' /> < author > < name >Panpan Zhan </ name > < email >[email protected] </ email > </ author > < g:target_country type ='text' >US </ g:target_country > < g:expiration_date type ='dateTime' >2038-01-19T03:14:07Z </ g:expiration_date > < g:customer_id type ='int' >6380400 </ g:customer_id > < g:item_language type ='text' >en </ g:item_language > < g:item_type type ='text' >repaceService </ g:item_type > < gd:feedLink xmlns:gd ='http://schemas.google.com/g/2005' rel ='media' href ='http://www.google.com/base/feeds/items/2139682888944988653/media' countHint ='0' /> </ entry >
这样就完成了一些简单的Gbase操作的例子。