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如何用Google APIs和Google的应用系统进行集成(3)----调用Google Discovery RESTful服务
说了这么多,那么首先允许我以Google Discovery RESTful服务为例,给大家演示如何用最普通的Java代码调用Google Discovery RESTful服务。
引言:
在“如何用Google APIs和Google的应用系统进行集成(2)”的下面,我列出了当前Google APIs支持的所有的Google APIs。其实这个表格是我用代码调用Google Discovery RESTFul服务自动生成的。具体的步骤和代码如下:
(1) 访问Google Discovery RESTFul的服务:https://www.googleapis.com/discovery/v1/apis 可以获得RESTFul服务返回的结果:通过访问 JSONtoStringConverter-->readJSONSAsString()
package com.henry.json.gson.googlediscovery; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; public class JSONtoStringConverter { private String url_path="https://www.googleapis.com/discovery/v1/apis"; public String readJSONSAsString(){ InputStream in=this.getJSONSchemaInputStream(); return readJSONSAsString(in); } private InputStream getJSONSchemaInputStream() { InputStream ipStream = null; if (url_path == null) { throw new IllegalArgumentException("The URL Path can't be empty!!!"); } try { URL url = new URL(url_path); HttpURLConnection httpConnection = (HttpURLConnection) url .openConnection(); httpConnection.setRequestMethod("GET"); httpConnection.setReadTimeout(30000); httpConnection.setDoInput(true); ipStream = httpConnection.getInputStream(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return ipStream; } private String readJSONSAsString(InputStream in){ String jsonString=""; ByteArrayOutputStream baosArrayOutputStream=new ByteArrayOutputStream(); byte[] bytes=new byte[1024]; int len=0; try { while((len=in.read(bytes))!=-1){ baosArrayOutputStream.write(bytes, 0, len); } jsonString=new String(baosArrayOutputStream.toByteArray(),"utf-8"); } catch (IOException e) { e.printStackTrace(); } System.out.println(jsonString); return jsonString; } public static void main(String[] args) { JSONtoStringConverter jSONtoStringConverter=new JSONtoStringConverter(); jSONtoStringConverter.readJSONSAsString(); } }
(2) 解析返回的JSON数据,但是解析以前,我们需要建立相应的JavaBean,这样就能把JSON的对象和Java的对象映射起来。
2.1 GoogleDiscoveryBean
package com.henry.json.gson.googlediscovery; import java.util.List; public class GoogleDiscoveryBean { private String kind; private String discoveryVersion; private List<Items> items; public String getKind() { return kind; } public void setKind(String kind) { this.kind = kind; } public String getDiscoveryVersion() { return discoveryVersion; } public void setDiscoveryVersion(String discoveryVersion) { this.discoveryVersion = discoveryVersion; } public List<Items> getItems() { return items; } public void setItems(List<Items> items) { this.items = items; } @Override public String toString(){ return kind+"--"+discoveryVersion+"--size:"+items.size(); } }
2.2 Items
package com.henry.json.gson.googlediscovery; /* "kind": "discovery#directoryItem", "id": "adexchangebuyer:v1", "name": "adexchangebuyer", "version": "v1", "title": "Ad Exchange Buyer API", "description": "Lets you manage your Ad Exchange Buyer account.", "discoveryRestUrl": "https://www.googleapis.com/discovery/v1/apis/adexchangebuyer/v1/rest", "discoveryLink": "./apis/adexchangebuyer/v1/rest", "icons": { "x16": "http://www.google.com/images/icons/product/doubleclick-16.gif", "x32": "http://www.google.com/images/icons/product/doubleclick-32.gif" }, "documentationLink": "https://developers.google.com/ad-exchange/buyer-rest", "preferred": false */ public class Items { private String kind; private String id; private String name; private String version; private String title; private String description; private String discoveryRestUrl; private String discoveryLink; private String documentationLink; private String preferred; public String getKind() { return kind; } public void setKind(String kind) { this.kind = kind; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getVersion() { return version; } public void setVersion(String version) { this.version = version; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } public String getDiscoveryRestUrl() { return discoveryRestUrl; } public void setDiscoveryRestUrl(String discoveryRestUrl) { this.discoveryRestUrl = discoveryRestUrl; } public String getDiscoveryLink() { return discoveryLink; } public void setDiscoveryLink(String discoveryLink) { this.discoveryLink = discoveryLink; } public String getDocumentationLink() { return documentationLink; } public void setDocumentationLink(String documentationLink) { this.documentationLink = documentationLink; } public String getPreferred() { return preferred; } public void setPreferred(String preferred) { this.preferred = preferred; } }
(3) 下载JSON java的库: http://code.google.com/p/google-gson/
GSon是谷歌官方提供的解析JSON数据:
1.谷歌GSON这个Java类库可以把Java对象转换成JSON,也可以把JSON字符串转换成一个相等的Java对象。
2.Gson支持任意复杂Java对象包括没有源代码的对象。
(4) 创建一个GoogleGSonTools: 这个类会把Google Discovery RESTful服务返回的JSON的字符串,自动转换成GoogleDiscoveryBean对象,这个方法不到10行,就这么简单。
package com.henry.json.gson.googlediscovery; import com.google.gson.Gson; public class GoogleGSonTools { public static <T> T getGoogleDiscoveryBean(String josnString, Class<T> clazz) { T t = null; try { Gson gson = new Gson(); t = gson.fromJson(josnString, clazz); } catch (Exception e) { } return t; } }
(5)结合上面的(1)~(4),我们把其返回的值,格式化成一个HTML的表格。
package com.henry.json.gson.googlediscovery; import java.util.List; public class GoogleAPIsListViewService { public String listAllGoogleAPIs(){ StringBuilder sbBuilder=new StringBuilder("<table border=\"1\" style=\"word-break:break-all; word-wrap:break-word;\"> <tr><td>序号</td><td>API 标题</td><td>名字</td><td>版本</td><td>RestFul请求的URL</td><td>RestFul请求的URL</td></tr>"); JSONtoStringConverter jSONtoStringConverter=new JSONtoStringConverter(); String json=jSONtoStringConverter.readJSONSAsString(); GoogleDiscoveryBean googleDiscoveryBean=GoogleGSonTools.getGoogleDiscoveryBean(json, GoogleDiscoveryBean.class); List<Items> listItems=googleDiscoveryBean.getItems(); if(listItems!=null&&listItems.size()>0){ for(int i=0;i<listItems.size();i++){ Items items=listItems.get(i); sbBuilder.append("<tr>"); sbBuilder.append("<td>").append(" "+(i+1)+" ").append("</td>"); sbBuilder.append("<td>").append(items.getTitle()).append("</td>"); sbBuilder.append("<td>").append(items.getName()).append("</td>"); sbBuilder.append("<td>").append(items.getVersion()).append("</td>"); sbBuilder.append("<td>").append(items.getDiscoveryRestUrl()).append("</td>"); sbBuilder.append("<td>").append(items.getDocumentationLink()).append("</td>"); sbBuilder.append("</tr>"); } } sbBuilder.append("</table>"); System.out.println(sbBuilder.toString()); return sbBuilder.toString(); } public static void main(String[] args) { GoogleAPIsListViewService gavs=new GoogleAPIsListViewService(); gavs.listAllGoogleAPIs(); } }
输出的结果就是,就是“如何用Google APIs和Google的应用系统进行集成(2)”文章中看到的表格的html源代码。
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