Hands-on: Using Google API to make searches on your applications

3017047-poster-1280-google
Standard

Welcome, dear reader, to another post of my blog. On this post, we will learn to use Google’s custom search API. With this API, you can make searches using Google’s infrastructure, enriching searching business features, like a web crawler, for example.

Pre-steps

Before we start coding, we need to create the keys to make our authentication with the API. One key is the API key itself and the other one is the search engine key. A search engine key is a key to a search engine you create to pre-filter the types of domains you want to make for your searches, so you dont end up searching sites in chinese, for example, if your application only want sites from England.

To start, access the site https://console.developers.google.com. After inputting our credentials, we get to the main site, where we can create a project, activate/deactivate APIs and generate a API key for the project. This tutorial from Google explain how to create API keys.

After that, we need to create the search engine key, on the site https://www.google.com/cse/all. We can follow this tutorial from Google to create the key.

Hands-on

On this hands-on, we will use Eclipse Luna and Maven 3.2.1. First, create a Maven project, without a archetype:

After creating our project, we add the dependencies. Instead of offering a Java library for the consumption, Google’s API consists of a URL, which is called by a simple GET execution, and returns a JSON structure. For the return, we will use a JSON API we used on our previous post. First, we add the following dependencies in our pom.xml:

<dependencies>
<dependency>
<groupId>javax.json</groupId>
<artifactId>javax.json-api</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.0.4</version>
</dependency>
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.7.2</version>
</dependency>
</dependencies>

Finally, with the dependencies included, we write our code. In this example, we will make a call to the API for a search with the string “java+android”. The API has a limit usage of 100 results per search – in the free mode -, and uses a pagination format of 10 results per page, so we will make 10 calls to the API. The following code make our example:

package com.technology.alexandreesl;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.net.HttpURLConnection;
import java.net.URL;

import javax.json.Json;
import javax.json.stream.JsonParser;
import javax.json.stream.JsonParser.Event;

public class GoogleAPIJava {

final static String apiKey = “<insert your API Key here>”;
final static String customSearchEngineKey = “<insert your search engine key here>”;

// base url for the search query
final static String searchURL = “https://www.googleapis.com/customsearch/v1?&#8221;;

public static void main(String[] args) {

int inicio = 1;

int contador = 0;

while (contador < 10) {

System.out
.println(“***************** SEARCH **************************”);
System.out.println(“”);

String result = “”;

result = read(“java+android”, inicio, 10);

JsonParser parser = Json.createParser(new StringReader(result));

while (parser.hasNext()) {
Event event = parser.next();

if (event == Event.KEY_NAME) {

if (parser.getString().equals(“htmlTitle”)) {
Event value = parser.next();

if (value == Event.VALUE_STRING)
System.out.println(“Title (HTML): ”
+ parser.getString());
}

if (parser.getString().equals(“link”)) {

Event value = parser.next();

if (value == Event.VALUE_STRING)
System.out.println(“Link: ” + parser.getString());
}

}

}

inicio = inicio + 10;

contador++;

System.out
.println(“**************************************************”);

}

}

private static String read(String qSearch, int start, int numOfResults) {
try {

String toSearch = searchURL + “key=” + apiKey + “&cx=”
+ customSearchEngineKey + “&q=”;

toSearch += qSearch;

toSearch += “&alt=json”;

toSearch += “&start=” + start;

toSearch += “&num=” + numOfResults;

URL url = new URL(toSearch);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
BufferedReader br = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
StringBuffer buffer = new StringBuffer();
while ((line = br.readLine()) != null) {
buffer.append(line);
}
return buffer.toString();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

}

As we can see above, we make use of the java.net standard classes to make the calls. Using counters to control the calls for the API. The result when we run the program is a list of sites for the search string printed on the console:

***************** SEARCH **************************

Title (HTML): Java Manager; Emulate <b>Java</b> – <b>Android</b> Apps on Google Play
Link: https://play.google.com/store/apps/details?id=com.java.manager
Title (HTML): How do I get <b>Java</b> for Mobile device?
Link: https://www.java.com/en/download/faq/java_mobile.xml
Title (HTML): AIDE – <b>Android</b> IDE – <b>Java</b>, C++ – <b>Android</b> Apps on Google Play
Link: https://play.google.com/store/apps/details?id=com.aide.ui
Title (HTML): Como obtenho o <b>Java</b> para Dispositivos Móveis?
Link: https://www.java.com/pt_BR/download/faq/java_mobile.xml
Title (HTML): Download <b>java</b> for <b>android</b> tablet – <b>Android</b> – <b>Android</b> Smartphones
Link: http://www.tomsguide.com/forum/id-1608121/download-java-android-tablet.html
Title (HTML): <b>java</b>.lang | <b>Android</b> Developers
Link: http://developer.android.com/reference/java/lang/package-summary.html
Title (HTML): Comparison of <b>Java</b> and <b>Android</b> API – Wikipedia, the free <b>…</b>
Link: http://en.wikipedia.org/wiki/Comparison_of_Java_and_Android_API
Title (HTML): Learn <b>Java</b> for <b>Android</b> Development: Introduction to <b>Java</b> – Tuts+ <b>…</b>
Link: http://code.tutsplus.com/tutorials/learn-java-for-android-development-introduction-to-java–mobile-2604
Title (HTML): <b>java</b>.text | <b>Android</b> Developers
Link: http://developer.android.com/reference/java/text/package-summary.html
Title (HTML): Apostila <b>Java</b> – Desenvolvimento Mobile com <b>Android</b> | K19
Link: http://www.k19.com.br/downloads/apostilas/java/k19-k41-desenvolvimento-mobile-com-android
**************************************************
***************** SEARCH **************************

Title (HTML): How can I access a <b>Java</b>-based website on an <b>Android</b> phone?
Link: http://www.makeuseof.com/answers/access-javabased-website-android-phone/
Title (HTML): Introduction to <b>Java</b> Variables | Build a Simple <b>Android</b> App (retired <b>…</b>
Link: http://teamtreehouse.com/library/build-a-simple-android-app/getting-started-with-android/introduction-to-java-variables-2
Title (HTML): <b>Java</b> Basics for <b>Android</b> Development – Part 1 – Treehouse Blog
Link: http://blog.teamtreehouse.com/java-basics-for-android-development-part-1
Title (HTML): GC: <b>android</b> – GrepCode <b>Java</b> Project Source
Link: http://grepcode.com/project/repository.grepcode.com/java/ext/com.google.android/android
Title (HTML): <b>Java</b> Essentials for <b>Android</b>
Link: https://www.udemy.com/java-essentials-for-android/
Title (HTML): How to Get <b>Java</b> on <b>Android</b>: 10 Steps (with Pictures) – wikiHow
Link: http://www.wikihow.com/Get-Java-on-Android
Title (HTML): Learn <b>Android</b> 4.0 Programming in <b>Java</b>
Link: https://www.udemy.com/android-tutorial/
Title (HTML): Trending <b>Java</b> repositories on GitHub today · GitHub
Link: https://github.com/trending?l=java
Title (HTML): Developing for <b>Android</b> in Eclipse: R.<b>java</b> not generating – Stack <b>…</b>
Link: http://stackoverflow.com/questions/2757107/developing-for-android-in-eclipse-r-java-not-generating
Title (HTML): Cling – <b>Java</b>/<b>Android</b> UPnP library and tools
Link: http://4thline.org/projects/cling/
**************************************************
***************** SEARCH **************************

Title (HTML): Getting Started | <b>Android</b> Developers
Link: https://developer.android.com/training/
Title (HTML): <b>Java</b> API – <b>Android</b> | Vuforia Developer Portal
Link: https://developer.vuforia.com/resources/api/main
Title (HTML): <b>Java</b> Programming for <b>Android</b> Developers For Dummies: Burd <b>…</b>
Link: http://www.amazon.com/Java-Programming-Android-Developers-Dummies/dp/1118504380
Title (HTML): <b>Android</b> Quickstart – Firebase
Link: https://www.firebase.com/docs/android/quickstart.html
Title (HTML): Learn <b>Java</b> for <b>Android</b> Development: Jeff Friesen: 9781430264545 <b>…</b>
Link: http://www.amazon.com/Learn-Java-Android-Development-Friesen/dp/1430264543
Title (HTML): Unity – Manual: Building Plugins for <b>Android</b>
Link: http://docs.unity3d.com/Manual/PluginsForAndroid.html
Title (HTML): Eclipse, <b>Android</b> and <b>Java</b> training and support
Link: http://www.vogella.com/
Title (HTML): AIDE – <b>Android Java</b> IDE download – Baixaki
Link: http://www.baixaki.com.br/android/download/aide-android-java-ide.htm
Title (HTML): <b>Java</b> Multi-Platform and <b>Android</b> SDK | Philips Hue API
Link: http://www.developers.meethue.com/documentation/java-multi-platform-and-android-sdk
Title (HTML): <b>Android</b> Client Tutorial – <b>Java</b> — Google Cloud Platform
Link: https://cloud.google.com/appengine/docs/java/endpoints/getstarted/clients/android/
**************************************************
***************** SEARCH **************************

Title (HTML): Gradle Plugin User Guide – <b>Android</b> Tools Project Site
Link: http://tools.android.com/tech-docs/new-build-system/user-guide
Title (HTML): Where is a download for <b>java</b> for <b>android</b> tablet? – Download <b>…</b>
Link: http://www.tomshardware.com/forum/52818-34-where-download-java-android-tablet
Title (HTML): Download <b>android java</b>
Link: http://www.softonic.com.br/s/android-java
Title (HTML): Binding a <b>Java</b> Library | Xamarin
Link: http://developer.xamarin.com/guides/android/advanced_topics/java_integration_overview/binding_a_java_library_(.jar)/
Title (HTML): <b>java</b>-ide-droid – JavaIDEdroid allows you to create native <b>Android</b> <b>…</b>
Link: http://code.google.com/p/java-ide-droid/
Title (HTML): Code Style Guidelines for Contributors | <b>Android</b> Developers
Link: https://source.android.com/source/code-style.html
Title (HTML): Eclipse Downloads
Link: https://eclipse.org/downloads/
Title (HTML): Open source <b>Java</b> for <b>Android</b>? Don’t bet on it | InfoWorld
Link: http://www.infoworld.com/article/2615512/java/open-source-java-for-android–don-t-bet-on-it.html
Title (HTML): Make your First <b>Android</b> App! – YouTube
Link: http://www.youtube.com/watch?v=A_qaarY4_lY
Title (HTML): Runtime for <b>Android</b> apps – BlackBerry Developer
Link: http://developer.blackberry.com/android/
**************************************************
***************** SEARCH **************************

Title (HTML): <b>Java</b> Mobile <b>Android</b> Basic Course Online
Link: http://www.vtc.com/products/javamobileandroidbasic.htm
Title (HTML): <b>Android</b> Game Development Tutorial – Kilobolt
Link: http://www.kilobolt.com/game-development-tutorial.html
Title (HTML): Learn <b>Java</b> for <b>Android</b> Development, 3rd Edition – Free Download <b>…</b>
Link: http://feedproxy.google.com/~r/IT-eBooks/~3/oITagjK1kYU/
Title (HTML): Cursos de <b>Android</b> e iOS | Caelum
Link: http://www.caelum.com.br/cursos-mobile/
Title (HTML): Autobahn|<b>Android</b> Documentation — AutobahnAndroid 0.5.2 <b>…</b>
Link: http://ottogrib.appspot.com/autobahn.ws/android
Title (HTML): Dagger ‡ A fast dependency injector for <b>Android</b> and <b>Java</b>.
Link: http://google.github.com/dagger/
Title (HTML): Dagger
Link: http://square.github.com/dagger/
Title (HTML): Setup – google-api-<b>java</b>-client – Download and Setup Instructions <b>…</b>
Link: https://code.google.com/p/google-api-java-client/wiki/Setup
Title (HTML): How to Write a ‘Hello World!’ app for <b>Android</b>
Link: http://www.instructables.com/id/How-to-Write-a-Hello-World-app-for-Android/
Title (HTML): The real history of <b>Java</b> and <b>Android</b>, as told by Google | ZDNet
Link: http://www.zdnet.com/article/the-real-history-of-java-and-android-as-told-by-google/
**************************************************
***************** SEARCH **************************

Title (HTML): Microsoft Releases SignalR SDK for <b>Android</b>, <b>Java</b> — Visual Studio <b>…</b>
Link: http://visualstudiomagazine.com/articles/2014/03/07/signalr-sdk-for-android-and-java.aspx
Title (HTML): <b>Android</b> Game Tutorials | <b>Java</b> Code Geeks
Link: http://www.javacodegeeks.com/tutorials/android-tutorials/android-game-tutorials/
Title (HTML): libgdx
Link: http://libgdx.badlogicgames.com/
Title (HTML): Buck: An <b>Android</b> (and <b>Java</b>!) build tool
Link: https://www.diigo.com/04w2jy
Title (HTML): Google copied <b>Java</b> in <b>Android</b>, expert says | Computerworld
Link: http://www.computerworld.com/article/2512514/government-it/google-copied-java-in-android–expert-says.html
Title (HTML): Reinventing Mobile Development (mobile app development mobile <b>…</b>
Link: http://www.codenameone.com/
Title (HTML): Understanding R.<b>java</b>
Link: http://knowledgefolders.com/akc/display?url=DisplayNoteIMPURL&reportId=2883&ownerUserId=satya
Title (HTML): Download <b>Java</b> Programming for <b>Android</b> Developers For Dummies <b>…</b>
Link: http://kickasstorrentsproxy.com/java-programming-for-android-developers-for-dummies-epub-pdf-t8208814.html
Title (HTML): Court sides with Oracle over <b>Android</b> in <b>Java</b> patent appeal – CNET
Link: http://www.cnet.com/news/court-sides-with-oracle-over-android-in-java-patent-appeal/
Title (HTML): Google Play <b>Android</b> Developer API Client Library for <b>Java</b> – Google <b>…</b>
Link: https://developers.google.com/api-client-library/java/apis/androidpublisher/v1
**************************************************
***************** SEARCH **************************

Title (HTML): Tape – A collection of queue-related classes for <b>Android</b> and <b>Java</b> by <b>…</b>
Link: http://shahmehulv.appspot.com/square.github.io/tape/
Title (HTML): <b>Android</b> Platform Guide
Link: http://cordova.apache.org/docs/en/4.0.0/guide_platforms_android_index.md.html
Title (HTML): OrmLite – Lightweight Object Relational Mapping (ORM) <b>Java</b> Package
Link: http://ormlite.com/
Title (HTML): <b>Android</b> Ported to C# | Xamarin Blog
Link: http://blog.xamarin.com/android-in-c-sharp/
Title (HTML): Tutorials | AIDE – <b>Android</b> IDE
Link: https://www.android-ide.com/tutorials.html
Title (HTML): All Tutorials on Mkyong.com
Link: http://www.mkyong.com/all-tutorials-on-mkyong-com/
Title (HTML): Top 10 <b>Android</b> Apps and IDE for <b>Java</b> Coders and Programmers
Link: https://blog.idrsolutions.com/2014/12/android-apps-ide-for-java-coder-programmers/
Title (HTML): <b>Java Android</b> developer information, news, and how-to advice <b>…</b>
Link: http://www.javaworld.com/category/java-android-developer
Title (HTML): Google <b>Android</b> e <b>Java</b> Micro Edition (ME)
Link: http://www.guj.com.br/forums/show/14.java
Title (HTML): <b>Java</b> &amp; <b>Android</b> Obfuscator | DashO
Link: http://www.preemptive.com/products/dasho/overview
**************************************************
***************** SEARCH **************************

Title (HTML): Using a Custom Set of <b>Java</b> Libraries In Your RAD Studio <b>Android</b> <b>…</b>
Link: http://docwiki.embarcadero.com/RADStudio/XE7/en/Using_a_Custom_Set_of_Java_Libraries_In_Your_RAD_Studio_Android_Apps
Title (HTML): 50. <b>Android</b> (DRD) – <b>java</b> – CERT Secure Coding Standards
Link: https://www.securecoding.cert.org/confluence/pages/viewpage.action?pageId=111509535
Title (HTML): Gameloft: Top Mobile Games for iOS, <b>Android</b>, <b>Java</b> &amp; more
Link: http://www.gameloft.com/
Title (HTML): <b>Android</b> and <b>Java</b> Developers: We Have a SignalR SDK for You!
Link: http://msopentech.com/blog/2014/03/06/android-java-developers-signalr-sdk/
Title (HTML): <b>Java</b> Swing UI on iPad, iPhone and <b>Android</b>
Link: http://www.creamtec.com/products/ajaxswing/solutions/java_swing_ui_on_ipad.html
Title (HTML): TeenCoder <b>Java</b> Series: Computer Programming Courses for Teens!
Link: http://www.homeschoolprogramming.com/teencoder/teencoder_jv_series.php
Title (HTML): Mixpanel <b>Java</b> API Overview – Mixpanel | Mobile Analytics
Link: https://mixpanel.com/help/reference/java
Title (HTML): AN 233 <b>Java</b> D2xx for <b>Android</b> API User Manual – FTDI
Link: http://www.ftdichip.com/Documents/AppNotes/AN_233_Java_D2XX_for_Android_API_User_Manual.pdf
Title (HTML): Xtend – Modernized <b>Java</b>
Link: http://eclipse.org/xtend/
Title (HTML): ProGuard
Link: http://freecode.com/urls/9ab4c148025d25c6eccd84906efb2c05
**************************************************
***************** SEARCH **************************

Title (HTML): FOSS Patents: Oracle wins <b>Android</b>-<b>Java</b> copyright appeal: API code <b>…</b>
Link: http://www.fosspatents.com/2014/05/oracle-wins-android-java-copyright.html
Title (HTML): <b>java android</b> 4.1.1 free download
Link: http://en.softonic.com/s/java-android-4.1.1
Title (HTML): Four reasons to stick with <b>Java</b>, and four reasons to dump it <b>…</b>
Link: http://www.javaworld.com/article/2689406/java-platform/four-reasons-to-stick-with-java-and-four-reasons-to-dump-it.html
Title (HTML): <b>Java</b> Programming for <b>Android</b> Developers For Dummies Cheat Sheet
Link: http://www.dummies.com/how-to/content/java-programming-for-android-developers-for-dummie.html
Title (HTML): Twitter4J – A <b>Java</b> library for the Twitter API
Link: http://twitter4j.org/
Title (HTML): Ignite Realtime: Smack API
Link: http://www.igniterealtime.org/projects/smack/
Title (HTML): <b>Java</b> Programming for <b>Android</b> Developers For Dummies
Link: http://allmycode.com/Java4Android
Title (HTML): Oracle ADF Mobile
Link: http://www.oracle.com/technetwork/developer-tools/adf-mobile/overview/adfmobile-1917693.html
Title (HTML): Introduction of How <b>Android</b> Works for <b>Java</b> Programmers
Link: http://javarevisited.blogspot.com/2013/06/introduction-of-how-android-works-Java-programmers.html
Title (HTML): Download <b>java</b> emulator for <b>Android</b> | JavaEmulator.com
Link: http://www.javaemulator.com/android-java-emulator.html
**************************************************
***************** SEARCH **************************

Title (HTML): Google hauls <b>Java</b>-on-<b>Android</b> spat into US Supreme Court • The <b>…</b>
Link: http://go.theregister.com/feed/www.theregister.co.uk/2014/10/09/google_takes_javaonandroid_case_to_supreme_court/
Title (HTML): <b>Android</b> SDK for Realtime Apps
Link: http://www.pubnub.com/docs/java/android/android-sdk.html
Title (HTML): Como Obter o <b>Java</b> no <b>Android</b>: 4 Passos (com Imagens)
Link: http://pt.wikihow.com/Obter-o-Java-no-Android
Title (HTML): If <b>Android</b> is so hot, why has <b>Java</b> ME overtaken it?
Link: http://fortune.com/2012/01/01/if-android-is-so-hot-why-has-java-me-overtaken-it/
Title (HTML): <b>Android</b> tutorial
Link: http://www.tutorialspoint.com/android/
Title (HTML): What’s New in IntelliJ IDEA 14
Link: https://www.jetbrains.com/idea/whatsnew/
Title (HTML): <b>Android</b> OnClickListener Example | Examples <b>Java</b> Code Geeks
Link: http://examples.javacodegeeks.com/android/core/view/onclicklistener/android-onclicklistener-example/
Title (HTML): JTwitter – the <b>Java</b> library for the Twitter API : Winterwell Associates <b>…</b>
Link: http://www.winterwell.com/software/jtwitter.php
Title (HTML): RL SYSTEM – Cursos Online de <b>Android</b>, .NET, <b>Java</b>, PHP, ASP <b>…</b>
Link: http://www.rlsystem.com.br/
Title (HTML): samples/ApiDemos/src/com/example/<b>android</b>/apis/app <b>…</b>
Link: https://android.googlesource.com/platform/development/+/master/samples/ApiDemos/src/com/example/android/apis/app/FragmentRetainInstance.java
**************************************************

Conclusion

And so we concluded our hands-on. With a simple usage, Google’s custom search API offers a simple but powerful tool in the belt of every developer who need to use a search engine of the internet in his solutions. Thank you for reading, until next time.

Source-code (Github)

Hands-on: JSON Java API

imagem_json
Standard

JSON (JavaScript Object Notation) is a notation for data communication, as well as XML, for example. Its popularity has grown with the growth of the REST Web Services, and today has long been used in the development of APIs.

In this hands-on, we will learn how to use a JSON Java API, present in Java EE 7. With it, you can parse JSON structures for reading the data, and generate their own structures.

Creating the project

In this hands-on we will use Eclipse. Create a Maven project in New> Other> Maven Project. If you do not have this option, open the Eclipse Marketplace on the IDE itself (Help menu), and look for the plugin “Maven Integration for Eclipse” on your version. At the end of this post, you can find a link to the source code of hands-on.

With the project done, we will add in the pom the following dependencies:

<dependencies>
<dependency>
<groupId>javax.json</groupId>
<artifactId>javax.json-api</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.0.4</version>
</dependency>
</dependencies>

With the dependencies created, we will begin to explore the API.

JsonParser

The first class we will talk about is the JsonParser. With this class, we can, from a JSON input, perform a parse of the structure. The code below demonstrates the use of the class:

.....
FileInputStream file = new FileInputStream("dados.json");
JsonParser parser = Json.createParser(file);
while (parser.hasNext()) {
Event evento = parser.next();
switch (evento) {
case KEY_NAME: {
System.out.print(parser.getString() + "=");
break;
}
case VALUE_STRING: {
System.out.println(parser.getString());
break;
}
case VALUE_NUMBER: {
System.out.println(parser.getString());
break;
}
case VALUE_NULL: {
System.out.println("null");
break;
}
case START_ARRAY: {
System.out.println("Inicio do Array de Telefone");
break;
}
case END_ARRAY: {
System.out.println("Final do Array de Telefone");
break;
}
case END_OBJECT: {
System.out.println("Final do Objeto Json");
break;
}
}
}
.....

As we can see in the code above, through the class we followed the whole json structure contained within the file “dados.json”. For example, with a file which has the following structure:

{
“id”:123,
“descricao”:”Produto 1″,
“Classificacao”:{
“nivel”:1,
“subnivel”:2,
“secao”:”eletrodomesticos”
},
“fornecedores”:[
{
“id”:1,
“descricao”:”brastemp”
},
{
“id”:2,
“descricao”:”consul”
},
{
“id”:3,
“descricao”:”eletrolux”
}
]
}

We have the following print on the console:

id:
123
descricao:
Produto 1
Classificacao:
nivel:
1
subnivel:
2
secao:
eletrodomesticos
Final do Objeto Json
fornecedores:
começo de um array
id:
1
descricao:
brastemp
Final do Objeto Json
id:
2
descricao:
consul
Final do Objeto Json
id:
3
descricao:
eletrolux
Final do Objeto Json
final de um array
Final do Objeto Json

JsonGenerator

With the JsonGenerator class, you can generate JSON structures.The usage is made by putting the openings and closings of the tags in a manual way,  through the API methods, generating the structure in a  sequentially way:

.....
JsonGeneratorFactory factory = Json.createGeneratorFactory(properties);
JsonGenerator jsonGen = factory.createGenerator(System.out);
jsonGen.writeStartObject().write("id", 123).write("descricao", "Produto 1").writeStartObject("Classificacao").write("nivel", 1).write("subnivel", 2).write("secao", "eletrodomesticos").writeEnd().writeStartArray("fornecedores").writeStartObject().write("id", 1).write("descricao", "brastemp").writeEnd().writeStartObject().write("id", 2).write("descricao", "consul").writeEnd().writeStartObject().write("id", 3).write("descricao", "eletrolux").writeEnd().writeEnd().writeEnd().close();
.....

The above code will generate an identical Json than shown above.

JsonObjectBuilder

In the example above, although the API facilitates the creation of the JSON, we have some problems. As we have to manually put the openings and closings of the tags, the result is a somewhat laborious code, which requires the developer to careful not generate invalid results. A better alternative is to generate Jsons with the JsonObjectBuilder class, which use a nearest OO API format, and therefore easier to program in the language:

.....
JsonBuilderFactory jBuilderFactory = Json.createBuilderFactory(null);
JsonObjectBuilder jObjectBuilder = jBuilderFactory
.createObjectBuilder();
jObjectBuilder
.add("id", 123)
.add("descricao", "Produto 1")
.add("Classificacao",
jBuilderFactory.createObjectBuilder().add("nivel", 1)
.add("subnivel", 2)
.add("secao", "eletrodomesticos"))
.add("fornecedores",
jBuilderFactory
.createArrayBuilder()
.add(jBuilderFactory.createObjectBuilder()
.add("id", 1)
.add("descricao", "brastemp"))
.add(jBuilderFactory.createObjectBuilder()
.add("id", 2)
.add("descricao", "consul"))
.add(jBuilderFactory.createObjectBuilder()
.add("id", 3)
.add("descricao", "eletrolux")));
JsonObject jObject = jObjectBuilder.build();
JsonWriter jWriterOut = Json.createWriter(System.out);
jWriterOut.writeObject(jObject);
jWriterOut.close();
.....

As in the other example, this code will generate the same JSON shown at the beginning of the post.

Conclusion

In this hands-on, we saw a sample of a JSON manipulation API of the Java language. With it, we can create Jsons more simply, beyond reading them. The reader may be wondering “but it is not easier to use the JAX-RS 2.0 to produce / consume Jsons”? It is true that the JAX-RS 2.0 has brought a simpler interface than the one presented here, where, basically, simply create a POJO to have a ready Json structure. The reader should remember, however, that the JSON is not a unique structure for use with REST services, and therefore, for scenarios where the use of the RS 2.0 is not appropriate, this API can become a good option. Out of curiosity, the JAX-RS 2.0 uses this API “under the hood”.

And so we ended our hands-on. Thanks to all who attended this post, until next time

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