====== Lesson 5 - REST, Jersey client, mashup ======

===== Lesson plan =====
  * Mashups
  * Jersey Java client API
  * XML Parsers

===== Mashups =====

Short external talk on web mashup: [[http://www.slideshare.net/amba_slide/web-mashup|Mashup architecture]]


===== Jersey Java client API =====
One may want to create a programmatic REST client using JAVA.

See the jersey documentation:  

[[https://jersey.java.net/documentation/latest/user-guide.html#client|Client API]]

Adding the Maven dependency:

<code>
<dependency>
    <groupId>org.glassfish.jersey.core</groupId>
    <artifactId>jersey-client</artifactId>
    <version>2.22.1</version>
</dependency>
</code>

Using the client API is very easy:

<code>
Client orderClient = ClientBuilder.newClient();

WebTarget target  = orderClient
                       .target("http://localhost:8082/rest-client-api-example/resources/orders/{id}");
Response response = target
                       .resolveTemplate("id", 1) // Resolves the {id} template
                       .request(MediaType.APPLICATION_JSON)
                       .get();
  
if(response.getStatus() == Status.OK.getStatusCode()){
 Order order = (Order) response.readEntity(Order.class);
  
 System.out.println("Id: " + order.getId());
 System.out.println("Name: " + order.getName());
 System.out.println("Price: " + order.getPrice());
}else{
 System.out.println(response.getStatus() + " " + response.getStatusInfo());
}
</code> 

==== Parsing JSON ====

=== Json-simple ===

Add the Maven dependency:
   <dependency>
     <groupId>com.googlecode.json-simple</groupId>
     <artifactId>json-simple</artifactId>
      <version>1.1</version>
   </dependency>

Sample usage:
   //Server output in String
   String output = response.getEntity(String.class);
   final JSONObject jsonObj = (JSONObject) parser.parse( output );
   if ( jsonObj != null && jsonObj.containsKey( "length" ) )
   {
      System.out.println(jsonObj.get( "length" ).toString());
   }

=== Google-gson ===
Using another JSON pareser:

Maven:
   <!--  Gson: Java to Json conversion -->
   <dependency>
      <groupId>com.google.code.gson</groupId>
      <artifactId>gson</artifactId>
      <version>2.2.4</version>
      <scope>compile</scope>
   </dependency>

Sample:
[[http://www.mkyong.com/java/how-do-convert-java-object-to-from-json-format-gson-api/]]


==== XML parsing ====

Using the DOM XML Parser:
http://www.mkyong.com/java/how-to-read-xml-file-in-java-dom-parser/