Using Java to implement RESTful Web Services: JAX-RS

Using Java to implement REST Web
Services: JAX-RS

Web Technology
2II25
Dr. Katrien Verbert
Dr. ir. Natasha Stash
Dr. George Fletcher

Restful Web Services Frameworks and APIs

• JAX-RS - The Java API for RESTful Web Services
• uses annotations to make plain old Java objects (POJOs) and
resources available through HTTP
• Sun Reference Project: Jersey
• Other Vendors: CXF (Apache), RESTEasy(JBoss) and Restlet

• JAX-RS tutorial:
http://docs.oracle.com/javaee/6/tutorial/doc/gilik.html

JAX-RS HTTP

• Templated mapping and subresources
@Path
• MIME handling
@Provides, @Consumes
• HTTP methods
@GET, @POST, @UPDATE, @DELETE, @HEAD,
@OPTIONS, @HttpMethod
• Caching
evaluatePreconditions

Example
package com.sun.jersey.samples.helloworld.resources;
import javax.ws.rs.GET;
import javax.ws.rs.Produces;
import javax.ws.rs.Path;

// The Java class will be hosted at the URI path "/helloworld"
@Path("/helloworld")
public class HelloWorldResource {

// The Java method will process HTTP GET requests
@GET
// The Java method will produce content identified by the MIME Media
// type "text/plain"
@Produces("text/plain")
public String getClichedMessage() {
// Return some cliched textual content
return "Hello World";
}
}

@Path Annotation and URI Path Templates

@Path annotation
• identifies the URI path template to which the resource responds
• is specified at the class or method level of a resource

URI path templates are URIs with variables embedded within the URI syntax
• these variables are substituted at runtime
• variables are denoted by braces ({ and })
@Path("/users/{username}")
• example request
http://example.com/users/Galileo

@PathParam annotation

To obtain the value of the user name, the @PathParam
annotation may be used on the method parameter of a
request method

@Path("/users/{username}")
public class UserResource {

@GET
@Produces("text/xml")
public String getUser(@PathParam("username") String userName) {
...
}
}

Examples of URI Path Templates

URI Path Template URI After Substitution

http://example.com/{name1}/{name2}/ http://example.com/james/gatz/

http://example.com/{question}/ http://example.com/why/why/why/
{question}/{question}/

http://example.com/maps/{location} http://example.com/maps/Main%20Street

@Produces Annotation

@Produces annotation is used to specify the MIME media
types or representations a resource can produce and
send back to the client

• applied at the class level: default for all methods
• applied at the method level overrides any @Produces
annotations applied at the class level

@produces annotation

@Path("/myResource")
@Produces("text/plain")
public class SomeResource {
@GET
public String doGetAsPlainText() {
...
}

@GET
@Produces("text/html")
public String doGetAsHtml() {
...
}
}

@Consumes Annotation

@Consumes annotation is used to specify which MIME media
types of representations a resource can accept

@POST
@Consumes("text/plain")
public void postClichedMessage(String message) {
// Store the message
}

Develop Restful service in Netbeans

03/28/11

package orders;
import javax.ws.rs.*;

@Path("order")
public class OrderResource {
public OrderResource() {
}

@GET
@Produces("application/xml")
public Order getLastOrder() {
return Orders.getLastOrder();
}

@PUT
@Consumes("application/xml")
public void putOrder(Order order) {
Orders.setLastOrder(order);
}
}

package orders;

public class Orders {

private static Order lastOrder=new Order();

public static Order getLastOrder() {
return lastOrder;
}

public static void setLastOrder(Order lastOrder) {
Orders.lastOrder = lastOrder;
}

}

Deploy Restful service in Netbeans

03/28/11

Test Restful service in Netbeans

03/28/11

Testing Restful services

Netbeans test client does not work well with XML
parameters

Better alternative:

RESTClient, a debugger for RESTful web services
https://addons.mozilla.org/nl/firefox/addon/restclient/

03/28/11

RESTClient

03/28/11

Testing Restful services

If you pass XML strings as parameters, you need to specify
this in the header

03/28/11

Add header parameters

03/28/11

Placing an order

03/28/11

k.verbert@tue.nl
n.v.stash@tue.nl
g.l.fletcher@tue.nl

03/28/11

Using Java to implement RESTful Web Services: JAX-RS

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Using Java to implement RESTful Web Services: JAX-RS

Editor's Notes