Jaxb in Restful webservices - rest

Question

I have worked on Web services using Jaxb earlier. I geneated Java from xsd, and then I used to post the xml request to the specified URL using HTTP post. Recently I heard about this Restful web services, on reading I felt that what I had been doing earlier is the restful web service only. But, I am not sure about it if its the same thing.
Can anyone explain please.

Answer 1

It sounds like you have been creating the same types of RESTful services. You may be referring to is JAX-RS with is a standard that defines an easier way of creating RESTful services where JAXB is the standard binding layer for the application/xml media type. Below is an example service:
package org.example;
import java.util.List;
import javax.ejb.*;
import javax.persistence.*;
import javax.ws.rs.*;
import javax.ws.rs.core.MediaType;
#Stateless
#LocalBean
#Path("/customers")
public class CustomerService {
#PersistenceContext(unitName="CustomerService",
type=PersistenceContextType.TRANSACTION)
EntityManager entityManager;
#POST
#Consumes(MediaType.APPLICATION_XML)
public void create(Customer customer) {
entityManager.persist(customer);
}
#GET
#Produces(MediaType.APPLICATION_XML)
#Path("{id}")
public Customer read(#PathParam("id") long id) {
return entityManager.find(Customer.class, id);
}
#PUT
#Consumes(MediaType.APPLICATION_XML)
public void update(Customer customer) {
entityManager.merge(customer);
}
#DELETE
#Path("{id}")
public void delete(#PathParam("id") long id) {
Customer customer = read(id);
if(null != customer) {
entityManager.remove(customer);
}
}
}
For More Information
http://blog.bdoughan.com/2010/08/creating-restful-web-service-part-45.html

Answer 2

When it comes to say 'RESTful', it's just an convention of HTTP methods and url patterns.
CRUD METHOD URL RESPONSE DESCRIPTION
----------------------------------------------------------------
CREATE POST http://www.doma.in/people 202 Creates a new person with given entity body
READ GET http://www.doma.in/people 200
READ GET http://www.doma.in/people/1 200 404 Reads a single person
UPDATE PUT http://www.doma.in/people/2 204 Updates a single person with given entity body
DELETE DELETE http://www.doma.in/people/1 204 Deletes a person mapped to given id(1)
You can even implement those kind of contracts with Sevlets. Actually I had done with Sevlets before the era of JAX-RS.
And your life will be much more easier when you use JAX-RS.
Here comes a slightly modified version of Mr. Blaise Doughan's.
Nothing's wrong with Mr. Blaise Doughan's code.
I just want to add more for above url patterns.
One of great things that JAX-RS can offer is that you can serve XMLs and JSONs as clients want if you have those fine JAXB classes. See #Producess and #Consumess for those two formats in same method.
When client want to receive as XML with Accept: application/xml, they just get the XML.
When client want to receive as JSON with Accept: application/json, they just get the JSON.
#Path("/customers");
public class CustomersResource {
/**
* Reads all person units.
*/
#POST
#Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
public Response read() {
final List<Customer> listed = customerBean.list();
final Customers wrapped = Customers.newInstance(listed);
return Response.ok(wrapped).build();
}
#POST
#Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
public Response createCustomer(final Customer customer) {
entityManager.persist(customer);
return Response.created("/" + customer.getId()).build();
}
#GET
#Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
#Path("/{id: \\d+}")
public Response read(#PathParam("id") final long id) {
final Customer customer = entityManager.find(Customer.class, id);
if (customer == null) {
return Response.status(Status.NOT_FOUND).build();
}
return Response.ok(customer).build();
}
#PUT
#Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
public void updateCustomer(final Customer customer) {
entityManager.merge(customer);
}
#DELETE
#Path("/{id: \\d+}")
public void deleteCustomer(#PathParam("id") final long id) {
final Customer customer = entityManager.find(Customer.class, id);
if (customer != null) {
entityManager.remove(customer);
}
return Response.status(Status.NO_CONTENT).build();
}
}
Say you want to serve some images?
#GET
#Path("/{id: \\d+}")
#Produces({"image/png", "image/jpeg"})
public Response readImage(
#HeaderParam("Accept") String accept,
#PathParam("id") final long id,
#QueryParam("width") #DefaultValue("160") final int width,
#QueryParam("height") #DefaultValue("160") final int height) {
// get the image
// resize the image
// make a BufferedImage for accept(MIME type)
// rewrite it to an byte[]
return Response.ok(bytes).build();
// you can event send as a streaming outout
return Response.ok(new StreamingOutput(){...}).build();
}