Why use JAX-RS / Jersey?

Why use JAX-RS / Jersey?

Short Answer

Because it makes the development of RESTful services easier.

Long Answer

JAX-RS is a standard that makes it easy to create a RESTful service that can be deployed to any Java application server: GlassFish, WebLogic, WebSphere, JBoss, etc.

JAX-RS is part of Java EE, and when JAX-RS is used with other Java EE technologies it becomes even easier to create your RESTful service:

• EJB - A session bean is used as the service implementation and also handles the transaction semantics.
• JAX-RS - Used to expose the session bean as a RESTful service
• JPA - Used to persist the POJOs to the database. Note how the EntityManager is injected onto the session bean.
• JAXB - Used to convert the POJO to/from XML (in GlassFish it can also be used to convert the POJO to/from JSON). JAX-RS by default handles the interaction with the JAXB implementation.

Sample JAX-RS 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);
        }
    }

    @GET
    @Produces(MediaType.APPLICATION_XML)
    @Path("findCustomersByCity/{city}")
    public List<Customer> findCustomersByCity(@PathParam("city") String city) {
        Query query = entityManager.createNamedQuery("findCustomersByCity");
        query.setParameter("city", city);
        return query.getResultList();
    }

}

For More Information:

• http://blog.bdoughan.com/2010/08/creating-restful-web-service-part-45.html

REST is an architecture, which inherently uses servlets.

No, it is not. REST is an architecture style which can be implemented using servlets, but does not inherently use them, nor inherently have anything to do with Java.

JAX-RS is a JSR Specification defining a Java API for RESTful Web Services.

Jersey is a specific implementation of JAX-RS.

As to whether to use Jersey or try to be compliant to the JAX-RS specification, that's sort of up to you. If it makes your work easier, great! If not no one's forcing you.