通用Crud Restfull服务

Question

I am senior Java developer (also new in stackoverflow) working on a client-server project:

• Server : javaee6 web project(Rest, EJB3.1, JPA)
• Clients: javaee6 Web project(JSF2.0) and Android device. Client will request for: Crud and Executing Some Store Procedures.
• Entities: They are all in java project which has entity class generated with JPA and eclipse-link as provider and with JAXB annotations. Its jar file has been added to the server project and also will be used by Clients.

For every entity clients just have to pass Class type of the entity and it will has desired functions.

So I tried to have a Generic Session bean which has Restful method findAll like this:

@Stateless
@Path("/DAOFacad/")
public class DAOFacade<T> {

     @PersistenceContext EntityManager entityManager;

     @PUT
     @Consumes("application/json")
     @Produces("application/json")
     public List findAll(Class type) {
        CriteriaQuery cq = entityManager.getCriteriaBuilder().createQuery();
        cq.select(cq.from(type));
        return entityManager.createQuery(cq).getResultList();
     }

}

In the Client web project, i have something like this:

public class Consumer {
    private WebResource webResource;
    private Client client;
    private static final String BASE_URI = "http://localhost:8181/ServerPRS/webresources";

    public Consumer() {
        com.sun.jersey.api.client.config.ClientConfig config = new com.sun.jersey.api.client.config.DefaultClientConfig();
        client = Client.create(config);
        webResource = client.resource(BASE_URI).path("DAOFacad");
    }

    public <T> T findAll(Class<T> responseType, Object requestEntity) throws UniformInterfaceException {
        return webResource.type(javax.ws.rs.core.MediaType.APPLICATION_JSON).put(responseType, requestEntity);
    }

    public void close() {
        client.destroy();
    }

}

A managed been:

public class AdminContollerMB {

Consumer consumer;
    /**
     * Creates a new instance of AdminContollerMB
     */
    public AdminContollerMB() {
        consumer = new Consumer();
    }

    public List<Bank> getAllBanks(){
        GenericType<List<Bank>> respT = new GenericType<List<Bank>>(){};
        return (List<Bank>) consumer.findAll(respT.getClass(),Bank.class);
    }

but after running i get error :

com.sun.jersey.api.client.ClientHandlerException: A message body writer for Java type, class java.lang.Class, and MIME media type, application/json, was not found

I have searched alot. i tried GenericEntity and GenericType in jersey api and also gson api of google but they didnt work out.

any help will be appreciated.

Answer 1

Your method is called findAll but accepts PUT . That is not how RESTful services are build.

I guess you want to GET all instances of some type of Resource. In a RESTful service, Resources have no relation to Java Classes. So if you want a generic findAll GET method, do something like this:

@GET
public Response findAll(@QueryParam("class") String clazz) {
    List<Object> instances = findAllInstancesOfClazz(clazz);
    return Response.ok(instances).build();
}

Call this method:

GET http://example.com/DAOFacade/?class=SomeClassName

Remember: REST is not RPC!