Vaadin - REST example

[Nazar10 (Nazar Medeiros)]

I want to add some REST-Modifications to my current vaadin project. Therefore I have implemented following code so far:

// calls findByName Method in the RestClient.class
List<Customer> customers = restClient.findByName(firstName.getValue(), lastName.getValue());

/* RestClient-class */
public List<Customer> findByName(String firstname,String lastname) {
        
         List<Customer>customerList = webtarget.path("server").
                 path("restserver").
                 path("findByName").
                 queryParam("firstname", firstname).
                 queryParam("lastname", lastname).
                 request().
                 accept(MediaType.TEXT_PLAIN). // Do I need this?
                 get(Customer.class); // How to cast here?
        
         return customerList;
    }
 
/* Server class - handling requests */
    @GET
    @Path("/findByName")
    @Produces(MediaType.TEXT_PLAIN)
    public List<Customer>findByName(@QueryParam("firstname")String firstname,@QueryParam("lastname")String lastname) throws ClassNotFoundException, SQLException {
        
        System.out.println("findByName in Server aufgerufen");
        customerService = new CustomerService();
        return customerService.findByName(firstname, lastname);
        
    }

My code is not working. I receive HTTP Status 500. I put some comments into the code section. Could you help me to answer these please?
Thanks!!
Best regards,
Nazar Medeiros

[Tobias17 (Tobias Demuth)]

Status Code 500 will always go hand in hand with some kind of stacktrace. Could you please provide this crucial information?

[Nazar10 (Nazar Medeiros)]

@Tobias Demuth

Status Code 500 will always go hand in hand with some kind of stacktrace. Could you please provide this crucial information?

Hi Tobias,
please find attached my stacktrace:

javax.ws.rs.InternalServerErrorException: HTTP 500 Internal Server Error at org.glassfish.jersey.client.JerseyInvocation.convertToException(JerseyInvocation.java:1032) at org.glassfish.jersey.client.JerseyInvocation.translate(JerseyInvocation.java:819) at org.glassfish.jersey.client.JerseyInvocation.access$700(JerseyInvocation.java:92) at org.glassfish.jersey.client.JerseyInvocation$2.call(JerseyInvocation.java:701) at org.glassfish.jersey.internal.Errors.process(Errors.java:315) at org.glassfish.jersey.internal.Errors.process(Errors.java:297) at org.glassfish.jersey.internal.Errors.process(Errors.java:228) at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:444) at org.glassfish.jersey.client.JerseyInvocation.invoke(JerseyInvocation.java:697) at org.glassfish.jersey.client.JerseyInvocation$Builder.method(JerseyInvocation.java:420) at org.glassfish.jersey.client.JerseyInvocation$Builder.get(JerseyInvocation.java:316) at com.example.restclient.RestClient.findByName(RestClient.java:87) at com.example.Vaadin_REST.MyUI$MainView.searchCustomer(MyUI.java:198) at com.example.Vaadin_REST.MyUI$MainView.lambda$0(MyUI.java:128) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:510) at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:200) at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:163) at com.vaadin.server.AbstractClientConnector.fireEvent(AbstractClientConnector.java:1015) at com.vaadin.ui.Button.fireClick(Button.java:377) at com.vaadin.ui.Button$1.click(Button.java:54) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:158) at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:119) at com.vaadin.server.communication.ServerRpcHandler.handleInvocation(ServerRpcHandler.java:435) at com.vaadin.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:407) at com.vaadin.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:273) at com.vaadin.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:90) at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41) at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1422) at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:379) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1452) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) Best regards,
Nazar

[Tobias17 (Tobias Demuth)]

I suspect that it is failing because you are requesting plain text and trying to convert it to a Customer. Try changing the media-type to JSON.

[Nazar10 (Nazar Medeiros)]

@Tobias Demuth

I suspect that it is failing because you are requesting plain text and trying to convert it to a Customer. Try changing the media-type to JSON.

Hmm… didn’t work. Do I have to use some Annotations in my Customer-class?

public class Customer implements Serializable {

    /**
     *
     */
    private static final long serialVersionUID = 1L;
    private Long id;
    private String firstName,lastName;
    
    public Customer(Long id,String firstName,String lastName) {
        
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    
    }

    @Override
    public String toString() {
        return "Customer [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]
";
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    
}

[Tobias17 (Tobias Demuth)]

Next problem might be the fact that you are requesting a Customer but actually receiving a List of Customers. As far as I remember, it is probably better to use array here and to pass the correct class-type into get().

(new Customer[0]
).getClass();

[Nazar10 (Nazar Medeiros)]

@Tobias Demuth

Next problem might be the fact that you are requesting a Customer but actually receiving a List of Customers. As far as I remember, it is probably better to use array here and to pass the correct class-type into get().

(new Customer[0]
).getClass();

No success

[Nazar10 (Nazar Medeiros)]

@Tobias Demuth

Next problem might be the fact that you are requesting a Customer but actually receiving a List of Customers. As far as I remember, it is probably better to use array here and to pass the correct class-type into get().

(new Customer[0]
).getClass();

Finally I could solve the problem. There were few steps I had to do. So let’s start with my model class
Customer.java

public class Customer {

    private String firstname;
    
    private String lastName;
    
    private Long id;
    
    public Customer() {
        
    }
    
    public Customer(Long id,String firstname,String lastname) {
        
        this.firstname = firstname;
        this.lastName = lastname;
        this.id = id;
        
    }
    
    @Override
    public String toString() {
        return "Customer [firstname=" + firstname + ", lastName=" + lastName + ", id=" + id + "]
";
    }

    public String getFirstname() {
        return firstname;
    }

    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

When using rest services with a content-type like json or xml you have to be sure, that your model class can be converted to the specific format. In my case I decided to use xml. Therefore I had to use the annotation
@XmlRootElement.
You only need to put this annotation at the top of your class… nothing more needed.

The next step was to edit my Rest-Client.java:

[code]
public ListfindByName(String firstname,String lastname) {

    List<Customer>customerList = new ArrayList<Customer>();
    
    customerList = webtarget.path("server").
                        path("restserver").
                        path("findByName").
                        queryParam("firstname", firstname).
                        queryParam("lastname", lastname).  
                        request().
                        accept(MediaType.APPLICATION_XML).
                        get(new GenericType<List<Customer>>(){});  
    return customerList;
    
}

[/code]I expect an xml content-type from the server. This is the reason why I use
accept(MediaType.APPLICATION_XML)
. In case you receive a list of items, you could use
GenericType<List>(){};

The fnal part - My Server.java:

@Path("/restserver")
public class Server {

    @Path("/findByName")
    @GET
    @Produces(MediaType.APPLICATION_XML)
    public GenericEntity<List<Customer>>findByName(@QueryParam("firstname")String firstname,@QueryParam("lastname") String lastname) throws ClassNotFoundException, SQLException
    {
        List<Customer>customerList = DBConnection.findByName(firstname, lastname);
        
         GenericEntity<List<Customer>>
            list = new GenericEntity<List<Customer>>(customerList) {
         };
         return list;
    }

Nothing special here. Just looking for some data in the database and returning them as a type of
List
.
I hope this information could be helpful for someone.
Best regards,
Nazar Medeiros