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Vaadin - REST example

Nazar Medeiros
6 years ago Oct 06, 2016 12:56pm
Tobias Demuth
6 years ago Oct 06, 2016 3:06pm

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

Nazar Medeiros
6 years ago Oct 07, 2016 6:49am
Tobias Demuth
6 years ago Oct 07, 2016 7:18am
Nazar Medeiros
6 years ago Oct 07, 2016 7:31am
Tobias Demuth
6 years ago Oct 07, 2016 8:00am
Nazar Medeiros
6 years ago Oct 07, 2016 9:42am
Nazar Medeiros
6 years ago Oct 09, 2016 10:52am

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;
    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:

public List<Customer>findByName(String firstname,String lastname) {
        List<Customer>customerList = new ArrayList<Customer>();
        customerList = webtarget.path("server").
                            queryParam("firstname", firstname).
                            queryParam("lastname", lastname).  
                            get(new GenericType<List<Customer>>(){});  
        return customerList;

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<Customer>>(){};

The fnal part - My Server.java:

public class Server {

    public GenericEntity<List<Customer>>findByName(@QueryParam("firstname")String firstname,@QueryParam("lastname") String lastname) throws ClassNotFoundException, SQLException
        List<Customer>customerList = DBConnection.findByName(firstname, lastname);
            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<Customer>.
I hope this information could be helpful for someone.
Best regards,
Nazar Medeiros