Does rest supports arraylist of objects?

Question

I am having a class BookMain which is returning an arraylist of objects. I am using REST service to get the output, but I am getting an error.

This is my BookMain class:

@GET
@Path("/get")
@Produces(MediaType.APPLICATION_XML)
public ArrayList<Object> addObjects() {

    Book book = new Book(); 
    book.setName("The Book");
    book.setAuthor("Author");

    BookStore bookstore = new BookStore();
    bookstore.setName("The Bookstore");
    bookstore.setLocation("UK");

    ArrayList<Object> list = new ArrayList<Object>();
    list.add(book);
    list.add(bookstore);

    return list;   
}

This is the error which I am getting:

11 Jul, 2013 3:36:52 PM com.sun.jersey.spi.container.ContainerResponse write
SEVERE: A message body writer for Java class java.util.ArrayList, and Java type java.util.ArrayList<java.lang.Object>, and MIME media type application/xml was not found 11 Jul, 2013 3:36:52 PM com.sun.jersey.spi.container.
ContainerResponse write SEVERE: The registered message body writers 
compatible with the MIME media type are:application/xml ->
com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider$App
com.sun.jersey.core.impl.provider.entity.DocumentProvider
com.sun.jersey.core.impl.provider.entity.SourceProvider$SourceWriter
com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider$App
com.sun.jersey.core.impl.provider.entity.XMLListElementProvider$App

Can anyone provide me a solution for it ?

Answer 1

Introduce a new class as below

@XmlRootElement(name = "responseList")
public class ResposeList {

    private List<Object> list;

    public List<Object> getList() {
        return list;
    }

    public void setList(List<Object> list) {
        this.list = list;
    }

}

and set the list as below

@GET
@Path("/get")
@Produces(MediaType.APPLICATION_XML)
public ResposeList addObjects() {

    Book book = new Book(); 
    book.setName("Here is the Game");
    book.setAuthor("HHH");

    BookStore bookstore = new BookStore();
    bookstore.setName("Prateek Bookstore");
    bookstore.setLocation("Vasanth Nagar");

    ArrayList<Object> list = new ArrayList<Object>();
    list.add(book);
    list.add(bookstore);
    ResposeList books=new ResposeList();
    books.setList(list);

    return books;   
}

Answer 2

You need to wrap your entity(Arraylist) under the Response object. Also your rest method return type should be Response. Here is what you need to do:

@GET
@Path("/get")
@Produces(MediaType.APPLICATION_XML)
public Response addObjects() {

    Book book = new Book(); 
    book.setName("Here is the Game");
    book.setAuthor("HHH");

    BookStore bookstore = new BookStore();
    bookstore.setName("Prateek Bookstore");
    bookstore.setLocation("Vasanth Nagar");

    ArrayList<Object> list = new ArrayList<Object>();
    list.add(book);
    list.add(bookstore);

    return Response.status(200).entity(list).build();
}

Also add @XmlElement on top of getter in your ResponseList bean

@XmlRootElement
public class ResponseList {

private ArrayList<Object> list;

@XMLElement("booksList")
public ArrayList<Object> getList() {
    return list;
}

public void setList(ArrayList<Object> list) {
    this.list = list;
}   
}