How to return An arraylist in Rest Webservice

Question

//Main service 

@Path("/test")
public class ReturnMultiple {

    public static ArrayList<String> al = new ArrayList<String>();

    @POST
    @Path("/new/{name}")
    @Produces(MediaType.TEXT_PLAIN)
    public ArrayList<String> display(@PathParam("name") String name) {
        al.clear();
        Todo td = new Todo();
        td.setName(name);
        al.add(td.getName());
        return al;
    }
}

// This is Pojo

public class Todo {

    private String name;

    public void setName(String name) {

        this.name = name;
    }

    public String getName() {
        return name;
    }

}

Whenever I hit the service I get this error as Below

A message body writer for Java class java.util.ArrayList, and Java type java.util.ArrayList, and MIME media type text/plain was not found

This static arraylist is not a good idea, what happen if two requests for /test/new/name arrive at the same time? — user180100
– user180100, Commented Jan 7, 2017 at 6:49
Regarding the error message, the framework used don't know how to make text from an ArrayList, that's the issue — user180100
– user180100, Commented Jan 7, 2017 at 6:50
when i use Application_Json in @produces it give me this error A message body writer for Java class java.util.ArrayList, and Java type java.util.ArrayList<java.lang.String>, and MIME media type application/json was not found — Vishal Rathore
– Vishal Rathore, Commented Jan 7, 2017 at 6:54

Ulises · Accepted Answer · 2017-01-07 07:04:43Z

1

You can't use ArrayList and produce TEXT_PLAIN. You'd have to use JSON. To setup JSON message body write in jax-rs you need to supply a @Provider for an ObjectMapper. Here's an example:

answered Jan 7, 2017 at 7:04

Ulises

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Comments

Rahul Kumar · Accepted Answer · 2017-01-07 08:01:57Z

0

I guess, you need a mapper implementation which helps in the serialization and deserialization. Without that it doesn't know how to convert an arraylist into text/plain or application/json or for that matter any other MIME type.

if you are dealing with application/json, jackson library works as really good mapper. It has messagebodyreader and messagebodywriter for you to do the difficult job.

you might have a way to provide a mapper for your rest services (as a provider), in some implementation it picks itself if you use jackson jar which I remember while using resteasy.

answered Jan 7, 2017 at 8:01

Rahul Kumar

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5 Comments

Vishal Rathore Over a year ago

I am new to this , may you please write a code for mapper ? Thanks

Rahul Kumar Over a year ago

In most cases when you include the jackson jar is automatically get registered github.com/FasterXML/jackson-jaxrs-providers as the link says so code won't be required probably, otheriwse here is an example of it with jersey mkyong.com/webservices/jax-rs/json-example-with-jersey-jackson

Vishal Rathore Over a year ago

I have included those jars and wrote like below : @POST @Path("/new/{name}") @Produces(MediaType.APPLICATION_JSON) public ArrayList<String> display(@PathParam("name") String name) { al.clear(); Todo td = new Todo(); td.setName(name); al.add(td.getName()); return al; }

Rahul Kumar Over a year ago

still you face the same issue? I am not sure what are you using jor jax-rs? is it jersey, resteasy, cxf, restlet, can you list down your jar in the question?

Vishal Rathore Over a year ago

jax-rs , i used Gson , and i am able to get the output , but now i want to know how can i put this arraylist and two boolean values in a hashmap and return the hashmap

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