RestLet: An exception occured writing the response entity

Question

I have just begun creating my first restlet application. I have followed the restlet first steps tutorial. I have created all the files exactly as stated and the server runs perfectly when I run it but then when I call my service via postman I get this error:

Error:

2015-04-20  20:39:53    0:0:0:0:0:0:0:1 -   -   8182    GET /firstSteps/hello   -   200 12  0   156 http://localhost:8182   Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.90 Safari/537.36    -
An exception occured writing the response entity

java.lang.ClassCastException: org.restlet.data.Header cannot be cast to org.restlet.engine.header.Header
    at org.restlet.ext.simple.internal.SimpleCall.writeResponseHead(SimpleCall.java:304)
    at org.restlet.engine.adapter.ServerCall.sendResponse(ServerCall.java:450)
    at org.restlet.engine.adapter.ServerAdapter.commit(ServerAdapter.java:187)
    at org.restlet.engine.adapter.HttpServerHelper.handle(HttpServerHelper.java:144)
    at org.restlet.ext.simple.internal.SimpleContainer.handle(SimpleContainer.java:80)
    at org.simpleframework.http.core.Dispatcher.dispatch(Dispatcher.java:121)
    at org.simpleframework.http.core.Dispatcher.run(Dispatcher.java:103)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Error while handling an HTTP server call

Here is my code:

Helloworld Class:

package smartRoom;


import org.restlet.resource.Get;
import org.restlet.resource.ServerResource;

/**
 * Resource which has only one representation.
 */
public class Helloworld extends ServerResource {


    @Get
    public String represent() {

        return "hello, world";
    }

}

and here is my application class:

package smartRoom;

import org.restlet.Application;
import org.restlet.Component;
import org.restlet.Restlet;
import org.restlet.data.Protocol;
import org.restlet.routing.Router;

public class HelloworldAppilcation extends Application {


    public static void main(String[] args) throws Exception {  
        // Create a new Component.  
        Component component = new Component();  

        // Add a new HTTP server listening on port 8182.  
        component.getServers().add(Protocol.HTTP, 8182);  

        // Attach the sample application.  
        component.getDefaultHost().attach("/firstSteps",  
                new HelloworldAppilcation());  

        // Start the component.  
        component.start();  
    }    



    /**
     * Creates a root Restlet that will receive all incoming calls.
     */
    @Override
    public synchronized Restlet createInboundRoot() {
        // Create a router Restlet that routes each call to a new instance of HelloWorldResource.
        Router router = new Router(getContext());

        // Defines only one route
        router.attach("/hello", Helloworld.class);

        return router;
    }

}

I have been unable to find any content online regarding this error. I re-created the project from scratch following the instructions to the tee and still got the same error. I am unsure as to what I am doing wrong and any help would be greatly apprecaited.

Update

yes I can confirm the port is open and listening

update Two

http://restlet.com/technical-resources/restlet-framework/guide/2.2/editions/jse/overview

I have now also tried the maven tutorial and got the same result.

Update Three

I gave it another go today and started from scratch re-downloading everything and it work perfectly this time. Not exactly sure what the problem was, but was most likely to do with the version of restlet is was using.

Answer 1

I would suggest you to use the version 2.3 of Restlet with a server connector like Jetty (add extension org.restlet.ext.jetty in your classpath).

As far as I can see, you did the right things to implement a starter application with Restlet.

Can you give us the exact version of Restlet you use?

Here is a sample of file pom.xml that you can try for your application:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.restlet</groupId>
    <artifactId>restlet-starter</artifactId>
    <name>${project.artifactId}</name>
    <packaging>jar</packaging>
    <version>1.0.0-snapshot</version>

    <properties>
        <restlet-version>2.3.1</restlet-version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.restlet.jse</groupId>
            <artifactId>org.restlet</artifactId>
            <version>${restlet-version}</version>
        </dependency>

        <dependency>
            <groupId>org.restlet.jse</groupId>
            <artifactId>org.restlet.ext.jetty</artifactId>
            <version>${restlet-version}</version>
        </dependency>
    </dependencies>

    <repositories>
        <repository>
            <id>maven-restlet</id>
            <name>Public online Restlet repository</name>
            <url>http://maven.restlet.com</url>
        </repository>
    </repositories>
</project>

Hope it helps you, Thierry