This is what I do underneath it all, then I call RestAssuredUtil.setup() from @Before public void setup().

package com.acme.web.service;

import com.jayway.restassured.RestAssured;
import com.acme.web.util.ApplicationProperties;

/**
 * Isolate set-up of REST-assured here in order not to have to change it
 * everywhere else.
 */
public class RestAssuredUtil
{
    public static final void setup()
    {
        RestAssured.baseURI  = "http://localhost";
        RestAssured.port     = ApplicationProperties.APPLICATION_PORT;
        RestAssured.basePath = "/acmewebservice/api/v1";
    }
}

Here's a working example that tests a ReST service named "langserv".

package com.acme.web.service;

import static com.jayway.restassured.RestAssured.expect;
import static com.jayway.restassured.RestAssured.given;
import static com.jayway.restassured.RestAssured.get;
import static org.hamcrest.Matchers.equalTo;

import org.junit.Before;
import org.junit.Test;

import com.acme.entity.Language;
import com.jayway.restassured.RestAssured;
import com.jayway.restassured.path.json.JsonPath;

/**
 * Note: In order for these tests to run, langserv must be launched in Tomcat.
 *
 * The point of this test is to try out the REST-assured framework. While this
 * mostly works, it a) requires a running Tomcat and underlying database with
 * real data inside, and b) might not really be something we need to test.
 *
 * Advantages to REST-assured!
 *
 *   - Self-documenting.
 *   - Statement of what URIs are supported.
 *   - Statement of what HTTP Status Codes are returned.
 *
 * These tests are a little brittle?
 *
 * This may be a reason not to do them. What's brittle in this testing is confined
 * especially to PUT and DELETE: you must know the id of something to update and/or
 * delete. There is a way to get the new id created by the POST operation, via the
 * name of the new language. See the first few lines at the top of testUpdate() and
 * testDelete().
 *
 * If this test fails, it will be necessary to reinitialize the database from
 * scratch before it will work. Specifically, testUpdate() will fail when it's
 * invoked after testDelete() fails (or isn't run) since the result of
 * get( "/language/name/Zzyzzx" ) will not be a single language, but two or more,
 * something like:
 *
 * {
 *     "language":
 *     [
 *         {
 *             "code":"zz",
 *             "id":"175",
 *             "name":"Zzyzzx"
 *         },
 *         {
 *             "code":"zz",
 *             "id":"176",
 *             "name":"Zzyzzx"
 *         }
 *     ]
 * }
 *
 * @author Russell Bateman
 */
public class LanguageWSTest
{
    @Before
    public void setup()
    {
        RestAssuredUtil.setup();
    }

    @Test
    public void testCreate()
    {
        Language language = new Language();

        language.setCode( "zz" );
        language.setName( "Zzyzzx" );

//      Language response =            --this sort of thing is possible for saving...

        given().contentType( "application/json" )
               .and()
               .body( language )
       .when().post( "/language" );

//     Integer id = response.getId();  --...this id for use in update and delete below
    }

    /**
     * We expect to find language 35 (should be English) in the database.
     */
    @Test
    public void testRead()
    {
        expect().statusCode( 200 )
        .when() .get ( "/language/35" );
    }

    /**
     * We expect to find language 35 (should be English) in the database.
     */
    @Test
    public void testRead_byId()
    {
        expect().body( "id",   equalTo( "35" ) )
                .body( "name", equalTo( "English" ) )
                .body( "code", equalTo( "en" ) )
        .when() .get ( "/language/35" );
    }

    /**
     * We expect not to find language 0 in the database.
     */
    @Test
    public void testRead_byId_not_found()
    {
        expect().statusCode( 404 )
       .when()  .get ( "/language/0" );
    }

    /**
     * We expect to find language 35 (should be English) in the database.
     */
    @Test
    public void testReadByPropertyAndValue()
    {
        expect().body( "code", equalTo( "en" ) )
        .when() .get ( "/language/35" );
    }

    /**
     * We expect that testCreate() above added language 174 to the
     * database and that we can muck with it.
     */
    @Test
    public void testUpdate()
    {
        /* If this bit goes well, we should know the id of the new language we added,
         * in testCreate(), so we can feel free to update or delete it in these tests.
         */
        String   json = get( "/language/name/Zzyzzx" ).asString();
        String   id   = JsonPath.with( json ).get( "language.id" );

        Language language = new Language();

        language.setId( Integer.parseInt( id ) );
        language.setCode( "z0" );
        language.setName( "Zzyzzx" );

        given().contentType( "application/json")
                .and()
                .body( language )
       .when()  .put ( "/language/" + id );
    }

    /**
     * We expect that testCreate() above added a new language, "Zzyzzx" to the
     * database and that we can delete it.
     */
    @Test
    public void testDelete()
    {
        String   json = get( "/language/name/Zzyzzx" ).asString();
        String   id   = JsonPath.with( json ).get( "language.id" );

        expect().statusCode( 200 )
        .when() .delete( "/language/" + id );
    }
}