Found answer for the below Request,

API request body,

[
  {
    "userId": "value1"
 },{
    "userId": "value2"
  }
]

Solution :

public String sendingRequest(String uid, String uid1){

   JSONObject user1 = new JSONObject();
   user1.put("userId", uid);

   JSONObject user2 = new JSONObject();
   user2.put("userId", uid1);

   JSONArray jsonArray = new JSONArray();
   jsonArray.put(user1);
   jsonArray.put(user2);

   String jsonStr = jsonArray.toString();

   System.out.println("jsonString: "+jsonStr);
   return jsonStr;
}

Outcome:

[{"userId":"ljtdmm"},{"userId":"BBLSHl"}]

The body() method accepts a path and a Hamcrest matcher (see the javadocs).

So, you could do this:

response.then().assertThat().body("$", customMatcher);

For example:

// 'expected' is the serialised form of your Person
// this is a crude way of creating that serialised form
// you'll probably use whatever JSON de/serialisaiotn library is in use in your project 
Map<String, Object> expected = new HashMap<String, Object>();
expected.put("id", 1);
expected.put("name", "text");

response.then().assertThat().body("$", Matchers.hasItem(expected));

I dit it:

.body("validSession",is(true))
.body("description[0].userType", equalTo(1))
.body("description[0].userTypeDescription", containsString("xxx"))
.body("description[0].uname", containsString("xx"))
.body("description[0].distributorId", equalTo(1));

I tested and it worked. but I did not understand why it only worked by putting all elements of the array with index zero.

Can you explain?

@GFB Did you set up the ContentType? Try to use something like this:

List<ProdReq> prodReq = new ArrayList<>();
... set up the data. 

given().contentType(ContentType.JSON).when().body(prodReq).post({{api_url}}).then().extract().response();

I'm using serialization of the object to JSON body without any problems in my project.

Solved! I have solved it this way:

@Test
public void test() {
    RestAssured.get("/foos").then().assertThat()
      .body("size()", is(2));
}

To save any clicking, you have to supply a redundant string to the body method call:

when().
   get("/names").
then().
   body("", hasItems("alice","jason","steve","alex"));

Additionally, even if you only have one item in your array, you still have to use hasItems rather than hasItem. For example:

when().
   get("/names").
then().
   body("", hasItems("alice"));