Rest API Automation in Java - Post Method

In this post, we will be using Rest-Assured library and TestNG to automate the http post method of a Rest-ful API. Rest Assured is a Java library using which we can test and validate the REST web services. Although Rest-assured provides its own validating mechanism(assertions for validating response) but we can combine Rest-assured with TestNG to get the best of both the libraries.

During the course of this tutorial, we will be using the following-

• Sample Rest API to be used in Automation - RestCountries API
• Rest-Assured and its dependencies (https://code.google.com/p/rest-assured/wiki/Downloads) (Remember to download and add to class path, the other dependencies also). POM dependencies for the Rest Assured and its dependencies-

  <dependency>
      <groupId>com.jayway.restassured</groupId>
      <artifactId>rest-assured</artifactId>
      <version>2.3.4</version>
  </dependency>
  
  <dependency>
   <groupId>org.codehaus.groovy</groupId>
   <artifactId>groovy-all</artifactId>
   <version>2.3.5</version>
  </dependency>
  

• TestNG as testing framework

Automating Rest API HTTP Post method

The following code snippet uses requestSpecBuilder to create a post request. We have used the following parameters in our code, you need to set them as per your requirement-

• APIUrl - Set APIUrl variable with the URL of the Rest API
• APIBody - Set APIBody variable with body of the Rest API containing parameters e.g. {"key1":"value1","key2":"value2"}
• setContentType() - Pass the "application/json", "application/xml" or "text/html" etc. headers to setContenType() method
• Authentication credentials - Pass the username and password to the basic() method and in case of no authentication leave them blank basic("","")

The comments in the following code make it self-explanatory.

@Test
public void httpPost() throws JSONException,InterruptedException {
  
 //Initializing Rest API's URL
 String APIUrl = "http://{API URL}";
  
 //Initializing payload or API body
 String APIBody = "{API Body}"; //e.g.- "{\"key1\":\"value1\",\"key2\":\"value2\"}"
    
 // Building request using requestSpecBuilder
 RequestSpecBuilder builder = new RequestSpecBuilder();
  
 //Setting API's body
 builder.setBody(APIBody);
  
 //Setting content type as application/json or application/xml
 builder.setContentType("application/json; charset=UTF-8");
  
 RequestSpecification requestSpec = builder.build();

 //Making post request with authentication, leave blank in case there are no credentials- basic("","")
 Response response = given().authentication().preemptive().basic({username}, {password})
    .spec(requestSpec).when().post(APIUrl);
 JSONObject JSONResponseBody = new JSONObject(response.body().asString());

 //Fetching the desired value of a parameter
 String result = JSONResponseBody.getString({key});
  
 //Asserting that result of Norway is Oslo
 Assert.assertEquals(result, "{expectedValue}");

 }