Apache HttpClient GET and POST examples

Apache HttpClient GET and POST examples

The Apache HttpClient library allows to handling HTTP requests.

In this tutorial we will see GET and POST methods with examples

Maven dependency

 

    org.apache.httpcomponents
    httpclient
    4.1.1

Apache HttpClient with GET API

Java program for how to send json data using http get request.

public static void demoGetRESTAPI() throws Exception 
{
    DefaultHttpClient httpClient = new DefaultHttpClient();
    try
    {
        //Define a HttpGet request; You can choose between HttpPost, HttpDelete or HttpPut also.
        //Choice depends on type of method you will be invoking.
        HttpGet getRequest = new HttpGet("https://run.mocky.io/v3/8ca4a60c-7bae-440f-94f6-909fceb75d5a");
         
        //Set the API media type in http accept header
        getRequest.addHeader("accept", "application/xml");
          
        //Send the request; It will immediately return the response in HttpResponse object
        HttpResponse response = httpClient.execute(getRequest);
         
        //verify the valid error code first
        int statusCode = response.getStatusLine().getStatusCode();
        if (statusCode != 200) 
        {
            throw new RuntimeException("Failed with HTTP error code : " + statusCode);
        }
         
        //Now pull back the response object
        HttpEntity httpEntity = response.getEntity();
        String apiOutput = EntityUtils.toString(httpEntity);
         
        //Lets see what we got from API
        System.out.println(apiOutput); //demouser
         
        //In realtime programming, you will need to convert this http response to some java object to re-use it.
        //Lets see how to jaxb unmarshal the api response content
        JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);
        Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
        Customer customer = (Customer) jaxbUnmarshaller.unmarshal(new StringReader(apiOutput));
         
         //Verify the populated object
        System.out.println(customer.getId());
        System.out.println(customer.getName());
        System.out.println(customer.getPhone());

System.out.println(customer.getAddress));

System.out.println(customer.getCity());


System.out.println(customer.getCountry());

System.out.println(customer.getPin());

    }
    finally
    {
        //Important: Close the connect
        httpClient.getConnectionManager().shutdown();
    }
}

Apache HttpClient with POST API

Java program for how to send json data to server using http post request.

public static void AddCustomer() throws Exception 
{
    DefaultHttpClient httpClient = new DefaultHttpClient();
 Customer customer = new Customer();
 customer.setId(2);
 customer.setName("Bala");
 customer.setPhone("0987654321");

customer.setAddress("xyz");
 customer.setCity("Mumbai");


customer.setCountry("India");

customer.setPin(400702);
 
    StringWriter writer = new StringWriter();
    JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);
    Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
    jaxbMarshaller.marshal(user, writer);
     
    try
    {
        //Define a postRequest request
        HttpPost postRequest = new HttpPost("http://localhost:8080/customer
         
        //Set the API media type in http content-type header
        postRequest.addHeader("content-type", "application/xml");
         
        //Set the request post body
        StringEntity userEntity = new StringEntity(writer.getBuffer().toString());
        postRequest.setEntity(userEntity);
          
        //Send the request; It will immediately return the response in HttpResponse object if any
        HttpResponse response = httpClient.execute(postRequest);
         
        //verify the valid error code first
        int statusCode = response.getStatusLine().getStatusCode();
        if (statusCode != 200) 
        {
            throw new Exception("Failed with HTTP error code : " + statusCode);
        }
    }
    finally
    {
        //Important: Close the connect
        httpClient.getConnectionManager().shutdown();
    }
}

In this article, we have seen Apache HttpClient GET and POST examples . All source code in the article can be found in the GitHub repository.