Apache HttpClient HTML Form POST Request Example

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Apache HttpClient Tutorial

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Introduction

Apache HttpClient is a powerful and flexible library for handling HTTP requests in Java. It supports various HTTP methods and can handle different types of request bodies, including HTML form data. This tutorial will demonstrate how to send an HTML form POST request using Apache HttpClient.

Maven Dependencies

To use Apache HttpClient, you need to add the following dependency to your pom.xml file:

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents.client5/httpclient5 -->
<dependency>
    <groupId>org.apache.httpcomponents.client5</groupId>
    <artifactId>httpclient5</artifactId>
    <version>5.3</version>
</dependency>

Example Scenario

We will create a simple Java class that sends a POST request with HTML form data to a specified URL and prints the response.

JSONPlaceholder API

For this example, we will use the JSONPlaceholder API. Although it is primarily used for JSON requests, it will still accept form data for testing purposes. The URL for the POST endpoint is:

https://jsonplaceholder.typicode.com/posts

Java Class for Sending HTML Form POST Request

Create a class named HttpClientFormPostExample with the following code:

import org.apache.hc.client5.http.classic.methods.HttpPost;
import org.apache.hc.client5.http.classic.methods.CloseableHttpResponse;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.io.entity.EntityUtils;
import org.apache.hc.core5.http.io.entity.StringEntity;
import org.apache.hc.core5.http.ContentType;

import java.util.ArrayList;
import java.util.List;

import org.apache.hc.core5.http.NameValuePair;
import org.apache.hc.core5.http.message.BasicNameValuePair;
import org.apache.hc.core5.net.URLEncodedUtils;

public class HttpClientFormPostExample {

    public static void main(String[] args) {
        String url = "https://jsonplaceholder.typicode.com/posts";

        // Create HttpClient
        try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
            
            // Create HttpPost request
            HttpPost request = new HttpPost(url);
            
            // Set form data
            List<NameValuePair> params = new ArrayList<>();
            params.add(new BasicNameValuePair("title", "foo"));
            params.add(new BasicNameValuePair("body", "bar"));
            params.add(new BasicNameValuePair("userId", "1"));
            String form = URLEncodedUtils.format(params, "UTF-8");
            StringEntity entity = new StringEntity(form, ContentType.APPLICATION_FORM_URLENCODED);
            request.setEntity(entity);
            
            // Set headers
            request.setHeader("Accept", "application/json");
            request.setHeader("Content-type", "application/x-www-form-urlencoded");
            
            // Execute the request
            try (CloseableHttpResponse response = httpClient.execute(request)) {
                
                // Get HttpResponse Status
                System.out.println("Response Code: " + response.getCode());
                
                // Get HttpResponse Content
                String content = EntityUtils.toString(response.getEntity());
                System.out.println("Response Content: \n" + content);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Explanation

1. Adding Maven Dependencies:

   • The org.apache.httpcomponents.client5:httpclient5 dependency provides the classes needed to create and execute HTTP requests using Apache HttpClient.

2. Creating HttpClient:

   • CloseableHttpClient httpClient = HttpClients.createDefault(); creates an instance of CloseableHttpClient using the default configuration.

3. Creating HttpPost Request:

   • HttpPost request = new HttpPost(url); creates an HttpPost request for the specified URL.

4. Setting Form Data:

   • Create a list of NameValuePair objects representing the form data fields.
   • Use URLEncodedUtils.format(params, "UTF-8"); to encode the form data as a URL-encoded string.
   • StringEntity entity = new StringEntity(form, ContentType.APPLICATION_FORM_URLENCODED); creates a StringEntity with the form data and sets the content type to application/x-www-form-urlencoded.
   • request.setEntity(entity); sets the entity (payload) for the POST request.

5. Setting Headers:

   • request.setHeader("Accept", "application/json"); sets the Accept header to application/json.
   • request.setHeader("Content-type", "application/x-www-form-urlencoded"); sets the Content-type header to application/x-www-form-urlencoded.

6. Executing the Request:

   • try (CloseableHttpResponse response = httpClient.execute(request)) { ... } executes the POST request and retrieves the response.

7. Getting HttpResponse Status:

   • System.out.println("Response Code: " + response.getCode()); prints the status code of the HTTP response.

8. Getting HttpResponse Content:

   • String content = EntityUtils.toString(response.getEntity()); converts the response entity to a string and prints the content.

Running the Example

To run the example, simply execute the HttpClientFormPostExample class. You should see the status code and the response content printed in the console.

Example Output

Response Code: 201
Response Content: 
{
  "title": "foo",
  "body": "bar",
  "userId": "1",
  "id": 101
}

Additional Configuration

Setting Custom Headers

You can set custom headers for the POST request by using the setHeader method on the HttpPost object.

request.setHeader("User-Agent", "Mozilla/5.0");

Handling Redirects

By default, Apache HttpClient handles redirects automatically. You can customize this behavior by using a custom HttpClientBuilder.

CloseableHttpClient httpClient = HttpClients.custom()
    .setRedirectStrategy(new DefaultRedirectStrategy() {
        @Override
        protected boolean isRedirectable(String method) {
            return true;
        }
    })
    .build();

Setting Timeouts

You can set connection and socket timeouts by using RequestConfig.

RequestConfig requestConfig = RequestConfig.custom()
    .setConnectTimeout(5000)
    .setSocketTimeout(5000)
    .build();

HttpPost request = new HttpPost(url);
request.setConfig(requestConfig);

Conclusion

Using Apache HttpClient to make an HTML form POST request is straightforward and flexible. By following this tutorial, you should now be able to create and execute POST requests with form data, handle responses, and customize various aspects of the HTTP request and response process. Apache HttpClient provides a comprehensive set of features that make it an excellent choice for handling HTTP operations in Java applications. The JSONPlaceholder API serves as a practical and convenient source for testing and prototyping your HTTP requests.

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Apache HttpClient Tutorial

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