How do I send an HTTP POST request?

The following code snippet will show you how to send an HTTP post request using the Apache HttpComponents. We will send a post request to http://localhost:8080/register, with some parameters to the request using the NameValuePair object.

To pass this parameters to the HTTP post request we create an instance of UrlEncodedFormEntity and pass a list of NameValuePair as the arguments. And before executing the request we set this entity object to the HttpPost.setEntity() method.

Let’s see the code below:

package org.kodejava.example.httpclient;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class HttpPostExample {
    public static void main(String[] args) {
        HttpClient client = HttpClientBuilder.create().build();
        HttpPost post = new HttpPost("http://localhost:8080/register");

        // Create some NameValuePair for HttpPost parameters
        List<NameValuePair> arguments = new ArrayList<>(3);
        arguments.add(new BasicNameValuePair("username", "admin"));
        arguments.add(new BasicNameValuePair("firstName", "System"));
        arguments.add(new BasicNameValuePair("lastName", "Administrator"));

        try {
            post.setEntity(new UrlEncodedFormEntity(arguments));
            HttpResponse response = client.execute(post);

            // Print out the response message
            System.out.println(EntityUtils.toString(response.getEntity()));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<!-- https://search.maven.org/remotecontent?filepath=org/apache/httpcomponents/httpclient/4.5.9/httpclient-4.5.9.jar -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.9</version>
</dependency>

Maven Central

How do I add query string to HttpMethod object?

To send query string information in HTTP GET command you either using passing a simple string or an array of NameValuePair object into the HttpMethod‘s setQueryString() method. We also need to encode the parameter values before passing it to the method.

package org.kodejava.example.commons.httpclient;

import org.apache.commons.httpclient.*;
import org.apache.commons.httpclient.util.URIUtil;
import org.apache.commons.httpclient.methods.GetMethod;

import java.io.IOException;

public class SendingQueryParameter {
    public static void main(String[] args) {
        HttpClient client = new HttpClient();
        HttpMethod method = new GetMethod("http://localhost:8080/hello.jsp");

        try {
            // Set query string information for accessing the page using a
            // simple string information.
            method.setQueryString(URIUtil.encodeQuery("catid=10&page=1"));
            client.executeMethod(method);

            // Other cleaner alternative is to use the NameValuePair object to
            // define the parameters for a HTTP GET method.
            NameValuePair param1 = new NameValuePair("catid", URIUtil.encodeQuery("20"));
            NameValuePair param2 = new NameValuePair("page", URIUtil.encodeQuery("2"));
            NameValuePair[] params = new NameValuePair[] {param1, param2};
            method.setQueryString(params);
            client.executeMethod(method);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            method.releaseConnection();
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/commons-httpclient/commons-httpclient/3.1/commons-httpclient-3.1.jar -->
<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>