How do I execute HTTP Get request?

By Wayan in Apache HttpComponents 0 Comment

Below is an example using HttpClient library to retrieve the response of HTTP GET request. We start by creating an instance of CloseableHttpClient class. We then define an HTTP GET request by create an instance of HttpGet class and specify the Url of a website we are going to retrieve.

To execute the request we call the HttpClient.execute() method and pass the HttpGet as the arguments. This execution return an HttpResponse object. From this response object we can read the content of response by accessing the getEntity().getContent() which will give us an InputStream to the content.

For more detail let’s see the code snippet below:

package org.kodejava.apache.http;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class HttpGetExample {
    public static void main(String[] args) {
        try (CloseableHttpClient client = HttpClientBuilder.create().build()) {
            HttpGet request = new HttpGet("https://httpbin.org/get?id=1");

            HttpResponse response = client.execute(request);
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                try (InputStream stream = entity.getContent()) {
                    BufferedReader reader =
                            new BufferedReader(new InputStreamReader(stream));
                    String line;
                    while ((line = reader.readLine()) != null) {
                        System.out.println(line);
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.14</version>
</dependency>

Maven Central

How do I get entity ContentType in HttpClient?

By Wayan in Apache HttpComponents 0 Comment

This code snippet show you how to get the content-type of an HTTP Get request. The ContentType can be obtained by using ContentType.getOrDefault() method and passing an HttpEntity as the argument. The HttpEntity can be obtained from the HttpResponse object.

From the ContentType object we can get the mime-type by calling the getMimeType() method. This method will return a string value. To get the charset we can call the getCharset() method which will return a java.nio.charset.Charset object.

package org.kodejava.apache.http;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;

import java.io.IOException;
import java.nio.charset.Charset;

public class EntityContentType {
    public static void main(String[] args) {
        EntityContentType demo = new EntityContentType();
        demo.getContentType("https://www.google.com");
        demo.getContentType("https://www.google.com/images/srpr/logo3w.png");
    }

    public void getContentType(String url) {
        try (CloseableHttpClient client = HttpClientBuilder.create().build()) {
            HttpGet request = new HttpGet(url);
            HttpResponse response = client.execute(request);
            HttpEntity entity = response.getEntity();
            showContentType(entity);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void showContentType(HttpEntity entity) {
        ContentType contentType = ContentType.getOrDefault(entity);
        String mimeType = contentType.getMimeType();
        Charset charset = contentType.getCharset();

        System.out.println("MimeType = " + mimeType);
        System.out.println("Charset  = " + charset);
    }
}

The output of our code snippet are:

MimeType = text/html
Charset  = ISO-8859-1
MimeType = image/png
Charset  = null

Maven Dependencies

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.14</version>
</dependency>

Maven Central

How do I get HTTP response body as a string?

By Wayan in Apache HttpComponents 6 Comments

This example show you how to get HTTP response body as a string when using the Apache HttpComponents library. To get the response body as a string we can use the EntityUtils.toString() method. This method read the content of an HttpEntity object content and return it as a string. The content will be converted using the character set from the entity object.

Let’s see the code snippet below:

package org.kodejava.apache.http;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class EntityAsString {
    public static void main(String[] args) {
        try (CloseableHttpClient client = HttpClientBuilder.create().build()) {
            HttpGet request = new HttpGet("https://kodejava.org");

            HttpResponse response = client.execute(request);
            HttpEntity entity = response.getEntity();

            // Read the contents of an entity and return it as a String.
            String content = EntityUtils.toString(entity);
            System.out.println(content);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.14</version>
</dependency>

Maven Central