Java HTTP Client (httpGet and httpPost with OAuth)

README.md

Java HTTP Client (httpGet, httpPost)

Full documentation see: XennisWiki - Java - JSON and REST

Used software

Used Java libraries

• Apache HttpClient (v.4.3.2)

Run

1. Included the necessary JARs in the Java build path

   • httpcomponents-client/lib/
     • commons-logging-1.1.3.jar
     • httpclient-4.3.2.jar
     • httpcore-4.3.1.jar

2. Compile all Java classes

Usage

Get JSON example with OAuth

String result = ApacheHttpClient.httpGet("http://example.org/api/message/", "application/json", "OAuth " + ACCESS_TOKEN);

Post JSON example wit OAuth

import org.apache.http.entity.ContentType;
// ...
boolean result = ApacheHttpClient.httpPost("http://example.org/api/message/", "OAuth " + ACCESS_TOKEN, stringEntity, ContentType.APPLICATION_JSON);

ApacheHttpClient.java

package org.example.sampleapi;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ConnectException;
import java.net.HttpURLConnection;

import org.apache.http.HttpHeaders;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClientBuilder;

/**
 * This class is used for GET and POST communication wit an Apache HTTP
 * server.
 * 
 * It requires:
 *   Apache HttpComponents "HttpClient" - http://hc.apache.org/downloads.cgi
 */
public class ApacheHttpClient {
	
	/**
	 * Do a HTTP GET request and return the result.
	 * 
	 * @param uri
	 *            URI for HTTP GET request
	 * @param headerAccept
	 *            Empty or header accept
	 * @param headerAuthorization
	 *            Empty or authorization header
	 * @return Response (content of the received entity)
	 * @throws RuntimeException
	 *             When status code is not HTTP_OK
	 */
	public static String httpGet(String uri, String headerAccept, String headerAuthorization) throws RuntimeException {
		StringBuilder result = new StringBuilder();
		HttpClient httpClient = HttpClientBuilder.create().build();

		try {
			HttpGet getRequest = new HttpGet(uri);
			if (!headerAccept.isEmpty()) {
				getRequest.addHeader(HttpHeaders.ACCEPT, headerAccept);				
			}
			if (!headerAuthorization.isEmpty()) {
				getRequest.addHeader(HttpHeaders.AUTHORIZATION, headerAuthorization);
			}
			HttpResponse response = httpClient.execute(getRequest);
			
			int statusCode = response.getStatusLine().getStatusCode();
			if (statusCode != HttpURLConnection.HTTP_OK) {
				throw new RuntimeException("ERROR: HTTP code: " + statusCode);
			}

			BufferedReader br = new BufferedReader(new InputStreamReader((response.getEntity().getContent())));
			
			String line = "";
			while((line = br.readLine()) != null){
				result.append(line);
			}
			br.close();

		} catch (ConnectException e) {
			System.err.println("ConnectException: " + e.getMessage());
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			httpClient.getConnectionManager().shutdown();
		}
		
		return result.toString();
	}
	
	/**
	 * Do a HTTT POST request and return the status code.
	 * 
	 * @param uri
	 *            URI for HTTP POST request
	 * @param headerAuthorization
	 *            Empty or authorization header
	 * @param stringEntity
	 *            String entity which will be posted
	 * @param entityConentType
	 *            Empty or entity content type
	 * @return True, when request was successful
	 * @throws RuntimeException
	 *             When status code is not HTTP_CREATED
	 */
	public static boolean httpPost(String uri, String headerAuthorization, String stringEntity, ContentType entityConentType) throws RuntimeException {
		HttpClient httpClient = HttpClientBuilder.create().build();
		
		try {
			HttpPost postRequest = new HttpPost(uri);
			if (!headerAuthorization.isEmpty()) {
				postRequest.addHeader(HttpHeaders.AUTHORIZATION, headerAuthorization);
			}
			
			StringEntity ent = new StringEntity(stringEntity);
			if (entityConentType != null) {
				ent.setContentType(entityConentType.toString());
			}
			postRequest.setEntity(ent);
			
			HttpResponse response = httpClient.execute(postRequest);
			
			int statusCode = response.getStatusLine().getStatusCode();			
			if (statusCode != HttpURLConnection.HTTP_CREATED) {
				throw new RuntimeException("ERROR: HTTP code: " + statusCode);
			}
			
			return true;

		} catch (IOException e) {
			e.printStackTrace();			
		} finally {
			httpClient.getConnectionManager().shutdown();
		}
		
		return false;
	}

}