Java client example using OAuth2

This example shows how to make a RESTful call using OAuth2 from Spring.

NB. I came across a bug where the server said it supported a token_type of "bearer", but actually only supported "Bearer". To get around it, I had to implement my own OAuth2RequestAuthenticator to force the case.

The code

Maven pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>darkmine</groupId>
	<artifactId>darkmine-oauth2</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>

		...

		<dependency>
			<groupId>org.springframework.security.oauth</groupId>
			<artifactId>spring-security-oauth2</artifactId>
			<version>2.0.9.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-web</artifactId>
			<version>4.2.5.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-core</artifactId>
			<version>2.7.3</version>
		</dependency>

		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.7.3</version>
		</dependency>

		...

	</dependencies>

</project>

Java client

Main program.

package org.darkmine.demo.oauth;

import org.springframework.http.ResponseEntity;
import org.springframework.security.oauth2.client.DefaultOAuth2ClientContext;
import org.springframework.security.oauth2.client.OAuth2RestTemplate;
import org.springframework.security.oauth2.client.token.grant.client.ClientCredentialsResourceDetails;
import org.springframework.web.util.UriComponentsBuilder;

import org.darkmine.demo.oauth.dto.Person;
import org.darkmine.demo.oauth.BearerAuthenticator;

public class OAuth2Demo {

	public static void main(String[] args) {

		// Setup
		
		String clientId = "CLIENT_ID";
		String clientSecret = "<SUPER_SECRET_CODE>";
		String url = "https://www.myprogram.url";
		
		// Prepare the credentials resource.
		
		ClientCredentialsResourceDetails resourceDetails = new ClientCredentialsResourceDetails();
		resourceDetails.setClientSecret(clientSecret);
		resourceDetails.setClientId(clientId);
		resourceDetails.setGrantType( "client_credentials" );
		resourceDetails.setAccessTokenUri( url + "/oauth");

		// Prepare our template and context (although the context isn't really needed in this example).
		
		DefaultOAuth2ClientContext clientContext = new DefaultOAuth2ClientContext();
		OAuth2RestTemplate oAuthRestTemplate = new OAuth2RestTemplate(resourceDetails,clientContext);
		oAuthRestTemplate.setAuthenticator( new BearerAuthenticator() );

		// Go fetch an access token.
		
		System.out.println( "AccessToken: " + oAuthRestTemplate.getAccessToken() );

		// Prepare our RESTful URL
		
		UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl( url + "/people");
		builder.queryParam( "countrycode" , "GBR" );

		// Make our API call.

		ResponseEntity<Person[]> pudoLocationsResponse = oAuthRestTemplate.getForEntity( builder.build().toUri() , Person[].class );

	}

}

This second class is used to get around a bug with some servers where the server said it supported a token_type of "bearer", but actually only supported "Bearer". Therefore we implement our own OAuth2RequestAuthenticator.

Lastly, setting the content-type here is not strictly necessary.

package org.darkmine.demo.oauth;

import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpRequest;
import org.springframework.security.oauth2.client.OAuth2ClientContext;
import org.springframework.security.oauth2.client.OAuth2RequestAuthenticator;
import org.springframework.security.oauth2.client.resource.OAuth2ProtectedResourceDetails;

public class BearerAuthenticator implements OAuth2RequestAuthenticator {

	@Override
	public void authenticate(OAuth2ProtectedResourceDetails resource, OAuth2ClientContext clientContext,ClientHttpRequest request) {
		request.getHeaders().set( "Authorization" , "Bearer " + clientContext.getAccessToken() );
		request.getHeaders().setContentType(MediaType.APPLICATION_JSON);
	}
	
}