Spring Boot + OAuth 2 Client Credentials Grant - Hello World Example

Parameter	Value
grant_type (required)	client_credentials
client_id(required)	The client id
client_secret(required)	The client secret key

Define the Spring Boot Main Application.

package com.javainuse;

import java.security.Principal;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.security.oauth2.config.annotation.web.configuration.EnableResourceServer;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@EnableResourceServer
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

    //This method will be used to check if the user has a valid token to access the resource
	@RequestMapping("/validateUser")
	public Principal user(Principal user) {
		return user;
	}
}

Configure the Authorization Server. The @EnableAuthorizationServer annotation is used to configure the OAuth 2.0 Authorization Server mechanism and defines the behaviour of various endpoints when interacting with the authorization server.

package com.javainuse.config;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.oauth2.config.annotation.configurers.ClientDetailsServiceConfigurer;
import org.springframework.security.oauth2.config.annotation.web.configuration.AuthorizationServerConfigurerAdapter;
import org.springframework.security.oauth2.config.annotation.web.configuration.EnableAuthorizationServer;
import org.springframework.security.oauth2.config.annotation.web.configurers.AuthorizationServerEndpointsConfigurer;

@Configuration
@EnableAuthorizationServer
public class AuthorizationServer extends AuthorizationServerConfigurerAdapter {

	@Autowired
	private AuthenticationManager authenticationManager;

	@Override
	public void configure(AuthorizationServerEndpointsConfigurer endpoints) throws Exception {
		endpoints.authenticationManager(authenticationManager);
	}

	@Override
	public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
		clients.inMemory().withClient("javainuse-client").secret("javainuse-secret")
				.authorizedGrantTypes("client_credentials").scopes("resource-server-read", "resource-server-write");
	}
}

Resource Server

Next create the Resource Server which has the reource to be accessed by the client. Maven Project will be as follows-

Spring Boot OAuth2 Client Credentials Grant Maven

Spring Boot OAuth2 Client Credentials Grant Maven

In the Maven we need the Spring oauth dependency. Maven will be as follows-

<?xml version="1.0" encoding="UTF-8"?>
<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>com.javainuse</groupId>
	<artifactId>boot-oauth2-resource-server</artifactId>
	<version>0.0.1.SNAPSHOT</version>


	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.3.0.RELEASE</version>
	</parent>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-security</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.security.oauth</groupId>
			<artifactId>spring-security-oauth2</artifactId>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>


</project>

Define the Spring Boot Main Application. Configure the Resource Serverusing @EnableResourceServer annotation. It means the service expects an access token in order to process the request. Access token should be obtained from Authorization Server by OAuth 2.0 Client before calling the Resource Server.

package com.javainuse;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.security.oauth2.config.annotation.web.configuration.EnableResourceServer;
import org.springframework.web.bind.annotation.RestController;

@EnableResourceServer
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
}

Define the Controller, to expose API which can be accessed only using valid token.

package com.javainuse.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

	@RequestMapping("/test")
	public String test() {
		return "Hello World";
	}
}

Next define the url of the authorization server to be called by the resource server for verifying the token in the application.yml as follows.

security:
  oauth2:
    resource:
      userInfoUri: http://localhost:8080/validateUser
server:
  port: 9090

Finally start the Authorization Server and the Resource Server.

First get the Access Token by making a POST request to localhost:8080/oauth/token
- Specify the client_id and client_secret in the header using base64 encoding.
- Next specify the grant type as Client Credentials in body and send the request.
  
  We get the token as response
Get the Resource using the access token received above and making a GET call to localhost:9090/test.
The token is specified as Authorization Bearer.

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Spring Boot + OAuth2 Authorization Server for Client Credentials Grant
Spring Boot + OAuth2 Resource Server for Client Credentials Grant

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Spring Boot + OAuth 2 Client Credentials Grant - Hello World Example

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