Spring Boot 2.1+ OAuth2 Client Keycloak

application.properties

spring.security.oauth2.client.registration.demo-client.client-id=demo
spring.security.oauth2.client.registration.demo-client.client-secret=${CLIENT_SECRET}
spring.security.oauth2.client.registration.demo-client.provider=keycloak
spring.security.oauth2.client.registration.demo-client.scope=openid

spring.security.oauth2.client.provider.keycloak.issuer-uri=http://localhost:8888/auth/realms/master
spring.security.oauth2.client.provider.keycloak.user-name-attribute=preferred_username

OidcConfig.java

@Configuration
public class OidcConfig {
    @Bean
    public GrantedAuthoritiesMapper authoritiesMapper() {
        return new GrantedAuthoritiesMapper() {
            @Override
            public Collection<? extends GrantedAuthority> mapAuthorities(Collection<? extends GrantedAuthority> authorities) {
                return authorities;
            }
        };
    }
}

pom.xml

<?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>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.3.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

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

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

</project>