dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    implementation 'org.springframework.boot:spring-boot-starter-security'
    implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-jdbc'
    implementation 'org.keycloak:keycloak-spring-boot-starter'
    runtimeOnly 'mysql:mysql-connector-java'
    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }
    testImplementation 'org.springframework.security:spring-security-test'
}

dependencyManagement {
    imports {
        mavenBom "org.keycloak.bom:keycloak-adapter-bom:11.0.2"
    }
}

package com.betterjavacode.keycloakdemo.keycloakdemo.controllers;
import com.betterjavacode.keycloakdemo.keycloakdemo.dto.TaskDto;
import com.betterjavacode.keycloakdemo.keycloakdemo.managers.TaskManager;
import org.keycloak.KeycloakSecurityContext;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import javax.servlet.http.HttpServletRequest;
import java.util.List;
@Controller
public class TaskController
{
    private final HttpServletRequest request;
    @Autowired
    public TaskController(HttpServletRequest request)
    {
        this.request = request;
    }
    @Autowired
    private TaskManager taskManager;
    @GetMapping(value="/")
    public String home()
    {
        return "index";
    }
    @GetMapping(value="/tasks")
    public String getTasks(Model model)
    {
        List tasks = taskManager.getAllTasks();
        model.addAttribute("tasks", tasks);
        model.addAttribute("name", getKeycloakSecurityContext().getIdToken().getGivenName());
        return "tasks";
    }
    private KeycloakSecurityContext getKeycloakSecurityContext()
    {
        return (KeycloakSecurityContext) request.getAttribute(KeycloakSecurityContext.class.getName());
    }
}

keycloak.auth-server-url=http://localhost:8180/auth
keycloak.realm=SpringBootKeycloakApp
keycloak.resource=SpringBootApp
keycloak.public-client=true
keycloak.principal-attribute=preferred_username

keycloak.security-constraints[0].authRoles[0]=ROLE_User
keycloak.security-constraints[0].securityCollections[0].patterns[0]=/tasks

    @Override
    protected void configure(HttpSecurity httpSecurity) throws Exception
    {
        super.configure(httpSecurity);
        httpSecurity.authorizeRequests()
                .antMatchers("/tasks").hasRole("User")
                .anyRequest().permitAll();
    }

package com.betterjavacode.keycloakdemo.keycloakdemo.config;
import org.keycloak.adapters.springsecurity.KeycloakConfiguration;
import org.keycloak.adapters.springsecurity.authentication.KeycloakAuthenticationProvider;
import org.keycloak.adapters.springsecurity.config.KeycloakWebSecurityConfigurerAdapter;
import org.keycloak.adapters.springsecurity.management.HttpSessionManager;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.core.authority.mapping.SimpleAuthorityMapper;
import org.springframework.security.core.session.SessionRegistryImpl;
import org.springframework.security.web.authentication.session.RegisterSessionAuthenticationStrategy;
import org.springframework.security.web.authentication.session.SessionAuthenticationStrategy;
@KeycloakConfiguration
public class SecurityConfig extends KeycloakWebSecurityConfigurerAdapter
{
    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder authenticationManagerBuilder)
    {
        SimpleAuthorityMapper simpleAuthorityMapper = new SimpleAuthorityMapper();
        simpleAuthorityMapper.setPrefix("ROLE_");
        KeycloakAuthenticationProvider keycloakAuthenticationProvider =
                keycloakAuthenticationProvider();
        keycloakAuthenticationProvider.setGrantedAuthoritiesMapper(simpleAuthorityMapper);
        authenticationManagerBuilder.authenticationProvider(keycloakAuthenticationProvider);
    }
    @Bean
    @Override
    protected SessionAuthenticationStrategy sessionAuthenticationStrategy ()
    {
        return new RegisterSessionAuthenticationStrategy(new SessionRegistryImpl());
    }
    @Bean
    @Override
    @ConditionalOnMissingBean(HttpSessionManager.class)
    protected HttpSessionManager httpSessionManager()
    {
        return new HttpSessionManager();
    }
    @Override
    protected void configure(HttpSecurity httpSecurity) throws Exception
    {
        super.configure(httpSecurity);
        httpSecurity.authorizeRequests()
                .antMatchers("/tasks").hasRole("User")
                .anyRequest().permitAll();
    }
}

package com.betterjavacode.keycloakdemo.keycloakdemo.config;
import org.keycloak.adapters.springboot.KeycloakSpringBootConfigResolver;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class KeycloakConfig
{
    @Bean
    public KeycloakSpringBootConfigResolver keycloakSpringBootConfigResolver()
    {
        return new KeycloakSpringBootConfigResolver();
    }
}