package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
// -- ★1. ここから --
import org.springframework.boot.autoconfigure.security.oauth2.client.EnableOAuth2Sso;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
// -- ★1. ここまで追加 --

@SpringBootApplication
// -- ★2. ここから --
@EnableWebSecurity
@EnableOAuth2Sso
// -- ★2. ここまで追加 --
public class DemoApplication extends WebSecurityConfigurerAdapter {  // -- ★3. WebSecurityConfigurerAdapter を extends する

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

    // -- ★4. ここから --
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .antMatcher("/**")
            .authorizeRequests()
            .antMatchers("/", "/login**", "/webjars/**", "/error**")
            .permitAll()
            .anyRequest()
            .authenticated();
        http
            .logout()
            .logoutSuccessUrl("/")
            .permitAll();
    }
    // -- ★4. ここまで追加 --
}

package com.example.demo.services;

import java.util.List;

import javax.annotation.PostConstruct;

import org.springframework.context.annotation.Scope;
import org.springframework.context.annotation.ScopedProxyMode;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.oauth2.provider.OAuth2Authentication;
import org.springframework.security.oauth2.provider.authentication.OAuth2AuthenticationDetails;
import org.springframework.stereotype.Service;
import org.springframework.web.context.WebApplicationContext;

import jp.co.freee.accounting.ApiClient;
import jp.co.freee.accounting.api.CompaniesApi;
import jp.co.freee.accounting.api.UsersApi;
import jp.co.freee.accounting.models.CompaniesIndexResponseCompanies;
import jp.co.freee.accounting.models.UsersMeResponseUser;

@Service
@Scope(value = WebApplicationContext.SCOPE_SESSION, proxyMode = ScopedProxyMode.TARGET_CLASS)
public class AccountingService {

    private ApiClient _apiClient;

    public AccountingService() {
    }

    @PostConstruct
    public void init() {
        OAuth2AuthenticationDetails details = (OAuth2AuthenticationDetails) ((OAuth2Authentication) SecurityContextHolder.getContext().getAuthentication()).getDetails();
        _apiClient = new ApiClient("oauth2");
        String token = details.getTokenValue();
        _apiClient.setAccessToken(token);
    }

    public UsersMeResponseUser getUserInfo() {
        UsersApi api = _apiClient.createService(UsersApi.class);
        return api.getUsersMe(null).blockingSingle().getUser();
    }

    public List<CompaniesIndexResponseCompanies> getCompanies() {
        CompaniesApi api = _apiClient.createService(CompaniesApi.class);
        return api.getCompanies().blockingSingle().getCompanies();
    }
}

package com.example.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class HomeController {
    @GetMapping("/")
    public ModelAndView home() {
        return new ModelAndView("home");
    }
}

package com.example.demo.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.servlet.ModelAndView;

import com.example.demo.services.AccountingService;

@Controller
public class FreeeController {

    @Autowired
    private AccountingService _accountingService;

    @GetMapping("/user")
    public ModelAndView user() {
        return new ModelAndView("user", "user", _accountingService.getUserInfo());
    }

    @GetMapping("/companies")
    public ModelAndView companies() {
        return new ModelAndView("companies", "companies", _accountingService.getCompanies());
    }
}

package com.example.demo;

import java.util.Map;

import org.springframework.boot.autoconfigure.security.oauth2.resource.PrincipalExtractor;

public class FreeePrincipalExtractor implements PrincipalExtractor {

    @Override
    @SuppressWarnings("unchecked")
    public Object extractPrincipal(Map<String, Object> map) {
        Map<String, ?> user = (Map<String, ?>) map.get("user");
        return user.get("last_name") + " " + user.get("first_name");
    }
}

// -- ★5. ここから --
import org.springframework.boot.autoconfigure.security.oauth2.resource.PrincipalExtractor;
import org.springframework.context.annotation.Bean;
// -- ★5. ここまでの import を追加する

// -- 中略 --

@SpringBootApplication
@EnableOAuth2Sso
public class DemoApplication extends WebSecurityConfigurerAdapter {
    // -- 中略 --

    // -- ★6. ここから --
    @Bean
    public PrincipalExtractor freeePrincipalExtractor() {
        return new FreeePrincipalExtractor();
    }
    // -- ★6. ここまで追加する --
}