/**
 * 只有當(dāng)應(yīng)用程序的類路徑中存在 RedisTemplate 類時(shí)，RedisConfiguration 類中定義的 redisTemplate() 方法才會(huì)被注冊(cè)為 Bean，并被 Spring 容器管理
 * 如果類路徑中不存在 RedisTemplate 類，則該配置類中的 Bean 將被忽略
 */
@Configuration
@ConditionalOnClass({org.springframework.data.redis.core.RedisTemplate.class})
public class RedisConfiguration {
    @Bean
    public RedisTemplate<String, Object> redisTemplate() {
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
        // 配置 RedisTemplate 的相關(guān)屬性
        return redisTemplate;
    }
}

/**
 * MyService 類被標(biāo)記為 @ConditionalOnBean(MyBean.class)，這意味著只有當(dāng)容器中存在 MyBean 類型的 Bean 時(shí)，MyService 才會(huì)被創(chuàng)建并添加到容器中
 */
@Configuration
public class MyConfiguration {
    @Bean
    public MyBean myBean() {
        return new MyBean();
    }
    @ConditionalOnBean(MyBean.class)
    @Bean
    public MyService myService() {
        return new MyService();
    }
}

/**
 * MyService 類被標(biāo)記為 @ConditionalOnBean({MyBean.class, AnotherBean.class})，這意味著只有當(dāng)容器中同時(shí)存在 MyBean 和 AnotherBean 類型的 Bean 時(shí)，MyService 才會(huì)被創(chuàng)建并添加到容器中
 */
@Configuration
public class MyConfiguration {
    @Bean
    public MyBean myBean() {
        return new MyBean();
    }
    @Bean
    public AnotherBean anotherBean() {
        return new AnotherBean();
    }
    @ConditionalOnBean({MyBean.class, AnotherBean.class})
    @Bean
    public MyService myService() {
        return new MyService();
    }
}

/**
 * MyService 類被標(biāo)記為 @ConditionalOnBean(name = {"myBean", "anotherBean"})，這意味著只有當(dāng)容器中同時(shí)存在名稱為 "myBean" 和 "anotherBean" 的 Bean 時(shí)，MyService 才會(huì)被創(chuàng)建并添加到容器中
 */
@Configuration
public class MyConfiguration {
    @Bean(name = "myBean")
    public MyBean myBean() {
        return new MyBean();
    }
    @Bean(name = "anotherBean")
    public AnotherBean anotherBean() {
        return new AnotherBean();
    }
    @ConditionalOnBean(name = {"myBean", "anotherBean"})
    @Bean
    public MyService myService() {
        return new MyService();
    }
}

/**
 * @ConditionalOnProperty 注解指定了一個(gè)名為myapp.feature.enabled 的屬性，當(dāng)這個(gè)屬性存在并且其值為"true"時(shí)，MyFeatureConfiguration 配置類中的配置會(huì)生效
 * havingValue 參數(shù)指定了期望的屬性值，如果沒有指定havingValue，則默認(rèn)匹配任何非空值
 * matchIfMissing 參數(shù)指定了當(dāng)配置文件中未設(shè)置該屬性時(shí)，是否應(yīng)該匹配。如果設(shè)置為 true，則表示當(dāng)屬性不存在時(shí)也匹配，這樣可以設(shè)置默認(rèn)行為
 */
@Configuration
@ConditionalOnProperty(
    name = "myapp.feature.enabled",
    havingValue = "true",
    matchIfMissing = true
)
public class MyFeatureConfiguration {
}

myapp.feature.enabled=true

/**
 * 檢查配置文件中的 my.config.enabled 屬性是否等于 'true'
 * 如果等于 'true'，則表達(dá)式結(jié)果為 true`，MyBean 實(shí)例將會(huì)被創(chuàng)建
 * 否則，表達(dá)式結(jié)果為 false，配置將被忽略，不會(huì)創(chuàng)建 MyBean 實(shí)例
 */
@Configuration
public class MyConfig {
    @Bean
    @ConditionalOnExpression("#{environment.getProperty('my.config.enabled') == 'true'}")
    public MyBean myBean() {
        // 配置生效時(shí)創(chuàng)建 MyBean 實(shí)例
        return new MyBean();
    }
}

/**
 * 使用 @ConditionalOnMissingBean 注解來判斷容器中是否已經(jīng)存在了 MyService 類型的 Bean
 * 如果不存在，則創(chuàng)建一個(gè) MyServiceImpl 實(shí)例并返回
 * 否則，不進(jìn)行任何操作。
 */
@Configuration
public class MyConfiguration {
    @Bean
    @ConditionalOnMissingBean(MyService.class)
    public MyService myService() {
        return new MyServiceImpl();
    }
}

/**
 * 郵件服務(wù)接口
 */
public interface EmailService {
    void sendWelcomeEmail(String email);
}
/**
 * 發(fā)送歡迎郵件
 */
@Service
public class EmailServiceImpl implements EmailService {
    @Override
    public void sendWelcomeEmail(String email) {
        // 發(fā)送歡迎郵件的邏輯
        System.out.println("Sending welcome email to: " + email);
    }
}

public interface UserService {
    public void registerUser(String email);
}
/**
 * 在用戶注冊(cè)時(shí)檢查是否已經(jīng)存在該用戶，如果不存在則發(fā)送歡迎郵件
 */
@Service
public class UserServiceImpl implements UserService {
    private final UserMapper userMapper;
    private final EmailService emailService;
    @Autowired
    public UserServiceImpl(UserMapper userMapper, EmailService emailService) {
        this.userMapper = userMapper;
        this.emailService = emailService;
    }
    @Override
    public void registerUser(String email) {
        if(!userMapper.existsByEmail(email)) {
            userMapper.save(email);
            emailService.sendWelcomeEmail(email);
        }else {
            throw new IllegalArgumentException("Email already exists");
        }
    }
}

/**
 * 不想使用數(shù)據(jù)庫，直接使用HashSet來模擬存儲(chǔ)用戶信息的email
 * 使用一個(gè)HashSet來存儲(chǔ)注冊(cè)過的email，HashSet不允許存儲(chǔ)重復(fù)的元素
 * @author LEK
 */
@Repository
public class UserMapper {
    private final Set<String> registeredEmails = new HashSet<>();
    public boolean existsByEmail(String email) {
        return registeredEmails.contains(email);
    }
    public void save(String email) {
        if (Objects.nonNull(email) && !email.isEmpty()) {
            registeredEmails.add(email);
        }
    }
}

@Configuration
public class EmailConfig {
    /**
     * 郵件配置
     * */
    @Bean
    @ConditionalOnMissingBean(EmailService.class)
    public EmailServiceImpl email() {
        return new EmailServiceImpl();
    }
}

@SpringBootTest
public class UserServiceImplTest {
    @Autowired
    private UserService userService;
    @Test
    public void testRegisterExistingUser() {
        String existingEmail = "existing@example.com";
        userService.registerUser(existingEmail);
        // 注冊(cè)已存在的用戶，預(yù)期會(huì)拋出 IllegalArgumentException
        userService.registerUser(existingEmail);
    }
}