@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
public @interface AutoConfiguration {
    
    /**
     * 自動(dòng)配置類的處理順序
     */
    AutoConfigurationPhase before() default AutoConfigurationPhase.NONE;
    
    /**
     * 在指定的自動(dòng)配置類之后處理
     */
    Class<?>[] after() default {};
    
    /**
     * 在指定的自動(dòng)配置類之前處理
     */
    Class<?>[] before() default {};
}

// 傳統(tǒng)方式
@Configuration
@ConditionalOnClass(DataSource.class)
@EnableConfigurationProperties(DataSourceProperties.class)
public class DataSourceAutoConfiguration {
    // 配置內(nèi)容
}

// 新方式（推薦）
@AutoConfiguration
@ConditionalOnClass(DataSource.class)
@EnableConfigurationProperties(DataSourceProperties.class)
public class DataSourceAutoConfiguration {
    // 配置內(nèi)容
}

// 明確表示這是一個(gè)自動(dòng)配置類
@AutoConfiguration
@ConditionalOnClass(RedisTemplate.class)
public class RedisAutoConfiguration {
    
    @Bean
    @ConditionalOnMissingBean
    public RedisTemplate redisTemplate() {
        return new RedisTemplate();
    }
}

// 控制自動(dòng)配置的執(zhí)行順序
@AutoConfiguration(
    before = DataSourceAutoConfiguration.class,
    after = WebMvcAutoConfiguration.class
)
@ConditionalOnClass(DataSource.class)
public class CustomDataSourceAutoConfiguration {
    // 配置內(nèi)容
}

@AutoConfiguration
@ConditionalOnClass(MyService.class)
@EnableConfigurationProperties(MyServiceProperties.class)
public class MyServiceAutoConfiguration {
    
    @Bean
    @ConditionalOnMissingBean
    public MyService myService(MyServiceProperties properties) {
        MyServiceImpl service = new MyServiceImpl();
        service.setConfig(properties);
        return service;
    }
}

@AutoConfiguration(
    before = {DataSourceAutoConfiguration.class},
    after = {WebMvcAutoConfiguration.class}
)
@ConditionalOnClass(CacheManager.class)
@EnableConfigurationProperties(CacheProperties.class)
public class CacheAutoConfiguration {
    
    @Bean
    @ConditionalOnMissingBean
    public CacheManager cacheManager(CacheProperties properties) {
        return new CustomCacheManager(properties);
    }
}

@AutoConfiguration
@ConditionalOnWebApplication
@ConditionalOnClass(Servlet.class)
@ConditionalOnProperty(prefix = "my.web", name = "enabled", havingValue = "true", matchIfMissing = true)
public class WebAutoConfiguration {
    
    @Bean
    public WebInterceptor webInterceptor() {
        return new WebInterceptor();
    }
    
    @Bean
    public WebFilter webFilter() {
        return new WebFilter();
    }
}

@AutoConfiguration
@ConditionalOnClass(JdbcTemplate.class)
@ConditionalOnProperty(name = "my.jdbc.enabled", havingValue = "true", matchIfMissing = true)
public class JdbcAutoConfiguration {
    
    @Bean
    @Primary
    @ConditionalOnMissingBean
    public JdbcTemplate jdbcTemplate(DataSource dataSource) {
        return new JdbcTemplate(dataSource);
    }
}

@AutoConfiguration
@EnableConfigurationProperties({
    DatabaseProperties.class,
    ConnectionProperties.class
})
@ConditionalOnClass(DataSource.class)
public class DatabaseAutoConfiguration {
    
    @Bean
    @ConditionalOnMissingBean
    public DataSource dataSource(DatabaseProperties dbProps, ConnectionProperties connProps) {
        // 創(chuàng)建數(shù)據(jù)源
        return createDataSource(dbProps, connProps);
    }
}

@AutoConfiguration(
    before = DataSourceAutoConfiguration.class,
    after = WebMvcAutoConfiguration.class
)

// 自定義屬性配置類
@ConfigurationProperties(prefix = "myapp.service")
public class MyServiceProperties {
    private String url = "http://localhost:8080";
    private int timeout = 5000;
    private boolean enabled = true;
    
    // getters and setters
}

// 自動(dòng)配置類
@AutoConfiguration
@ConditionalOnClass(MyService.class)
@ConditionalOnProperty(prefix = "myapp.service", name = "enabled", havingValue = "true", matchIfMissing = true)
@EnableConfigurationProperties(MyServiceProperties.class)
public class MyServiceAutoConfiguration {
    
    @Bean
    @ConditionalOnMissingBean
    public MyService myService(MyServiceProperties properties) {
        MyService service = new MyServiceImpl();
        service.setUrl(properties.getUrl());
        service.setTimeout(properties.getTimeout());
        return service;
    }
    
    @Bean
    @ConditionalOnMissingBean
    public MyServiceClient myServiceClient(MyService myService) {
        return new MyServiceClient(myService);
    }
}