SpringBoot加载相关注解

springBoot加载

@Configuration

表明该类是一个配置类常常配合@Bean使用，让容器管理对象

@Configuration(proxyBeanMethods = true)

proxyBeanMethods = true表示@Configuration注解的类走不走代理，如果走代理会从单例池拿对象，拿到的对象是同一个，不走代理不会从单例池拿对象

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
}

@Bean

将指定类交给spring容器管理

@SpringBootApplication
public class TestSpringBootAnnoApplication {

    @Bean
    public UserService userService(){
        return new UserService();
    }

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(TestSpringBootAnnoApplication.class, args);
        UserService userService = context.getBean(UserService.class);
        System.out.println(userService);
    }

}

@Lazy

类的懒加载，调用时加载类并交给spring管理。

@Scope

指定交给spring容器管理的bean对象是单例或是多例的

@Scope(ConfigurableBeanFactory.SCOPE_SINGLETON)

@Scope("singleton")单例(默认) @Scope("prototype")多例

@SpringBootApplication
public class TestSpringBootAnnoApplication {

    @Bean
    @Scope("prototype")
    public UserService userService(){
        return new UserService();
    }

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(TestSpringBootAnnoApplication.class, args);
        UserService userService = context.getBean(UserService.class);
        UserService userService2 = context.getBean(UserService.class);
        System.out.println(userService==userService2);
    }

}

spring.factories

springboot在启动时会先寻找resource/META-INFO文件夹下有没有spring.factories文件，如果有就会解析，注入相应的类

META-INFO

#Auto
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.example.testspringbootanno.service.UserService

@ComponentScan

定义spring容器扫描的路径，扫描的spring注解才会被解析

@Profile

指定注入到spring容器的Bean生效的范围

spring.profiles.active=dev

@SpringBootApplication
public class TestSpringBootAnnoApplication {

    @Bean
    @Scope("prototype")
    @Profile("dev")
    public UserService userService(){
        return new UserService();
    }

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(TestSpringBootAnnoApplication.class, args);
        UserService userService = context.getBean(UserService.class);
        UserService userService2 = context.getBean(UserService.class);
        System.out.println(userService==userService2);
    }

}

@ConditionalOnBean

满足spring容器有某个springBean对象条件时把该对象交给spring管理。

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }

    @Bean
    @ConditionalOnBean(name = "oderService")
    public UserService userService(){
        return new UserService();
    }
}

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }

    @Bean
    @ConditionalOnBean(OrderService.class)
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnMissingBean

满足spring容器没有某个springBean对象条件时把该对象交给spring管理。

@Configuration
public class Appconfig {

    //@Bean
    public OrderService oderService(){
        return new OrderService();
    }

    @Bean
    @ConditionalOnMissingBean(OrderService.class)
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnSingleCandidate

是否符合指定的类型只有一个

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
    @Bean
    public OrderService oderService1(){
        return new OrderService();
    }

    @Bean
    @ConditionalOnSingleCandidate(OrderService.class)
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnClass

存在某个class生效

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
    @Bean
    @ConditionalOnClass(name = "com.example.testspringbootanno.service.OrderService")
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnMissingClass

不存在某个class生效

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
    @Bean
    @ConditionalOnMissingClass("com.example.testspringbootanno.service.OrderService")
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnExpression

根据表达式结果判断是否生效

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
    @Bean
    @ConditionalOnExpression("${test.condition}==true")
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnJava

指定的java版本生效

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
    @Bean
    @ConditionalOnJava(JavaVersion.ELEVEN)
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnWebApplication

Web环境生效

@ConditionalOnNotWebApplication

不是Web环境生效

@ConditionalOnProperty

判断配置文件中某个key是否存在

test.condition=true

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
    @Bean
    @ConditionalOnProperty(name = "test.condition")
    //@ConditionalOnProperty(name = "test1.condition",matchIfMissing = true) 确实了照样匹配
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnResource

某个资源存在时生效、

@Configuration
public class Appconfig {

    @Bean
    public OrderService oderService(){
        return new OrderService();
    }
    @Bean
    @ConditionalOnResource(resources = "http://www.baidu.com")
    public UserService userService(){
        return new UserService();
    }
}

@ConditionalOnWarDeployment

应用是war包时生效

@ConditionalOnCloudPlatform

应用在某个云平台时生效

读取配置文件

方法一：

@Component
@ConfigurationProperties(prefix = "user")
public class Aconfig {
    private String username;
    private String password;
}

方法二：

@ConfigurationProperties(prefix = "user")
public class Aconfig {
    private String username;
    private String password;
}

@Configuration
@EnableConfigurationProperties(Aconfig.class)
public class Appconfig {

}

还可以扫描,用于properties文件过多统一管理

@Configuration
@ConfigurationPropertiesScan("com.zhuoyue.properties")
public class Appconfig {

}

配置文件加载顺序

JVM环境变量(Envionment variables)>电脑环境变量>application.properties>application.yml