底层注解@Configuration

springboot底层注解

@Configuration

@Configuration //告诉springboot这是一个配置类 默认是单实例 配置类也是组件
public class myConfig {
    //@Bean 给容器中添加组件 以方法名作为组件的id 返回值类型就是组件的类型 返回的值就是组件的实例
    //默认@Bean是以方法名作为组件id  如需添加自定义组件名称 就需要给@bean添加名称 例:@bean("Cat") 其中Cat就是组件的名字
    @Bean("Cat")
    public Pet getPet(){
        return new Pet("cat","eight");
    }
    @Bean("Xm")
    public User getUser(){
        return new User("小明");
    }
}

//Pet类
public class Pet {
    private String name;
    private String age;

    public Pet() {
    }

    public Pet(String name, String age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Pet{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }

}

//User类
public class User {
    private String name;

    public User() {
    }

    public User(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                '}';
    }
}
//检测组件是否成功注入
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(Application.class, args);
        boolean containsCat = applicationContext.containsBean("Cat");
        System.out.println("是否包含Cat:"+containsCat);
        boolean containsXm = applicationContext.containsBean("xm");
        System.out.println("是否包含User:"+containsXm);
    }
}
/**运行结果
是否包含Cat:true
是否包含User:true
*/

@import

@Import({User.class,String.class})//给组件中自动添加{}中类型的组件 {}为数组类型

@conditional

条件装配：满足conditional指定的条件 则进行组件注入

例子:

@Configuration() 
public class myConfig {
    @Bean("Cat")
    public Pet getPet(){
        return new Pet("cat","eight");
    }

    @ConditionalOnBean(name = "Cat") //如果容器中有Cat组件 将注入此组件 否则将不创建 此时容器中有Cat组件将会被注入
    @Bean("xm")
    public User getUser(){
        return new User("小明");
    }
}

//测试
@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(Application.class, args);
        boolean containsCat = applicationContext.containsBean("Cat");
        System.out.println("是否包含Cat:"+containsCat);
        boolean containsXm = applicationContext.containsBean("xm");
        System.out.println("是否包含User:"+containsXm);
    }

}
/**运行结果

是否包含Cat:true
是否包含User:true

*/

//下例为不满足条件 
@Configuration() 
public class myConfig {
    //@Bean("Cat")  将bean注释 此方法变为普通方法 容器中将不存在Cat这个组件
    public Pet getPet(){
        return new Pet("cat","eight");
    }

    @ConditionalOnBean(name = "Cat") //如果容器中有Cat组件 将注入此组件 否则将不创建 此时容器没有Cat组件将不会被注入
    @Bean("xm")
    public User getUser(){
        return new User("小明");
    }
}
//测试
@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(Application.class, args);
        boolean containsCat = applicationContext.containsBean("Cat");
        System.out.println("是否包含Cat:"+containsCat);
        boolean containsXm = applicationContext.containsBean("xm");
        System.out.println("是否包含User:"+containsXm);
    }

}
/**运行结果

是否包含Cat:false
是否包含User:false

*/

@ImportResource

@ImportResource("classpath:beans.xml") //将传统的xml配置导入到配置类中 并自动注入

@ConfigurationProperties---配置绑定

第一种方式:@component+@ConfigurationProperties

//Pet类
@Component
@ConfigurationProperties(prefix = "mypet")  //注：名称不能使用驼峰命名法
public class Pet {
    private String name;
    private String age;

    public Pet() {
    }

    public Pet(String name, String age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Pet{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }

}
//配置文件
mypet.name = dog
mypet.age = 1
//测试
@RestController
public class Controller1 {

    @Autowired
    Pet pet;
    @RequestMapping("/pet")
    Pet hasPet(){
        return pet;
    }
}

结果：

第二种方式：@EnableConfigurationProperties+@ConfigurationProperties

//配置类   @EnableConfigurationProperties()需要在配置类中使用
@Configuration()
@EnableConfigurationProperties(Pet.class)//为Pet类开启配置绑定 并自动注入到容器中
public class myConfig {
   
}
//配置文件 properties
mypet.name = dog
mypet.age = 1
//测试
@RestController
public class Controller1 {

    @Autowired
    Pet pet;
    @RequestMapping("/pet")
    Pet hasPet(){
        return pet;
    }
}

结果：