Java SpringBoot自動設定原理詳情

#############################Configuration使用範例######################################################
/**
 * 1、設定類裡面使用@Bean標註在方法上給容器註冊元件，預設也是單範例的
 * 2、設定類本身也是元件
 * 3、proxyBeanMethods：代理bean的方法
 *      Full(proxyBeanMethods = true)、【保證每個@Bean方法被呼叫多少次返回的元件都是單範例的】
 *      Lite(proxyBeanMethods = false)【每個@Bean方法被呼叫多少次返回的元件都是新建立的】
 *      元件依賴必須使用Full模式預設。其他預設是否Lite模式
 *
 *
 *
 */
@Configuration(proxyBeanMethods = false) //告訴SpringBoot這是一個設定類 == 組態檔
public class MyConfig {
    /**
     * Full:外部無論對設定類中的這個元件註冊方法呼叫多少次獲取的都是之前註冊容器中的單範例物件
     * @return
     */
    @Bean //給容器中新增元件。以方法名作為元件的id。返回型別就是元件型別。返回的值，就是元件在容器中的範例
    public User user01(){
        User zhangsan = new User("zhangsan", 18);
        //user元件依賴了Pet元件
        zhangsan.setPet(tomcatPet());
        return zhangsan;
    }
    @Bean("tom")
    public Pet tomcatPet(){
        return new Pet("tomcat");
    }
}
################################@Configuration測試程式碼如下########################################
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan("com.atguigu.boot")
public class MainApplication {
    public static void main(String[] args) {
        //1、返回我們IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
 
        //2、檢視容器裡面的元件
        String[] names = run.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
        //3、從容器中獲取元件
        Pet tom01 = run.getBean("tom", Pet.class);
        Pet tom02 = run.getBean("tom", Pet.class);
        System.out.println("元件："+(tom01 == tom02));

        //4、com.atguigu.boot.config.MyConfig$$EnhancerBySpringCGLIB$$51f1e1ca@1654a892
        MyConfig bean = run.getBean(MyConfig.class);
        System.out.println(bean);
 
        //如果@Configuration(proxyBeanMethods = true)代理物件呼叫方法。SpringBoot總會檢查這個元件是否在容器中有。
        //保持元件單範例
        User user = bean.user01();
        User user1 = bean.user01();
        System.out.println(user == user1);
        User user01 = run.getBean("user01", User.class);
        Pet tom = run.getBean("tom", Pet.class);
        System.out.println("使用者的寵物："+(user01.getPet() == tom));

    }
}

 * 4、@Import({User.class, DBHelper.class})
 *      給容器中自動建立出這兩個型別的元件、預設元件的名字就是全類名
 *
 *
 *
 */
@Import({User.class, DBHelper.class})
@Configuration(proxyBeanMethods = false) //告訴SpringBoot這是一個設定類 == 組態檔
public class MyConfig {
}

=====================測試條件裝配==========================
@Configuration(proxyBeanMethods = false) //告訴SpringBoot這是一個設定類 == 組態檔
//@ConditionalOnBean(name = "tom")
@ConditionalOnMissingBean(name = "tom")
public class MyConfig {
    /**
     * Full:外部無論對設定類中的這個元件註冊方法呼叫多少次獲取的都是之前註冊容器中的單範例物件
     * @return
     */
    @Bean //給容器中新增元件。以方法名作為元件的id。返回型別就是元件型別。返回的值，就是元件在容器中的範例
    public User user01(){
        User zhangsan = new User("zhangsan", 18);
        //user元件依賴了Pet元件
        zhangsan.setPet(tomcatPet());
        return zhangsan;
    }
 
    @Bean("tom22")
    public Pet tomcatPet(){
        return new Pet("tomcat");
    }
}
public static void main(String[] args) {
        //1、返回我們IOC容器
        ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
 
        //2、檢視容器裡面的元件
        String[] names = run.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
        boolean tom = run.containsBean("tom");
        System.out.println("容器中Tom元件："+tom);
        boolean user01 = run.containsBean("user01");
        System.out.println("容器中user01元件："+user01);
        boolean tom22 = run.containsBean("tom22");
        System.out.println("容器中tom22元件："+tom22);
    }

======================beans.xml=========================
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
 
    <bean id="haha" class="com.atguigu.boot.bean.User">
        <property name="name" value="zhangsan"></property>
        <property name="age" value="18"></property>
    </bean>
 
    <bean id="hehe" class="com.atguigu.boot.bean.Pet">
        <property name="name" value="tomcat"></property>
    </bean>
</beans>

@ImportResource("classpath:beans.xml")
public class MyConfig {}
 
======================測試=================
        boolean haha = run.containsBean("haha");
        boolean hehe = run.containsBean("hehe");
        System.out.println("haha："+haha);//true
        System.out.println("hehe："+hehe);//true

public class getProperties {
     public static void main(String[] args) throws FileNotFoundException, IOException {
         Properties pps = new Properties();
         pps.load(new FileInputStream("a.properties"));
         Enumeration enum1 = pps.propertyNames();//得到組態檔的名字
         while(enum1.hasMoreElements()) {
             String strKey = (String) enum1.nextElement();
             String strValue = pps.getProperty(strKey);
             System.out.println(strKey + "=" + strValue);
             //封裝到JavaBean。
         }
     }
 }

/**
 * 只有在容器中的元件，才會擁有SpringBoot提供的強大功能
 */
@Component
@ConfigurationProperties(prefix = "mycar")
public class Car {
    private String brand;
    private Integer price;
 
    public String getBrand() {
        return brand;
    }
    public void setBrand(String brand) {
        this.brand = brand;
    }
    public Integer getPrice() {
        return price;
    }
    public void setPrice(Integer price) {
        this.price = price;
    }
    @Override
    public String toString() {
        return "Car{" +
                "brand='" + brand + ''' +
                ", price=" + price +
                '}';
    }
}

@Import(AutoConfigurationPackages.Registrar.class)  //給容器中匯入一個元件
public @interface AutoConfigurationPackage {}

//利用Registrar給容器中匯入一系列元件
//將指定的一個包下的所有元件匯入進來，MainApplication 所在包下。