01.Spring Framework 之組件註冊

1. Spring 組件注入

Spring 組件注入有 4 種方式

• 包掃描 + 組件標註註解（@Controller、@Service、@Repository、@Component），配合 @ComponentScan 註解使用，主要用於自己寫的類

• @Bean（導入第三方的組件）

• @Import：給容器中導入一個組件

  • @Import：向容器中註冊組件一個 class，id 默認是全類名

  • ImportSelector：返回需要導入的組件的全類名數組

  • ImportBeanDefinitionRegistrar：手動註冊 bean 到容器中

• FactoryBean（工廠 Bean）

1.1 @ComponentScan

代碼已經上傳至 https://github.com/masteryourself-tutorial/tutorial-spring ，詳見 tutorial-spring-framework/tutorial-spring-framework-register/tutorial-spring-framework-register-componentscan 工程

1.1.1 使用方式

@ComponentScan：指定要掃描的包

• excludeFilters=ComponentScan.Filter[]，按照規則排除某些組件

• includeFilters=ComponentScan.Filter[]，按照規則包含某些組件，需要將 useDefaultFilters=false 纔會生效

1.1.2 環境搭建

1. SpringConfig

/**
 * <p>description : SpringConfig
 * 第一個 {@link ComponentScan} 排除了 {@link Repository} 和 {@link Controller} 註解，即只掃描了 {@link PersonService}
 * 第二個 {@link ComponentScan} 掃描了 {@link Controller} 註解類型和 {@link PersonDao} 類型，注意這裏要把 useDefaultFilters 屬性設置爲 false
 * 第三個 {@link ComponentScan} 根據 {@link CustomTypeFilter} 自定義加載 bean
 *
 * <p>
 * FilterType.ANNOTATION 按照註解匹配
 * FilterType.ASSIGNABLE_TYPE 按照指定的類型
 * FilterType.ASPECTJ 使用 ASPECTJ 表達式
 * FilterType.REGEX 使用正則表達式
 * FilterType.CUSTOM 使用自定義方式
 *
 * <p>blog : https://blog.csdn.net/masteryourself
 *
 * @author : masteryourself
 * @version : 1.0.0
 * @date : 2020/3/28 20:20
 */
@Configuration
@ComponentScan(
        value = "pers.masteryourself.tutorial.spring.framework.register",
        excludeFilters = {@ComponentScan.Filter(type = FilterType.ANNOTATION, value = {Repository.class, Controller.class})}
)
@ComponentScan(
        value = "pers.masteryourself.tutorial.spring.framework.register",
        includeFilters = {
                @ComponentScan.Filter(type = FilterType.ANNOTATION, value = Controller.class),
                @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, value = PersonDao.class)
        }, useDefaultFilters = false
)
@ComponentScan(value = "pers.masteryourself.tutorial.spring.framework.register", includeFilters = {
        @ComponentScan.Filter(type = FilterType.CUSTOM, classes = CustomTypeFilter.class)
}, useDefaultFilters = false)
public class SpringConfig {
}

1.2 @Bean

代碼已經上傳至 https://github.com/masteryourself-tutorial/tutorial-spring ，詳見 tutorial-spring-framework/tutorial-spring-framework-register/tutorial-spring-framework-register-bean 工程

1.2.1 使用方式

@Configuration：聲明是一個配置類，相當於 xml 配置文件

@Bean：給容器注入一個 bean，類型爲返回值的類型，id 默認是方法名作爲 id，可以通過 name 修改

1.2.2 環境搭建

1. SpringConfig

@Configuration
public class SpringConfig {

	@Bean(name = "personXxx")
	public Person person() {
		return new Person();
	}

}

1.3 @Import

代碼已經上傳至 https://github.com/masteryourself-tutorial/tutorial-spring ，詳見 tutorial-spring-framework/tutorial-spring-framework-register/tutorial-spring-framework-register-import 工程

1.3.1 使用方式

@Import：向容器中註冊組件一個 class，id 默認是全類名

ImportSelector：返回需要導入的組件的全類名數組

ImportBeanDefinitionRegistrar：手工註冊 bean 到容器中

1.3.2 環境搭建

1. ExtImportSelector

public class ExtImportSelector implements ImportSelector {

    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        return new String[]{"pers.masteryourself.tutorial.spring.framework.register.bean.Dog"};
    }

}

2. ExtImportBeanDefinitionRegistrar

public class ExtImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {

    @Override
    public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry registry) {
        Map<String, Object> annotationAttributes = annotationMetadata.getAnnotationAttributes(Import.class.getName());
        // 獲取註解元數據：
        // {value=[
        // class pers.masteryourself.tutorial.spring.framework.register.bean.Cat,
        // class pers.masteryourself.tutorial.spring.framework.register.config.ExtImportSelector,
        // class pers.masteryourself.tutorial.spring.framework.register.config.ExtImportBeanDefinitionRegistrar]
        // }
        System.out.println("獲取註解元數據：" + annotationAttributes);
        // 指定 bean 定義信息
        BeanDefinition beanDefinition = new RootBeanDefinition(Mouse.class);
        // 手工註冊
        registry.registerBeanDefinition("mouse", beanDefinition);
    }

}

3. SpringConfig

@Import({Cat.class, ExtImportSelector.class, ExtImportBeanDefinitionRegistrar.class})
public class SpringConfig {
}

1.4 FactoryBean

代碼已經上傳至 https://github.com/masteryourself-tutorial/tutorial-spring ，詳見 tutorial-spring-framework/tutorial-spring-framework-register/tutorial-spring-framework-register-factorybean 工程

1.4.1 使用方式

FactoryBean：使用 spring 提供的 FactoryBean（工廠 bean）

默認獲取到的是工廠 bean 調用 getObject() 方法創建的對象

要獲取工廠 bean 本身，需要在 id 前面加一個 &

1.4.2 環境搭建

1. PersonFactoryBean

public class PersonFactoryBean implements FactoryBean<Person> {

    @Override
    public Person getObject() throws Exception {
        System.out.println("調用了 PersonFactoryBean.getObject() 方法");
        return new Person();
    }

    @Override
    public Class<?> getObjectType() {
        return Person.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }

}

2. SpringConfig

@Configuration
public class SpringConfig {

    @Bean(name = "person")
    public PersonFactoryBean personFactoryBean() {
        return new PersonFactoryBean();
    }

}

3. FactoryBeanTest

public class FactoryBeanApplication {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
        // 調用了 PersonFactoryBean.getObject() 方法
        Person person1 = context.getBean("person", Person.class);
        Person person2 = context.getBean("person", Person.class);
        // true
        System.out.println(person1 == person2);
        // class pers.masteryourself.tutorial.spring.framework.register.bean.Person
        System.out.println(person1.getClass());
        PersonFactoryBean personFactoryBean1 = context.getBean(PersonFactoryBean.class);
        PersonFactoryBean personFactoryBean2 = context.getBean("&person", PersonFactoryBean.class);
        // true
        System.out.println(personFactoryBean1 == personFactoryBean2);
        // class pers.masteryourself.tutorial.spring.framework.register.config.PersonFactoryBean
        System.out.println(personFactoryBean1.getClass());
    }

}

2. 其他註解

2.1 @Scope

代碼已經上傳至 https://github.com/masteryourself-tutorial/tutorial-spring ，詳見 tutorial-spring-framework/tutorial-spring-framework-register/tutorial-spring-framework-register-scope 工程

2.1.1 使用方式

@Scope：指定作用域範圍

• prototype：多實例，ioc 容器啓動並不會去調用方法創建對象放在容器中，每次獲取的時候纔會調用方法創建對象

• singleton：單實例（默認值），ioc 容器啓動會調用方法創建對象放到 ioc 容器中，以後獲取就是直接從容器中獲取

• request：同一個請求創建一個實例

• session：同一個 session 創建一個實例

2.1.2 環境搭建

1. SpringConfig

@Configuration
public class SpringConfig {

    @Scope(value = ConfigurableBeanFactory.SCOPE_PROTOTYPE)
    @Bean(name = "person")
    public Person person() {
        return new Person("張三");
    }

    @Scope(value = ConfigurableBeanFactory.SCOPE_SINGLETON)
    @Bean(name = "person2")
    public Person person2() {
        return new Person("李四");
    }

}

2. ScopeTest

public class ScopeApplication {

    public static void main(String[] args) {
        // 【李四】 用戶創建成功
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
        // ioc 容器創建完成
        System.out.println("ioc 容器創建完成");
        // 【張三】 用戶創建成功
        Person person1 = context.getBean("person", Person.class);
        // 【張三】 用戶創建成功
        Person person2 = context.getBean("person", Person.class);
        // false
        System.out.println(person1 == person2);
        context.getBean("person2", Person.class);
    }
    
}

2.2 @Lazy

代碼已經上傳至 https://github.com/masteryourself-tutorial/tutorial-spring ，詳見 tutorial-spring-framework/tutorial-spring-framework-register/tutorial-spring-framework-register-lazy 工程

2.2.1 使用方式

@Lazy：懶加載，只針對於單實例（因爲單實例 bean 默認在容器啓動時候加載），在第一次使用的時候創建對象

2.2.2 環境搭建

1. SpringConfig

@Configuration
public class SpringConfig {

    @Scope(value = ConfigurableBeanFactory.SCOPE_SINGLETON)
    @Bean(name = "person")
    @Lazy
    public Person person() {
        return new Person();
    }

}

2. LazyTest

public class LazyApplication {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
        // ioc 容器創建完成
        System.out.println("ioc 容器創建完成");
        // 創建 peron 對象
        context.getBean("person", Person.class);
        context.getBean("person", Person.class);
    }

}

2.3 @Conditional

代碼已經上傳至 https://github.com/masteryourself-tutorial/tutorial-spring ，詳見 tutorial-spring-framework/tutorial-spring-framework-register/tutorial-spring-framework-register-conditional 工程

2.3.1 使用方式

@Conditional：按照一定條件進行判斷，滿足條件給容器中註冊 bean

2.3.2 環境搭建

1. BatCondition

public class BatCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		LocalDateTime now = LocalDateTime.now();
		int hour = now.getHour();
		return hour >= 18 || hour <= 6;
	}

}

2. DogCondition

public class DogCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		LocalDateTime now = LocalDateTime.now();
		int hour = now.getHour();
		return hour > 6 && hour < 18;
	}

}

3. SpringConfig

@Configuration
public class SpringConfig {

    @Bean
    @Conditional(value = DogCondition.class)
    public Animal dog() {
        return new Animal("小狗");
    }

    @Bean
    @Conditional(value = BatCondition.class)
    public Animal bat() {
        return new Animal("蝙蝠");
    }
}

4. ConditionalTest

public class ConditionalApplication {

    public static void main(String [] args){
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
        Map<String, Animal> beansOfType = context.getBeansOfType(Animal.class);
        // Animal{name='蝙蝠'}
        beansOfType.forEach((name,animal) -> System.out.println(animal));
    }

}