Spirng-IOC零碎知识点

Spirng IOC

依赖注入

根据名称注入

xml 复制代码

<?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:util="http://www.springframework.org/schema/util"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/util
        http://www.springframework.org/schema/util/spring-util.xsd">
    <bean id="foo" class="com.liyong.learn.inject.Foo">
        <property name="name" value="liyong"></property>
        <property name="age" value="22"></property>
    </bean>
    <bean id="foo1" class="com.liyong.learn.inject.Foo">
        <property name="name" value="liyong1`"></property>
        <property name="age" value="221"></property>
    </bean>
    <bean id="bar" class="com.liyong.learn.inject.Bar">
        <property name="name" value="liyong"></property>
        <property name="age" value="22"></property>
        <property name="addr" value="cq"></property>
    </bean>
    <bean id="list" class="com.liyong.learn.inject.ListFoo">
        <property name="list">
        	<!-- 注入List -->
            <util:list>
                <ref bean="foo"></ref>
                <ref bean="foo1"></ref>
            </util:list>
        </property>
    </bean>
</beans>

注入的时候也可以直接注入：

xml 复制代码

<bean id="list" class="com.liyong.learn.inject.ListFoo" autowire="byType"></bean>

xml 复制代码

<?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:util="http://www.springframework.org/schema/util"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util.xsd">
  <!-- 导入资源 -->
  <import resource="beans.xml"></import>
</beans>

java 复制代码

public static void main(String[] args) {
    BeanFactory beanFactory = new ClassPathXmlApplicationContext("inject.xml");
    Bar bean = beanFactory.getBean(Bar.class);
    System.out.println(bean);
    ListFoo listFoo = beanFactory.getBean(ListFoo.class);
    listFoo.getList().stream().forEach(System.out::println);
}

重点关注util 注入和byType注入

根据Bean类型注入
- 单个Bean对象
- 集合Bean对象
注入非Bean对象
注入容器内建Bean对象
注入类型
- 实时注入
- 延迟注入

java 复制代码

public class ListFoo {
  private Collection<Foo> list;
  private BeanFactory beanFactory;
  private ObjectFactory<ApplicationContext> objectFactory;
}

java 复制代码

public static void main(String[] args) {
    BeanFactory beanFactory = new ClassPathXmlApplicationContext("inject.xml");
    Bar bean = beanFactory.getBean(Bar.class);
    System.out.println(bean);
    ListFoo listFoo = beanFactory.getBean(ListFoo.class);
    listFoo.getList().stream().forEach(System.out::println);
    System.out.println(listFoo.getBeanFactory());
    // false 这里注入的bean 并不是beanFactory
    System.out.println(beanFactory == listFoo.getBeanFactory());
    // 输出为 DefaultListableBeanFactory
    System.out.println(listFoo.getBeanFactory().getClass());
    // 会错误 没有这个bean 说明我们依赖注入和依赖查找并不是同源的
    beanFactory.getBean(BeanFactory.class);
    System.out.println(beanFactory == listFoo.getObjectFactory().getObject());
}

SpirngIOC 依赖来源

自定义Bean（配置的bean xml 或者注解）
容器内建对象（例如Environment Bean 容器默认初始化）
容器内建依赖（比如上面例子中的BeanFactory就是内建依赖）

Spring配置元信息

bean定义配置
- 基于XML
- 基于Properties文件
- 基于Java注解
- 基于JavaAPI
IOC容器配置
- 基于XML文件
- 基于Java注解
- 基于JavaAPI
外部化配置
基于Java注解

BeanFactory还是ApplicationContext？

java 复制代码

// 为什么这个表达式不会成立呢？因为他们是两个不同的对象 他们只是复用同一个接口
System.out.println(beanFactory == listFoo.getBeanFactory());

ApplicationContext是BeanFactory的一个超集,提供了更多企业级的功能。通过源码也可以看到我们下面的ApplicationContext是通过组合进来了一个BeanFactory。

BeanFactory 与 ApplicationContext的对比
官网推荐我们使用ApplicationContext,因为BeanFactory 有的能力BeanFactory都有

ApplicationContext 除了IOC容器角色还提供那些特性？

面向切面AOP
配置元信息
资源管理
事件
国际化
注解
Environment抽象

使用BeanFactory 与 ApplicationContext

1 XML的方式使用

直接使用，但是这样的话就不会提供事件机制比如BeanPostProcessor

java 复制代码

DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
reader.loadBeanDefinitions("inject.xml");
Bar bean = factory.getBean(Bar.class);
// 如果需要支持BeanPostProcessor 通过下面的方式进行设置
factory.addBeanPostProcessor(new MyBeanPostProcessor());

2 注解的方式使用

java 复制代码

@Configuration
public class Main {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        context.register(Main.class);
        context.refresh();
        Bar bean = context.getBean(Bar.class);
        System.out.println(bean);
    }
    @Bean
    public Bar initBar() {
        return new Bar();
    }
}

SpringIOC容器生命周期

1 启动

java 复制代码

public void refresh() throws BeansException, IllegalStateException {
// 加锁 因为不确定是单线程还是在多线程的环境中会创建 ApplicationContext
synchronized (this.startupShutdownMonitor) {
	// Prepare this context for refreshing.
	prepareRefresh();

	// Tell the subclass to refresh the internal bean factory.
	ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

	// Prepare the bean factory for use in this context.
	// 内建对象
	prepareBeanFactory(beanFactory);
	try {
		// Allows post-processing of the bean factory in context subclasses.
		postProcessBeanFactory(beanFactory);

		// Invoke factory processors registered as beans in the context.
		invokeBeanFactoryPostProcessors(beanFactory);

		// Register bean processors that intercept bean creation.
		registerBeanPostProcessors(beanFactory);

		// Initialize message source for this context.
		initMessageSource();

		// Initialize event multicaster for this context.
		initApplicationEventMulticaster();

		// Initialize other special beans in specific context subclasses.
		onRefresh();

		// Check for listener beans and register them.
		registerListeners();

		// Instantiate all remaining (non-lazy-init) singletons.
		finishBeanFactoryInitialization(beanFactory);

		// Last step: publish corresponding event.
		finishRefresh();
	}

	catch (BeansException ex) {
		if (logger.isWarnEnabled()) {
			logger.warn("Exception encountered during context initialization - " +
					"cancelling refresh attempt: " + ex);
		}

		// Destroy already created singletons to avoid dangling resources.
		destroyBeans();

		// Reset 'active' flag.
		cancelRefresh(ex);

		// Propagate exception to caller.
		throw ex;
	}

	finally {
		// Reset common introspection caches in Spring's core, since we
		// might not ever need metadata for singleton beans anymore...
		resetCommonCaches();
	}
}
}

2 停止

java 复制代码

protected void doClose() {
		// Check whether an actual close attempt is necessary...
		if (this.active.get() && this.closed.compareAndSet(false, true)) {
			if (logger.isDebugEnabled()) {
				logger.debug("Closing " + this);
			}
			LiveBeansView.unregisterApplicationContext(this);
			try {
				// Publish shutdown event.
				publishEvent(new ContextClosedEvent(this));
			}
			catch (Throwable ex) {
				logger.warn("Exception thrown from ApplicationListener handling ContextClosedEvent", ex);
			}
			// Stop all Lifecycle beans, to avoid delays during individual destruction.
			if (this.lifecycleProcessor != null) {
				try {
					this.lifecycleProcessor.onClose();
				}
				catch (Throwable ex) {
					logger.warn("Exception thrown from LifecycleProcessor on context close", ex);
				}
			}
			// Destroy all cached singletons in the context's BeanFactory.
			destroyBeans();
			// Close the state of this context itself.
			closeBeanFactory();
			// Let subclasses do some final clean-up if they wish...
			onClose();
			// Reset local application listeners to pre-refresh state.
			if (this.earlyApplicationListeners != null) {
				this.applicationListeners.clear();
				this.applicationListeners.addAll(this.earlyApplicationListeners);
			}
			// Switch to inactive.
			this.active.set(false);
		}
	}

BeanFactory 是容器区别于 FactoryBean

FactoryBean 是 Spring 框架提供的一种特殊的工厂 Bean 接口，用于创建复杂的 Bean 对象。与普通的 Bean 不同，FactoryBean 实现类不直接返回实例化的 Bean 对象，而是通过工厂方法来创建 Bean 实例。这样可以为 Bean 的创建和初始化过程提供更多的灵活性和控制。

下面是一些 FactoryBean 的主要用途和特点：

定制化实例化逻辑：通过实现 FactoryBean 接口，你可以自定义创建 Bean 实例的逻辑，包括可能需要的条件判断、初始化过程和配置管理等。
延迟初始化：FactoryBean 可以实现延迟加载，即在需要时才实际创建对象，而不是在应用启动时就建。
装饰器模式：通过 FactoryBean，你可以实现装饰器模式，对原始 Bean 进行一些额外的处理或包装。
对象的复用：FactoryBean 可以控制对象的创建与返回，从而实现对象的重用，避免重复创建实例。
提供灵活性：FactoryBean 的存在使得 Spring 容器中的 Bean 创建更加灵活，可以根据需求定制不同的创建逻辑。

BeanDefinition 元信息

1 定义bean

java 复制代码

// 1 通过 BeanDefinitionBuilder 构建
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(Foo.class);
builder.addPropertyValue("name", "liyong");
builder.addPropertyValue("age", 11);
// 这里还可以对 beanDefinition 进行修改
BeanDefinition beanDefinition = builder.getBeanDefinition();
//2  通过 AbstractBeanDefinition 以及派生类
GenericBeanDefinition genericBeanDefinition = new GenericBeanDefinition();
// 设置Bean类型
genericBeanDefinition.setBeanClass(Foo.class);
MutablePropertyValues values = new MutablePropertyValues();
values.addPropertyValue("name", "liyong");
values.addPropertyValue("age", 11);
genericBeanDefinition.setPropertyValues(values);

2 命名Bean

命名规范可以按照参数的命名规范（xml一般自定义名称比较多）
DefaultBeanNameGenerator 是Spirng提供的一个API用于生成BeanName
AnnotationBeanNameGenerator 基于注解扫描的BeanNameGenerator实现

3 别名Bean

xml 复制代码

<!--  将 foo -> 映射别名 aliasFoo  -->
<alias name="foo" alias="aliasFoo"></alias>

java 复制代码

BeanFactory beanFactory = new ClassPathXmlApplicationContext("beans.xml");
Foo aliasFoo = (Foo) beanFactory.getBean("aliasFoo");
Foo foo = (Foo) beanFactory.getBean("foo");
System.out.println(foo == aliasFoo);

注册BeanDefinition

1 xml配置

2 注解配置元信息

@Bean

@Component

@Import
通过注解我们的Bean，Spring容器不会重复注册同样的bean

java 复制代码

@Import({Demo.Config.class})
public class Demo {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        context.register(Demo.class);
        context.refresh();
        // 通过 命名生产器生成的 如果没有生成兜底策略为类名称
        Map<String, Config> beansOfType = context.getBeansOfType(Config.class);
        System.out.println(beansOfType);
        Map<String, Bar> barMap = context.getBeansOfType(Bar.class);
        System.out.println(barMap);
        context.close();
    }
    @Component
    static class Config {
        @Bean
        public Bar userBean() {
            Bar bar = new Bar();
            bar.setAddr("fdsa");
            bar.setName("li");
            bar.setAge(10);
            return bar;
        }
    }
}

3 Java Api 配置元信息

BeanDefinitionRegistry#registerBeanDefinition （用于命名方式）
BeanDefinitionReaderUtils#registerWithGeneratedName （用于非命令方式）
AnnotatedBeanDefinitionReader（配置类的方式）

java 复制代码

  public static void registerFooBeanDefinition(BeanDefinitionRegistry registry, String beanName) {
        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(Bar.class);
        builder.addPropertyValue("name", "liyong");
        builder.addPropertyValue("age", 20);
        if (StringUtils.hasText(beanName)) {
            registry.registerBeanDefinition(beanName, builder.getBeanDefinition());
        } else {
            BeanDefinitionReaderUtils.registerWithGeneratedName(builder.getBeanDefinition(), registry);
        }
    }

实例化Spring Bean

Bean 实例化
- 常规方式
  - 通过构造器（配置元信息：XML，Java注解和Java API）
  - 通过静态工厂方法（配置元信息：XML 和 Java API）
  - 通过Bean工厂方法（配置元信息：XML 和 Java API）
  - 通过FactoryBean （配置元信息：XML，Java注解和Java API）
- 特殊方式
  - 通过ServiceLoaderFactoryBean(配置元信息：XML，Java注解和Java API)
  - 通过AutowireCapableBeanFactory#createBean(Class,boolean)
  - 通过BeanDefinitionRegistry#registerBeanDefinition(String,BeanDefiniton)
    通过静态方法

xml 复制代码

 <bean id="developer" class="com.liyong.learn.createbean.HighDeveloper" factory-method="createDeveloper"></bean>

在类里面定义静态的构造Bean的方法如下，省略get,set

java 复制代码

public class HighDeveloper {
    private String name;
    private Integer salary;
    public HighDeveloper() {
    }
    public HighDeveloper(String name, Integer salary) {
        this.name = name;
        this.salary = salary;
    }
    @Override
    public String toString() {
        return "HighDeveloper{" +
                "name='" + name + '\'' +
                ", salary=" + salary +
                '}';
    }
    public static HighDeveloper createDeveloper() {
        HighDeveloper developer = new HighDeveloper();
        developer.setName("ly");
        developer.setSalary(15 * 15);
        return developer;
    }
}

通过Bean工厂方法

xml 复制代码

<bean id="developer" class="com.liyong.learn.createbean.HighDeveloper" factory-method="createDeveloper"></bean>
<bean id="developerFactory" class="com.liyong.learn.createbean.DefaultDeveloperCreateFactory"></bean>
<bean id="developerByFc" class="com.liyong.learn.createbean.HighDeveloper" factory-bean="developerFactory" factory-method="createDeveloper"></bean>

java 复制代码

BeanFactory beanFactory = new ClassPathXmlApplicationContext("bean-create.xml");
HighDeveloper developer = beanFactory.getBean("developer", HighDeveloper.class);
HighDeveloper developerFc = beanFactory.getBean("developerByFc", HighDeveloper.class);
System.out.println(developer);
System.out.println(developerFc);
System.out.println(developer == developerFc);

通过FactoryBean

这里和上面有所区别，这里我们只需要定义工厂就行了，不需要先定义工厂，然后还要定义具体的bean来指定实现工厂。

xml 复制代码

<bean id="developer-by-factory-bean"  class="com.liyong.learn.createbean.DeveloperFactoryBean"></bean>

java 复制代码

HighDeveloper developerFcBean = beanFactory.getBean("developer-by-factory-bean", HighDeveloper.class);

通过ServiceLoaderFactoryBean的方式

java 复制代码

public static void main(String[] args) {
   BeanFactory beanFactory = new ClassPathXmlApplicationContext("bean-create.xml");
   // 基于xml配置的bean
   ServiceLoader<DeveloperCreateFactory> bean = beanFactory.getBean(ServiceLoader.class);
   Iterator<DeveloperCreateFactory> it = bean.iterator();
   while (it.hasNext()) {
       DeveloperCreateFactory next = it.next();
       System.out.println(next.createDeveloper());
   }
   // ServiceLoader 加载的bean
   ServiceLoader<DeveloperCreateFactory> load = ServiceLoader.load(DeveloperCreateFactory.class, Thread.currentThread().getContextClassLoader());
   Iterator<DeveloperCreateFactory> iterator = load.iterator();
   while (iterator.hasNext()) {
       DeveloperCreateFactory next = iterator.next();
       System.out.println(next.createDeveloper());
   }
}

基于xml

java 复制代码

<bean id="developerFactoryServiceLoader" class="org.springframework.beans.factory.serviceloader.ServiceLoaderFactoryBean">
   <property name="serviceType" value="com.liyong.learn.createbean.DeveloperCreateFactory"></property>
</bean>

基于ServiceLoader也就是SPI机制，需要再这个目录下放置文件：

AutowireCapableBeanFactory

java 复制代码

ApplicationContext context = new ClassPathXmlApplicationContext("bean-create.xml");
AutowireCapableBeanFactory autowireCapableBeanFactory = context.getAutowireCapableBeanFactory();
HighDeveloper developer = autowireCapableBeanFactory.createBean(HighDeveloper.class);
System.out.println(developer);

Bean初始化

@PostConstruct
实现InitializingBean 接口的afterPropertiesSet()方法
自定义初始化方法
- xml 指定 inti-method
- 注解 @Bean(initMethod = 'init')
- Java API AbstractBeanDefinition#setInitMethodName(String)

在bean中指定init方法，在创建bean的时候回去调用这个初始化方法

java 复制代码

@PostConstruct
public void init() {
    System.out.println("init ing");
}

@Bean 指定initMethod

java 复制代码

@Bean(initMethod = "initMethod")
public HighDeveloper highDeveloper() {
   return new HighDeveloper();
}
// 在类中添加方法
public void initMethod() {
     System.out.println("@Bean inti ing");
 }

通过InitializingBean 的实现

java 复制代码

public class HighDeveloper implements InitializingBean {
 @Override
 public void afterPropertiesSet() throws Exception {
     System.out.println("InitializingBean init ing");
 }

三者的顺序：PostConstruct -> InitializingBean -> @Bean

通过AbstractBeanDefinition的方式

java 复制代码

AnnotationConfigApplicationContext beanFactory = new AnnotationConfigApplicationContext();
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(HighDeveloper.class);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
beanDefinition.setInitMethodName("initMethod");
BeanDefinitionReaderUtils.registerWithGeneratedName(beanDefinition, beanFactory);
beanFactory.refresh();
HighDeveloper developer = beanFactory.getBean(HighDeveloper.class);
System.out.println(developer);

延迟初始化SpringBean

xml配置（Lazy-init="true"）
Java 注解 @Lazy(true)
不使用延迟初始化

java 复制代码

public static void main(String[] args) {
     AnnotationConfigApplicationContext beanFactory = new AnnotationConfigApplicationContext();
     beanFactory.register(Client.class);
     beanFactory.refresh();
     System.out.println("context finish");
     HighDeveloper developer = beanFactory.getBean(HighDeveloper.class);
     System.out.println(developer);
 }
 @Bean(initMethod = "initMethod")
 @Lazy(value = false)
 public HighDeveloper highDeveloper() {
     return new HighDeveloper();
 }

使用延迟初始化

java 复制代码

@Lazy(value = true)
public HighDeveloper highDeveloper() {
    return new HighDeveloper();
}

总结：对比上面我们可以发现，如果不使用延迟加载在上下文刷新的时候Bean的初始化已经完成了。延迟加载的话，在真正使用的时候才会进行初始化。

Bean的销毁阶段

1 通过标注注解 @PreDestory

2 实现DisposableBean 接口的destory()方法

3 自定义销毁方法

XML配置 bean destory='destory'
Java注解 @Bean(destory='destory')
Java API：AbstractBeanDefiniton#setDestoryMethodName()

java 复制代码

public class Client implements DisposableBean {
    public Client(){

    }
    private String name;
    private Integer age;
    public Client(String name, Integer age) {
        this.age = age;
        this.name = name;
    }

    @PreDestroy
    public void preDestroy () {
        System.out.println("PreDestroy ......");
    }
    @Override
    public String toString() {
        return "Client{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
    public void beanDestroy() {
        System.out.println("beanDestroy ....");
    }
    @Override
    public void destroy() throws Exception {
        System.out.println("disposableDestroy ...");
    }
}

java 复制代码

@Configuration
public class BeanDemo  {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        context.register(BeanDemo.class);
        context.refresh();
        Object demo = context.getBean("demo");
        System.out.println(demo);
        context.close();
    }
    @Bean(destroyMethod = "beanDestroy")
    public Client demo() {
        return new Client();
    }
}

Bean 垃圾回收

1 关闭上下文

2 调用GC

3 覆盖Object finalize() 方法

java 复制代码

AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
 context.register(BeanDemo.class);
 context.refresh();
 Object demo = context.getBean("demo");
 System.out.println(demo);
 context.close();
 Thread.sleep(5000L);
 System.gc();
 Thread.sleep(5000L);

java 复制代码

@Override
public void finalize() throws Throwable {
    System.out.println("finalize");
}