Spring IoC 依赖查找

Spring IoC 依赖查找

第五章 Spring 依赖查找.pdf

单一类型查找 - BeanFactory

根据Bean名称查找
- getBean(String)
- Spring 2.5覆盖默认参数：getBean(String,Object…)

根据Bean类型查找

Bean实时查找
- Spring 3.0getBean(Class)
- Spring 4.1覆盖默认参数：getBean(Class,Object…)

Spring 5.1Bean延迟查找

getBeanProvider(Class)

getBeanProvider(ResolvableType)

private static void beanFactoryLookupDemo(BeanFactory beanFactory) {
// 根据名称实时查找
System.out.println(beanFactory.getBean("user"));
// 根据类型实时查找
System.out.println(beanFactory.getBean(User.class));
// 根据类型延迟查找
ObjectProvider<User> beanProvider = beanFactory.getBeanProvider(User.class);
System.out.println(beanProvider.getObject());
}

根据Bean名称+类型查找：getBean(String,Class)

集合类型查找 - ListableBeanFactory
根据Bean类型查找
- 获取同类型Bean名称列表
  - getBeanNamesForType(Class)
  - Spring 4.2getBeanNamesForType(ResolvableType)
- 获取同类型Bean实例列表
  - getBeansOfType(Class)以及重载方法
通过注解类型查找
- Spring 3.0获取标注类型Bean名称列表
  - getBeanNamesForAnnotation(Class<? extends Annotation>)
- Spring 3.0获取标注类型Bean实例列表
  - getBeansWithAnnotation(Class<? extends Annotation>)
- Spring 3.0获取指定名称+标注类型Bean实例
  - findAnnotationOnBean(String,Class<? extends Annotation>) ```java private static void listableBeanFactoryDemo(ListableBeanFactory listableBeanFactory) { // 根据类型获取所有同类型Bean System.out.println(listableBeanFactory.getBeansOfType(User.class));
  // 获取有指定注解的全部Bean System.out.println(listableBeanFactory.getBeansWithAnnotation(Vip.class)); } ```
  
  层次性依赖查找 - HierarchicalBeanFactory
双亲BeanFactory：getParentBeanFactory()
层次性查找
- 根据Bean名称查找
  - 基于containsLocalBean方法实现 ```java public static void main(String[] args) {
  AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BeanConfig.class); context.setParent(new ClassPathXmlApplicationContext(“classpath:META-INF/dependency-lookup-context.xml”)); hierarchicalBeanFactoryDemo(context); }

private static void hierarchicalBeanFactoryDemo(HierarchicalBeanFactory hierarchicalBeanFactory) { // getParentBeanFactory HierarchicalBeanFactory parentBeanFactory = (HierarchicalBeanFactory) hierarchicalBeanFactory.getParentBeanFactory(); System.out.println(parentBeanFactory.getBean(User.class)); System.out.println(parentBeanFactory.containsLocalBean(“user”)); System.out.println(parentBeanFactory.containsBean(“user”)); }


   - 根据Bean类型查找实例列表
      - 单一类型：BeanFactoryUtils#beanOfType
      - 集合类型：BeanFactoryUtils#beansOfTypeIncludingAncestors
   - 根据Java注解查找名称列表
      - BeanFactoryUtils#beanNamesForTypeIncludingAncestors
```java
private static void beanFactoryUtilsDemo(ListableBeanFactory listableBeanFactory){
    System.out.println(BeanFactoryUtils.beanOfType(listableBeanFactory,UserVip.class));
    System.out.println(BeanFactoryUtils.beansOfTypeIncludingAncestors(listableBeanFactory, User.class));
    System.out.println(Arrays.toString(BeanFactoryUtils.beanNamesForTypeIncludingAncestors(listableBeanFactory, User.class)));
}

延迟依赖查找

org.springframework.beans.factory.ObjectFactory
org.springframework.beans.factory.ObjectProvider
- Spring 5对Java 8特性扩展
  - 函数式接口
    - getIfAvailable(Supplier)
    - ifAvailable(Consumer)
  - Stream扩展- stream()
    安全依赖查找
    
    内建可查找依赖
    
    依赖查找中的异常
    
    面试题
ObjectFactory与BeanFactory的区别？