1 什么是BeanFactory?
BeanFactory 是 Ioc 的底层容器，更具体的说应该是 DefaultListableBeanFactory ，该类实现 AutowireCapableBeanFactory 、ListableBeanFactory 和 BeanDefinitionRegistry 接口，从而实现了Ioc的依赖注入和依赖查找。
1.1 AutowireCapableBeanFactory
该接口是 BeanFactory 扩展，具有自动装配能力，并且能把这种能力暴露给外部应用，则需要实现此接口。
简单应用
/**
* Bean 实例化
*/
public class SpecialBeanInstantinationDemo {
public static void main(String[] args) {
//配置 XML 配置文件
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:/META-INF/special-bean-instantiation-context.xml");
AutowireCapableBeanFactory beanFactory = applicationContext.getAutowireCapableBeanFactory();
ServiceLoader serviceLoader = beanFactory.getBean("userFactoryServiceLoader", ServiceLoader.class);
//通过 ServiceLoaderFactoryBean 方式
displayServiceLoader(serviceLoader);
//原生 serviceLoader 方式
demoServiceLoader();
//创建 UserFactory 对象，通过 AutowireCapableBeanFactory 方式
UserFactory userFactory = beanFactory.createBean(DefaultUserFactory.class);
System.out.println(userFactory.createUser());
}
public static void demoServiceLoader() {
ServiceLoader<UserFactory> serviceLoader = ServiceLoader.load(UserFactory.class, Thread.currentThread().getContextClassLoader());
displayServiceLoader(serviceLoader);
}
private static void displayServiceLoader(ServiceLoader<UserFactory> serviceLoader){
Iterator<UserFactory> iterator = serviceLoader.iterator();
while (iterator.hasNext()){
UserFactory userFactory = iterator.next();
System.out.println(userFactory.createUser());
}
}
}
1.2 ListableBeanFactory
该接口是 BeanFactory 扩展，可以枚举它们的所有bean实例，而不是根据需要逐个尝试bean查找，预加载所有 bean 定义(如基于 xml 的工厂) 的 BeanFactory，则需要实现此接口。
简单示例：
/*
* 依赖查找
*/
public class DependecyLookupDemo {
public static void main(String[] args) {
BeanFactory beanFactory = new ClassPathXmlApplicationContext("classpath:/META-INF/dependecy-lookup-context.xml");
lookupByType(beanFactory);
lookupByColletionType(beanFactory);
lookupByAnnotaionType(beanFactory);
// lookupInRealTime(beanFactory);
// lookupInLazy(beanFactory);
}
private static void lookupByAnnotaionType(BeanFactory beanFactory) {
if (beanFactory instanceof ListableBeanFactory) {
ListableBeanFactory listableBeanFactory = (ListableBeanFactory) beanFactory;
Map<String, User> users = (Map) listableBeanFactory.getBeansWithAnnotation(Super.class);
System.out.println("查找标注 @Super 所有的USser 集合对象：" + users);
}
}
private static void lookupByColletionType(BeanFactory beanFactory) {
if (beanFactory instanceof ListableBeanFactory) {
ListableBeanFactory listableBeanFactory = (ListableBeanFactory) beanFactory;
Map<String, User> users = listableBeanFactory.getBeansOfType(User.class);
System.out.println("查找到的所有的USser 集合对象：" + users);
}
}
private static void lookupByType(BeanFactory beanFactory) {
User user = beanFactory.getBean(User.class);
System.out.println("实时查找" + user);
}
private static void lookupInLazy(BeanFactory beanFactory) {
ObjectFactory<User> objectFactory = (ObjectFactory<User>) beanFactory.getBean("objectFactory");
User user = objectFactory.getObject();
System.out.println("延迟查找" + user);
}
private static void lookupInRealTime(BeanFactory beanFactory) {
User user = (User) beanFactory.getBean("user");
System.out.println("实时查找" + user);
}
}
1.3 BeanDefinitionRegistry
顾名思义就是对 BeanDefinition 进行注册。
简单示例
//@Import方式
@Import(AnnotaionBeanDefinitionDemo.Config.class)
public class AnnotaionBeanDefinitionDemo {
public static void main(String[] args) {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
//注册配置类
applicationContext.register(AnnotaionBeanDefinitionDemo.class);
//通过 BeanDefinition 注册API实现
//命名 bean
registerUserBeanDefinition(applicationContext, "niangao-user");
//非命名
registerUserBeanDefinition(applicationContext);
//启动 Spring 应用上下文
applicationContext.refresh();
//依赖查找
System.out.println("Config 类型的所有 Beans：" + applicationContext.getBeansOfType(Config.class));
System.out.println("User 类型的所有 Beans：：" + applicationContext.getBeansOfType(User.class));
applicationContext.close();
}
/**
* 命名 Bean 的注册方式
* @param registry
* @param beanName
*/
public static void registerUserBeanDefinition(BeanDefinitionRegistry registry, String beanName) {
BeanDefinitionBuilder beanDefinitionBuilder = genericBeanDefinition(User.class);
beanDefinitionBuilder
.addPropertyValue("id", 1L)
.addPropertyValue("name", "王明高");
if (StringUtils.hasText(beanName)) {
//命名注册
registry.registerBeanDefinition(beanName, beanDefinitionBuilder.getBeanDefinition());
} else {
//非命名注册方式
BeanDefinitionReaderUtils.registerWithGeneratedName(beanDefinitionBuilder.getBeanDefinition(), registry);
}
}
public static void registerUserBeanDefinition(BeanDefinitionRegistry registry) {
registerUserBeanDefinition(registry, null);
}
//@Component方式
@Component
public static class Config {
//@Bean方式
@Bean(name = {"user", "wangminggao-user"})
public User user() {
User user = new User();
user.setId(1L);
user.setName("王明高");
return user;
}
}
2 什么是FactoryBean？
是创建 Bean 的一种方式，帮助实现复杂的初始化逻辑。
简单示例
public class UserFactoryBean implements FactoryBean {
@Override
public Object getObject() throws Exception {
User user = new User();
user.setId(1L);
user.setName("niangao");
return user;
}
@Override
public Class<?> getObjectType() {
return User.class;
}
@Override
public boolean isSingleton() {
return false;
}
}
