Spring学习笔记

IOC

spring的bean创建过程（粗略的）

读取配置
将各种bean的定义封装为BeanDefinition，存入到beanDefinitionMap中
调用BeanFactoryPostProcessor的postProcessBeanFactory方法（可以自己实现BeanFactoryPostProcessor，做到例如修改某个BeanDefinition、自己往beanDefinitionMap注册额外的BeanDefinition等事情）
遍历beanDefinitionMap，根据beanDefinition通过反射创建实例
给每个bean填充属性
调用BeanPostProcessor的postProcessBeforeInitialization方法
调用InitialingBean的afterPropertiesSet方法
调用BeanPostProcessor的postProcessAfterInitialization方法

Bean工厂后处理器（BeanFactoryPostProcessor）

示例（自己注册BeanDefinition）

java 复制代码

@SpringBootApplication
public class SpringDemoApplication {
  public static void main(String[] args) {
    ConfigurableApplicationContext context = SpringApplication.run(SpringDemoApplication.class, args);
    // 容器启动后该方法会被调用，即使MyTestBean并没有加@Component注解被扫描为bean
    context.getBean("myTestBean", MyTestBean.class).test();
  }
}

java 复制代码

public class MyTestBean {
  public void test() {
    System.out.println("================ MyTestBean test method called");
  }
}

java 复制代码

@Component
public class MyBeanDefinitionRegistry implements BeanDefinitionRegistryPostProcessor {
  @Override
  public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
    System.out.println("================ postProcessBeanDefinitionRegistry called");
    BeanDefinition bdf = new GenericBeanDefinition();
    bdf.setBeanClassName("com.example.demo.ioc.MyTestBean");
    registry.registerBeanDefinition("myTestBean", bdf);
  }
}

Bean后处理器（BeanPostProcessor）

java 复制代码

@SpringBootApplication
public class SpringDemoApplication {
  public static void main(String[] args) {
    ConfigurableApplicationContext context = SpringApplication.run(SpringDemoApplication.class, args);;
    context.getBean(MyTestBean.class).test();
  }
}

java 复制代码

public class MyTestBean {
  public void test() {
    System.out.println("================ MyTestBean test method called");
  }
}

java 复制代码

@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
  @Override
  public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    if (bean instanceof MyTestBean) {
      System.out.println("================ bean后处理器的before方法执行: MyTestBean");
    }
    return bean;
  }

  @Override
  public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    if (bean instanceof MyTestBean) {
      System.out.println("================ bean后处理器的after方法执行: MyTestBean");
    }
    return bean;
  }
}

容器启动后打印结果：

ini 复制代码

================ bean后处理器的before方法执行: MyTestBean
================ bean后处理器的after方法执行: MyTestBean
================ MyTestBean test method called

InitializingBean

实现了InitializingBean接口的bean在填充完属性之后它的afterPropertiesSet方法会被自动调用（在BeanPostProcessor的before方法之后，after方法之前），没什么好说的

java 复制代码

@Component
public class MyTestBean implements InitializingBean {
  public void test() {
    System.out.println("================ MyTestBean test method called");
  }

  @Override
  public void afterPropertiesSet() throws Exception {
    System.out.println("================ MyTestBean afterPropertiesSet method called");
  }
}

容器启动后打印结果：

ini 复制代码

================ bean后处理器的before方法执行: MyTestBean
================ MyTestBean afterPropertiesSet method called
================ bean后处理器的after方法执行: MyTestBean
================ MyTestBean test method called

AOP

基础示例

启动类

java 复制代码

@SpringBootApplication
@EnableAspectJAutoProxy
public class SpringDemoApplication {
  public static void main(String[] args) {
    ConfigurableApplicationContext context = SpringApplication.run(SpringDemoApplication.class, args);;
    context.getBean(MyAopTestBean.class).test("spring aop");
  }
}

测试bean

java 复制代码

@Component
public class MyAopTestBean {
  public void test(String name) {
    System.out.println("hi " + name);
  }
}

切面配置

java 复制代码

@Aspect
@Component
public class MyAspect {
  @Before("execution(* com.example.demo.aop.MyAopTestBean.*(..))")
  public void before() {
    System.out.println("======== 前置通知执行");
  }

  @Around("execution(* com.example.spring_demo.aop.MyAopTestBean.*(..))")
  public void around(ProceedingJoinPoint joinPoint) throws Throwable {
    System.out.println("======== 环绕通知 - before 参数：" + Arrays.toString(joinPoint.getArgs()));
    joinPoint.proceed(joinPoint.getArgs());
    System.out.println("======== 环绕通知 - after");
  }
}

容器启动后打印结果：

diff 复制代码

======== 环绕通知 - before 参数：[spring aop]
======== 前置通知执行
hi spring aop
======== 环绕通知 - after