@Service("aService")
@Slf4j
public class AService  {

    @Autowired
    private BService bService;

   //......

}

@Autowired
    private ApplicationContext applicationContext;

    public Object getBean(String beanName) {
        Object bean = applicationContext.getBean(beanName);
        return bean;
    }

//雇員類(lèi)
public class EmployeeDTO {

 private Integer id;
 private String firstName;
 private String lastName;
 private String designation;

 //Setters and Getters are hidden behind this comment.


 public Integer getId() {
  return id;
 }

 public void setId(Integer id) {
  this.id = id;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 public String getDesignation() {
  return designation;
 }

 public void setDesignation(String designation) {
  this.designation = designation;
 }

 @Override
 public String toString() {
  return "Employee [id=" + id + ", firstName=" + firstName
    + ", lastName=" + lastName + ", type=" + designation + "]";
 }
}

public class EmployeeFactoryBean extends AbstractFactoryBean<Object> {
 // 根據(jù)這個(gè)值決定創(chuàng)建主管還是經(jīng)理
 private String designation;

 public String getDesignation() {
  return designation;
 }

 public void setDesignation(String designation) {
  this.designation = designation;
 }

 //This method will be called by container to create new instances
 @Override
 protected Object createInstance() throws Exception {
  EmployeeDTO employee = new EmployeeDTO();
  employee.setId(-1);
  employee.setFirstName("dummy");
  employee.setLastName("dummy");
  //Set designation here
  employee.setDesignation(designation);
  return employee;
 }

 //This method is required for autowiring to work correctly
 @Override
 public Class<EmployeeDTO> getObjectType() {
  return EmployeeDTO.class;
 }
}

<!--factoryBean使用示例-->
<!--經(jīng)理工廠-->
 <bean id="manager"  class="com.study.service.EmployeeFactoryBean">
  <property name="designation" value="Manager" />
 </bean>
<!--主管工廠-->
 <bean id="director"  class="com.study.service.EmployeeFactoryBean">
  <property name="designation" value="Director" />
 </bean>

ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
  Object factory =  context.getBean("&director");
  System.out.println(factory);
  //工廠方法模式，通過(guò)單一職責(zé)的工廠獲取專(zhuān)門(mén)的類(lèi)
  System.out.println(((EmployeeFactoryBean) factory).getObject());

ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");

  EmployeeDTO manager = (EmployeeDTO) context.getBean("manager");
  System.out.println(manager);

  Object director =  context.getBean("director");
  System.out.println(director);

@Nullable
 protected Object getSingleton(String beanName, boolean allowEarlyReference) {
  // Quick check for existing instance without full singleton lock
  Object singletonObject = this.singletonObjects.get(beanName);
  //一級(jí)緩存沒(méi)有需要的bean，進(jìn)入該邏輯
  if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
   singletonObject = this.earlySingletonObjects.get(beanName);
   if (singletonObject == null && allowEarlyReference) {
    //二級(jí)對(duì)象也沒(méi)有，上鎖進(jìn)入創(chuàng)建邏輯
    synchronized (this.singletonObjects) {
     // 再次檢查一級(jí)緩存也沒(méi)有，避免重復(fù)創(chuàng)建問(wèn)題
     singletonObject = this.singletonObjects.get(beanName);
     if (singletonObject == null) {
      //......
      //創(chuàng)建對(duì)象存入二級(jí)緩存中
      }
     }
    }
   }
  }
  return singletonObject;
 }

public Object getProxy(@Nullable ClassLoader classLoader) {
  // 忽略代碼
  Class<?>[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true);
  findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
  //通過(guò)被代理的類(lèi)的接口以及增強(qiáng)邏輯創(chuàng)建一個(gè)增強(qiáng)的用戶(hù)所需要的類(lèi)
  return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
 }

@CallerSensitive
    public static Object newProxyInstance(ClassLoader loader,
                                          Class<?>[] interfaces,
                                          InvocationHandler h)
        throws IllegalArgumentException
    {
     //......
       //獲取接口類(lèi)類(lèi)型
        Class<?> cl = getProxyClass0(loader, intfs);

      //......
      //從緩存中獲取代理類(lèi)的構(gòu)造方法
            final Constructor<?> cons = cl.getConstructor(constructorParams);
            final InvocationHandler ih = h;
           //......
           //基于InvocationHandler 和構(gòu)造方法完成代理類(lèi)創(chuàng)建
            return cons.newInstance(new Object[]{h});
        } catch (IllegalAccessException|InstantiationException e) {
           //......
        } catch (InvocationTargetException e) {
           //......
        } catch (NoSuchMethodException e) {
            throw new InternalError(e.toString(), e);
        }
    }

@Override
 public void refresh() throws BeansException, IllegalStateException {
  // 給容器refresh加鎖，避免容器處在refresh階段時(shí)，容器進(jìn)行了初始化或者銷(xiāo)毀的操作
  synchronized (this.startupShutdownMonitor) {
   // .........

   try {
    // .........
    //定義了相關(guān)接口給用戶(hù)實(shí)現(xiàn)，該方法會(huì)通過(guò)回調(diào)的方式調(diào)用這些方法,已經(jīng)實(shí)現(xiàn)好的細(xì)節(jié)
    invokeBeanFactoryPostProcessors(beanFactory);

    // 注冊(cè)攔截bean創(chuàng)建過(guò)程的BeanPostProcessor，已經(jīng)實(shí)現(xiàn)好的細(xì)節(jié)
    registerBeanPostProcessors(beanFactory);

    //模板方法的體現(xiàn)，用戶(hù)可自定義重寫(xiě)該方法
    onRefresh();

    //.......
   }

   // .......
  }
 }

public class DemoEvent extends ApplicationEvent {
    private String msg;

    public DemoEvent(Object source, String msg) {
        super(source);
        this.msg = msg;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

@Component
public class DemoListener implements ApplicationListener<DemoEvent> {
    private static Logger logger = LoggerFactory.getLogger(DemoListener.class);

    @Override
    public void onApplicationEvent(DemoEvent event) {

        logger.info("收到消息，消息內(nèi)容:{}", event.getMsg());
    }
}

@Autowired
    private ApplicationContext applicationContext;


  @Test
    public void sendMsg() {
        DemoEvent event = new DemoEvent(this, "你好");
        applicationContext.publishEvent(event);
    }

2022-11-22 13:03:15.814  INFO 15600 --- [           main] com.example.demo.DemoListener            : 收到消息，消息內(nèi)容:你好

@Override
 public void destroy() {
  //......
  //如果是接口實(shí)現(xiàn)則執(zhí)行該類(lèi)實(shí)現(xiàn)的destroy方法
  if (this.invokeDisposableBean) {
   //......
   try {
    if (System.getSecurityManager() != null) {
    //......
    }
    else {
    //
     ((DisposableBean) this.bean).destroy();
    }
   }
   catch (Throwable ex) {
    //......
   }
  }
  
  //如果有注解或者xml配置的方法，則走invokeCustomDestroyMethod進(jìn)行調(diào)用
  if (this.destroyMethod != null) {
   invokeCustomDestroyMethod(this.destroyMethod);
  }
  else if (this.destroyMethodName != null) {
   Method methodToInvoke = determineDestroyMethod(this.destroyMethodName);
   if (methodToInvoke != null) {
    invokeCustomDestroyMethod(ClassUtils.getInterfaceMethodIfPossible(methodToInvoke));
   }
  }
 }

//繼承Cache 類(lèi)
public class TransactionAwareCacheDecorator implements Cache {

 //行為需要擴(kuò)展的目標(biāo)類(lèi)
 private final Cache targetCache;



// 從接口那里獲得的put方法，通過(guò)對(duì)targetCache的put進(jìn)行進(jìn)一步封裝實(shí)現(xiàn)功能的包裝
 @Override
 public void put(final Object key, @Nullable final Object value) {
  if (TransactionSynchronizationManager.isSynchronizationActive()) {
   TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {
    @Override
    public void afterCommit() {
     TransactionAwareCacheDecorator.this.targetCache.put(key, value);
    }
   });
  }
  else {
   this.targetCache.put(key, value);
  }
 }

}

public interface CreateObjStrategy {

    Object createObj();
}

@Component("createObj_str")
public class CreateStrObjStrategy implements CreateObjStrategy {
    @Override
    public Object createObj() {
        Map<String, Object> map = new HashMap<>();
        map.put("name", "xiaoming");
        return JSONUtil.toJsonStr(map);
    }
}

@Component("createObj_json")
public class CreateJsonObjStrategy implements CreateObjStrategy {
    @Override
    public Object createObj() {
        JSONObject obj = new JSONObject();
        obj.put("name", "zhangsan");
        return obj;
    }
}

public class CreateJsonObjContext {

    private CreateObjStrategy createObjStrategy;

    public CreateJsonObjContext(CreateObjStrategy strategy) {
        this.createObjStrategy = strategy;
    }


    public Object createObj() {
        return createObjStrategy.createObj();
    }


}

@Component
public class CreateJsonObjContext implements ApplicationContextAware {

    private CreateObjStrategy createObjStrategy;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        //從容器中拿到由我們配置后容器中所設(shè)置的CreateObjStrategy設(shè)置到Context中
        CreateObjStrategy bean = applicationContext.getBean(CreateObjStrategy.class);
        createObjStrategy = bean;
    }

    public Object createObj() {
        return createObjStrategy.createObj();
    }

    
}

private Object instantiate(String beanName, RootBeanDefinition mbd,
   @Nullable Object factoryBean, Method factoryMethod, Object[] args) {

  try {
  
   else {
   //通過(guò)getInstantiationStrategy獲取上下文中對(duì)應(yīng)的創(chuàng)建策略完成bean的創(chuàng)建
    return this.beanFactory.getInstantiationStrategy().instantiate(
      mbd, beanName, this.beanFactory, factoryBean, factoryMethod, args);
   }
  }
  catch (Throwable ex) {
   //......
  }
 }