import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

@Service
public class DataProcessor {

    @Autowired
    private DataSource dataSource; // 依賴會(huì)被先注入

    private Connection connection;

    public DataProcessor() {
        System.out.println("1. 調(diào)用構(gòu)造函數(shù): dataSource is null? " + (dataSource == null));
    }

    @PostConstruct
    public void openConnection() {
        System.out.println("3. 執(zhí)行 @PostConstruct: dataSource is null? " + (dataSource == null));
        System.out.println("正在打開(kāi)數(shù)據(jù)庫(kù)連接...");
        // 此時(shí) dataSource 已經(jīng)被注入，可以安全使用
        // this.connection = dataSource.getConnection(); 
    }

    public void process() {
        System.out.println("正在處理數(shù)據(jù)...");
    }

    @PreDestroy
    public void closeConnection() {
        System.out.println("執(zhí)行 @PreDestroy: 正在關(guān)閉數(shù)據(jù)庫(kù)連接...");
        // if (this.connection != null) this.connection.close();
    }
}

import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.DisposableBean;

@Component
public class LegacyService implements InitializingBean, DisposableBean {

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("執(zhí)行 InitializingBean.afterPropertiesSet()");
    }

    @Override
    public void destroy() throws Exception {
        System.out.println("執(zhí)行 DisposableBean.destroy()");
    }
}

<bean id="myService" class="com.example.MyService" 
      init-method="customInit" 
      destroy-method="customCleanup"/>

@Configuration
public class AppConfig {
    @Bean(initMethod = "customInit", destroyMethod = "customCleanup")
    public MyService myService() {
        return new MyService();
    }
}

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;

@Component
public class MyBeanPostProcessor implements BeanPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("質(zhì)檢員[Before]: 正在檢查 " + beanName);
        return bean; // 必須返回 bean，否則后續(xù)流程拿不到對(duì)象
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("質(zhì)檢員[After]: " + beanName + " 已完成初始化。");
        // 這里可以返回原始 bean，也可以返回一個(gè)包裝后的代理 bean
        return bean;
    }
}

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class AwareService implements ApplicationContextAware {

    private ApplicationContext context;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        System.out.println("AwareService 感知到了 ApplicationContext");
        this.context = applicationContext;
    }
    
    public void doSomething() {
        // 可以通過(guò) context 手動(dòng)獲取其他 bean
        DataProcessor processor = context.getBean(DataProcessor.class);
        processor.process();
    }
}