【面试题】2、Docker和Spring相关

/**
 * 使用BeanPostProcessor生命周期为指定bean生成代理对象
 * 目的是：为Bean增加日志打印的功能
 */
public class LogProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        Class<?> beanCls = bean.getClass();
        Class<?>[] interfaceArr = beanCls.getInterfaces();
        // 如果当前bean没有实现过接口: 无法通过JDK的方式为其增加额外功能
        if (interfaceArr.length < 1) return bean;
        return Proxy.newProxyInstance(
            getClass().getClassLoader(),
            interfaceArr,
            new LogInvocationHandlerImpl(bean)
        );
    }
    /**
     * 实现InvocationHandler接口, 重写它的invoke方法（编写附加代码）
     */
    private static class LogInvocationHandlerImpl implements InvocationHandler {
        private final Object targetBean;
        public LogInvocationHandlerImpl(Object targetBean) {
            this.targetBean = targetBean;
        }
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            System.out.println("LogInvocationHandlerImpl 附加代码1");
            Object retVal = method.invoke(targetBean, args);
            System.out.println("LogInvocationHandlerImpl 附加代码2");
            return retVal;
        }
    }
}

/**
 * 通过CGLib的方式为指定目标类的目标方法增加额外功能, 生成该目标类的代理类
 */
public class LogProcessorByCGLib implements BeanPostProcessor {
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        Enhancer enhancer = new Enhancer();
        // 设置类加载器
        enhancer.setClassLoader(getClass().getClassLoader());
        // 设置目标类
        enhancer.setSuperclass(bean.getClass());
        // 设置目标代码
        enhancer.setCallback(new LogMethodInterceptorImpl(bean));
        return enhancer.create(); // 创建代理类
    }
    /**
     * 实现MethodInterceptor接口, 增加附加功能
     * MethodInterceptor是Callback接口的子接口
     */
    private static class LogMethodInterceptorImpl implements MethodInterceptor {
        private final Object targetBean;
        public LogMethodInterceptorImpl(Object targetBean) {
            this.targetBean = targetBean;
        }
        @Override
        public Object intercept(Object proxy,
                                Method method,
                                Object[] args,
                                MethodProxy methodProxy) throws Throwable {
            System.out.println("LogMethodInterceptorImpl 日志1");
            // 调用目标方法
            Object retVal = method.invoke(targetBean, args);
            System.out.println("LogMethodInterceptorImpl 日志2");
            return retVal;
        }
    }
}

<dependency>
       <groupId>org.aspectj</groupId>
       <artifactId>aspectjrt</artifactId>
       <version>1.9.6</version>
   </dependency>
   <dependency>
       <groupId>org.aspectj</groupId>
       <artifactId>aspectjweaver</artifactId>
       <version>1.9.6</version>
   </dependency>

/**
 * 实现MethodBeforeAdvice接口, 在该接口的before方法中编写AOP的附加代码
 */
public class LogMethodBeforeAdvice implements MethodBeforeAdvice {
    @Override
    public void before(Method method, Object[] args, Object o) throws Throwable {
        System.out.println("LogMethodBeforeAdvice_before: " + Arrays.toString(args));
    }
}

/**
 * 通过实现org.aopalliance.intercept.MethodInterceptor接口添加附加代码
 */
public class LogMethodInterceptor implements MethodInterceptor {
    @Override
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
        System.out.println("LogMethodInterceptor_附加代码1");
        Object retVal = methodInvocation.proceed();
        System.out.println("LogMethodInterceptor_附加代码2");
        return retVal;
    }
}

<!-- 附加代码 -->
 <bean id="logMethodBeforeAdvice" class="com.guoqing.aop.LogMethodBeforeAdvice"/>
 <aop:config>
     <!-- 配置切入点 -->
     <!-- 切入任意方法 -->
     <aop:pointcut id="pointcut1" expression="execution(* *(..))"/>
     <!--切入方法名以【Impl】结尾的方法 -->
     <aop:pointcut id="pointcut2" expression="execution(* *Impl(..))"/>
     <!-- 在切入点pointcut1处添加附加代码logMethodBeforeAdvice -->
     <aop:advisor advice-ref="logMethodBeforeAdvice" pointcut-ref="pointcut1"/>
 </aop:config>

public class UserServiceImpl implements UserService,
    ApplicationContextAware,
    BeanNameAware {
    private String beanName;
    private ApplicationContext ctx;
    public boolean login(String username, String password) {
        System.out.println("login_" + username + "_" + password);
        // 拿到代理对象
        UserService proxyObj = (UserService) ctx.getBean(beanName);
        // 代理对象调用目标方法
        proxyObj.register(username, password, "16685", "520112");
        return false;
    }
    public boolean register(String username, String password, String phone, String idCard) {
        System.out.println("register_" + username + "_" + password + "_" + phone + "_" + idCard);
        return false;
    }
    @Override
    public void setBeanName(String name) {
        beanName = name;
    }
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        ctx = applicationContext;
    }
}

@Component
@Aspect // 表示当前类是一个切面类
public class LogAspect {
    @Pointcut("execution(* *(..))")
    private void pointcut() {}
    // @Around("execution(* *(..))")
    @Around("pointcut()")
    public Object log(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("log---------1");
        Object ret = pjp.proceed();
        System.out.println("log---------2");
        return ret;
    }
    // @Around("execution(* *(..))")
    @Around("pointcut()")
    public Object watch(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("watch---------1");
        Object ret = pjp.proceed();
        System.out.println("watch---------2");
        return ret;
    }
}

public class DogFactoryBean implements FactoryBean<Dog> {
    @Override
    public Dog getObject() throws Exception {
        Dog dog = new Dog();
        dog.setName("小狗");
        return dog;
    }
    @Override
    public Class<?> getObjectType() {
        return Dog.class;
    }
}

public class MyTest {
    @Test
    public void t() {
        ApplicationContext ctx =
                new ClassPathXmlApplicationContext("applicationContext.xml");
        Object dog1 = ctx.getBean("dog");
        Object dog2 = ctx.getBean("&dog");
        // dog1 = Dog{name='小狗'}
        System.out.println("dog1 = " + dog1);
        // dog2 = com.guoqing.myfactorybean.DogFactoryBean@52e6fdee
        System.out.println("dog2 = " + dog2);
    }
}

@Configuration
public class BeanConfiguration {
    @Bean
    public DogFactoryBean dog() {
        // 实际会调用DogFactoryBean的getObject()方法
        return new DogFactoryBean();
    }
}

<!-- @Resource、@PostConstruct、@PreDestroy -->
   <dependency>
       <groupId>javax.annotation</groupId>
       <artifactId>javax.annotation-api</artifactId>
       <version>1.3.2</version>
   </dependency>
   <!-- @Inject -->
   <dependency>
       <groupId>javax.inject</groupId>
       <artifactId>javax.inject</artifactId>
       <version>1</version>
   </dependency>

@Inject
    public Person(@Named("niceDog") Dog dog, @Nullable String name) {
        System.out.println("有参构造_" + name);
        this.dog = dog;
    }

@Configuration
public class MyBeanConfig {
    @Bean
    public PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
        PropertySourcesPlaceholderConfigurer configurer = new PropertySourcesPlaceholderConfigurer();
        configurer.setLocation(new ClassPathResource("child.properties"));
        return configurer;
    }
}