使用ApplicationRunner,以注解的方式直接注入基类,解决继承父类后,不再复写获取getBaseDao()方法

• 继承ApplicationRunner接口,可以在ApplicationContext加载完成后被调用
• 执行顺序是在所有的初始化和自动配置完成之后
• 可以使用@Component或@Configuration标记
• 当有多个继承ApplicationRunner的事后,执行的顺序是根据其注入的顺序决定的。如果想要指定顺序执行可以使用@Order进行排序
• 除了ApplicationRunner外,CommandLineRunner也提供了相似的功能,最大的区别在于一个用ApplicationArguments接收参数,一个用Sting数组进行接收参数

示例,修改传统实现获取基础持久对象方法,主动注入基类
原始调用方法

//传统实现调用方式1
@Slf4j
@Repository
@RequiredArgsConstructor
public class UserRepository extends BaseRepository<User, Long> {
	private final UserDao userDao;
	@Override
	public BaseDao<User, Long> getBaseDao(){
		return userDao;
	}
}

//传统实现调用方式2
@Slf4j
@Repository
@RequiredArgsConstructor
public class UserRepository extends BaseRepository<User, Long> {
	private final UserDao userDao;
	//PostConstruct会在初始化对象技术,并且注入完类后,BeanPostProcessor后置处理器之前执行
	@PostConstruct
	public void init(){
		this.baseDao = userDao;
	}
}

修改后注入方式

//启动注入方式
@Slf4j
@Repository
@RequiredArgsConstructor
@AutomaticInjectionClassProvider(value = UserDao.class, fieldName = "baseDao")
public class UserRepository extends BaseRepository<User, Long> {
}

继承ApplicationRunner,当ApplicationContext加载完成后被调用，并且在所有的初始化和自动配置完成之后执行

@Configuration
@RequiredArgsConstructor
public class AutomaticInjectionPostProcessor implements ApplicationRunner {

	private final ApplicationContext applicationContext;

	@Override
	public void run(ApplicationArguments args) throws Exception {
		Map<String, Object> beans = applicationContext.getBeansWithAnnotation(AutomaticInjectionClassProvider.class);
		Collection<Object> values = beans.values();
		for (Object beanObject : values) {
			Class<?> beanClass = beanObject.getClass();
			AutomaticInjectionClassProvider injectionClassProvider = beanClass.getAnnotation(AutomaticInjectionClassProvider.class);
			Class<?> injectionClassProviderClass = injectionClassProvider.value();
			String fieldName = injectionClassProvider.fieldName();
			Object providerObject = SpringUtil.getBean(injectionClassProviderClass);
			if (Objects.isNull(providerObject)) {
				throw new RuntimeException("启动注入异常,类未实例化: " + beanObject.getClass().getTypeName());
			}
			this.injectObject(beanObject, fieldName, providerObject);
		}
	}

	/**
	 * 注入对象
	 *
	 * @param beanObject     被注入对象
	 * @param fieldName      注入字段名
	 * @param providerObject 注入对象
	 * @throws Exception
	 */
	public void injectObject(Object beanObject, String fieldName, Object providerObject) throws Exception {

		Field baseDaoField = this.getClassByName(beanObject, fieldName);
		if (Objects.isNull(baseDaoField)) {
			throw new RuntimeException("启动注入异常: " + beanObject.getClass().getTypeName());
		}
		baseDaoField.setAccessible(true);

		if (AopUtils.isCglibProxy(beanObject)) {
			Object target = this.getProxyObject(beanObject);
			try {
				baseDaoField.set(target, providerObject);
			} catch (Exception e) {
				e.printStackTrace();
			}

		} else {
			baseDaoField.set(beanObject, providerObject);
		}
	}

	/**
	 * 根据字段名称查找字段
	 *
	 * @param object 被查找对象
	 * @param name   字段名
	 * @return
	 */
	public Field getClassByName(Object object, String name) {
		Assert.notNull(object, "Class must not be null");
		Assert.isTrue(!Object.class.getName().equals(object.getClass().getName()), "没有找到被注入的字段,  fieldName: " + name);
		Class<?> clazz = object.getClass();
		Field baseDaoField = ReflectionUtils.findField(clazz, name);
		if (Objects.isNull(baseDaoField)) {
			Class<?> superclass = clazz.getSuperclass();
			if (Object.class.getTypeName().equals(superclass.getTypeName())) {
				return null;
			}
			return getClassByName(clazz.getSuperclass(), name);
		}
		return baseDaoField;
	}

	/**
	 * 获取代理类
	 *
	 * @param obj 被代理类
	 * @return 代理对象
	 * @throws Exception 异常
	 */
	public Object getProxyObject(Object obj) throws Exception {
		Field cglib$CALLBACK_0 = obj.getClass().getDeclaredField("CGLIB$CALLBACK_0");
		cglib$CALLBACK_0.setAccessible(true);
		Object cglibSupperObject = cglib$CALLBACK_0.get(obj);

		Field advised = cglibSupperObject.getClass().getDeclaredField("advised");
		advised.setAccessible(true);
		Object target = ((AdvisedSupport) advised.get(cglibSupperObject)).getTargetSource().getTarget();

		if (AopUtils.isCglibProxy(target)) {
			return this.getProxyObject(target);
		}
		return target;
	}

}

@Inherited
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface AutomaticInjectionClassProvider {

	Class<?> value();

	String fieldName();

}