文章目录
1.基础工程创建
1.创建一个maven工程
依赖如下：
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.2.12.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>5.2.12.RELEASE</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.25</version>
</dependency>
</dependencies>
2.创建一个Spring的配置类
@ComponentScan("cn.redocloud.service")
public class AppConfig {
}
这里需要注意一点，需要放进Spring容器；里或者使用了Spring注解的类，如果不再同一包下时，如果新增一个类，不再原有包下时，需要添加扫描路径,如我最终的扫包为如下
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:11
* @Describe:
*/
@ComponentScan({"cn.redocloud.service","cn.redocloud.mapper","cn.redocloud.config"})
public class AppConfig {
}
其中，"cn.redocloud.service"为我存放业务类的包（主要做包扫描，生成对象后放入Sping容器）
3.模拟Mapper
接口声明
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:40
* @Describe:
*/
public interface UserMapper {
/**
* 获取用户
* @return
*/
List<User> getUser();
}
模拟实现
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:42
* @Describe:
*/
@Repository
public class UserMapperImpl implements UserMapper {
@Override
public List<User> getUser() {
List<User> users = new ArrayList<>();
User user = User.builder().username("1800000000").password("123456").build();
users.add(user);
return users;
}
}
4.业务处理
业务接口
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:12
* @Describe:
*/
public interface UserService {
/**
* 登录
* @param username
* @param password
* @return
*/
String login(String username,String password);
}
实现类
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:12
* @Describe:
*/
@Service
@Slf4j
public class UserServiceImpl implements UserService {
@Override
public String login(String username, String password) {
log.info("用户{},执行登录",username);
return username;
}
}
2.问题及测试
前置，测试类如下
public class Test {
public static void main(String[] args) {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
UserService userService = applicationContext.getBean(UserService.class);
userService.login("1800000000","123456");
}
}
1.测试生命周期过程中，我们可以如何在这个过程中介入
修改UserServiceImpl为如下：
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:12
* @Describe:
*/
@Service
@Slf4j
public class UserServiceImpl implements UserService, InitializingBean, BeanNameAware , ApplicationContextAware , BeanFactoryAware {
@Autowired
UserMapper userMapper;
private Map<String, User> userCache = new ConcurrentHashMap<>(10);
public UserServiceImpl(){
log.info("这是UserServiceImpl构造方法,userMapper为{}",userMapper);
}
@PostConstruct
public void postConstruct(){
log.info("这是PostConstruct方法,userMapper为{}",userMapper);
}
@Override
public String login(String username, String password) {
log.info("用户{},执行登录",username);
User user = userCache.get(username);
log.info("该用户完整信息为{}",user);
return username;
}
@Override
public void afterPropertiesSet() throws Exception {
List<User> users = userMapper.getUser();
if(!CollectionUtils.isEmpty(users)){
users.forEach(user -> userCache.put(user.getUsername(),user));
}
log.info("执行初始化方法afterPropertiesSet,userMapper为{}",userMapper);
}
@Override
public void setBeanName(String s) {
log.info("beanNameAware名:{},userMapper为{}",s,userMapper);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
log.info("applicationContextAware,userMapper为{}",userMapper);
}
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
log.info("beanFactoryAware,userMapper为{}",userMapper);
}
}
如上，分別在构造方法、 @PostConstruct注解方法、InitializingBean接口的afterPropertiesSet以及三种Aware接口的子接口BeanNameAware的setBeanName、ApplicationContextAware 接口的setApplicationContext方法、BeanFactoryAware的setBeanFactory接口中打印一些话
测试结果如下：
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 这是UserServiceImpl构造方法,userMapper为null
[main] INFO cn.redocloud.service.impl.UserServiceImpl - beanNameAware名:userServiceImpl,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@646007f4
[main] INFO cn.redocloud.service.impl.UserServiceImpl - beanFactoryAware,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@646007f4
[main] INFO cn.redocloud.service.impl.UserServiceImpl - applicationContextAware,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@646007f4
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 这是PostConstruct方法,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@646007f4
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行初始化方法afterPropertiesSet,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@646007f4
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 用户1800000000,执行登录
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 该用户完整信息为User(username=1800000000, password=123456)
说明这些情况下的执行顺序为:构造方法=>BeanNameAware=>BeanFactoryAware=>ApplicationContextAware=>@PostConstruct=>InitializingBean
2.体验Aop编程的实现
1.Spring提供了一些扩展点，如
BeanPostProcessor 接口
public interface BeanPostProcessor {
@Nullable
default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
@Nullable
default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
}
如上，上面只是单纯得返回的是传进来的bean，而在这个时候，我们其实可以生成一个代理对象返回，也就实现了我们的Aop
2.Jdk动态代理(此处仅以Jdk代理实现Aop为例，Cglib本质上差不多，只是他不需要实现接口，他是以生成子类对象，调用父类方法来实现的Aop)
代理时，我们的被代理类（UserServiceImpl）中加入一个注解，如下
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 12:41
* @Describe:
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@Documented
@Inherited
public @interface Required {
}
原UserServiceImpl修改为(只是修改了打印的提示语，外加在login方法上加上了我们新增的Required注解)
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:12
* @Describe:
*/
@Service
@Slf4j
public class UserServiceImpl implements UserService, InitializingBean, BeanNameAware , ApplicationContextAware , BeanFactoryAware {
@Autowired
UserMapper userMapper;
private Map<String, User> userCache = new ConcurrentHashMap<>(10);
public UserServiceImpl(){
log.info("这是UserServiceImpl构造方法,userMapper为{}",userMapper);
}
@PostConstruct
public void postConstruct(){
log.info("这是PostConstruct方法,userMapper为{}",userMapper);
}
@Override
@Required
public String login(String username, String password) {
log.info("用户{},执行登录",username);
User user = userCache.get(username);
log.info("该用户完整信息为{}",user);
return username;
}
@Override
public void afterPropertiesSet() throws Exception {
List<User> users = userMapper.getUser();
if(!CollectionUtils.isEmpty(users)){
users.forEach(user -> userCache.put(user.getUsername(),user));
}
log.info("执行InitializingBean接口的初始化方法afterPropertiesSet,userMapper为{}",userMapper);
}
@Override
public void setBeanName(String s) {
log.info("执行beanNameAware的setBeanName方法,Bean的名称为:{},userMapper为{}",s,userMapper);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
log.info("执行applicationContextAware接口的setApplicationContext方法,userMapper为{}",userMapper);
}
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
log.info("执行beanFactoryAware的setBeanFactory方法,userMapper为{}",userMapper);
}
}
工具类，从被代理对象中获取到注解信息
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 11:12
* @Describe: 直接使用代理类时获取方法上的注解是获取不到的，必须要用target（被代理）对象才行
*/
public class DynamicProxyAnnotationUtil {
public static boolean findAnnotationFromProxy(Class<?> cusAnnotation, Object target, Method method) throws NoSuchMethodException {
Annotation[] annotations = target.getClass().getMethod(method.getName(), method.getParameterTypes()).getAnnotations();
boolean hasAnnotation = Arrays.stream(annotations).filter(annotation -> {
return annotation.annotationType().isAssignableFrom(cusAnnotation);
}).count() > 0;
return hasAnnotation;
}
}
代理对象生成类
@Slf4j
public class AopProxy implements InvocationHandler {
private Object target;
public AopProxy(Object target){
this.target = target;
}
public Object createProxy(Object target) {
this.target = target;
return createProxy();
}
public Object createProxy() {
if(target == null){
throw new RuntimeException("target object can not be null");
}
return Proxy.newProxyInstance(target.getClass().getClassLoader(),
target.getClass().getInterfaces(), this);
}
/**
* @param proxy 代理监控对象
* @param method doSome()方法
* @param args doSome()方法执行时接收的实参
* @return
* @throws Throwable
*/
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
boolean required = DynamicProxyAnnotationUtil.findAnnotationFromProxy(Required.class,target,method);
if(required){
//这里只做模拟，Spring中加入了AspectJ的概念和注解，你看，我们这里可以拿到对象，也可以拿到方法，所以字段、方法上有什么我们都能获取到，要做点什么都很好办吧，这不就是Spring里面的@Before方法吗
log.info("UserService调用前做的增强···");
}
//这个地方是不是可能会抛出异常，这不就是Spring中的@AfterThrowing吗
Object result = method.invoke(target, args);
if(required){
//你看，这不就是我们处理完以后的方法吗@After
log.info("UserService调用后做的增强···");
}
return result;
}
public Object getTarget() {
return target;
}
}
3.实现BeanPostProcessor 接口
我这里做了一个判断，就是属于UserService的实现类时，才需要做一些打印或者处理（主要目的是查看Bean生成的完整顺序）
/**
* @Author: ChenTaoTao
* @Date: 2022/4/30 12:23
* @Describe:
*/
@Slf4j
@Component
public class AppBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if(bean instanceof UserService){
log.info("AppBeanPostProcessor=>postProcessBeforeInitialization:beanName {}",beanName);
}
return BeanPostProcessor.super.postProcessBeforeInitialization(bean, beanName);
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
// 为当前 bean 对象注册监控代理对象，负责增强 bean 对象方法的能力
Class beanClass = bean.getClass();
if (bean instanceof UserService) {
log.info("AppBeanPostProcessor=>postProcessAfterInitialization:beanName {},类名为 {}",beanName,beanClass.getName());
//JDK生成代理类
Object proxy = new AopProxy(bean).createProxy();
log.info("代理类{}",proxy.getClass().getName());
return proxy;
}
return bean;
}
}
此时的运行结果如下:
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 这是UserServiceImpl构造方法,userMapper为null
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行beanNameAware的setBeanName方法,Bean的名称为:userServiceImpl,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行beanFactoryAware的setBeanFactory方法,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行applicationContextAware接口的setApplicationContext方法,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.config.AppBeanPostProcessor - AppBeanPostProcessor=>postProcessBeforeInitialization:beanName userServiceImpl
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 这是PostConstruct方法,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行InitializingBean接口的初始化方法afterPropertiesSet,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.config.AppBeanPostProcessor - AppBeanPostProcessor=>postProcessAfterInitialization:beanName userServiceImpl,类名为 cn.redocloud.service.impl.UserServiceImpl
[main] INFO cn.redocloud.config.AppBeanPostProcessor - 代理类com.sun.proxy.$Proxy13
[main] INFO cn.redocloud.config.AopProxy - UserService调用前做的增强···
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 用户1800000000,执行登录
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 该用户完整信息为User(username=1800000000, password=123456)
[main] INFO cn.redocloud.config.AopProxy - UserService调用后做的增强···
可以看到Spring提供的BeanPostProcessor扩展点对生命周期的影响节点为Aware接口后，@PostConstruct前；以及InitializingBean提供的afterPropertiesSet接口后
最后生成的代理类：
通过上面的运行结果，也就可以看出在AopProxy中加入的两个打印也生效了
由于UserServiceImpl方法中只有一个login方法，且加上了@Required注解，现在新增一个接口，测试下看是否会影响结果:
UserServiceImpl类新增方法
@Override
public String test() {
log.info("test");
return "test";
}
此方法上没有添加我们自定义的注解@Required
修改测试类为如下
public class Test {
public static void main(String[] args) {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
UserService userService = applicationContext.getBean(UserService.class);
// userService.login("1800000000","123456");
userService.test();
}
}
执行结果
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 这是UserServiceImpl构造方法,userMapper为null
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行beanNameAware的setBeanName方法,Bean的名称为:userServiceImpl,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行beanFactoryAware的setBeanFactory方法,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行applicationContextAware接口的setApplicationContext方法,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.config.AppBeanPostProcessor - AppBeanPostProcessor=>postProcessBeforeInitialization:beanName userServiceImpl
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 这是PostConstruct方法,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.service.impl.UserServiceImpl - 执行InitializingBean接口的初始化方法afterPropertiesSet,userMapper为cn.redocloud.mapper.impl.UserMapperImpl@df27fae
[main] INFO cn.redocloud.config.AppBeanPostProcessor - AppBeanPostProcessor=>postProcessAfterInitialization:beanName userServiceImpl,类名为 cn.redocloud.service.impl.UserServiceImpl
[main] INFO cn.redocloud.config.AppBeanPostProcessor - 代理类com.sun.proxy.$Proxy13
[main] INFO cn.redocloud.service.impl.UserServiceImpl - test
以上则说明没有@Required注解时，是不会通过我们编写的额外逻辑(Aop)的，Spring声明式事务的实现也许就是如此