Spring核心概念解析之IOC、DI与AOP使用方式

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// 使用BeanFactory
Resource resource = new ClassPathResource("applicationContext.xml");
BeanFactory factory = new XmlBeanFactory(resource);
UserService userService = (UserService) factory.getBean("userService");

​

// 使用ApplicationContext
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
UserService userService = context.getBean(UserService.class);

@Service
public class UserService {
    private final UserDao userDao;
    
    // 构造器注入
    @Autowired
    public UserService(UserDao userDao) {
        this.userDao = userDao;
    }
}

@Service
public class UserService {
    private UserDao userDao;
    
    // Setter方法注入
    @Autowired
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
}

@Service
public class UserService {
    // 字段注入
    @Autowired
    private UserDao userDao;
}

// 1. 定义切面
@Aspect
@Component
public class LoggingAspect {

// 2. 定义切点：匹配com.example.service包下所有类的所有方法
@Pointcut("execution(* com.example.service.*.*(..))")
public void serviceMethods() {}

// 3. 定义前置通知
@Before("serviceMethods()")
public void logBefore(JoinPoint joinPoint) {
    String methodName = joinPoint.getSignature().getName();
    Object[] args = joinPoint.getArgs();
    System.out.println("调用方法: " + methodName + ", 参数: " + Arrays.toString(args));
}

// 4. 定义后置通知
@After("serviceMethods()")
public void logAfter(JoinPoint joinPoint) {
    String methodName = joinPoint.getSignature().getName();
    System.out.println("方法" + methodName + "执行完毕");
}

// 5. 定义返回通知
@AfterReturning(pointcut = "serviceMethods()", returning = "result")
public void logAfterReturning(JoinPoint joinPoint, Object result) {
    String methodName = joinPoint.getSignature().getName();
    System.out.println("方法" + methodName + "返回结果: " + result);
}

// 6. 定义异常通知
@AfterThrowing(pointcut = "serviceMethods()", throwing = "ex")
public void logAfterThrowing(JoinPoint joinPoint, Exception ex) {
    String methodName = joinPoint.getSignature().getName();
    System.out.println("方法" + methodName + "抛出异常: " + ex.getMessage());
}

// 7. 定义环绕通知
@Around("serviceMethods()")
public Object logAround(ProceedingJoinPoint joinPoint) throws Throwable {
    String methodName = joinPoint.getSignature().getName();
    
    // 方法执行前
    long startTime = System.currentTimeMillis();
    
    // 执行目标方法
    Object result = joinPoint.proceed();
    
    // 方法执行后
    long endTime = System.currentTimeMillis();
    System.out.println("方法" + methodName + "执行时间: " + (endTime - startTime) + "ms");
    
    return result;
}

}
启用AOP支持：
@Configuration
@ComponentScan(“com.example”)
@EnableAspectJAutoProxy // 启用AOP支持
public class AppConfig {
}

com.example
├── config
│ └── AppConfig.java // 配置类
├── dao
│ ├── UserDao.java // 数据访问接口
│ └── UserDaoImpl.java // 数据访问实现
├── service
│ ├── UserService.java // 业务服务接口
│ └── UserServiceImpl.java // 业务服务实现
├── aspect
│ └── LoggingAspect.java // 日志切面
└── Main.java // 主程序

// UserDao.java
public interface UserDao {
void addUser(String username);
String getUserById(int id);
}

// UserDaoImpl.java
@Repository
public class UserDaoImpl implements UserDao {
@Override
public void addUser(String username) {
System.out.println("数据库中添加用户: " + username);
}

@Override
public String getUserById(int id) {
    System.out.println("从数据库中查询ID为" + id + "的用户");
    return "用户" + id; // 模拟查询结果
}

// UserService.java
public interface UserService {
void registerUser(String username);
String getUserInfo(int id);
}

// UserServiceImpl.java
@Service
public class UserServiceImpl implements UserService {
private final UserDao userDao;

// 构造器注入
@Autowired
public UserServiceImpl(UserDao userDao) {
    this.userDao = userDao;
}

@Override
public void registerUser(String username) {
    if (username == null || username.isEmpty()) {
        throw new IllegalArgumentException("用户名不能为空");
    }
    userDao.addUser(username);
}

@Override
public String getUserInfo(int id) {
    if (id <= 0) {
        throw new IllegalArgumentException("用户ID必须为正数");
    }
    return userDao.getUserById(id);
}

// LoggingAspect.java
@Aspect
@Component
public class LoggingAspect {
// 定义切点：匹配UserService接口的所有方法
@Pointcut(“execution(* com.example.service.UserService.*(…))”)
public void userServicePointcut() {}

// 前置通知
@Before("userServicePointcut()")
public void logBefore(JoinPoint joinPoint) {
    String methodName = joinPoint.getSignature().getName();
    Object[] args = joinPoint.getArgs();
    System.out.println("[前置日志] 调用方法: " + methodName + ", 参数: " + Arrays.toString(args));
}

// 返回通知
@AfterReturning(pointcut = "userServicePointcut()", returning = "result")
public void logAfterReturning(JoinPoint joinPoint, Object result) {
    String methodName = joinPoint.getSignature().getName();
    System.out.println("[返回日志] 方法" + methodName + "返回: " + result);
}

// 异常通知
@AfterThrowing(pointcut = "userServicePointcut()", throwing = "ex")
public void logAfterThrowing(JoinPoint joinPoint, Exception ex) {
    String methodName = joinPoint.getSignature().getName();
    System.out.println("[异常日志] 方法" + methodName + "抛出异常: " + ex.getMessage());
}

// 环绕通知
@Around("userServicePointcut()")
public Object logAround(ProceedingJoinPoint joinPoint) throws Throwable {
    String methodName = joinPoint.getSignature().getName();
    long startTime = System.currentTimeMillis();
    
    Object result = null;
    try {
        result = joinPoint.proceed();
    } finally {
        long endTime = System.currentTimeMillis();
        System.out.println("[性能日志] 方法" + methodName + "执行时间: " + 
                          (endTime - startTime) + "ms");
    }
    return result;
}

// AppConfig.java
@Configuration
@ComponentScan(“com.example”)
@EnableAspectJAutoProxy
public class AppConfig {
}

// Main.java
public class Main {
public static void main(String[] args) {
// 创建IOC容器
ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

    // 从容器中获取UserService
    UserService userService = context.getBean(UserService.class);
    
    // 测试正常调用
    userService.registerUser("张三");
    String userInfo = userService.getUserInfo(1);
    System.out.println("获取到的用户信息: " + userInfo);
    
    // 测试异常情况
    try {
        userService.registerUser("");
    } catch (IllegalArgumentException e) {
        // 异常已被切面捕获并记录
    }
}