javax.annotation注解全面解析：从基础使用到高级实战

import javax.annotation.Resource;
import javax.sql.DataSource;

public class UserService {
    
    @Resource(name = "jdbc/UserDB")
    private DataSource dataSource;
    
    @Resource
    private UserRepository userRepository;
    
    public void processUser() {
        // 使用注入的dataSource和userRepository
    }
}

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

public class DatabaseInitializer {
    
    @PostConstruct
    public void initialize() {
        System.out.println("数据库连接初始化...");
        // 执行初始化逻辑
    }
    
    @PreDestroy
    public void cleanup() {
        System.out.println("清理数据库资源...");
        // 执行清理逻辑
    }
}

import javax.annotation.Generated;

@Generated(value = "com.example.CodeGenerator", 
           date = "2024-01-01T10:00:00",
           comments = "自动生成的DTO类")
public class UserDTO {
    private String name;
    private String email;
    
    // 自动生成的getter/setter
}

import javax.annotation.ManagedBean;
import javax.enterprise.context.RequestScoped;

@ManagedBean
@RequestScoped
public class LoginBean {
    private String username;
    private String password;
    
    public String login() {
        // 登录逻辑
        return "success";
    }
    
    // getter和setter
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getPassword() { return password; }
    public void setPassword(String password) { this.password = password; }
}

import javax.annotation.*;
import javax.sql.DataSource;
import java.util.logging.Logger;

/**
 * 用户服务类示例
 */
public class UserService {
    
    private static final Logger logger = Logger.getLogger(UserService.class.getName());
    
    @Resource(lookup = "java:comp/env/jdbc/userDS")
    private DataSource dataSource;
    
    private boolean initialized = false;
    
    @PostConstruct
    public void init() {
        logger.info("UserService初始化开始...");
        try {
            // 验证数据源连接
            dataSource.getConnection();
            initialized = true;
            logger.info("UserService初始化完成");
        } catch (Exception e) {
            logger.severe("初始化失败: " + e.getMessage());
        }
    }
    
    @PreDestroy
    public void destroy() {
        logger.info("UserService销毁开始...");
        // 清理资源
        initialized = false;
        logger.info("UserService已销毁");
    }
    
    public void processUserData(String userId) {
        if (!initialized) {
            throw new IllegalStateException("服务未初始化");
        }
        
        // 处理用户数据的业务逻辑
        logger.info("处理用户数据: " + userId);
    }
    
    // 使用@Resource进行方法级别注入
    private UserRepository userRepository;
    
    @Resource
    public void setUserRepository(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
}

// 辅助类
class UserRepository {
    public void save(User user) {
        // 保存用户逻辑
    }
}

class User {
    private String id;
    private String name;
    
    // getter和setter
    public String getId() { return id; }
    public void setId(String id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

<dependency>
    <groupId>javax.annotation</groupId>
    <artifactId>javax.annotation-api</artifactId>
    <version>1.3.2</version>
</dependency>