简单的例子

以下两个类分别定义了User和Article两个对象，每个用户拥有多个Article，每个article只有一个作者(user)

实体类：User

@Entity 
@Table(name = "user") 
public class User implements Serializable {
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id; 
    
    @Basic
    @Column(name = "username")
    private String username; 
    
    @Basic
    @Column(name = "password")
    private String password;
    
    @ManyToOne(mappedBy="author")
    Set<Article> articles;
    
    // 此处省略 getter 和 setter 。
}

实体类：Article

@Entity 
@Table(name = "article") 
public class Article implements Serializable { 
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id; 
    
    @Basic
    @Column(name = "content")
    private String content; 
    
    @OneToMany
    @JoinColumn(name = "author_id")
    private User author;
 
    // 此处省略 getter 和 setter 。
}

DAO

//User类的DAO：
public interface UserRepository extends JpaRepository<Privilege, Integer>  {
}

//Article的DAO：
public interface ArticleRepository extends JpaRepository<Privilege, Integer>  {
}

使用：

public class UserService{
    @Resource
    UserRepository userRepository;
    
    List<User> getUserList(){
        return userRepository.findAll();
    }
    
    List<Article> getArticleListByUserId(Long userId){
        return userRepository.getOne(userId).getArticles();
    }
    
}

几个注解

实体

@Entity

@Table(name = “t”)

@Table(name = “t”)

### 属性

#### Id

#### Column

#### Basic

### 关系

#### OneToOne

#### OneToMany

#### ManyToOne

#### ManyToMany

#### JoinTable

参考文档

Spring Data JPA 官方文档