单向

一对一

实体:

@Entity
@Table(name="tb_product")
public class Product {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;
    private String name;
    @OneToOne
    @JoinColumn(name="dir_id")
    private ProductDir dirId;
    /**
     * @return the id
     */
    public Long getId() {
        return id;
    }
    /**
     * @param id the id to set
     */
    public void setId(Long id) {
        this.id = id;
    }
    /**
     * @return the name
     */
    public String getName() {
        return name;
    }
    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }
    /**
     * @return the dirId
     */
    public ProductDir getDirId() {
        return dirId;
    }
    /**
     * @param dirId the dirId to set
     */
    public void setDirId(ProductDir dirId) {
        this.dirId = dirId;
    }
    /** 
     * @Title: toString
     * @author zjh
     * @Desc: 
     * @return 
     * @see java.lang.Object#toString() 
     */
    @Override
    public String toString() {
        return "Product [id=" + id + ", name=" + name + ", dirId=" + dirId
                + "]";
    }
}
@Entity
@Table(name="tb_productDir")
public class ProductDir {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;
    private String name;
    /**
     * @return the id
     */
    public Long getId() {
        return id;
    }
    /**
     * @param id the id to set
     */
    public void setId(Long id) {
        this.id = id;
    }
    /**
     * @return the name
     */
    public String getName() {
        return name;
    }
    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }
    /** 
     * @Title: toString
     * @author zjh
     * @Desc: 
     * @return 
     * @see java.lang.Object#toString() 
     */
    @Override
    public String toString() {
        return "ProductDir [id=" + id + ", name=" + name + "]";
    }
}

测试

public class TestDemo {
    IProductDao iProductDao = new ProductDaoImpl();
    IProductDirDao iProductDirDao =  new ProductDirDaoImpl();
    @org.junit.Test
    public void Test(){
        ProductDir productDir = new ProductDir();
        productDir.setName("食品");
        Product product = new Product();
        product.setName("牛肉");
        product.setDirId(productDir);
        iProductDirDao.save(productDir);
        iProductDao.save(product);
    }
}

控制台打印

Hibernate: insert into tb_productDir (name) values (?)
Hibernate: insert into tb_product (dir_id, name) values (?, ?)

多对一

一的实体

一对多

一的实体

@Entity
public class Teacher {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    @OneToMany
    //这里如果是要一对多关系模式的话，必须加上JoinColumn()注解，否则会生成一张关联表，那样的话就会被误解为多对多
    @JoinColumn(name="student_id")
    private List<Student> students = new ArrayList<>();
    /**
     * @return the id
     */
    public Long getId() {
        return id;
    }
    /**
     * @param id the id to set
     */
    public void setId(Long id) {
        this.id = id;
    }
    /**
     * @return the name
     */
    public String getName() {
        return name;
    }
    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }
    /**
     * @return the students
     */
    public List<Student> getStudents() {
        return students;
    }
    /**
     * @param students the students to set
     */
    public void setStudents(List<Student> students) {
        this.students = students;
    }
    /** 
     * @Title: toString
     * @author zjh
     * @Desc: 
     * @return 
     * @see java.lang.Object#toString() 
     */
    @Override
    public String toString() {
        return "Teacher [id=" + id + ", name=" + name + "]";
    }
}

多的实体

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    /**
     * @return the id
     */
    public Long getId() {
        return id;
    }
    /**
     * @param id the id to set
     */
    public void setId(Long id) {
        this.id = id;
    }
    /**
     * @return the name
     */
    public String getName() {
        return name;
    }
    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }
    /** 
     * @Title: toString
     * @author zjh
     * @Desc: 
     * @return 
     * @see java.lang.Object#toString() 
     */
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + "]";
    }
}

测试代码

public class OneToManyTest {
    @Test
    public void testAdd(){
        Student student = new Student();
        student.setName("tom");
        Student student2 = new Student();
        student2.setName("jreey");
        Teacher teacher = new Teacher();
        teacher.setName("jack");
        teacher.getStudents().add(student);
        teacher.getStudents().add(student2);
        EntityManagerFactory entityManagerFactory = JPAUtils.getEntityManagerFactory();
        EntityManager createEntityManager = entityManagerFactory.createEntityManager();
        EntityTransaction transaction = createEntityManager.getTransaction();
        transaction.begin();
        createEntityManager.persist(teacher);
        createEntityManager.persist(student);
        createEntityManager.persist(student2);
        transaction.commit();
        createEntityManager.close();
    }
}

日志

Hibernate: insert into Teacher (name) values (?)
Hibernate: insert into Student (name) values (?)
Hibernate: insert into Student (name) values (?)
Hibernate: update Student set student_id=? where id=?
Hibernate: update Student set student_id=? where id=?