一、一对多关系
1、在上一篇日志中用.xml配置文件项目基础上，再往lib目录先添加一个包-hibernate-jpa-2.0-api-1.0.0.Final.jar
2、新建一个com.st.bean4 包，往包里面添加两个含有注解的类：
a)、DeptBean2类：
1 package com.st.bean4;
2
3 import java.util.HashSet;
4 import java.util.Set;
5
6
7 import javax.persistence.Column;
8 import javax.persistence.Entity;
9 import javax.persistence.GeneratedValue;
10 import javax.persistence.Id;
11 import javax.persistence.JoinColumn;
12 import javax.persistence.OneToMany;
13 import javax.persistence.Table;
14
15 import org.hibernate.annotations.Cascade;
16 import org.hibernate.annotations.CascadeType;
17 import org.hibernate.annotations.GenericGenerator;
18
19 @Entity //指定实体类
20 @Table(name="DEPT") //对应表的名称
21 @GenericGenerator(name="genID", strategy="increment") //声明主键生成策略
22 public class DeptBean2 {
23 @Id //指定主键
24 @GeneratedValue(generator="genID") //设定主键生成策略
25 @Column(name="ID") //指定类中的属性与表中的列的对应关系
26 private long id;
27 @Column(name="NAME") //指定类中的属性与表中的列的对应关系
28 private String name;
29
30 @OneToMany //指定一对多关系
31 @Cascade(value={CascadeType.SAVE_UPDATE}) //设定级联关系
32 @JoinColumn(name="dept_id") //指定与本类主键所对应的外表的外键
33 private Set<EmployeeBean2> emp = new HashSet<EmployeeBean2>();
34 @Override
35 public String toString() {
36 return "DeptBean [id=" + id + ", name=" + name +"]";
37 }
38 public long getId() {
39 return id;
40 }
41 public void setId(long id) {
42 this.id = id;
43 }
44 public String getName() {
45 return name;
46 }
47 public void setName(String name) {
48 this.name = name;
49 }
50 public Set<EmployeeBean2> getEmp() {
51 return emp;
52 }
53 public void setEmp(Set<EmployeeBean2> emp) {
54 this.emp = emp;
55 }
56 }
b）、EmployeeBean类：
1 package com.st.bean4;
2
3 import javax.persistence.Column;
4 import javax.persistence.Entity;
5 import javax.persistence.GeneratedValue;
6 import javax.persistence.Id;
7 import javax.persistence.JoinColumn;
8 import javax.persistence.ManyToOne;
9 import javax.persistence.Table;
10
11 import org.hibernate.annotations.GenericGenerator;
12
13 @Entity //指定一个实体
14 @Table(name="employee") //指定表的名称
15 @GenericGenerator(name="genID", strategy="increment") //声明主键生成策略
16 public class EmployeeBean2 {
17 @Id //指定主键
18 @GeneratedValue(generator="genID") //设定主键生成策略
19 @Column(name="ID") //类中的属性和表中的列名的对应关系
20 private long id;
21 @Column(name="NAME")
22 private String name;
23 @Column(name="SEX")
24 private String sex;
25 @Column(name="JOB")
26 private String job;
27 @ManyToOne// 指定多对一关系 //指定多对一关系
28 @JoinColumn(name="DEPT_ID")
29 //一个员工对应于一个部门号，所以这里不用集合
30 private DeptBean2 dept ; //注意这个地方不要new对象，否则会无法运行
31 public long getId() {
32 return id;
33 }
34 public void setId(long id) {
35 this.id = id;
36 }
37 public String getName() {
38 return name;
39 }
40 public void setName(String name) {
41 this.name = name;
42 }
43 public String getSex() {
44 return sex;
45 }
46 public void setSex(String sex) {
47 this.sex = sex;
48 }
49 public String getJob() {
50 return job;
51 }
52 public void setJob(String job) {
53 this.job = job;
54 }
55 public DeptBean2 getDept() {
56 return dept;
57 }
58 public void setDept(DeptBean2 dept) {
59 this.dept = dept;
60 }
61 @Override
62 public String toString() {
63 return "EmployeeBean [id=" + id + ", name=" + name + ", sex=" + sex
64 + ", job=" + job + ", dept=" + dept
65 + "]";
66 }
67 }
3、在hibernate.cfg.xml文件中引入上面两个类的映射
1 <mapping class="com.st.bean5.UserBean2" />
2 <mapping class="com.st.bean5.RoleBean2" />
4、在BeanTest中添加相应的测试方法：
1 @Test
2 public void bean4test1(){
3 Session session = HibernateTools.openSession();
4 Transaction tran = session.beginTransaction();
5 //首先在dept中新增一条数据，再关联的在employee中新增一条数据
6 //DeptBean2 dept = new DeptBean2();
7 //先读去dept中的数据，再在读取的基础上关联的在employee中新增一条数据
8 DeptBean2 dept = (DeptBean2) session.get(DeptBean2.class,1L); //1L代表主键
9 EmployeeBean2 emp = new EmployeeBean2();
10 //dept.setName("技术部");
11 emp.setName("陈泽俊");
12 emp.setSex("男");
13 emp.setJob("STM32");
14 dept.getEmp().add(emp);
15 session.save(dept);
16 //确认提交事物
17 tran.commit();
18 }
二、多对多关系
1、新建一个com.st.bean4 包，往包里面添加两个含有注解的类
a）、UserBean2：
1 package com.st.bean5;
2 import java.util.HashSet;
3 import java.util.Set;
4
5 import javax.persistence.Column;
6 import javax.persistence.Entity;
7 import javax.persistence.GeneratedValue;
8 import javax.persistence.Id;
9 import javax.persistence.JoinColumn;
10 import javax.persistence.JoinTable;
11 import javax.persistence.ManyToMany;
12 import javax.persistence.Table;
13
14 import org.hibernate.annotations.Cascade;
15 import org.hibernate.annotations.CascadeType;
16 import org.hibernate.annotations.GenericGenerator;
17
18 @Entity //实体
19 @Table(name="T_USER") //表名
20 @GenericGenerator(name="genID", strategy="increment") //声明主键生成策略
21 public class UserBean2 {
22 @Id //指定主键
23 @GeneratedValue(generator="genID") //设定主键生成策略
24 @Column(name="ID") //指定类的属性和表的字段的对应关系
25 private long id;
26 @Column(name="NAME")
27 private String name;
28 @Column(name="SEX")
29 private String sex;
30 @ManyToMany //指定多对多关系
31 @Cascade(value={CascadeType.SAVE_UPDATE}) //设置级联关系
32 @JoinTable(name="USER_ROLE", //指定第三张表
33 joinColumns={@JoinColumn(name="USER_ID")}, //本表与中间表的外键对应
34 inverseJoinColumns={@JoinColumn(name="ROLE_ID")}) //另一张表与第三张表的外键的对应关系
35 private Set<RoleBean2> role = new HashSet<RoleBean2>();
36 public long getId() {
37 return id;
38 }
39 public void setId(long id) {
40 this.id = id;
41 }
42 public String getName() {
43 return name;
44 }
45 public void setName(String name) {
46 this.name = name;
47 }
48 public String getSex() {
49 return sex;
50 }
51 public void setSex(String sex) {
52 this.sex = sex;
53 }
54 public Set<RoleBean2> getRole() {
55 return role;
56 }
57 public void setRole(Set<RoleBean2> role) {
58 this.role = role;
59 }
60 @Override
61 public String toString() {
62 return "UserBean [id=" + id + ", name=" + name + ", sex=" + sex
63 + ", role=" + role + "]";
64 }
65 }
b）、RoleBean类：
1 package com.st.bean5;
2 import java.util.HashSet;
3
4 import java.util.Set;
5
6 import javax.persistence.Column;
7 import javax.persistence.Entity;
8 import javax.persistence.GeneratedValue;
9 import javax.persistence.Id;
10 import javax.persistence.JoinColumn;
11 import javax.persistence.JoinTable;
12 import javax.persistence.ManyToMany;
13 import javax.persistence.Table;
14
15 import org.hibernate.annotations.Cascade;
16 import org.hibernate.annotations.CascadeType;
17 import org.hibernate.annotations.GenericGenerator;
18
19 @Entity //实体
20 @Table(name="T_ROLE") //表名
21 @GenericGenerator(name="genID", strategy="increment")//声明主键生成策略
22 public class RoleBean2 {
23 @Id //主键
24 @GeneratedValue(generator="genID") //设置主键生成策略
25 @Column(name="ID") //类中的属性与表的字段的对应关系
26 private long id;
27 @Column(name="POST")
28 private String post;//职位
29 @Column(name="PAY")
30 private int pay; //薪资
31 @ManyToMany //多对多关系
32 @Cascade(value={CascadeType.SAVE_UPDATE}) //级联关系
33 @JoinTable(name="USER_ROLE", //中间表的名称
34 joinColumns={@JoinColumn(name="ROLE_ID")}, //本表与中间表的外键对应关系
35 inverseJoinColumns={@JoinColumn(name="USER_ID")}) //另一张表与中间表的外键的对应关系
36 private Set<UserBean2> user = new HashSet<UserBean2>();
37
38 public long getId() {
39 return id;
40 }
41 public void setId(long id) {
42 this.id = id;
43 }
44 public String getPost() {
45 return post;
46 }
47 public void setPost(String post) {
48 this.post = post;
49 }
50 public int getPay() {
51 return pay;
52 }
53 public void setPay(int pay) {
54 this.pay = pay;
55 }
56 public Set<UserBean2> getUser() {
57 return user;
58 }
59 public void setUser(Set<UserBean2> user) {
60 this.user = user;
61 }
62 @Override
63 public String toString() {
64 return "RoleBean [id=" + id + ", post=" + post + ", pay=" + pay + "]";
65 }
66 }
2、在hibernate.cfg.xml中引入UserBean2和RoleBean2这两个类的映射：
1 <mapping class="com.st.bean5.UserBean2" />
2 <mapping class="com.st.bean5.RoleBean2" />
3、在BeanTest类中添加测试方法：
1 @Test
2 public void bean5test1(){
3 // 获取一个会话
4 Session session = HibernateTools.openSession();
5 //开启一次事物
6 Transaction tran = session.beginTransaction();
7 UserBean2 user = new UserBean2();
8 // RoleBean2 role = (RoleBean2) session.get(RoleBean2.class,1L);
9 RoleBean2 role = new RoleBean2();
10
11 user.setName("汪文仕");
12 user.setSex("男");
13
14 role.setPost("博士");
15 role.setPay(10000);
16
17 role.getUser().add(user);
18 session.save(role);
19 //确认提交事物
20 tran.commit();
21 }
22 @Test
23 public void bean5test2(){
24 // 获取一个会话
25 Session session = HibernateTools.openSession();
26 /* List<UserBean> list = session.createCriteria(UserBean.class).list();
27 for(UserBean user : list)
28 System.out.println(user);*/
29 String hql = "select new Map(u.name as name,u.sex as sex,r.post as post,r.pay as pay) from UserBean2 u join u.role r";
30 List<Map<String,Object>> list = session.createQuery(hql).list();
31 for(Map<String,Object> data : list)
32 System.out.println(data);
33 }
三、注意：
1、引入了注解需要的jar包后要先删除Java EE 5 Library这个库，否则会两个jar包中的类产生冲突
2、在多表操作时最好设置级联关系，不然对表操作时要先读取一个类的数据，再将新建的一个类的数据添加到这个类上才成功对三张表同时操作。