首页 > 代码库 > 2.2、Hibernate用注解方式实现一对多、多对多关系
2.2、Hibernate用注解方式实现一对多、多对多关系
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=http://www.mamicode.com/{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 @Override35 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 @Override62 public String toString() {63 return "EmployeeBean [id=" + id + ", name=" + name + ", sex=" + sex64 + ", job=" + job + ", dept=" + dept65 + "]";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=http://www.mamicode.com/{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 @Override61 public String toString() {62 return "UserBean [id=" + id + ", name=" + name + ", sex=" + sex63 + ", 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=http://www.mamicode.com/{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 @Override63 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 @Test23 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 }
2.2、Hibernate用注解方式实现一对多、多对多关系
声明：以上内容来自用户投稿及互联网公开渠道收集整理发布，本网站不拥有所有权，未作人工编辑处理，也不承担相关法律责任，若内容有误或涉及侵权可进行投诉： 投诉/举报 工作人员会在5个工作日内联系你，一经查实，本站将立刻删除涉嫌侵权内容。