Hibernate之关系映射的两种方式（xml映射、annotation注解映射）

小咪咪 2022-07-14 15:16 119阅读 0赞

> 本文列出了两种关系映射包括一对一和一对多（多对一），并且列出了两种方式（xml映射和annotation注解映射）分别对一对一和一对多的代码，关键地方标有注释解释。可供初学者参考。  
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## **主键关系映射代码之一对一**\#\# ##

一个学生对应一条登录信息（用户名、密码），一条登录信息对于一个学生  
一.xml文件映射  
1.在Student类中加入一个对方类型的属性，即登录信息类的实例。

package com.ffy.studentmanage;
    
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.OneToOne;
    import javax.persistence.PrimaryKeyJoinColumn;
    import javax.persistence.Table;
    public class Student { 
        private int id;
        private int sid;
        private String firstName;
        private String lastName;
        private String gender;
        private String phone;
        private String email;
        private String dateOfBirth;
        private double height=160;
        private int studentStatusID;
    
        //在student表中加入StudentLogin属性
        private StudentLogin studentLogin;
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public int getSid() {
            return sid;
        }
        public void setSid(int sid) {
            this.sid = sid;
        }
        public String getFirstName() {
            return firstName;
        }
        public void setFirstName(String firstName) {
            this.firstName = firstName;
        }
        public String getLastname() {
            return lastName;
        }
        public void setLastname(String lastName) {
            this.lastName = lastName;
        }
        public String getGender() {
            return gender;
        }
        public void setGender(String gender) {
            this.gender = gender;
        }
        public String getPhone() {
            return phone;
        }
        public void setPhone(String phone) {
            this.phone = phone;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getDateOfBirth() {
            return dateOfBirth;
        }
        public void setDateOfBirth(String dateOfBirth) {
            this.dateOfBirth = dateOfBirth;
        }
        public double getHeight() {
            return height;
        }
        public void setHeight(double height) {
            this.height = height;
        }
        public String getLastName() {
            return lastName;
        }
        public void setLastName(String lastName) {
            this.lastName = lastName;
        }
        public int getStudentStatusID() {
            return studentStatusID;
        }
        public void setStudentStatusID(int studentStatusID) {
            this.studentStatusID = studentStatusID;
        }
    
        public StudentLogin getStudentLogin() {
            return studentLogin;
        }
        public void setStudentLogin(StudentLogin studentLogin) {
            this.studentLogin = studentLogin;
        }
        public String toString(){
            return this.id+":"+this.lastName+this.firstName+this.gender+":"+this.phone+":"+this.email+";username"+studentLogin.getUsername()+";password:"+studentLogin.getPassword();
        }
    }

2.配置student.hbm.xml,基本属性配置方法不变，StudentLogin的配置如下。

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    <hibernate-mapping>
        <class name="com.ffy.studentmanage.Student" table="student">
            <id name="id" column="id">
                <generator class="assigned"></generator>
            </id>
            <property name="sid" column="sid"></property>
            <property name="firstName" column="firstname"></property>
            <property name="lastName" column="lastname"></property>
            <property name="gender" column="gender"></property>
            <property name="phone" column="phone"></property>
            <property name="email" column="email"></property>
            <property name="dateOfBirth" column="date_of_birth"></property>
            <property name="studentStatusID" column="student_status_id"></property>
            <property name="height" column="height"></property>
            //对方的属性的映射，name属性为，Student的studentLogin属性，class为对方类，意味将studentLogin属性与studentLogin类建立一对一的映射关系
            <one-to-one name="studentLogin" class="com.ffy.studentmanage.StudentLogin" cascade="all"></one-to-one>
        </class>
    </hibernate-mapping>

3.在hibernate.cfg.xml注册student.hbm.xml文件

二.annotation注解映射  
1.在hibernate.cfg.xml注册StudentLogin类

2.在Student中添加注解

package com.ffy.studentmanage;
    
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.OneToOne;
    import javax.persistence.PrimaryKeyJoinColumn;
    import javax.persistence.Table;
    @Entity
    @Table(name="student")
    public class Student { 
        @Id
        @Column(name="id")
        private int id;
        @Column(name="sid")
        private int sid;
        @Column(name="firstname")
        private String firstName;
        @Column(name="lastname")
        private String lastName;
        @Column(name="gender")
        private String gender;
        @Column(name="phone")
        private String phone;
        @Column(name="email")
        private String email;
        @Column(name="date_of_birth")
        private String dateOfBirth;
        @Column(name="height")
        private double height=160;
        @Column(name="student_status_id")
        private int studentStatusID;
    
        //在student表中加入StudentLogin属性，并标注为一对一属性
        @OneToOne
        @PrimaryKeyJoinColumn
        private StudentLogin studentLogin;
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public int getSid() {
            return sid;
        }
        public void setSid(int sid) {
            this.sid = sid;
        }
        public String getFirstName() {
            return firstName;
        }
        public void setFirstName(String firstName) {
            this.firstName = firstName;
        }
        public String getLastname() {
            return lastName;
        }
        public void setLastname(String lastName) {
            this.lastName = lastName;
        }
        public String getGender() {
            return gender;
        }
        public void setGender(String gender) {
            this.gender = gender;
        }
        public String getPhone() {
            return phone;
        }
        public void setPhone(String phone) {
            this.phone = phone;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getDateOfBirth() {
            return dateOfBirth;
        }
        public void setDateOfBirth(String dateOfBirth) {
            this.dateOfBirth = dateOfBirth;
        }
        public double getHeight() {
            return height;
        }
        public void setHeight(double height) {
            this.height = height;
        }
        public String getLastName() {
            return lastName;
        }
        public void setLastName(String lastName) {
            this.lastName = lastName;
        }
        public int getStudentStatusID() {
            return studentStatusID;
        }
        public void setStudentStatusID(int studentStatusID) {
            this.studentStatusID = studentStatusID;
        }
    
        public StudentLogin getStudentLogin() {
            return studentLogin;
        }
        public void setStudentLogin(StudentLogin studentLogin) {
            this.studentLogin = studentLogin;
        }
        public String toString(){
            return this.id+":"+this.lastName+this.firstName+this.gender+":"+this.phone+":"+this.email+";username"+studentLogin.getUsername()+";password:"+studentLogin.getPassword();
        }
    }

## **主键关系映射代码之多对一（一对多）**\#\# ##

一个学生对应一条状态，一条状态对应多个学生

一.xml文件映射

# *多方代码*\# #

1.在Student类（多的那方）中加入一个对方类型的属性，即登录信息类的实例。

@Table(name="student")
    public class Student {
        private int id;
        private int sid;
        private String firstName;
        private String lastName;
        private String gender;
        private String phone;
        private String email;
        private String dateOfBirth;
        private double height=160;
    
        //多的一方，加入对方的一个类的属性。一个学生对于一个状态。
        private StudentStatus status;
    
        private StudentLogin studentLogin;
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public int getSid() {
            return sid;
        }
        public void setSid(int sid) {
            this.sid = sid;
        }
        public String getFirstName() {
            return firstName;
        }
        public void setFirstName(String firstName) {
            this.firstName = firstName;
        }
        public String getLastname() {
            return lastName;
        }
        public void setLastname(String lastName) {
            this.lastName = lastName;
        }
        public String getGender() {
            return gender;
        }
        public void setGender(String gender) {
            this.gender = gender;
        }
        public String getPhone() {
            return phone;
        }
        public void setPhone(String phone) {
            this.phone = phone;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getDateOfBirth() {
            return dateOfBirth;
        }
        public void setDateOfBirth(String dateOfBirth) {
            this.dateOfBirth = dateOfBirth;
        }
        public double getHeight() {
            return height;
        }
        public void setHeight(double height) {
            this.height = height;
        }
        public String getLastName() {
            return lastName;
        }
        public void setLastName(String lastName) {
            this.lastName = lastName;
        }
    
        public StudentStatus getStatus() {
            return status;
        }
        public void setStatus(StudentStatus status) {
            this.status = status;
        }
        public StudentLogin getStudentLogin() {
            return studentLogin;
        }
        public void setStudentLogin(StudentLogin studentLogin) {
            this.studentLogin = studentLogin;
        }
        public String toString(){
            return this.id+":"+this.lastName+this.firstName+this.gender+":"+this.phone+":"+this.email+";username"+studentLogin.getUsername()+";password:"+studentLogin.getPassword();
        }
    }

2.配置student.hbm.xml,基本属性配置方法不变，StudentStatus的配置如下。

<class name="com.ffy.studentmanage.Student" table="student">
            <id name="id" column="id">
                <generator class="assigned"></generator>
            </id>
            <property name="sid" column="sid"></property>
            <property name="firstName" column="firstname"></property>
            <property name="lastName" column="lastname"></property>
            <property name="gender" column="gender"></property>
            <property name="phone" column="phone"></property>
            <property name="email" column="email"></property>
            <property name="dateOfBirth" column="date_of_birth"></property>
            <property name="studentStatusID" column="student_status_id"></property>
            <property name="height" column="height"></property>
            <one-to-one name="studentLogin" class="com.ffy.studentmanage.StudentLogin" cascade="all"></one-to-one>
            //表明多个学生可以对应一条状态，name对应Student类中的属性status，id为student_status表中的id字段（即student表中有一个外键student_status_id,对应student_status表的id字段，class表示一的一方为StudentStatus类）
            <many-to-one name="status" column="id" class="com.ffy.studentmanage.StudentStatus"></many-to-one>
        </class>

# **一方代码** #

1.在StudentStatus类（一的那方）中加入一个对方（多方）类型的属性，即学生信息类的实例。

public class StudentStatus {
        private int id;
        private String code;
        private String name;
        private String description;
    
        //加入一个集合，泛型为Student，用于存放该状态对应的学生，因为一条状态对呀多个学生，所以需要用集合表示
        private Set<Student> students=new HashSet<>();
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getCode() {
            return code;
        }
        public void setCode(String code) {
            this.code = code;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getDescription() {
            return description;
        }
        public void setDescription(String description) {
            this.description = description;
        }
    
        public Set<Student> getStudents() {
            return students;
        }
        public void setStudents(Set<Student> students) {
            this.students = students;
        }
        public String toString(){
            return "id:"+this.id+";name"+this.name+";code:"+this.code;
        }
    }

2.配置studentStatus.hbm.xml,基本属性配置方法不变，Students的配置如下。

<hibernate-mapping>
        <class name="com.ffy.studentmanage.StudentStatus" table="student_status">
            <id name="id" column="id">
                <generator class="assigned"></generator>
            </id>
            <property name="code" column="code"></property>
            <property name="name" column="name"></property>
            <property name="description" column="description"></property>
            //集合存放该状态对应的多个学生，name为属性名（即集合名称）,column表示相关联的外键，
            <set name="students" cascade="all" inverse="true">
                <key column="student_status_id"></key>  
                //表示一个状态对应多个学生，calss表示对应的多的那方的类（即与之相对应的类）
                <one-to-many class="com.ffy.studentmanage.Student"/>
            </set>
        </class>
    </hibernate-mapping>

二、annotation注解映射

# **多的那方** #

1.在hibernate.cfg.xml注册Student类

2.在Student类中添加注解

@Entity
    @Table(name="student")
    public class Student { 
        @Id
        @Column(name="id")
        private int id;
        @Column(name="sid")
        private int sid;
        @Column(name="firstname")
        private String firstName;
        @Column(name="lastname")
        private String lastName;
        @Column(name="gender")
        private String gender;
        @Column(name="phone")
        private String phone;
        @Column(name="email")
        private String email;
        @Column(name="date_of_birth")
        private String dateOfBirth;
        @Column(name="height")
        private double height=160;
    
        /* * 多的一方，加入对方的一个类的属性。一个学生对于一个状态。 * name="student_status_id"表明一的那方为外键student_status_id锁对应的表 */
        @ManyToOne
        @JoinColumn(name="student_status_id")
        private StudentStatus status;
    
        @OneToOne
        @PrimaryKeyJoinColumn
        private StudentLogin studentLogin;
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public int getSid() {
            return sid;
        }
        public void setSid(int sid) {
            this.sid = sid;
        }
        public String getFirstName() {
            return firstName;
        }
        public void setFirstName(String firstName) {
            this.firstName = firstName;
        }
        public String getLastname() {
            return lastName;
        }
        public void setLastname(String lastName) {
            this.lastName = lastName;
        }
        public String getGender() {
            return gender;
        }
        public void setGender(String gender) {
            this.gender = gender;
        }
        public String getPhone() {
            return phone;
        }
        public void setPhone(String phone) {
            this.phone = phone;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getDateOfBirth() {
            return dateOfBirth;
        }
        public void setDateOfBirth(String dateOfBirth) {
            this.dateOfBirth = dateOfBirth;
        }
        public double getHeight() {
            return height;
        }
        public void setHeight(double height) {
            this.height = height;
        }
        public String getLastName() {
            return lastName;
        }
        public void setLastName(String lastName) {
            this.lastName = lastName;
        }
    
        public StudentStatus getStatus() {
            return status;
        }
        public void setStatus(StudentStatus status) {
            this.status = status;
        }
        public StudentLogin getStudentLogin() {
            return studentLogin;
        }
        public void setStudentLogin(StudentLogin studentLogin) {
            this.studentLogin = studentLogin;
        }
        public String toString(){
            return this.id+":"+this.lastName+this.firstName+this.gender+":"+this.phone+":"+this.email+";username"+studentLogin.getUsername()+";password:"+studentLogin.getPassword();
        }
    }

# **一的那方**\# #

1.在hibernate.cfg.xml注册StudentStatus类

2.在StudentStatus类中添加注解

package com.ffy.studentmanage;
    
    import java.util.HashSet;
    import java.util.Set;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.OneToMany;
    import javax.persistence.Table;
    
    @Table(name="student_status")
    @Entity
    public class StudentStatus { 
        @Id()
        @Column(name="id")
        private int id;
        @Column(name="code")
        private String code;
        @Column(name="name")
        private String name;
        @Column(name="description")
        private String description;
    
        /* * 加入一个集合，泛型为Student，用于存放该状态对应的学生，因为一条状态对呀多个学生，所以需要用集合表示 * name="id"：student_status表的主键为Student表的外键，这样子就能找到Student(多的那方) * 的student_status_id为student_status表的id的字段，两者对应 */
        @OneToMany
        @JoinColumn(name="id")
        private Set<Student> students=new HashSet<>();
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getCode() {
            return code;
        }
        public void setCode(String code) {
            this.code = code;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getDescription() {
            return description;
        }
        public void setDescription(String description) {
            this.description = description;
        }
    
        public Set<Student> getStudents() {
            return students;
        }
        public void setStudents(Set<Student> students) {
            this.students = students;
        }
        public String toString(){
            return "id:"+this.id+";name"+this.name+";code:"+this.code;
        }
    }