hibernate映射的两种方式

我就是我 2022-07-14 14:51 238阅读 0赞

# hibernate之映射的两种方式 #

将实体类映射到数据库中的表的方式有两种，包括通过xml文件映射以及通过注解映射。个人认为通过注解映射更加直观，出错率低一些吧。下面是简单的步骤介绍以及代码演示。

一、xml方式进行映射

1.在hibernate.cfg.xml为映射进行配置（需要放在src目录下，否则需要重新设置映射的路径）

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd">
    <hibernate-configuration>
    <session-factory>
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="connection.url">jdbc:mysql://localhost:3306/students?useSSL=false&serverTimezone=UTC&</property>
    <property name="connection.username">root</property>
    <property name="connection.password">root</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
    
    <mapping resource="Accommodation.hbm.xml"/>
    </session-factory>
    </hibernate-configuration>

2.添加映射的文件Student.hbm.xml(在上一个文件的同级目录下)

<?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.hibernate.Student" table="student">
    <id name="id" column="id">
    <generator class="assigned"></generator> </id>
    <property name="sid" column="sid"></property>
    //这是将数据库的字段与java的属性对应
    <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>
    </class>
    </hibernate-mapping>

这样，就完成了利用xml的方式数据库的实体与java实体类进行映射了。  
二、注解方式进行映射  
1.在配置文件中指定要进行映射的类

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd">
    <hibernate-configuration>
    <session-factory>
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="connection.url">jdbc:mysql://localhost:3306/students?useSSL=false&serverTimezone=UTC&</property>
    <property name="connection.username">root</property>
    <property name="connection.password">root</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
    <mapping class="com.ffy.hibernate.Student"/> <mapping class="com.ffy.hibernate.StudentStatus"/>
    <mapping class="com.ffy.hibernate.Apartment"/>
    </session-factory>
    </hibernate-configuration>

2.在需要映射的类中加上注解

@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;
    @Column(name="student_status_id")
    private int studentStatusID;
    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 String toString(){
    return this.id+":"+this.lastName+this.firstName+this.gender+":"+this.phone+":"+this.email;
    }
    }