hibernate之初學一對多和多對一配置及使用

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按查詢及存取速率來說的一對多用的相對多對一少一些，這裡唯寫主要設定檔的代碼

首先是hibernate的設定檔

<!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">        <hibernate-configuration>            <session-factory>                <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>                <property name="hibernate.connection.url">jdbc:mysql:///webproject</property>                <property name="hibernate.connection.username">root</property>                            <property name="hibernate.connection.password">123456</property>                            <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>                <property name="hibernate.show_sql">true</property>                <property name="hibernate.hbm2ddl.auto">create</property>                <mapping resource="com/shaoxin/entity/Dept.hbm.xml"/>                <mapping resource="com/shaoxin/entity/Employee.hbm.xml"/>            </session-factory>        </hibernate-configuration>

一對多的設定檔代碼，很明顯使用到了set集合

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">    <hibernate-mapping package="com.shaoxin.entity">        <class name="Dept" table="dept">            <id name="deptid" column="deptid">                <generator class="native"></generator>            </id>            <property name="deptName" column="deptname"></property><!--            一對多設定外鍵方式，class代表外鍵類型            --><set name="setEmployees" table="employee">                <key column="dept_id"></key>                <one-to-many class="Employee"/>            </set>        </class>    </hibernate-mapping>

對應的實體類：

package com.shaoxin.entity;import java.util.HashSet;import java.util.Set;public class Dept {    private int deptid;    private String deptName;    private Set<Employee> setEmployees = new HashSet<Employee>();    public int getDeptid() {        return deptid;    }    public void setDeptid(int deptid) {        this.deptid = deptid;    }    public String getDeptName() {        return deptName;    }    public void setDeptName(String deptName) {        this.deptName = deptName;    }    public Set<Employee> getSetEmployees() {        return setEmployees;    }    public void setSetEmployees(Set<Employee> setEmployees) {        this.setEmployees = setEmployees;    }}

多對一的設定檔代碼，很明顯是一個物件類型

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">    <hibernate-mapping package="com.shaoxin.entity">        <class name="Employee"  table="employee">            <id name="employeeid" column="employeeid">                <generator class="native"></generator>            </id>            <property name="employeeName" column="employeename"/><!--            多對一建立外鍵方式：屬性分別為：外鍵對應的表，外鍵欄位，外鍵類型            --><many-to-one name="dept" column="dept_id" class="Dept"></many-to-one>        </class>    </hibernate-mapping>

對應的實體類

package com.shaoxin.entity;public class Employee {    private int employeeid;    private String employeeName;    private Dept dept;    public int getEmployeeid() {        return employeeid;    }    public void setEmployeeid(int employeeid) {        this.employeeid = employeeid;    }    public String getEmployeeName() {        return employeeName;    }    public void setEmployeeName(String employeeName) {        this.employeeName = employeeName;    }    public Dept getDept() {        return dept;    }    public void setDept(Dept dept) {        this.dept = dept;    }}

測試這兩個儲存方式

package com.shaoxin.entity;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.hibernate.classic.Session;import org.junit.Test;public class TestMany2Many {    static SessionFactory sf;    static {        sf = new Configuration().configure().buildSessionFactory();    }    @Test    public void testOne2Many() throws Exception {        Session openSession = sf.openSession();        Transaction beginTransaction = openSession.beginTransaction();        Employee empzs = new Employee();        Employee empls = new Employee();        empls.setEmployeeName("李四");        empzs.setEmployeeName("張三");        Dept dept = new Dept();        dept.getSetEmployees().add(empls);        dept.getSetEmployees().add(empzs);        dept.setDeptName("應用開發");        openSession.save(empls);        openSession.save(empzs);        openSession.save(dept);        beginTransaction.commit();        openSession.close();    }    @Test    public void testMany2One() throws Exception {        Session openSession = sf.openSession();        Transaction beginTransaction = openSession.beginTransaction();        Employee empzs = new Employee();        Employee empls = new Employee();        Dept dept = new Dept();        dept.setDeptName("應用開發");        empls.setEmployeeName("李四");        empzs.setEmployeeName("張三");        empls.setDept(dept);        empzs.setDept(dept);        openSession.save(dept);        openSession.save(empls);        openSession.save(empzs);        beginTransaction.commit();        openSession.close();    }}

 

hibernate之初學一對多和多對一配置及使用