第四節 基於XML映射文件的Hibernate關聯映射

基於XML映射文件的Hibernate關聯映射

一對一關聯映射

一對一映射本質上是一對多映射的一個特例，因此具體操作過程參考一對多映射。

一對多關聯映射

Employee.java

package cn.edu.scnu.xmlcurd.entity;

public class Employee {
    private Integer id;
    private String name;
    private Integer age;
    private String gender;

    private Department dept;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Department getDept() {
        return dept;
    }

    public void setDept(Department dept) {
        this.dept = dept;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", gender='" + gender+
                '}';
    }

    //注意toString方法不能包含dept
}

Employee.hbm.xml

<?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="cn.edu.scnu.xmlcurd.entity">
    <class name="Employee" table="employee" catalog="hibernate">
        <id name="id" type="java.lang.Integer">
            <column name="id"/>
            <generator class="native"/>
        </id>
        <property name="name" type="java.lang.String">
            <column name="name" length="16" not-null="true"/>
        </property>
        <property name="age" type="java.lang.Integer">
            <column name="age"/>
        </property>
        <property name="gender" type="java.lang.String">
            <column name="gender"/>
        </property>

        <!--多對一-->
        <!--
            lazy懶加載，在執行employee.getDept時，纔會執行sql語句。
            立即加載，指在獲取employee的時候，就會把dept給獲取到。
            cascade="all" fetch="join"  設置級聯操作


　　　　　　　all: 所有情況下均進行關聯操作，即save-update和delete。
　　　　　　　none: 所有情況下均不進行關聯操作。這是默認值。
　　　　　　　save-update: 在執行save/update/saveOrUpdate時進行關聯操作。
　　　　　　　delete: 在執行delete 時進行關聯操作。
　　　　　　　all-delete-orphan: 當一個節點在對象圖中成爲孤兒節點時，刪除該節點

            inverse:指定維護外鍵的一方
        -->
        <many-to-one name="dept" column="deptId" class="Department" cascade="all" fetch="join"/>
    </class>

</hibernate-mapping>

Department.java

package cn.edu.scnu.xmlcurd.entity;

import java.util.HashSet;
import java.util.Set;

public class Department {
    private Integer id;
    private String deptName;

    private Set employeeSet = new HashSet<Employee>();

    public Set getEmployeeSet() {
        return employeeSet;
    }

    public void setEmployeeSet(Set employeeSet) {
        this.employeeSet = employeeSet;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDeptName() {
        return deptName;
    }

    public void setDeptName(String deptName) {
        this.deptName = deptName;
    }

    @Override
    public String toString() {
        return "Department{" +
                "id=" + id +
                ", deptName='" + deptName + '\'' +
                ", employeeSet=" + employeeSet +
                '}';
    }
}

Department.hbm.xml

<?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="cn.edu.scnu.xmlcurd.entity">
    <class name="Department" table="dept" catalog="hibernate">
        <id name="id" column="id" type="java.lang.Integer">
            <generator class="native"/>
        </id>
        <property name="deptName" type="java.lang.String">
            <column name="deptName" length="16" not-null="true"/>
        </property>

        <!--一對多-->
        <!--
            key:指定1端的id

            inverse的值是boolean值，也就是能設置爲true或false。

         如果一方的映射文件中設置爲true，說明在映射關係(一對多，多對多等)中讓對方來維護關係。
         如果爲false，就自己來維護關係。默認值是true。 並且這屬性只能在一端設置。
         比如一對多，這個一端。也就是在有set集合的這方設置。
        -->
        <set name="employeeSet" inverse="true">
            <key column="deptId"></key>
            <one-to-many class="Employee"/>
        </set>

    </class>
</hibernate-mapping>

ManyToOneTest.java

public class ManyToOneTest {
    private SessionFactory sessionFactory;
    private Session session;
    private Transaction tx;

    @Before
    public void init(){
        sessionFactory = new Configuration().configure().buildSessionFactory();
        session = sessionFactory.openSession();
        tx = session.beginTransaction();
    }

    @After
    public void destroy(){
        tx.commit();
        session.close();
        sessionFactory.close();
    }
    /*
    增加操作：建議從多的一端操作：
     */
    @Test
    public void add(){
        Employee employee = new Employee();
        employee.setName("小李");
        employee.setAge(12);
        employee.setGender("男");

        Employee employee1 = new Employee();
        employee1.setName("小王");
        employee1.setAge(23);
        employee1.setGender("女");

        Employee employee2 = new Employee();
        employee2.setName("小芳");
        employee2.setAge(34);
        employee2.setGender("女");

        Department department = new Department();
        department.setDeptName("銷售部");
        Department department1 = new Department();
        department1.setDeptName("法務部");

        employee.setDept(department);
        employee1.setDept(department1);
        employee2.setDept(department);

//        先增加1的一方，再保存多的一方
        // 如果設置了級聯操作，那麼只需要保存employee即可

//        session.save(department);
//        session.save(department1);

        session.save(employee);
        session.save(employee1);
        session.save(employee2);
    }


    @Test
    public void delete(){


        //先刪除

        //刪除employee

        Employee employee = (Employee)session.get(Employee.class,14);
        System.out.println(employee.toString());
        session.delete(employee);

        //刪除department

//        Department department=(Department)session.get(Department.class,6);
//        session.delete(department);

    }
    @Test
    public void update(){

        Employee employee = session.get(Employee.class,13);
        System.out.println(employee.toString());
        employee.getDept().setDeptName("研發部");
        session.save(employee);

    }
    @Test
    public void findOne(){
        Employee employee = session.get(Employee.class,13);
        System.out.println(employee.getDept().getDeptName());
    }

    @Test
    public void findAll(){
        String hql = "from Employee";
        List<Employee> employees = session.createQuery(hql).list();

        for(Employee employee :employees){
            System.out.println(employee.toString());
        }
    }
}

關於級聯操作

inverse屬性

1. inverse=false，不反轉，當前方有控制權，可以清除關係，可以刪除，刪除的時候會清空外鍵然後刪除。
2. inverse=true，反轉，對方有控制權
   

cascade級聯

all：級聯保存，更新，刪除

save-update：級聯保存，更新

delete：級聯刪除

none：默認值，不級聯操作

關於懶加載

一般默認即可，默認的情況是啓動懶加載。即在employee.getDept()的時候纔會通過sql加載Department

注意

一般在Set一方設置inverse
一般在Set一方的key設置自身作爲對方的外鍵

<one-to-many>和<many-to-many>在set裏面，設置自己的外鍵

多對多關聯映射

Student.java

package cn.edu.scnu.xmlcurd.entity;

import java.util.HashSet;
import java.util.Set;

public class Student {
    private Integer id;
    private String name;
    private Integer age;

    private Set courseSet = new HashSet<Course>();

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Set getCourseSet() {
        return courseSet;
    }

    public void setCourseSet(Set courseSet) {
        this.courseSet = courseSet;
    }
}

Student.hbm.xml

<?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="cn.edu.scnu.xmlcurd.entity">
<!--
    private Integer id;
    private String name;
    private Integer age;

    private Set courseSet = new HashSet();
-->
    <class name="Student" table="student" catalog="hibernate">
        <id name="id" type="java.lang.Integer">
            <column name="id"/>
            <generator class="native"/>
        </id>
        <property name="name" type="java.lang.String">
            <column name="stuname"/>
        </property>
        <property name="age" type="java.lang.Integer">
            <column name="age"/>
        </property>

        <set name="courseSet" table="stu_course">
            <key column="stuId"></key>
            <many-to-many column="cid" class="Course"/>
        </set>
    </class>
</hibernate-mapping>

Course.java

package cn.edu.scnu.xmlcurd.entity;

import java.util.HashSet;
import java.util.Set;

public class Course {
    private Integer id;
    private String c_name;

    private Set stuSet = new HashSet<Student>();

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getC_name() {
        return c_name;
    }

    public void setC_name(String c_name) {
        this.c_name = c_name;
    }

    public Set getStuSet() {
        return stuSet;
    }

    public void setStuSet(Set stuSet) {
        this.stuSet = stuSet;
    }

    @Override
    public String toString() {
        return "Course{" +
                "id=" + id +
                ", c_name='" + c_name + '\'' +
                '}';
    }
}

Course.hbm.xml

<?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="cn.edu.scnu.xmlcurd.entity">
<!--
    private Integer id;
    private String c_name;

    private Set stuSet = new HashSet();
-->
    <class name="Course" table="course" catalog="hibernate">
        <id name="id" type="java.lang.Integer">
            <column name="id"/>
            <generator class="native"/>
        </id>
        <property name="c_name" type="java.lang.String">
            <column name="cname"/>
        </property>
        <set name="stuSet">
            <key column="cid"></key>
            <many-to-many column="stuId" class="Student"/>
        </set>
    </class>
</hibernate-mapping>

ManyToManyTest.java

package cn.edu.scnu.xmlcurd.dao.impl;

import cn.edu.scnu.xmlcurd.entity.Course;
import cn.edu.scnu.xmlcurd.entity.Student;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.Set;

public class ManyToManyTest {
    private SessionFactory sessionFactory;
    private Session session;
    private Transaction tx;

    @Before
    public void init(){
        sessionFactory = new Configuration().configure().buildSessionFactory();
        session = sessionFactory.openSession();
        tx = session.beginTransaction();
    }
    @After
    public void destroy(){
        tx.commit();
        session.close();
        sessionFactory.close();
    }

    @Test
    public void add(){
        Student stu1 = new Student();
        stu1.setName("小王");
        stu1.setAge(13);
        Student stu2 = new Student();
        stu2.setName("小李");
        stu2.setAge(23);

        Course course = new Course();
        course.setC_name("計算機");
        Course course1 = new Course();
        course1.setC_name("化學");

        stu1.getCourseSet().add(course);
        stu1.getCourseSet().add(course1);
        stu2.getCourseSet().add(course);

        course.getStuSet().add(stu1);
        course.getStuSet().add(stu2);
        course1.getStuSet().add(stu2);

        session.save(stu1);
        session.save(stu2);
        session.save(course);
        session.save(course1);
    }
    @Test
    public void delete(){
        Student s =  session.get(Student.class,1);
        System.out.println(s.toString());
        Set<Course> courses = s.getCourseSet();
        for(Course course:courses){
            System.out.println(course.toString());
        }
        session.delete(s);
    }
    @Test
    public void update(){
        Course course = session.get(Course.class,3);
        course.setC_name("物理學");
        session.update(course);
    }
}