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hibernate之7.one2many双向

2024-07-29 15:40:31   225人阅读

表结构



实体类关系


实体类源码

Student

package com.demo.model;

import java.io.UnsupportedEncodingException;
import java.util.Set;

/**学生信息
 * @author wobendiankun
 *2014-10-19 下午08:54:29
 */
public class Student {
	private int studentId ;
	private String studentName ;
	private int age;
	private Set<Certificate> certificates ;
	public int getStudentId() {
		return studentId;
	}
	public void setStudentId(int studentId) {
		this.studentId = studentId;
	}
	public String getStudentName() {
		return studentName;
	}
	public void setStudentName(String studentName) {
		this.studentName = studentName;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		String str="";
		if(studentName!=null){
			try {
				str=new String(studentName.getBytes("UTF-8"));
			} catch (UnsupportedEncodingException e) {
				e.printStackTrace();
			}
		}
		return "Student [studentId=" + studentId + ", studentName="
				+ str + ", age=" + age + "]";
	}
	public Set<Certificate> getCertificates() {
		return certificates;
	}
	public void setCertificates(Set<Certificate> certificates) {
		this.certificates = certificates;
	}
	
}

Certificate

package com.demo.model;

/**从业资格证书
 * @author wobendiankun
 *2014-10-25 上午11:43:21
 */
public class Certificate {
	/**
	 * 证书id
	 */
	private int certificateId ;
	/**
	 * 证书名称
	 */
	private String certificateName;
	/**
	 *证书编号
	 */
	private String certificateNo ;
	
	private Student student ;
	public int getCertificateId() {
		return certificateId;
	}
	public void setCertificateId(int certificateId) {
		this.certificateId = certificateId;
	}
	public String getCertificateName() {
		return certificateName;
	}
	public void setCertificateName(String certificateName) {
		this.certificateName = certificateName;
	}
	public String getCertificateNo() {
		return certificateNo;
	}
	public void setCertificateNo(String certificateNo) {
		this.certificateNo = certificateNo;
	}
	public Student getStudent() {
		return student;
	}
	public void setStudent(Student student) {
		this.student = student;
	}
	
}


xml配置:

Student.hbm.xml

<?xml version="1.0"?>
<!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.demo.model.Student" table="t_student">
		<id name="studentId" column="student_id">
			<generator class="sequence">
				<param name="sequence">SEQ_T_STUDENT</param>
			</generator>
		</id>
		<property name="studentName" column="student_name" />
		<property name="age" />
		
		<set name="certificates" lazy="extra"><!-- lazy="extra" -->
			<key column="student_id"></key>
			<one-to-many class="com.demo.model.Certificate"/>
		</set>
	</class>
</hibernate-mapping>

Certificate.hbm.xml

<?xml version="1.0"?>
<!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.demo.model.Certificate" table="t_certificate">
        <id name="certificateId" column="certificate_id">
            <generator class="sequence"><param name="sequence">SEQ_T_CERTIFICATE</param></generator>
        </id>
        <property name="certificateName" column="certificate_name"/>
        <property name="certificateNo" column="certificate_no"/>
        <many-to-one name="student" column="student_id"></many-to-one>
    </class>
</hibernate-mapping>


CRUD:

add:

@Test
	public void addTest(){
		Set<Certificate> certificates=new HashSet<Certificate>();
		Student student = new Student();
		student.setStudentName("王五");
		student.setAge(35);
		
		Certificate certificate1 = new Certificate();
		certificate1.setCertificateName("aa");
		certificate1.setCertificateNo("3a10001");
		certificate1.setStudent(student);
		Certificate certificate2 = new Certificate();
		certificate2.setCertificateName("bb");
		certificate2.setCertificateNo("3a10002");
		certificate2.setStudent(student);
		
		Session session = null;
		
		try {
			session = HibernateUtil.openSession();
			session.beginTransaction();
			// 先保存one,再保存many
			session.save(student);
			session.save(certificate1);
			session.save(certificate2);
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			HibernateUtil.closeSession(session);
		}
	}


发出的SQL:

Hibernate: insert into t_student (student_name, age, student_id) values (?, ?, ?)
Hibernate: insert into t_certificate (certificate_name, certificate_no, student_id, certificate_id) values (?, ?, ?, ?)
Hibernate: insert into t_certificate (certificate_name, certificate_no, student_id, certificate_id) values (?, ?, ?, ?)


update:

@Test
	public void updateStudentTest(){
		Student student=new Student();
		student.setStudentId(63);
		student.setStudentName("李九");
		Session session = null;
		try {
			session = HibernateUtil.openSession();
			session.beginTransaction();
			session.update(student);
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			HibernateUtil.closeSession(session);
		}
	}


发出的SQL:

Hibernate: update t_student set student_name=?, age=? where student_id=?
Hibernate: update t_certificate set student_id=null where student_id=?


由于Student为one的一方,默认发维护关联字段，会多发送一条更新语句,解决方式为加入配置 inverse="true" (Student.hbm.xml的set元素中，添加属性),

 inverse="true" 代表由:many的一方来维护关联字段

Student.hbm.xml:

<?xml version="1.0"?>
<!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.demo.model.Student" table="t_student">
		<id name="studentId" column="student_id">
			<generator class="sequence">
				<param name="sequence">SEQ_T_STUDENT</param>
			</generator>
		</id>
		<property name="studentName" column="student_name" />
		<property name="age" />
		
		<set name="certificates" lazy="extra" inverse="true">
			<key column="student_id"></key>
			<one-to-many class="com.demo.model.Certificate"/>
		</set>
	</class>
</hibernate-mapping>


updateInverse

@Test
	public void updateStudentWithInverseTest(){
		Student student=new Student();
		student.setStudentId(63);
		student.setStudentName("李九");
		Session session = null;
		try {
			session = HibernateUtil.openSession();
			session.beginTransaction();
			session.update(student);
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			HibernateUtil.closeSession(session);
		}
	}


发出的SQL:

Hibernate: update t_student set student_name=?, age=? where student_id=?

维护关联字段的update语句不出现了



loadCertificate:

@Test
	public void loadCertificateTest(){
		Session session = null;
		try {
			session = HibernateUtil.openSession();
			session.beginTransaction();
			Certificate certificate=(Certificate)session.load(Certificate.class, 65);
			Certificate certificate2=(Certificate)session.load(Certificate.class, 66);
			System.out.println("编号:"+certificate.getCertificateNo());
			System.out.println("姓名:"+certificate.getStudent().getStudentName());
			System.out.println("---------------------------");
			System.out.println("编号:"+certificate2.getCertificateNo());
			System.out.println("姓名:"+certificate2.getStudent().getStudentName());
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			HibernateUtil.closeSession(session);
		}
	}


发出的SQL:

Hibernate: select certificat0_.certificate_id as certific1_1_0_, certificat0_.certificate_name as certific2_1_0_, certificat0_.certificate_no as certific3_1_0_, certificat0_.student_id as student4_1_0_ from t_certificate certificat0_ where certificat0_.certificate_id=?
编号:3a10001
Hibernate: select student0_.student_id as student1_0_0_, student0_.student_name as student2_0_0_, student0_.age as age0_0_ from t_student student0_ where student0_.student_id=?
姓名:李九
---------------------------
Hibernate: select certificat0_.certificate_id as certific1_1_0_, certificat0_.certificate_name as certific2_1_0_, certificat0_.certificate_no as certific3_1_0_, certificat0_.student_id as student4_1_0_ from t_certificate certificat0_ where certificat0_.certificate_id=?
编号:3a10002
姓名:李九

共三条查询语句,查询id为66的记录时，由于id为63的Student对象已经变化在session中，所以不会再发出查询id为63的语句


loadStudent:

@Test
	public void loadStudentTest(){
		Session session = null;
		try {
			session = HibernateUtil.openSession();
			session.beginTransaction();
			Student student=(Student)session.load(Student.class, 63);
			System.out.println("姓名:"+student.getStudentName());
			for(Certificate c:student.getCertificates()){
				System.out.println("\t编号:"+c.getCertificateNo());
			}
			System.out.println("-------------------");
			Certificate c1=(Certificate)session.get(Certificate.class, 65);
			System.out.println("编号:"+c1.getCertificateNo());
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			HibernateUtil.closeSession(session);
		}
	}


发出的SQL

Hibernate: select student0_.student_id as student1_0_0_, student0_.student_name as student2_0_0_, student0_.age as age0_0_ from t_student student0_ where student0_.student_id=?
姓名:李九
Hibernate: select certificat0_.student_id as student4_0_1_, certificat0_.certificate_id as certific1_1_, certificat0_.certificate_id as certific1_1_0_, certificat0_.certificate_name as certific2_1_0_, certificat0_.certificate_no as certific3_1_0_, certificat0_.student_id as student4_1_0_ from t_certificate certificat0_ where certificat0_.student_id=?
	编号:3a10001
	编号:3a10002
-------------------
编号:3a10001

id为65的Certificate对象，已经存在session中，所以session.get(Certificate.class, 65);不会发送查询语句



hibernate之7.one2many双向


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