hibernate之7.one2many双向

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;}@Overridepublic 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:

@Testpublic 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manysession.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:

@Testpublic 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

@Testpublic 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:

@Testpublic 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:3a10001Hibernate: 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:

@Testpublic 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