Hibernate(七)一对一映射
一、创建数据库表
--班级表 create table grade ( gid number primary key, --班级ID gname varchar2(50), --班级名称 gdesc varchar2(50) --班级介绍 ); --学生表 create table student ( sid number primary key, --主键ID学生ID sname varchar2(20), --学生姓名 sex varchar2(20), --学生性别 gid number references grade(gid) ---外键班级ID ); --学生证表 create table paper ( pid number primary key, pdesc varchar2(100) , sid number references student(sid) not null );
二、创建配置文件和持久化类
学生类
package entity; /* * 学生类 */ public class Student implements java.io.Serializable { // Fields private static final long serialVersionUID = 1L; private int sid; private String sname; private String sex; //增加班级属性 private Grade grade; //学生证类 private Paper paper; // Constructors /** default constructor */ public Student() { } /** minimal constructor */ public Student(int sid) { this.sid = sid; } /** full constructor */ public Student(int sid, String sname, String sex ) { this.sid = sid; this.sname = sname; this.sex = sex; } // Property accessors public int getSid() { return this.sid; } public void setSid(int sid) { this.sid = sid; } public String getSname() { return this.sname; } public void setSname(String sname) { this.sname = sname; } public String getSex() { return this.sex; } public void setSex(String sex) { this.sex = sex; } public Grade getGrade() { return grade; } public void setGrade(Grade grade) { this.grade = grade; } public Paper getPaper() { return paper; } public void setPaper(Paper paper) { this.paper = paper; } }
学生证类
package entity; /* * 学生证类 */ public class Paper implements java.io.Serializable { // Fields private static final long serialVersionUID = 1L; private int pid; private Student student; private String pdesc; // Constructors /** default constructor */ public Paper() { } /** minimal constructor */ public Paper(int pid) { this.pid = pid; } /** full constructor */ public Paper(int pid, Student student, String pdesc) { this.pid = pid; this.student = student; this.pdesc = pdesc; } // Property accessors public int getPid() { return this.pid; } public void setPid(int pid) { this.pid = pid; } public Student getStudent() { return this.student; } public void setStudent(Student student) { this.student = student; } public String getPdesc() { return this.pdesc; } public void setPdesc(String pdesc) { this.pdesc = pdesc; } }
hibernate.cfg.xml配置文件
<?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="dialect"> org.hibernate.dialect.Oracle9Dialect </property> <property name="connection.url"> jdbc:oracle:thin:@localhost:1521:orcl </property> <property name="connection.username">root</property> <property name="connection.password">root</property> <property name="connection.driver_class"> oracle.jdbc.OracleDriver </property> <property name="show_sql">true</property> <property name="format_sql">true</property> <mapping resource="entity/Grade.hbm.xml" /> <mapping resource="entity/Student.hbm.xml" /> <mapping resource="entity/Paper.hbm.xml" /> </session-factory> </hibernate-configuration>
学生类配置文件
<?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="entity.Student" table="STUDENT" schema="ROOT"> <id name="sid" type="java.lang.Integer"> <column name="SID" precision="22" scale="0" /> <generator class="assigned" /> </id> <property name="sname" type="java.lang.String"> <column name="SNAME" length="20" /> </property> <property name="sex" type="java.lang.String"> <column name="SEX" length="20" /> </property> <!--配置grade属性 --> <many-to-one name="grade" class="entity.Grade" cascade="save-update"> <!--指定学生表中的外键 --> <column name="GID" /> </many-to-one> <!-- 添加学生证的配置 --> <one-to-one name="paper" class="entity.Paper" cascade="all" lazy="false"/> </class> </hibernate-mapping>
学生证类配置文件
<?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"> <!-- Mapping file autogenerated by MyEclipse Persistence Tools --> <hibernate-mapping> <class name="entity.Paper" table="PAPER" schema="ROOT"> <id name="pid" type="java.lang.Integer"> <column name="PID" precision="22" scale="0" /> <generator class="assigned" /> </id> <property name="pdesc" type="java.lang.String"> <column name="PDESC" length="100" /> </property> <!-- 学生信息 unique唯一的--> <many-to-one name="student" class="entity.Student" unique="true" lazy="false"> <column name="SID" precision="22" scale="0" /> </many-to-one> </class> </hibernate-mapping>
测试类
package Test; import org.hibernate.Session; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import entity.Paper; import entity.Student; public class Demo6 { public static void main(String[] args) { save(); find(); } public static void save() { Student stu1 = new Student(); stu1.setSid(20151109); stu1.setSname("钱七"); stu1.setSex("女"); Paper paper=new Paper(); paper.setPid(9001); paper.setPdesc("钱七的学生证"); paper.setStudent(stu1); stu1.setPaper(paper); // 建立session Session session = new Configuration().configure().buildSessionFactory() .openSession(); // 开始事务 Transaction transaction = session.beginTransaction(); // 保存学生证 session.save(stu1); // 提交事务 transaction.commit(); // 关闭session session.close(); } public static void find() { // 建立session Session session = new Configuration().configure().buildSessionFactory() .openSession(); Paper paper=(Paper) session.get(Paper.class, 9001); System.out.println(paper.getPid()+paper.getPdesc()); Student stu1=paper.getStudent(); System.out.println(stu1.getSid()+"\t"+stu1.getSname()); } }
发现可以 通过学生证，找到学生
但反过来，如果通过学生，找到学生证呢，显示是不能的，因为学生类中配置文件没有实现关联
修改学生类的配置文件 property-ref="student"用来指定Paper类中的属性
<?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="entity.Student" table="STUDENT" schema="ROOT"> <id name="sid" type="java.lang.Integer"> <column name="SID" precision="22" scale="0" /> <generator class="assigned" /> </id> <property name="sname" type="java.lang.String"> <column name="SNAME" length="20" /> </property> <property name="sex" type="java.lang.String"> <column name="SEX" length="20" /> </property> <!--配置grade属性 --> <many-to-one name="grade" class="entity.Grade" cascade="save-update"> <!--指定学生表中的外键 --> <column name="GID" /> </many-to-one> <!-- 添加学生证的配置 --> <one-to-one name="paper" class="entity.Paper" cascade="all" lazy="false" property-ref="student"/> </class> </hibernate-mapping>
测试类
package Test; import org.hibernate.Session; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import entity.Paper; import entity.Student; public class Demo6 { public static void main(String[] args) { findByStu(); } public static void save() { Student stu1 = new Student(); stu1.setSid(20151109); stu1.setSname("钱七"); stu1.setSex("女"); Paper paper=new Paper(); paper.setPid(9001); paper.setPdesc("钱七的学生证"); paper.setStudent(stu1); stu1.setPaper(paper); // 建立session Session session = new Configuration().configure().buildSessionFactory() .openSession(); // 开始事务 Transaction transaction = session.beginTransaction(); // 保存学生证 session.save(stu1); // 提交事务 transaction.commit(); // 关闭session session.close(); } public static void find() { // 建立session Session session = new Configuration().configure().buildSessionFactory() .openSession(); Paper paper=(Paper) session.get(Paper.class, 9001); System.out.println(paper.getPid()+paper.getPdesc()); Student stu1=paper.getStudent(); System.out.println(stu1.getSid()+"\t"+stu1.getSname()); } public static void findByStu() { // 建立session Session session = new Configuration().configure().buildSessionFactory() .openSession(); Student stu=(Student) session.get(Student.class, 20151109); System.out.println(stu.getSname()); Paper paper=stu.getPaper(); System.out.println(paper.getPid()+"\t"+paper.getPdesc()); } }
