hibernate关联映射

学生类代码

package cn.bdqn.entity;import java.util.HashSet;import java.util.Set;public class Student {private int sid;private String sname;private String sex;private Grade grade;private Paper paper;private Set<Course> course = new HashSet<Course>();public Set<Course> getCourse() {return course;}public void setCourse(Set<Course> course) {this.course = course;}public Paper getPaper() {return paper;}public void setPaper(Paper paper) {this.paper = paper;}public int getSid() {return sid;}public void setSid(int sid) {this.sid = sid;}public String getSname() {return sname;}public void setSname(String sname) {this.sname = sname;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public Grade getGrade() {return grade;}public void setGrade(Grade grade) {this.grade = grade;}public Student(int sid, String sname, String sex) {super();this.sid = sid;this.sname = sname;this.sex = sex;}public Student() {super();}}

班级类代码

package cn.bdqn.entity;import java.util.HashSet;import java.util.Set;public class Grade {private int gid;private String gname;private String gdesc;private Set<Student> students = new HashSet<Student>();public int getGid() {return gid;}public void setGid(int gid) {this.gid = gid;}public String getGname() {return gname;}public void setGname(String gname) {this.gname = gname;}public String getGdesc() {return gdesc;}public void setGdesc(String gdesc) {this.gdesc = gdesc;}public Set<Student> getStudents() {return students;}public void setStudents(Set<Student> students) {this.students = students;}}

下面的红色字体是关键代码

1.单向一对多关联关系

映射文件关键代码

Grade.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 package="cn.bdqn.entity">    <class name="Grade" table="grade">       <id name="gid" column="gid" type="java.lang.Integer">           <generator class="assigned"/>       </id>       <property name="gname" type="java.lang.String" column="gname"/>       <property name="gdesc" type="java.lang.String" column="gdesc"/>      <span style="color:#ff0000;"> <set name="students"  cascade="save-update" inverse="true">            <key column="gid"/>            <one-to-many class="Student"/>        </set></span>    </class></hibernate-mapping>

2.单向多对一关联关系

映射文件关键代码

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 package="cn.bdqn.entity"><class name="Student" table="pb_student"><id name="sid" column="sid" type="java.lang.Integer"><generator class="assigned" /></id><property name="sname" type="java.lang.String" column="sname" /><property name="sex" type="java.lang.String" column="sex" /><span style="color:#ff0000;"><many-to-one name="grade" class="Grade" cascade="save-update"><column name="gid"></column></many-to-one></span></class></hibernate-mapping>

3.一对一关联关系

映射文件关键代码

Student.hbm.xml中添加如下代码

<span style="font-size:12px;"><span style="color:#ff0000;"><one-to-one name="paper" class="Paper" cascade="all" lazy="false" </span><span style="color: rgb(255, 0, 0); font-family: Arial, Helvetica, sans-serif;">property-ref="student"></one-to-one></span></span>

学生证类

package cn.bdqn.entity;public class Paper {private int pid;private String pdesc;private Student student;public Paper() {super();}public Paper(int pid, String pdesc) {super();this.pid = pid;this.pdesc = pdesc;}public Student getStudent() {return student;}public void setStudent(Student student) {this.student = student;}public int getPid() {return pid;}public void setPid(int pid) {this.pid = pid;}public String getPdesc() {return pdesc;}public void setPdesc(String pdesc) {this.pdesc = pdesc;}}

映射文件Paper.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 package="cn.bdqn.entity">    <class name="Paper" table="paper">        <id name="pid" column="pid" type="java.lang.Integer">            <generator class="assigned"/>        </id>        <property name="pdesc" type="java.lang.String" column="pdesc"/>        <span style="color:#ff0000;"><many-to-one name="student" class="Student"  unique="true" lazy="false">        <column name="sid"></column>        </many-to-one> </span>       </class></hibernate-mapping>

4.多对多关联关系

映射文件关键代码

Student.hbm.xml中添加如下代码

<span style="color:#ff0000;"><set name="course" table="sc" cascade="save-update"> <key column="sid"></key> <many-to-many class="Course" column="cid"></many-to-many> </set></span>

课程表类

package cn.bdqn.entity;import java.util.HashSet;import java.util.Set;public class Course {private int cid;private String cname;private String cdesc;private Set<Student> student = new HashSet<Student>();public int getCid() {return cid;}public void setCid(int cid) {this.cid = cid;}public String getCname() {return cname;}public void setCname(String cname) {this.cname = cname;}public String getCdesc() {return cdesc;}public void setCdesc(String cdesc) {this.cdesc = cdesc;}public Set<Student> getStudent() {return student;}public void setStudent(Set<Student> student) {this.student = student;}}

映射文件Course.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 package="cn.bdqn.entity">    <class name="Course" table="course">        <id name="cid" column="CID" type="java.lang.Integer">            <generator class="assigned"/>        </id>        <property name="cname" type="java.lang.String" column="CNAME"/>        <property name="cdesc" type="java.lang.String" column="CDESC"/>        <!-- 和学生为多对多映射 -->       <span style="color:#ff0000;"> <set name="student" table="sc" cascade="save-update" inverse="true">        <key column="cid"></key>        <many-to-many class="Student" column="sid"></many-to-many>        </set></span>    </class></hibernate-mapping>