Hibernate高级实体关联映射之多值的实体关联(map实现三重关联,单向导航)

Hibernate高级实体关联映射之多值的实体关联(map实现三重关联,单向导航)

这只是一个单向导航的例子。
如果联结表上没有额外的列，这个策略就很合适。这个策略的好处在于不需要任何中间类，不需要实体或者值类型。
这里的联结表是A_CLASS.

pom.xml:

]<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>
<groupId>hibernateTest</groupId>
<artifactId>hibernateTest</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hibernateTest</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>3.3.1.GA</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.5.2</version>
</dependency>
<dependency>
<groupId>javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.4.GA</version>
</dependency>
<dependency>
<groupId>c3p0</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.1</version>
</dependency>
<dependency>
<groupId>com.oracle</groupId>
<artifactId>ojdbc14</artifactId>
<version>10.2.0.3.0</version>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<finalName>hibernateTest</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
</resource>
<resource>
<directory>src/main/java</directory>
<excludes>
<exclude>**/*.java</exclude>
</excludes>
</resource>
</resources>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>

resources/hibernate.cfg.xml:

]<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration
PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory name="sessionFactory">
<!-- 指定连接数据库所用的驱动 -->
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<!-- 指定连接数据库的url，hibernate连接的数据库名 -->
<property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:XE</property>
<property name="hibernate.connection.useUnicode">true</property>
<property name="hibernate.connection.characterEncoding">gbk</property>
<!-- 指定连接数据库的用户名 -->
<property name="hibernate.connection.username">system</property>
<!-- 指定连接数据库的密码 -->
<property name="hibernate.connection.password">password</property>
<!-- 指定连接池里最大连接数 -->
<property name="hibernate.c3p0.max_size">20</property>
<!-- 指定连接池里最小连接数 -->
<property name="hibernate.c3p0.min_size">5</property>
<!-- 指定连接池里连接的超时时长,以秒为单位 -->
<property name="hibernate.c3p0.timeout">120</property>
<!-- 指定连接池里最大缓存多少个Statement对象 -->
<property name="hibernate.c3p0.max_statements">100</property>
<!-- 每隔XX秒检查连接池里的空闲连接 ，单位是秒 -->
<property name="hibernate.c3p0.idle_test_period">120</property>
<!-- 当连接池里面的连接用完的时候，C3P0一次获取的新的连接数 -->
<property name="hibernate.c3p0.acquire_increment">2</property>
<!-- 指定数据库方言 -->
<property name="dialect">org.hibernate.dialect.OracleDialect</property>
<!-- 显示Hibernate持久化操作所生成的SQL -->
<property name="show_sql">true</property>
<!-- 将SQL脚本进行格式化后再输出 -->
<property name="hibernate.format_sql">true</property>
<!-- 罗列所有的映射文件 -->
<mapping resource="pojo/Student.hbm.xml" />
<mapping resource="pojo/Teacher.hbm.xml" />
<mapping resource="pojo/Group.hbm.xml" />
</session-factory>
</hibernate-configuration>

pojo/Teacher.java:

]package pojo;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
public class Teacher implements Serializable{
private String teacher_id;
private String teacher_name;
private int teacher_age;
//注意这里
private Map<Student,Group> myClassMap = new HashMap<Student,Group>();

public String getTeacher_id() {
return teacher_id;
}
@SuppressWarnings("unused")
private void setTeacher_id(String teacher_id) {
this.teacher_id = teacher_id;
}
public String getTeacher_name() {
return teacher_name;
}
public void setTeacher_name(String teacher_name) {
this.teacher_name = teacher_name;
}
public int getTeacher_age() {
return teacher_age;
}
public void setTeacher_age(int teacher_age) {
this.teacher_age = teacher_age;
}
public Map<Student, Group> getMyClassMap() {
return myClassMap;
}
public void setMyClassMap(Map<Student, Group> myClassMap) {
this.myClassMap = myClassMap;
}
}

pojo/Teacher.hbm.xml:

]<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="pojo">
<class name="Teacher" table="A_TEACHER" dynamic-insert="true" dynamic-update="true">
<id name="teacher_id" column="TEACHER_ID" type="string">
<generator class="uuid.hex" />
</id>
<property name="teacher_name" column="TEACHER_NAME" type="string"/>
<property name="teacher_age" column="TEACHER_AGE" type="integer"/>
<!-- 注意这里不能加inverse="true" -->
<map name="myClassMap" table="A_CLASS">
<key column="TEACHER_ID" not-null="true"/>
<!-- 这里是map的键 -->
<map-key-many-to-many column="STUDENT_ID" class="Student"/>
<many-to-many column="GROUP_ID" class="Group"/>
</map>
</class>
</hibernate-mapping>

pojo/Student.java:

]package pojo;
import java.io.Serializable;
public class Student implements Serializable{
private String student_id;
private String student_name;
private int student_age;

public String getStudent_id() {
return student_id;
}
@SuppressWarnings("unused")
private void setStudent_id(String student_id) {
this.student_id = student_id;
}
public String getStudent_name() {
return student_name;
}
public void setStudent_name(String student_name) {
this.student_name = student_name;
}
public int getStudent_age() {
return student_age;
}
public void setStudent_age(int student_age) {
this.student_age = student_age;
}
}

pojo/Student.hbm.xml:

]<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="pojo">
<class name="Student" table="A_STUDENT" dynamic-insert="true" dynamic-update="true">
<id name="student_id" column="STUDENT_ID" type="string">
<generator class="uuid.hex" />
</id>
<property name="student_name" column="STUDENT_NAME" type="string"/>
<property name="student_age" column="STUDENT_AGE" type="integer"/>
</class>
</hibernate-mapping>

pojo/Group.java:

]package pojo;
import java.io.Serializable;
public class Group implements Serializable{
private String group_id;
private String group_name;
private int group_num;

public String getGroup_id() {
return group_id;
}
@SuppressWarnings("unused")
private void setGroup_id(String group_id) {
this.group_id = group_id;
}
public String getGroup_name() {
return group_name;
}
public void setGroup_name(String group_name) {
this.group_name = group_name;
}
public int getGroup_num() {
return group_num;
}
public void setGroup_num(int group_num) {
this.group_num = group_num;
}
}

pojo/Group.hbm.xml:

]<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="pojo">
<class name="Group" table="A_GROUP" dynamic-insert="true" dynamic-update="true">
<id name="group_id" column="GROUP_ID" type="string">
<generator class="uuid.hex" />
</id>
<property name="group_name" column="GROUP_NAME" type="string"/>
<property name="group_num" column="GROUP_NUM" type="integer"/>
</class>
</hibernate-mapping>

util/HibernateUtil.java:

]package util;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static SessionFactory sessionFactory;
static{
try {
sessionFactory = new Configuration().configure().buildSessionFactory();
} catch (Throwable e) {
throw new ExceptionInInitializerError(e);
}
}
public static SessionFactory getSessionFactory(){
return sessionFactory;
}
public static void shutdown(){
getSessionFactory().close();
}
}

util/Manager.java:

]package util;
import org.hibernate.Session;
import org.hibernate.Transaction;
import pojo.Group;
import pojo.Student;
import pojo.Teacher;

public class Manager {
public static void main(String[] args) {

Teacher t = new Teacher();
t.setTeacher_name("fhd");
t.setTeacher_age(35);

Student s = new Student();
s.setStudent_name("fuhaidong");
s.setStudent_age(30);

Group g = new Group();
g.setGroup_name("group111");
g.setGroup_num(80);

Session session = HibernateUtil.getSessionFactory().openSession();
Transaction transaction = session.beginTransaction();

session.save(t);
session.save(s);
session.save(g);

//添加
t.getMyClassMap().put(s, g);
session.flush();

//删除
t.getMyClassMap().remove(s);

transaction.commit();
session.close();
}
}

表结构：

]A_TEACHER表：
TEACHER_ID,
TEACHER_NAME,
TEACHER_AGE
A_STUDENT表：
STUDENT_ID,
STUDENT_NAME,
STUDENT_AGE
A_GROUP表：
GROUP_ID,
GROUP_NAME,
GROUP_NUM
A_CLASS表：
TEACHER_ID,
STUDENT_ID,
GROUP_ID

注意：为了在所有三个实体之间创建一个链接，如果你的所有实例都已经处于持久化状态，就添加一个新的项到该映射中：如：t.getMyClassMap().put(s, g);
要移除链接，就从该映射中移除：
t.getMyClassMap().remove(s);