Hibernate的多对多的XML映射教程

1。创建数据库
在这个例子中，我们将MySQL数据库。我们使用的是一个多一对多的关系。例如员工会议之间的关系。每个员工都可以达到一个以上的会议，每个会议可以有一个以上的雇员
。许多到许多关系图

CREATE TABLE `employee` (
`employee_id` BIGINT(10) NOT NULL AUTO_INCREMENT,
`firstname` VARCHAR(50) NULL DEFAULT NULL,
`lastname` VARCHAR(50) NULL DEFAULT NULL,
PRIMARY KEY (`employee_id`)
)

CREATE TABLE `meeting` (
`meeting_id` BIGINT(20) NOT NULL AUTO_INCREMENT,
`subject` VARCHAR(50) NOT NULL,
`meeting_date` DATE NOT NULL,
PRIMARY KEY (`meeting_id`)
)

CREATE TABLE `employee_meeting` (
`employee_id` BIGINT(20) NOT NULL,
`meeting_id` BIGINT(20) NOT NULL,
PRIMARY KEY (`employee_id`, `meeting_id`),
INDEX `FK_MEETING` (`meeting_id`),
CONSTRAINT `FK_EMPLOYEE` FOREIGN KEY (`employee_id`) REFERENCES `employee` (`employee_id`),
CONSTRAINT `FK_MEETING` FOREIGN KEY (`meeting_id`) REFERENCES `meeting` (`meeting_id`)
)
2。Hibernate的Maven的依赖关系
我们正在使用Maven的依赖管理。复制后，在pom.xml。

文件：pom.xml的

<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>net.viralpatel.hibernate</groupId>
<artifactId>HibernateHelloWorldXML</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>HibernateHelloWorldXML</name>
<url>http://maven.apache.org</url>
<dependencies>
  <dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>5.1.10</version>
  </dependency>
  <dependency>
   <groupId>org.hibernate</groupId>
   <artifactId>hibernate</artifactId>
   <version>3.2.6.ga</version>
  </dependency>
</dependencies>
</project>
3。Hibernate的模型类
员工和部门创建模型类映射到相应的数据库表。

文件“：Employee.java”

package net.viralpatel.hibernate;

import java.util.HashSet;
import java.util.Set;

public class Employee {

private Long employeeId;
private String firstname;
private String lastname;

private Set<Meeting> meetings = new HashSet<Meeting>();

public Employee() {
}

public Employee(String firstname, String lastname) {
this.firstname = firstname;
this.lastname = lastname;
}

// Getter and Setter methods
}
文件“：Meeting.java”

package net.viralpatel.hibernate;

import java.util.Date;
import java.util.HashSet;
import java.util.Set;

public class Meeting {

private Long meetingId;
private String subject;
private Date meetingDate;

private Set<Employee> employees = new HashSet<Employee>();

public Meeting(String subject) {
this.subject = subject;
this.meetingDate = new Date();
}

// Getter and Setter methods
}
4。Hibernate工具类
要访问Hibernate的API，我们将创建一个包装器实用工具类，它为我们提供了SessionFactory的。

文件“：HibernateUtil.java”

package net.viralpatel.hibernate;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

private static final SessionFactory sessionFactory = buildSessionFactory();

private static SessionFactory buildSessionFactory() {
  try {
   // Create the SessionFactory from hibernate.cfg.xml
   return new Configuration().configure().buildSessionFactory();
  } catch (Throwable ex) {
   System.err.println("Initial SessionFactory creation failed." + ex);
   throw new ExceptionInInitializerError(ex);
  }
}

public static SessionFactory getSessionFactory() {
return sessionFactory;
}
}
5。Hibernate映射XML（HBM）
以下是为每个enitity员工和部门的Hibernate映射文件。

文件“：Employee.hbm.xml”

<?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 package="net.viralpatel.hibernate">

</class>
</hibernate-mapping>
文件“：Meeting.hbm.xml”

<?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 package="net.viralpatel.hibernate">

</class>
</hibernate-mapping>
有一件事是值得一提的是

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