hibernate注解方式实现一对多映射。
首先是在hibernate.cfg.xml中引入要映射的class
<?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=”hibernate.connection.driver_class”>com.mysql.jdbc.Driver</property>
<property name=”hibernate.connection.url”>jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=GBK</property>
<property name=”hibernate.connection.username”>root</property>
<property name=”hibernate.connection.password”>sa</property>
<property name=”hibernate.dialect”>org.hibernate.dialect.MySQLDialect</property>
<property name=”show_sql”>true</property>
<property name=”hibernate.hbm2ddl.auto”>update</property>
<mapping/>
<mapping/>
</session-factory>
</hibernate-configuration>
我们分别看看reader.java和book.java文件
Reader.java
package com.sszd.hibernate;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name=”reader”)
public class Reader {
@Id
@Column(name=”ID”)
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;
@Column(name=”MENO”)
private String meno;
@Column(name=”NAME”)
private String name;
@OneToMany(mappedBy = “reader”, cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Set<Book> books = new HashSet<Book>();
public Reader()
{
}
public Set getBooks() {
return books;
}
public void setBooks(Set books) {
this.books = books;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getMeno() {
return meno;
}
public void setMeno(String meno) {
this.meno = meno;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
book.java
package com.sszd.hibernate;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name=”book”)
public class Book {
@Id
@Column(name=”ID”)
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;
@Column(name=”TITLE”)
private String title;
@ManyToOne(cascade = CascadeType.ALL, optional = false)
@JoinColumn(name=”rea_id”, referencedColumnName=”id”)//外键为sut_id，与student中的id关联
private Reader reader;
public int getId() {
return id;
}
public Reader getReader() {
return reader;
}
public void setReader(Reader reader) {
this.reader = reader;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
接下来是我们的本地测试用例
package com.sszd.main;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration;
import com.sszd.hibernate.Book;
import com.sszd.hibernate.Reader;
public class ReaderToBooks {
private static SessionFactory sessionFactory;
public static void main(String[] args) {
sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
Session session = sessionFactory.openSession();
Reader r = new Reader();
r.setName(“Reader zhang”);
Book b1 = new Book();
b1.setTitle(“title1″);
Book b2 = new Book();
b2.setTitle(“title2″);
b1.setReader(r);
b2.setReader(r);
r.getBooks().add(b1);
r.getBooks().add(b2);
Transaction trx = session.beginTransaction();
session.save(r);
trx.commit();
session.close();
}
}