Hibernate List集合映射简单例子
建两个相应的表:
email_list:
create table email_list( id int(11) not null, email_id int(11) not null, email varchar(100) not null default '' )engine=innodb default charset=gbk;
user_list:
create table user_list( id int(11) not null auto_increment, name varchar(100) not null default '', primary key(id) )engine=innodb default charset=gbk;建立UserList.java实体类:
package collect.list; import java.util.ArrayList; import java.util.List; public class UserList implements java.io.Serializable { // Fields private Integer id; private String name; private List emails = new ArrayList(); // Constructors /** default constructor */ public UserList() { } /** full constructor */ public UserList(String name) { this.name = name; } // Property accessors public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public List getEmails() { return emails; } public void setEmails(List emails) { this.emails = emails; } public void addEmail(String email) { emails.add(email); } public void removeEmail(String email) { emails.remove(email); } }建立映射文件UserList.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"> <!-- Mapping file autogenerated by MyEclipse Persistence Tools --> <hibernate-mapping> <class name="collect.list.UserList" table="user_list" catalog="ssh"> <id name="id" type="java.lang.Integer"> <column name="id" /> <generator class="native" /> </id> <property name="name" type="java.lang.String"> <column name="name" length="100" not-null="true" /> </property> <list name="emails" table="email_list"> <key column="id"></key> <index column="email_id"></index> <element type="java.lang.String" column="email"></element> </list> </class> </hibernate-mapping>
注解:其中List类型映射中<index>标签指定email_id字段记录List元素序号。
将该映射文件加入到Hibernate配置文件中,建立测试类Test.java:
package collect.list; import java.util.List; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; public class Test { public static void main(String[] args) { // Configuration管理Hibernate配置 Configuration config = new Configuration().configure(); // 根据Configuration建立 SessionFactory // SessionFactory用来建立Session SessionFactory sessionFactory = config.buildSessionFactory(); // 创建实例 UserList user1 = new UserList(); user1.setName("user1"); user1.addEmail("email1"); user1.addEmail("email2"); user1.addEmail("email1"); user1.addEmail("email3"); UserList user2 = new UserList(); user2.setName("user2"); user2.addEmail("email3"); user2.addEmail("email4"); // 添加数据 Session session = sessionFactory.openSession(); Transaction tx = null; try { tx = session.beginTransaction(); // INSERT到数据库 session.save(user1); session.save(user2); tx.commit(); } catch (RuntimeException e) { if (tx != null) tx.rollback(); throw e; } finally { session.close(); } // 关闭sessionFactory sessionFactory.close(); } }日志配置文件log4j.properties:(通过查看合适的日志,便于分析运行过程)
### direct log messages to stdout ### log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.Target=System.out log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n ### direct messages to file hibernate.log ### #log4j.appender.file=org.apache.log4j.FileAppender #log4j.appender.file.File=hibernate.log #log4j.appender.file.layout=org.apache.log4j.PatternLayout #log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n ### set log levels - for more verbose logging change 'info' to 'debug' ### #log4j.rootLogger=warn, stdout log4j.rootLogger=debug, stdout #log4j.logger.org.hibernate=info log4j.logger.org.hibernate=warn ### log HQL query parser activity #log4j.logger.org.hibernate.hql.ast.AST=debug ### log just the SQL log4j.logger.org.hibernate.SQL=debug ### log JDBC bind parameters ### #log4j.logger.org.hibernate.type=info log4j.logger.org.hibernate.type=warn ### log schema export/update ### log4j.logger.org.hibernate.tool.hbm2ddl=warn ### log HQL parse trees log4j.logger.org.hibernate.hql=debug ### log cache activity ### log4j.logger.org.hibernate.cache=debug ### log transaction activity log4j.logger.org.hibernate.transaction=warn ### log JDBC resource acquisition log4j.logger.org.hibernate.jdbc=warn ### enable the following line if you want to track down connection ### ### leakages when using DriverManagerConnectionProvider ### #log4j.logger.org.hibernate.connection.DriverManagerConnectionProvider=trace
运行结果:
控制台:
22:21:25,196 DEBUG SQL:346 - insert into ssh.user_list (name) values (?)
22:21:25,213 DEBUG SQL:346 - insert into ssh.user_list (name) values (?)
22:21:25,220 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,221 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,221 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,223 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,223 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
22:21:25,224 DEBUG SQL:346 - insert into email_list (id, email_id, email) values (?, ?, ?)
数据库:
对比Set集合映射中没有email_id字段,就是因为Set集合中的元素是无序不重复的,而List集合中元素是有序可重复的。对于Set集合而言,email中重复的记录会被覆盖,这样一来email_id字段就没有意义了。而对于List集合,email联合字段email_id才可唯一确定一个有序email,emial_id相当于是List类型映射中<index>标签的index(索引,从下标0开始)了。