Hibernate与H2

Hibernate与H2

Jar:

<dependency>

    <groupId>com.h2database</groupId>

    <artifactId>h2</artifactId>

    <version>1.2.144</version>

</dependency>

           

<dependency>

    <groupId>org.jsoup</groupId>

    <artifactId>jsoup</artifactId>

    <version>1.7.2</version>

</dependency>

   <dependency>

    <groupId>org.hibernate</groupId>

    <artifactId>hibernate-core</artifactId>

    <version>3.3.2.GA</version>

</dependency>

<dependency>

    <groupId>javassist</groupId>

    <artifactId>javassist</artifactId>

    <version>3.9.0.GA</version>

</dependency>

<dependency>

    <groupId>cglib</groupId>

    <artifactId>cglib</artifactId>

    <version>2.2</version>

</dependency>

           

<dependency>

    <groupId>asm</groupId>

    <artifactId>asm</artifactId>

    <version>1.5.3</version>

</dependency>

  <dependency>

    <groupId>junit</groupId>

    <artifactId>junit</artifactId>

    <version>4.7</version>

    </dependency>

    <dependency>

       <groupId>org.slf4j</groupId>

       <artifactId>slf4j-log4j12</artifactId>

       <version>1.5.8</version>

    </dependency>                           

Hibernate配置文件：

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

        "-//Hibernate/HibernateConfiguration DTD 3.0//EN"

        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

 

<hibernate-configuration>

 

    <session-factory>

 

        <!--Database connection settings -->

        <propertyname="connection.driver_class">org.h2.Driver</property>

        <propertyname="connection.url">jdbc:h2:E://Java\\JavaEE\\wordDatabase\\words</property>

        <propertyname="connection.username">sa</property>

        <propertyname="connection.password"></property>

 

        <!-- JDBCconnection pool (use the built-in) -->

        <propertyname="connection.pool_size">1</property>

 

        <!-- SQLdialect -->

<propertyname="dialect">org.hibernate.dialect.H2Dialect</property>

 

        <!-- EnableHibernate's automatic session context management -->

        <propertyname="current_session_context_class">thread</property>

 

        <!--Disable the second-level cache  -->

        <propertyname="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

 

        <!-- Echoall executed SQL to stdout -->

        <propertyname="show_sql">true</property>

 

        <!-- Dropand re-create the database schema on startup -->

        <propertyname="hbm2ddl.auto">update</property>

 

        <mappingresource="com/gathershell/domain/QueryWord.hbm.xml"/>

        <mappingresource="com/gathershell/domain/Word.hbm.xml"/>

 

    </session-factory>

 

</hibernate-configuration> 

对于这个：

<property name="hbm2ddl.auto">none</property>比较奇怪，我之前一直用update可以应对一切情况。但这次不行，只要是update就会报错。org.h2.jdbc.JdbcSQLException: Table"SYSTEM_SEQUENCES" not found; SQL statement:

要先用create去创建数据库和表，然后写成none才行。

发现原因了：

上面的配置是从hibernate的文档中复制改了改的，可惜改的不彻底。

<propertyname="dialect">org.hibernate.dialect.HSQLDialect</property>

这句不对，应该用成H2的。

<property name="dialect">org.hibernate.dialect.H2Dialect</property>

Mapping文件：

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

      "-//Hibernate/HibernateMapping DTD 3.0//EN"

          "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

 

<hibernate-mappingpackage="com.gathershell.domain">

   

    <class name="Word" table="Word">

    <id name="id">

        <generatorclass="native"/>

    </id>

        <propertyname="name"not-null="true"/>

        <propertyname="meaning"not-null="true"></property>    </class>

 

</hibernate-mapping>

Util类创建sessionFactory:

public classHibernateUtil {

     private static finalSessionFactory sessionFactory = buildSessionFactory();

 

        private staticSessionFactory buildSessionFactory() {

           try {

               // Create the SessionFactory from hibernate.cfg.xml

               return newConfiguration().configure().buildSessionFactory();

           }

           catch (Throwable ex) {

               // Make sure you log the exception, as it might be swallowed

               System.err.println("InitialSessionFactory creation failed." + ex);

               throw newExceptionInInitializerError(ex);

           }

        }

 

        public staticSessionFactory getSessionFactory() {

           return sessionFactory;

        }

 

}

Dao的编写：

public booleansave(Word word) {

       booleanresult=false;

       Session session=HibernateUtil.getSessionFactory().getCurrentSession();

       Transactiontx=session.beginTransaction();

       try {

           String name=word.getName();

           if(StringUtil.isBlank(name,word.getName())){

              throw newRuntimeException("word name must not null!");

           }

           Query query=session.createQuery("fromWord where name=?");

           query.setString(0, name);

           Word databaseWord=(Word)query.uniqueResult();

           //if this wordhas not existed in database

           if(databaseWord==null){

              session.save(word);

              result=true;

           }else{

              logger.debug(name+"hasbe in the database.");

           }

           tx.commit();

       } catch(HibernateException e) {

           tx.rollback();

           e.printStackTrace();

       }finally{

           if(session!=null&&session.isOpen()){

              session.close();

           }

       }

       returnresult;

    }

注意：由于hbm2ddl.auto配置为none,以后数据库要有任何改变，都要按以上步骤，create->none,做一遍。

例如我将一个属性由int改为String直接运行就出现了以下错误:

org.hibernate.exception.GenericJDBCException:could not insert: [com.gathershell.domain.QueryWord]

    atorg.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:126)

    atorg.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:114)

    atorg.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)

 

Caused by: org.h2.jdbc.JdbcSQLException: Dataconversion error converting "'free' (NAME INTEGER NOT NULL)"; SQLstatement:

这种none的配置用作开发后患无穷，因为时常你会忘了去这样做。

6)  某一个属性不能插入数据库

我最后查看数据库发现有一个类的某个属性没有插入数据库中，表中少了这列。后来发现原来在mapping文件中把<property>写成<properties>了，唉，它也没报啥异常，整的我一直没发现。

7) h2数据表不显示外键列

今天在浏览器中查看h2的数据表时，发现外键那一列没有显示，还以为是hibernate配置有问题呢，不过查询时也能查出外键来，看来只是没有显示，数据是在的。

后来发现确实有问题，我要显示一个表格写明商品和它所属的类别，但只有一行显示出来了。后来发现是hibernate配置错了。应是<many-to-onename="bigType"lazy="false"></many-to-one>，却写成了<one-to-one>，唉，它也没报异常。