Hibernate3源码分析之SettingsFactory类

Hibernate3源码分析之SettingsFactory类

Hibernate版本(hibernate-distribution-3.3.1.GA)

一、hibernate.cfg.xml文件的概述

      使用过Hibernate的朋友对hibernate.cfg.xml这个配置文件一点也不会陌生吧，hibernate.cfg.xml之于Hibernate就相当于web.config之于asp.net，二者是密不可分的。hibernate.cfg.xml包含了一系列的属性配置，当程序运行时 会读取该文件并对其进行解析,解析出来的部分内容将会赋值给Setting类的实例。

二、通过Configruation类构造SessionFactory类的实例

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package com.laoyangx;

 

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

 

public class MainConsole {

 

    public static void main(String[] args) {

         

        Configuration conf=new Configuration();

        conf.configure();

         

        SessionFactory factory=conf.buildSessionFactory(); 

    }

}

上面的代码演示的是如何通过Configuration类构造SessionFactory类的实例，虽然只有三行代码，但实际上执行的代码远远不止三行。Configuration类位于org.hibernate.cfg包中，当使用无参构造函数实例化Configuration类的同时也会初时化一个SettingsFactory类的实例。

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protected Configuration(SettingsFactory settingsFactory) {

    this.settingsFactory = settingsFactory;

    reset();

}

 

public Configuration() {

       this(new SettingsFactory() );

}

对Configruation类进行实例化后，接下来就调用该实例的configure()方法,该方法将会读取hibernate.cfg.xml文件

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public Configuration configure() throws HibernateException {

    configure("/hibernate.cfg.xml" );

    return this;

}

这个函数还会执行许多的其它函数，其最终将会调用HbmBinder类(位于org.hibernate.cfg包中)中相关函数，对  *.hbm.xml 映射文件进行解析，这不是本文的重点，就此跳过。我们把目光转向conf.buildSessionFactory(); 这个函数的源码如下：

public SessionFactory buildSessionFactory() throws HibernateException {

          

                //...省略

 

        Settings settings = buildSettings( copy );

 

               //...省略

    }

 

public Settings buildSettings(Properties props) throws HibernateException {

        return settingsFactory.buildSettings( props );

}

可以看出最终将会使用前面已经提到使用无参构造函数实例化Configuration类时也会对SettingsFactory进行实例化的实例来调用SettingsFactory中的buildSettings方法。props参数可以看作是hibernate.cfg.xml配置文件中的property元素在内存中的载体。

三、通过SettingsFactory构造Settings实例

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public Settings buildSettings(Properties props) {

   Settings settings = new Settings();

   //...省略

}

可以看到在SettingsFactory类的buildSettings方法中，对Settings类实例化了一个 settings实例。代码中的省略部分就是对其进行赋值。

四、对Settings类的实例进行赋值

   1. JDBC and connection settings:

 SettingsFactory.java

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public Settings buildSettings(Properties props) {

       Settings settings = new Settings();

                 

                   //...省略    

                 

           //JDBC and connection settings:

           ConnectionProvider connections = createConnectionProvider(props);

       settings.setConnectionProvider(connections);

                

              //...省略    

                 

}

 

protected ConnectionProvider createConnectionProvider(Properties properties) {

        return ConnectionProviderFactory.newConnectionProvider(properties);

}

上面这段代码可以看出是使用了工厂模式创建ConnectionProvider(位于org.hibernate.connection包中)的实例，其涉及到hibernate.cfg.xml文件中的 hibernate.connection.provider_class 的配置。涉及到ConnectionProviderFactory中newConnectionProvider详细的执行过程，不是本文的重点，跳过。

   2. SQL Dialect:

 SettingsFactory.java

public Settings buildSettings(Properties props) {

    Settings settings = new Settings();

         

       //...省略

 

      //SQL Dialect:

    Dialect dialect = determineDialect( props, databaseName, databaseMajorVersion );

    settings.setDialect(dialect);

             

       //...省略

}  

 

private Dialect determineDialect(Properties props, String databaseName, int databaseMajorVersion) {

        return DialectFactory.buildDialect( props, databaseName, databaseMajorVersion );

}

上面代码是初始化所使用的数据库方言。其涉及到hibernate.cfg.xml文件中 hibernate.dialect 的配置。也使用了工厂模式

创建Dialect实例。继承Dialect的类太多，就不用UML表示了。在线API文档的 url:http://www.renren.it/my/api/Hibernate3.3.1GA/org/hibernate/dialect/Dialect.html 

    3. Transaction Settings

 SettingsFactory.java

public Settings buildSettings(Properties props) {

    Settings settings = new Settings();

         

       //...省略

 

      // Transaction settings:

         

    TransactionFactory transactionFactory = createTransactionFactory(properties);

      settings.setTransactionFactory(transactionFactory);

      settings.setTransactionManagerLookup( createTransactionManagerLookup(properties) );

             

       //...省略

}  

 

protected TransactionFactory createTransactionFactory(Properties properties) {

        return TransactionFactoryFactory.buildTransactionFactory(properties);

    }

     

protected TransactionManagerLookup createTransactionManagerLookup(Properties properties) {

    return  TransactionManagerLookupFactory.getTransactionManagerLookup(properties);       

}

上面的代码分别创建一个TransactionFactory和TransactionManagerLookup的实例。涉及到hibernate.cfg.xml文件中的两个配置项 hibernate.transaction.factory_class 和 hibernate.transaction.manager_lookup_class

创建TransactionManagerLookup的实例也是使用工厂模式，但是涉及到类太多，就不用UML图表示，给出在线API文档的url:http://www.renren.it/my/api/Hibernate3.3.1GA/org/hibernate/transaction/TransactionManagerLookup.html

    4. BatcherFactory

SettingsFactory.java

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public Settings buildSettings(Properties props) {

    Settings settings = new Settings();

         

       //...省略

 

     settings.setBatcherFactory( createBatcherFactory(properties, batchSize) );

             

       //...省略

}  

 

protected BatcherFactory createBatcherFactory(Properties properties, int batchSize) {

        String batcherClass = properties.getProperty(Environment.BATCH_STRATEGY);

        if (batcherClass==null) {

            return batchSize==0 ?

                    (BatcherFactory)new NonBatchingBatcherFactory() :

                    (BatcherFactory)new BatchingBatcherFactory();

        }

        else {

            log.info("Batcher factory: " + batcherClass);

            try {

            return (BatcherFactory) ReflectHelper.classForName(batcherClass).newInstance();

            }

            catch (Exception cnfe) {

                       throw new HibernateException("could not instantiate BatcherFactory: " + batcherClass, cnfe);

            }

        }

    }

上面的代码是创建BatcherFactory的实例，涉及到hibernate.cfg.xml文件中的 hibernate.jdbc.factory_class 配置

   5. Query parser settings

SettingsFactory.java

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public Settings buildSettings(Properties props) {

    Settings settings = new Settings();

         

       //...省略

 

     //Query parser settings:

      settings.setQueryTranslatorFactory( createQueryTranslatorFactory(properties) );

             

       //...省略

}  

 

protected QueryTranslatorFactory createQueryTranslatorFactory(Properties properties) {

    String className = PropertiesHelper.getString(

    Environment.QUERY_TRANSLATOR, properties, "org.hibernate.hql.ast.ASTQueryTranslatorFactory");

     

    log.info("Query translator: " + className);

 

     try {

        return (QueryTranslatorFactory) ReflectHelper.classForName(className).newInstance();

     }catch (Exception cnfe) {

          throw new HibernateException("could not instantiate QueryTranslatorFactory: " + className, cnfe);

       }

}

上面的代码是创建QueryTranslatorFactory 的实例 默认值是 org.hibernate.hql.ast.ASTQueryTranslatorFactory，涉及到hibernate.cfg.xml文件中的 hibernate.query.factory_class 配置

    6. RegionFactory

SettingsFactory.java

public Settings buildSettings(Properties props) {

    Settings settings = new Settings();

         

           //...省略

 

          // The cache provider is needed when we either have second-level cache enabled

         // or query cache enabled.  Note that useSecondLevelCache is enabled by default

         settings.setRegionFactory( createRegionFactory( properties, ( useSecondLevelCache || useQueryCache ) ) );

             

       //...省略

}  

 

protected RegionFactory createRegionFactory(Properties properties, boolean cachingEnabled) {

     

      String regionFactoryClassName = PropertiesHelper.getString( Environment.CACHE_REGION_FACTORY, properties,null );

            if ( regionFactoryClassName == null && cachingEnabled ) {

            String providerClassName = PropertiesHelper.getString( Environment.CACHE_PROVIDER, properties,null );

            if ( providerClassName != null ) {

                // legacy behavior, apply the bridge...

                regionFactoryClassName = RegionFactoryCacheProviderBridge.class.getName();

            }

        }

        if ( regionFactoryClassName == null ) {

            regionFactoryClassName = DEF_CACHE_REG_FACTORY;

        }

        log.info("Cache region factory : " + regionFactoryClassName );

        try {

            return ( RegionFactory ) ReflectHelper.classForName( regionFactoryClassName )

                    .getConstructor(new Class[] { Properties.class } )

                    .newInstance(new Object[] { properties } );

        }

        catch ( Exception e ) {

            throw new HibernateException("could not instantiate RegionFactory [" + regionFactoryClassName + "]", e );

        }

    }

上面的代码是创建 RegionFactory 的实例 其默认值是 NoCachingRegionFactory 涉及到hibernate.cfg.xml文件中的 hibernate.cache.region.factory_class  配置和hibernate.cache.provider_class

   7. QueryCacheFactory

public Settings buildSettings(Properties props) {

    Settings settings = new Settings();

         

           //...省略

 

       settings.setQueryCacheFactory( createQueryCacheFactory(properties) );

             

       //...省略

}  

 

protected QueryCacheFactory createQueryCacheFactory(Properties properties) {

        String queryCacheFactoryClassName = PropertiesHelper.getString(

        Environment.QUERY_CACHE_FACTORY, properties, "org.hibernate.cache.StandardQueryCacheFactory");

        log.info("Query cache factory: " + queryCacheFactoryClassName);

        try {

            return (QueryCacheFactory) ReflectHelper.classForName(queryCacheFactoryClassName).newInstance();

        }

        catch (Exception cnfe) {

        throw new HibernateException("could not instantiate QueryCacheFactory: " + queryCacheFactoryClassName, cnfe);

        }

}

上面的代码是创建 QueryCacheFactory的实例 其默认值是 org.hibernate.cache.StandardQueryCacheFactory 涉及到hibernate.cfg.xml文件中的 hibernate.cache.query_cache_factory 配置

简单分析了下SettingsFactory类，该类作用就是将hibernate.cfg.xml文件中的部分内容赋值给其实例化的Settings类 。通过阅读该类的源码，对设计模式的中工厂模式有了非常清楚的认识。加深了对hibernate.cfg.xml配置文件中有关配置项的理解