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
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。
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
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
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
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
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
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