Hibernate_hibernate.cfg.xml加载流程源码分析

在使用hibernate的时候，需要创建一个configuration对象来加载xml文件

Configuration configuration = new Configuration();configuration.configure();

我们来跟一下configure方法

public Configuration configure() throws HibernateException {configure( "/hibernate.cfg.xml" );return this;}

public Configuration configure(String resource) throws HibernateException {LOG.configuringFromResource( resource );InputStream stream = getConfigurationInputStream( resource );return doConfigure( stream, resource );}

有两个方法，一个没有参数，一个有参数，可以发现，其实没有参数的configure方法也是调用了有参数的configure方法，参数为"hibernate.cfg.xml"，所以，如果你调用了没有参数的configure方法，那么就要把xml文件放到src下面，否则就要把xml文件的目录作为参数传进去

不管LOG，这里有两个方法被执行了

1.InputStream stream = getConfigurationInputStream(resource); 

protected InputStream getConfigurationInputStream(String resource) throws HibernateException {LOG.configurationResource( resource );return ConfigHelper.getResourceAsStream( resource );}

继续看ConfigHelper.getResourceAsStream(resource);

public static InputStream getResourceAsStream(String resource) {String stripped = resource.startsWith("/") ?resource.substring(1) : resource;InputStream stream = null;ClassLoader classLoader = ClassLoaderHelper.getContextClassLoader();if (classLoader!=null) {stream = classLoader.getResourceAsStream( stripped );}if ( stream == null ) {stream = Environment.class.getResourceAsStream( resource );}if ( stream == null ) {stream = Environment.class.getClassLoader().getResourceAsStream( stripped );}if ( stream == null ) {throw new HibernateException( resource + " not found" );}return stream;}

到了这里，就获取了xml的stream
2.doConfigure( stream, resource );

protected Configuration doConfigure(InputStream stream, String resourceName) throws HibernateException {try {ErrorLogger errorLogger = new ErrorLogger( resourceName );Document document = xmlHelper.createSAXReader( errorLogger,  entityResolver ).read( new InputSource( stream ) );if ( errorLogger.hasErrors() ) {throw new MappingException( "invalid configuration", errorLogger.getErrors().get( 0 ) );}doConfigure( document );}catch (DocumentException e) {throw new HibernateException( "Could not parse configuration: " + resourceName, e );}finally {try {stream.close();}catch (IOException ioe) {LOG.unableToCloseInputStreamForResource( resourceName, ioe );}}return this;}

可以看到，使用SAX解析了xml文件，然后执行了doConfigure(document)；

看一下doConfigure方法

protected Configuration doConfigure(Document doc) throws HibernateException {Element sfNode = doc.getRootElement().element( "session-factory" );String name = sfNode.attributeValue( "name" );if ( name != null ) {properties.setProperty( Environment.SESSION_FACTORY_NAME, name );}addProperties( sfNode );parseSessionFactory( sfNode, name );Element secNode = doc.getRootElement().element( "security" );if ( secNode != null ) {parseSecurity( secNode );}LOG.configuredSessionFactory( name );LOG.debugf( "Properties: %s", properties );return this;}

到了这里，我们可以看到，sfNode获得了xml中<session-factory>节点的内容，然后执行了addProperties(sfnode)

private void addProperties(Element parent) {Iterator itr = parent.elementIterator( "property" );while ( itr.hasNext() ) {Element node = (Element) itr.next();String name = node.attributeValue( "name" );String value = node.getText().trim();LOG.debugf( "%s=%s", name, value );properties.setProperty( name, value );if ( !name.startsWith( "hibernate" ) ) {properties.setProperty( "hibernate." + name, value );}}Environment.verifyProperties( properties );}

通过迭代之后，把所有属性加载完毕。