在hibernate.cfg.xml中配置的数据源只能在web环境下使用,我们可以通过下面的例子来比较.
　　
　　如果我们在hibernatesessionfactory中加上测试,代码如下:
　　package sc.pro.forum.util;
　　
　　import net.sf.hibernate.hibernateexception;
　　import net.sf.hibernate.session;
　　import net.sf.hibernate.cfg.configuration;
　　
　　/**
　　* configures and provides access to hibernate sessions, tied to the
　　* current thread of execution.　follows the thread local session
　　* pattern, see {@link http://hibernate.org/42.html}.
　　*/
　　public class hibernatesessionfactory {
　　
　　/**
　　* location of hibernate.cfg.xml file.
　　* notice: location should be on the classpath as hibernate uses
　　* #resourceasstream style lookup for its configuration file. that
　　* is place the config file in a java package - the default location
　　* is the default java package.<br><br>
　　* examples: <br>
　　* <code>config_file_location = "/hibernate.conf.xml".
　　* config_file_location = "/com/foo/bar/myhiberstuff.conf.xml".</code>
　　*/
　　private static string config_file_location = "/hibernate.cfg.xml";
　　
　　/** holds a single instance of session */
　　private static final threadlocal threadlocal = new threadlocal();
　　
　　/** the single instance of hibernate configuration */
　　private static final configuration cfg = new configuration();
　　
　　/** the single instance of hibernate sessionfactory */
　　private static net.sf.hibernate.sessionfactory sessionfactory;
　　
　　/**
　　* returns the threadlocal session instance.　lazy initialize
　　* the <code>sessionfactory</code> if needed.
　　*
　　*　@return session
　　*　@throws hibernateexception
　　*/
　　public static session currentsession() throws hibernateexception {
　　session session = (session) threadlocal.get();
　　
　　if (session == null) {
　　if (sessionfactory == null) {
　　try {
　　cfg.configure(config_file_location);
　　sessionfactory = cfg.buildsessionfactory();
　　}
　　catch (exception e) {
　　system.err.println("%%%% error creating sessionfactory %%%%");
　　e.printstacktrace();
　　}
　　}
　　session = sessionfactory.opensession();
　　threadlocal.set(session);
　　}
　　
　　return session;
　　}
　　
　　/**
　　*　close the single hibernate session instance.
　　*
　　*　@throws hibernateexception
　　*/
　　public static void closesession() throws hibernateexception {
　　session session = (session) threadlocal.get();
　　threadlocal.set(null);
　　
　　if (session != null) {
　　session.close();
　　}
　　}
　　
　　public static void main(string[] args){
　　system.out.println("sdfsdfsd");
　　try{
　　session　session=hibernatesessionfactory.currentsession();
　　if(session==null)
　　system.out.println("session is null");
　　else
　　system.out.println("session　is　not　null");
　　}catch(exception e){
　　e.printstacktrace();
　　}
　　}
　　
　　/**
　　* default constructor.
　　*/
　　private hibernatesessionfactory() {
　　}
　　
　　}
　　执行时,程序会给我们如下的错误:
　　environment - hibernate 2.1.7
　　environment - hibernate.properties not found
　　environment - using cglib reflection optimizer
　　environment - using jdk 1.4 java.sql.timestamp handling
　　sdfsdfsd
　　configuration - configuring from resource: /hibernate.cfg.xml
　　configuration - configuration resource: /hibernate.cfg.xml
　　dtdentityresolver - trying to locate http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd in classpath under net/sf/hibernate/
　　dtdentityresolver - found http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd in classpath
　　configuration - connection.datasource=java:comp/env/jdbc/forum
　　configuration - show_sql=true
　　configuration - dialect=net.sf.hibernate.dialect.sqlserverdialect
　　configuration - null<-org.dom4j.tree.defaultattribute@18088c0 [attribute: name resource value "sc/pro/forum/dao/userinfo.hbm.xml"]
　　configuration - mapping resource: sc/pro/forum/dao/userinfo.hbm.xml
　　dtdentityresolver - trying to locate http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd in classpath under net/sf/hibernate/
　　dtdentityresolver - found http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd in classpath
　　binder - mapping class: sc.pro.forum.dao.userinfo -> userinfo
　　binder - mapped property: userid -> userid, type: integer
　　binder - mapped property: password -> password, type: string
　　binder - mapped property: nickname -> nickname, type: string
　　configuration - configured sessionfactory: null
　　configuration - properties: {java.runtime.name=java(tm) 2 runtime environment, standard edition, sun.boot.library.path=c:/program files/java/j2re1.4.2_03/bin, java.vm.version=1.4.2_03-b02, connection.datasource=java:comp/env/jdbc/forum, java.vm.vendor=sun microsystems inc., java.vendor.url=http://java.sun.com/, path.separator=;, java.vm.name=java hotspot(tm) client vm, file.encoding.pkg=sun.io, user.country=cn, sun.os.patch.level=service pack 4, java.vm.specification.name=java virtual machine specification, user.dir=e:/86vr/forum, java.runtime.version=1.4.2_03-b02, java.awt.graphicsenv=sun.awt.win32graphicsenvironment, java.endorsed.dirs=c:/program files/java/j2re1.4.2_03/lib/endorsed, os.arch=x86, java.io.tmpdir=c:/docume~1/zhangyi/locals~1/temp/, line.separator=
　　, java.vm.specification.vendor=sun microsystems inc., user.variant=, os.name=windows 2000, sun.java2d.fontpath=, hibernate.connection.datasource=java:comp/env/jdbc/forum, java.library.path=c:/program files/java/j2re1.4.2_03/bin;.;c:/winnt/system32;c:/winnt;c:/winnt/system32;c:/winnt;c:/winnt/system32/wbem;d:/program files/cvsnt;d:/j2sdk1.4/bin;c:/program files/microsoft sql server/80/tools/binn;c:/program files/cvsnt/, java.specification.name=java platform api specification, java.class.version=48.0, java.util.prefs.preferencesfactory=java.util.prefs.windowspreferencesfactory, os.version=5.0, user.home=c:/documents and settings/zhangyi, user.timezone=, java.awt.printerjob=sun.awt.windows.wprinterjob, file.encoding=gbk, java.specification.version=1.4, show_sql=true, user.name=zhangyi, java.class.path=e:/86vr/forum/webroot/web-inf/classes;e:/86vr/forum/webroot/web-inf/lib/ant-1.5.3.jar;e:/86vr/forum/webroot/web-inf/lib/ant-optional-1.5.3.jar;e:/86vr/forum/webroot/web-inf/lib/c3p0-0.8.4.5.jar;e:/86vr/forum/webroot/web-inf/lib/cglib-full-2.0.2.jar;e:/86vr/forum/webroot/web-inf/lib/commons-collections-2.1.1.jar;e:/86vr/forum/webroot/web-inf/lib/commons-dbcp-1.2.1.jar;e:/86vr/forum/webroot/web-inf/lib/commons-lang-1.0.1.jar;e:/86vr/forum/webroot/web-inf/lib/commons-logging-1.0.4.jar;e:/86vr/forum/webroot/web-inf/lib/commons-pool-1.2.jar;e:/86vr/forum/webroot/web-inf/lib/concurrent-1.3.3.jar;e:/86vr/forum/webroot/web-inf/lib/connector.jar;e:/86vr/forum/webroot/web-inf/lib/dom4j-1.4.jar;e:/86vr/forum/webroot/web-inf/lib/ehcache-0.9.jar;e:/86vr/forum/webroot/web-inf/lib/hibernate2.jar;e:/86vr/forum/webroot/web-inf/lib/jaas.jar;e:/86vr/forum/webroot/web-inf/lib/jboss-cache.jar;e:/86vr/forum/webroot/web-inf/lib/jboss-common.jar;e:/86vr/forum/webroot/web-inf/lib/jboss-jmx.jar;e:/86vr/forum/webroot/web-inf/lib/jboss-system.jar;e:/86vr/forum/webroot/web-inf/lib/jcs-1.0-dev.jar;e:/86vr/forum/webroot/web-inf/lib/jdbc2_0-stdext.jar;e:/86vr/forum/webroot/web-inf/lib/jgroups-2.2.7.jar;e:/86vr/forum/webroot/web-inf/lib/jta.jar;e:/86vr/forum/webroot/web-inf/lib/junit-3.8.1.jar;e:/86vr/forum/webroot/web-inf/lib/log4j-1.2.8.jar;e:/86vr/forum/webroot/web-inf/lib/msbase.jar;e:/86vr/forum/webroot/web-inf/lib/mssqlserver.jar;e:/86vr/forum/webroot/web-inf/lib/msuti