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Comments on Ag, DAO, and pluggable persistence?

Comments[5] by Dave in Java

Below is the email that I sent to the Hibernate and Castor mailing lists to ask for comments on Ag:

I've written a simple example application that shows how to create a simple web application (a newsfeed aggregator) with a pluggable persistence layer. I used the tried and true DAO pattern to hide the database access mechanism from the rest of the application. I implemented the DAO interface with both Hibernate and Castor.

I did this to learn:
  • What are the drawbacks of hiding powerful persistence engine behind a simple DAO interface. What do you loose? Will long transaction support work? What about lazy loading?
  • What are the differences between and strenghts/weaknesses of Castor and Hibernate?
  • What is the best way to implement DAO with each of the tools?

The code is very simple and (I hope) easy to follow, so if you have a chance please take a look. Look at the HibeAggregatorDAO and CastorAggregatorDAO implementations to see how I used Hiberate and Castor to implement the very same DAO. I'd love to get your opinions on the above topics.

Ag Download: http://sourceforge.net/project/shownotes.php?release_id=125110
Ag Readme: http://sourceforge.net/project/showfiles.php?group_id=47722



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Comments:

I was trying to download the ag.jar file from <a href="http://sourceforge.net/project/showfiles.php?group_id=47722">this</a> SF url but the file doesn't appear to be there. Any idea on how I can download this file? Thanks!!

Posted by Kurt Wiersma on December 02, 2002 at 12:29 AM EST #

I had no problem downloading from the URL and it looks like about 20 other people have had success as well. Could it be a temporary SF problem?

Posted by Dave Johnson on December 02, 2002 at 01:42 PM EST #

thanks for your cool hiberate example.:) It seems something wrong,working with jdk1.4.1. buid error msg: ------------------------------------------------- D:\devhome\Tomcat 4.1\webapps\ch10>build start-hsql D:\devhome\Tomcat 4.1\webapps\ch10>REM java -Djava.home=d:\devhome\j2sdk1.4.1 -D ant.home=d:\devhome\jakarta-ant-1.5 -classpath d:\devhome\j2sdk1.4.1\lib\tools.j ar;d:\devhome\jakarta-ant-1.5\lib\ant.jar;d:\devhome\jakarta-ant-1.5\lib\optiona l.jar;d:\devhome\jakarta-ant-1.5\lib\xercesImpl.jar;d:\devhome\jakarta-ant-1.5\l ib\xml-apis.jar org.apache.tools.ant.Main start-hsql D:\devhome\Tomcat 4.1\webapps\ch10>java -Dant.home=d:\devhome\jakarta-ant-1.5 -c lasspath d:\devhome\j2sdk1.4.1\lib\tools.jar;d:\devhome\jakarta-ant-1.5\lib\ant. jar;d:\devhome\jakarta-ant-1.5\lib\optional.jar;d:\devhome\jakarta-ant-1.5\lib\x ercesImpl.jar;d:\devhome\jakarta-ant-1.5\lib\xml-apis.jar org.apache.tools.ant.M ain start-hsql Buildfile: build.xml BUILD FAILED java.lang.UnsupportedClassVersionError: com/sun/javadoc/Doc (Unsupported major.m inor version 48.0) at java.lang.ClassLoader.defineClass0(Native Method) at java.lang.ClassLoader.defineClass(Unknown Source) at java.security.SecureClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.access$100(Unknown Source) at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at org.apache.tools.ant.AntClassLoader.findBaseClass(AntClassLoader.java :1102) at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:919 ) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at java.lang.Class.getConstructor0(Native Method) at java.lang.Class.getConstructor(Unknown Source) at org.apache.tools.ant.IntrospectionHelper.<init>(IntrospectionHelper.j ava:328) at org.apache.tools.ant.IntrospectionHelper.getHelper(IntrospectionHelpe r.java:384) at org.apache.tools.ant.helper.ProjectHelperImpl$NestedElementHandler.in it(ProjectHelperImpl.java:949) at org.apache.tools.ant.helper.ProjectHelperImpl$TaskHandler.startElemen t(ProjectHelperImpl.java:870) at org.apache.xerces.parsers.AbstractSAXParser.startElement(AbstractSAXP arser.java:415) at org.apache.xerces.impl.XMLNamespaceBinder.startElement(XMLNamespaceBi nder.java:571) at org.apache.xerces.impl.dtd.XMLDTDValidator.startElement(XMLDTDValidat or.java:756) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanStartElemen t(XMLDocumentFragmentScannerImpl.java:752) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContent Dispatcher.dispatch(XMLDocumentFragmentScannerImpl.java:1453) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(XM LDocumentFragmentScannerImpl.java:333) at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.jav a:524) at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.jav a:580) at org.apache.xerces.parsers.XMLParser.parse(XMLParser.java:152) at org.apache.xerces.parsers.AbstractSAXParser.parse(AbstractSAXParser.j ava:1169) at org.apache.tools.ant.helper.ProjectHelperImpl.parse(ProjectHelperImpl .java:155) at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.jav a:117) at org.apache.tools.ant.Main.runBuild(Main.java:597) at org.apache.tools.ant.Main.start(Main.java:196) at org.apache.tools.ant.Main.main(Main.java:235) Total time: 8 seconds ....

Posted by Aaron Tang on December 31, 2002 at 11:39 PM EST #

thanks for your cool hiberate example.:) It seems something wrong,working with jdk1.4.1. buid error msg: ------------------------------------------------- D:\devhome\Tomcat 4.1\webapps\ch10>build start-hsql D:\devhome\Tomcat 4.1\webapps\ch10>REM java -Djava.home=d:\devhome\j2sdk1.4.1 -D ant.home=d:\devhome\jakarta-ant-1.5 -classpath d:\devhome\j2sdk1.4.1\lib\tools.j ar;d:\devhome\jakarta-ant-1.5\lib\ant.jar;d:\devhome\jakarta-ant-1.5\lib\optiona l.jar;d:\devhome\jakarta-ant-1.5\lib\xercesImpl.jar;d:\devhome\jakarta-ant-1.5\l ib\xml-apis.jar org.apache.tools.ant.Main start-hsql D:\devhome\Tomcat 4.1\webapps\ch10>java -Dant.home=d:\devhome\jakarta-ant-1.5 -c lasspath d:\devhome\j2sdk1.4.1\lib\tools.jar;d:\devhome\jakarta-ant-1.5\lib\ant. jar;d:\devhome\jakarta-ant-1.5\lib\optional.jar;d:\devhome\jakarta-ant-1.5\lib\x ercesImpl.jar;d:\devhome\jakarta-ant-1.5\lib\xml-apis.jar org.apache.tools.ant.M ain start-hsql Buildfile: build.xml BUILD FAILED java.lang.UnsupportedClassVersionError: com/sun/javadoc/Doc (Unsupported major.m inor version 48.0) at java.lang.ClassLoader.defineClass0(Native Method) at java.lang.ClassLoader.defineClass(Unknown Source) at java.security.SecureClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.access$100(Unknown Source) at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at org.apache.tools.ant.AntClassLoader.findBaseClass(AntClassLoader.java :1102) at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:919 ) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at java.lang.Class.getConstructor0(Native Method) at java.lang.Class.getConstructor(Unknown Source) at org.apache.tools.ant.IntrospectionHelper.<init>(IntrospectionHelper.j ava:328) at org.apache.tools.ant.IntrospectionHelper.getHelper(IntrospectionHelpe r.java:384) at org.apache.tools.ant.helper.ProjectHelperImpl$NestedElementHandler.in it(ProjectHelperImpl.java:949) at org.apache.tools.ant.helper.ProjectHelperImpl$TaskHandler.startElemen t(ProjectHelperImpl.java:870) at org.apache.xerces.parsers.AbstractSAXParser.startElement(AbstractSAXP arser.java:415) at org.apache.xerces.impl.XMLNamespaceBinder.startElement(XMLNamespaceBi nder.java:571) at org.apache.xerces.impl.dtd.XMLDTDValidator.startElement(XMLDTDValidat or.java:756) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanStartElemen t(XMLDocumentFragmentScannerImpl.java:752) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContent Dispatcher.dispatch(XMLDocumentFragmentScannerImpl.java:1453) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(XM LDocumentFragmentScannerImpl.java:333) at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.jav a:524) at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.jav a:580) at org.apache.xerces.parsers.XMLParser.parse(XMLParser.java:152) at org.apache.xerces.parsers.AbstractSAXParser.parse(AbstractSAXParser.j ava:1169) at org.apache.tools.ant.helper.ProjectHelperImpl.parse(ProjectHelperImpl .java:155) at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.jav a:117) at org.apache.tools.ant.Main.runBuild(Main.java:597) at org.apache.tools.ant.Main.start(Main.java:196) at org.apache.tools.ant.Main.main(Main.java:235) Total time: 8 seconds ....

Posted by Aaron Tang on January 01, 2003 at 01:12 AM EST #

When i use jdk1.4.1 & ant-1.5, errors above come up against me. but Exception's getCause() method only "since 1.4" could anybody help me out of such trouble? thanks a lot. And I really appriciate that anyone should email me a solution.

Posted by Aaron Tang on January 01, 2003 at 02:01 AM EST #

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