Which is better ? Toplink Java objects or Toplink Entities ?

Hi
We are planing to use Toplink JPA that comes with JDeveloper 11g preview release
I have a question here!
I would like to get clarified which is better to use :
1. Toplink Java Objects from Tables ,
2.Toplink Entities from Tables
Could you suggest the best approach, and pros and cons of both the approaches?
Thanking you ,
Samba

Samba,
Ultimately both are using the same TopLink runtime. In the case of Entities you are using JPA and Java Objects you are using TopLink native API and metadata.
Going forward I would recommend JPA with TopLink extensions as required.
Doug

Similar Messages

Which is better C++/JAVA?

Could someone give me an explaination as to why
C++/OpenGL is better than Java when trying to program 3D
objects?? Also could you plsss tell me the pros and cons
for each one?? Though i was thinking of using JAVA.
thx

You can't really say one is 'better' than the other. As far as 3d programming goes, it's likely you could achieve faster, smoother 3d programming (comparable to current PC games) with C++ but you at the sacrifce of much time and greater knowledge. Although Java3d is arguably not as fast as C++ it has been optimized for speed. If you're writing applications on your own then I'd strongly recommend Java. It's easier to pick up and will give you a good starting ground if you ever decide to take up C++. Also, with j3d you can write one program and (in theory ) it should be able to run w/ either DirectX or OpenGL.

Persistenance for Java Objects Using Toplink

Hi All Happy New Year
I am trying the a tutorial in Jdeveloper 10.1.3.0.4 called
Provide Persistenance for Java Objects Using Toplink.
I have followed the instructions and get the following error.
com.evermind.reflect.UndeclaredExceptionTypeException: oracle.oc4j.rmi.OracleRemoteException
at __Proxy1.persistEntity(Unknown Source)
at acme.ejb.session.EmpSessionClient.main(EmpSessionClient.java:29)
oracle.oc4j.rmi.OracleRemoteException: Invocation error: java.lang.NoSuchMethodException: acme.ejb.session.EmpSession.persistEntity(java.lang.Object)
The release notes mention TopLink POJO's Must Implement java.io.Serializable When Returned From a Session Bean's Remote Interface (4902787) When creating a session bean facade for TopLink POJO objects, you must implement java.io.Serializable for each of the TopLink POJO objects returned from the SessionBean facade through a remote interface. This is typically required when using ADF Swing, a EJB Sample Client, or when your EJB Session Bean resides on a separate application server from the client. You can also tell you you need to implement java.io.Serializable when you get the following exception:
com.evermind.reflect.UndeclaredExceptionTypeException:
/oracle.oc4j.rmi.OracleRemoteException/
at __Proxy1.[Your Class Name Here] (Unknown Source)
The workaround is to manually edit each POJO object to implement java.io.Serializable.
I have only one POJO which is declared as follows:
public class EmpInfo implements Serializable {
Can anybody help me understand what I need to do to get it to work?
Many Thanks in Advance

Hi,
can you send me your test scenario/project at anuj dot k dot jain at oracle dot com. I tried reproducing this but was unable to do so.
Thanks,
anuj dot k dot jain at oracle dot com

ConcurrentModificationException when creating Toplink java object

When I am adding a new java object based on a view, i get at the end of the wizard this exception and jdeveloper freezes.
I'm using Jdeveloper 10.1.3 (latest version)
java.util.ConcurrentModificationException
     at java.util.HashMap$HashIterator.nextEntry(HashMap.java:787)
     at java.util.HashMap$EntryIterator.next(HashMap.java:829)
     at java.util.HashMap$EntryIterator.next(HashMap.java:827)
     at oracle.ideimpl.controls.SwitchablePanel.getTabPageForComponent(SwitchablePanel.java:556)
     at oracle.ideimpl.controls.FlatTabbedWindow.getTabPageForComponent(FlatTabbedWindow.java:304)
     at oracle.ideimpl.log.TabbedPage.getTabPageForLogPage(TabbedPage.java:238)
     at oracle.ideimpl.log.TabbedLogManager.getMsgPage(TabbedLogManager.java:100)
     at oracle.toplink.addin.log.POJOGenerationLoggingAdapter.updateTask(POJOGenerationLoggingAdapter.java:42)
     at oracle.toplink.addin.mappingcreation.MappingCreatorImpl.fireTaskUpdated(MappingCreatorImpl.java:1049)
     at oracle.toplink.addin.mappingcreation.MappingCreatorImpl.generateMappedDescriptorsForTables(MappingCreatorImpl.java:231)
     at oracle.toplink.addin.mappingcreation.MappingCreatorImpl.generateMappedDescriptorsForTables(MappingCreatorImpl.java:201)
     at oracle.toplink.addin.wizard.jobgeneration.JobWizard$1.construct(JobWizard.java:401)
     at oracle.ide.util.SwingWorker$1.run(SwingWorker.java:119)
     at java.lang.Thread.run(Thread.java:595)
Does anyone know what the reason might be?

Could it be you are creating a collection that can be modified when an iterator is al ready going over this collection.
Could you be more specific on your project, any other toplink objects that might be manipulating the same data?
kind regards.

Error Generating Java Objects using TopLink

Running online tutorial: Build a Web Application with ADF Faces and Oracle TopLink
Generated errors when trying to build Java Objects From Table Wizard at step 9.
[b]java.lang.NullPointerException
     at oracle.ideimpl.log.TabbedLogManager.getMsgPage(TabbedLogManager.java:101)
     at oracle.toplink.addin.log.POJOGenerationLoggingAdapter.updateTask(POJOGenerationLoggingAdapter.java:42)
     at oracle.toplink.addin.mappingcreation.MappingCreatorImpl.fireTaskUpdated(MappingCreatorImpl.java:1049)
     at oracle.toplink.addin.mappingcreation.MappingCreatorImpl.generateMappedDescriptorsForTables(MappingCreatorImpl.java:231)
     at oracle.toplink.addin.mappingcreation.MappingCreatorImpl.generateMappedDescriptorsForTables(MappingCreatorImpl.java:201)
     at oracle.toplink.addin.wizard.jobgeneration.JobWizard$1.construct(JobWizard.java:401)
     at oracle.ide.util.SwingWorker$1.run(SwingWorker.java:119)
     at java.lang.Thread.run(Thread.java:595)
Any help welcomed
regards
John

Solved!!!
I had installed JDeveloper 10g inside a directory that had a space in the directory name.

2 TopLink Java Object from Table to be used in single selectOneChoice

Hello everyone, can I ask for help on how to solve my problem....
Here's my scenario, I have 2 tables namely tblCollege and tblCourse, they are related through tblCourse.CollegeCode = tblCollege.Code.
I use the jdeveloper wizard using TopLink -> Java Object from Table to add these table to my project. I created an EJB Data Control so that I can use them to my Userinterface using ADF Faces.
What I really want to do is that I need to have selectOneChoice component displaying:
tblCollege.Name + tblCourse.Name, and it should have a value of tblCollege.Code + tblCourse.Code,
so for example in my
tblCollege:
Code---------Name
1---------------Science
2---------------Music
tblCourse
Code-------Name-----------CollegeCode
1-------------Biology----------1
2-------------Computer-------1
3-------------Guitar------------2
what I want in my selectOneChoice is like this:
value----------display
1-1--------------Science-Biology
1-2--------------Science-Computer
2-3--------------Music-Guitar
I'm a little stuck on how I'm going to that. Thanks.

Bawasi,
I see a couple of angles of attack, but this really depends on the technologies involved. If you are using ADF Bindings in combination with ADF Faces then you need to shape the data at the entity level. If ADF Bindings are no the in equation, you can take a less aggressive approach and shape the data in a managed bean. What is not clear to me is the end-to-end use-case. I see the read-only (i.e. how to get data to the drop box), but I am
not certain what attribute on an entity you are attempting to set. Are you trying to set the course for the current user or for a master schedule? Finally, notice that the final shape of your data set shows a unique combinations, you could increase the performance of your use-case and ease of development simply by denormalizing your schema.
--RiC

Which database is better with JAVA ?

Which database is better with JAVA Oracle of MySQL ?

your question is too general but i prefer oracle for large projectsAs long as somebody else is paying the license fee.
and mysql for small projects.And this contributes what new information to the discussion?
>
you might also consider using postgresql. also an
open-source but much better than mysql :-)Much better, indeed. Thanks for the second.
you might also consider the use of
object-relational-mapping (ex.hibernate)
for your database and application so your application
written
on java wont be much dependent on the database :-)Your application won't be any less dependent on the database. It will make it possible to switch databases just by changing the Hibernate dialect.
I would not recommend Hibernate to someone who has to ask this question.
%

Which is better? JDO or Java Persistance API?

Hi folks
I'm trying to build an app on Google's cloud service.
Looking into this ( [http://code.google.com/appengine/docs/java/overview.html|http://code.google.com/appengine/docs/java/overview.html]), it tells me that for java projects there are 2 possibilities for persistance - JDO , and Java Persistance. Does anyone have any advice on which is better and/or easier? Also, if anyone has a small example they could post, that would be very useful too.
this isn't exactly a JDBC question, and maybe this should be posted somewhere else? If so please tell me where I should be asking this question.
Thanks!
-Tom

I personally find Java Persistence to be easy to use and it works just fine.
I can't say if you would agree. You'll just have to judge that for yourself, which means: put some effort into trying it out. I'd start by not requesting small examples in a forum, but by actually looking for them yourself using your search engine of choice.

Hi All, which is better while creating an object

Hi All, which is better while creating an object,
for ex:
public class Joe {
public void disp() {
System.out.println("Joe.disp");
(1) Joe j = new Joe();
j.disp();
(2) new Joe().disp();
of course, both are equal, which is better in performance perspective

I suggest you just write code and when the assignment is done, AND you have a performance issue, only then try to improve things. The question you're asking now is likely of no relevance to the performance of you application.
You can run your application through a profiler to see what specific part of it is consuming (too) much memory.

Generation of XML file from Java objects using castor

I have the following java file(Customer.java).
public class Customer
     private String ID;
     private FirstName firstName;
     private MiddleName middleName;
     private LastName lastName;
     private ArrayList address;
     public ArrayList getAddress() {
          return address;
     public void setAddress(ArrayList address) {
          this.address = address;
     public FirstName getFirstName() {
          return firstName;
     public void setFirstName(FirstName firstName) {
          this.firstName = firstName;
     public String getID() {
          return ID;
     public void setID(String id) {
          ID = id;
     public LastName getLastName() {
          return lastName;
     public void setLastName(LastName lastName) {
          this.lastName = lastName;
     public MiddleName getMiddleName() {
          return middleName;
     public void setMiddleName(MiddleName middleName) {
          this.middleName = middleName;
Using castor i have created an xml file(customer.xml) which has the following format.
<?xml version="1.0" encoding="UTF-8" ?>
- <customer ID="fbs0001">
<FIRSTNAME>Fred</FIRSTNAME>
<MIDDLENAME>B</MIDDLENAME>
<LASTNAME>Scerbo</LASTNAME>
- <ADDRESS>
<FIRSTLINE>No 18, Sheshadri road</FIRSTLINE>
<SECONDLINE>Gandhinagar Bangalore</SECONDLINE>
</ADDRESS>
- <ADDRESS>
<FIRSTLINE>ITPL</FIRSTLINE>
<SECONDLINE>Whitefield Bangalore</SECONDLINE>
</ADDRESS>
</customer>
I have used a mapping file to get this output.Is there a way where i can get the output xml in the following format without changing the Java object structure.If yes then please suggest how this can be done.
<?xml version="1.0" encoding="UTF-8" ?>
- <customer ID="fbs0001">
<FIRSTNAME>Fred</FIRSTNAME>
<MIDDLENAME>B</MIDDLENAME>
<LASTNAME>Scerbo</LASTNAME>
</customer>
<ADDRESS>
<FIRSTLINE>No 18, Sheshadri road</FIRSTLINE>
<SECONDLINE>Gandhinagar Bangalore</SECONDLINE>
</ADDRESS>
- <ADDRESS>
<FIRSTLINE>ITPL</FIRSTLINE>
<SECONDLINE>Whitefield Bangalore</SECONDLINE>
</ADDRESS>
I mean the output xml file should have the address as a separate tag not withing the root tag customer.

Hello,
Castor's own discussion groups might be able to point you to the solution you're looking for (if this use case is possible using Castor).
Oracle has its own object-to-XML mapping tool that is part of the TopLink product. It allows you to map existing objects to an existing XML Schema. This can be done visually using the TopLink Workbench, or programmatically using the TopLink APIs. TopLink OXM also supports the JAXB specification.
Using TopLink OXM to get the desired XML result I would recommend the following. Map the Customer and Address classes to XML, but don't map the relationship between Customer and Address. Then make the calls to the marshaller something like the following:
marshaller.marshal(aCustomer, System.out);
for(int x=0; x<aCustomer.getAddress().size(); x++) {
     marshal(aCustomer.getAddress().get(x), System.out);
Example - Using TopLink OXM to map an existing object model to an existing XML Schema:
http://www.oracle.com/technology/products/ias/toplink/preview/10.1.3dp4/howto/ox/index.htm
For more information on TopLink object-to-XML mapping:
http://www.oracle.com/technology/products/ias/toplink/preview/10.1.3dp4/objectxml/index.html
-Blaise

Urgent: How to find out the size in bytes of java object

Hi Experts,
We've a requirement that we need to find out the size of a java object at run time, is there a direct java API to get the size of a composite object in memory?
Here is my requirement: We are adding string objects (which is an xml string of considerable size) into a List. After reaching certain size limit (lets say 5MB) of the list i need to put this data into DB as a CLOB. So every time I add a string object to the list, I need to see if the total size of the list exceeds the limit and if yes, flush the results into DB.
I am not sure if java has a direct API for this, if not what is the beast way to do it, it s critical requirement for us.
It would be really great if someone could help us out.
Thank you,
-Shibu.

>
We've a requirement that we need to find out the size of a java object at run time, is there a direct java API to get the size of a composite object in memory?
Here is my requirement: We are adding string objects (which is an xml string of considerable size) into a List. After reaching certain size limit (lets say 5MB) of the list i need to put this data into DB as a CLOB. So every time I add a string object to the list, I need to see if the total size of the list exceeds the limit and if yes, flush the results into DB.
I am not sure if java has a direct API for this, if not what is the beast way to do it, it s critical requirement for us.
It would be really great if someone could help us out.
>
Could you explain your actual requirement a little more fully.
1. Is each individual string a separate XML string? Or is it just a fragment? Why would you just concatenate them together into a CLOB? That won't produce valid XML and it won't let you easily separate the pieces again later. So provide a simple example showing some strings and how you need to manipulate them.
2. Are you using these xml strings in Java at all? Or are you just loading them into the database?
For example if you are just loading them into the database you don't need to create a list. Just create a CLOB in Java and append each string to the CLOB. Before you append each one you can check to see if the new string will put you over your length limit. If it will then you write the CLOB to the database, empty the CLOB and start appending again to the new clob instance.
If you explain what you are really trying to do we might be able to suggest some better ways to do it.

Parse of a xml file to an java object model

Hello,
I'm trying to do a program that receive an xml file and ought to create all the neccesary java objects according to the content of the parsed xml file.
I've all the class created for all the objects that could be present into the xml and the idea is to go down in the tree of nodes recursively until it returns nodes more simple. Then, I create the last object and while I come back of the recursively calls, I create the objects more complex until I reached to the main object.
Until now, I have part of this code, that is the one wich have to parse the parts of the xml.
public static void readFile(String root){
          DocumentBuilderFactory factory = DocumentBuilderFactory
               .newInstance();
          try {
               DocumentBuilder builder = factory.newDocumentBuilder();
               Scanner scanner = new Scanner(new File(root)).useDelimiter("\\Z");
               String contents = scanner.next();
               scanner.close();
               Document document = builder.parse(new ByteArrayInputStream(contents.getBytes()));
               Node node = null;
               NodeList nodes = null;
               Element element = document.getDocumentElement();
               System.out.println(element.getNodeName());
               NodeList subNodes;
               NamedNodeMap attributes;
               //if (element.hasAttributes())
               visitNodes(element);
          } catch (ParserConfigurationException e) {
               e.printStackTrace();
          } catch (SAXException e) {
               e.printStackTrace();
          } catch (IOException e) {
               e.printStackTrace();
     private static void visitNodes (Node node){
          for(Node childNode = node.getFirstChild(); childNode!=null;){
               if (childNode.getNodeType() == childNode.DOCUMENT_NODE){
                    System.out.println("Document node Name " + childNode.getNodeName());
                    visitNodes(childNode);
               }else if (childNode.getNodeType() == childNode.ELEMENT_NODE){
                    System.out.println("Node Name " + childNode.getNodeName());
                    if (childNode.hasAttributes()){
                         visitAttributes(childNode.getAttributes());
                    if (childNode.hasChildNodes()){
                         visitNodes(childNode);
               }else if (childNode.getNodeType() == childNode.TEXT_NODE && !childNode.getNodeValue().contains("\n\t")){
                    System.out.println("Node value " + childNode.getNodeValue());
               Node nextChild = childNode.getNextSibling();
               childNode = nextChild;
     private static void visitAttributes(NamedNodeMap attributes){
          Node node;
          for(int i = 0; i < attributes.getLength(); i++){
               node = attributes.item(i);
               System.out.print(node.getNodeName() + " ");
               System.out.print(node.getNodeValue() + " ");
              }I don't know the use of childNodeType. For example, I expected that the XML tags with childs in his structure, enter by the option NODE_DOCUMENT and the tags without childs by the ELEMENT_NODE.
But the most important problem I've found are the nodes [#text] because after one ELEMENT_NODE I always found this node and when I ask if the node hasChilds, always returns true by this node.
Has any option to obtain this text value, that finally I want to display without doing other recursively call when I enter into the ELEMENT_NODE option?
When one Node is of type DOCUMENT_NODE or DOCUMENT_COMMENT? My program always enter by the ELEMENT_NODE type
Have you any other suggestions? All the help or idea will be well received.
Thanks for all.

Hello again,
My native language is Spanish and sorry by my English I attemp write as better I can, using my own knowledge and the google traductor.
I have solved my initial problem with the xml parser.
Firstly, I read the complete XML file, validated previously.
The code I've used is this:
public static String readCompleteFile (String root){
          String content = "";
          try {
               Scanner scanner = new Scanner(new File(root)).useDelimiter("\\Z");
               content = scanner.next();
               scanner.close();
          } catch (IOException e) {
               e.printStackTrace();
          return content;
     }Now, I've the file in memory and I hope I can explain me better.
I can receive different types of XML that could be or not partly equals.
For this purpose I've created an external jar library with all the possible objects contained in my xml files.
Each one of this objects depend on other, until found leaf nodes.
For example, If I receive one xml with a scheme like the next:
<Person>
    <Name>Juliet</Name>
    <Father Age="30r">Peter</Father>
    <Mother age="29">Theresa</Mother>
    <Brother>
    </Brother>
    <Education>
        <School>
        </school>
    </education>
</person>
<person>
</person>The first class, which initializes the parse, should selecting all the person tags into the file and treat them one by one. This means that for each person tag found, I must to call each subobject wich appears in the tag. using as parameter his own part of the tag and so on until you reach a node that has no more than values and or attributes. When the last node is completed I'm going to go back for completing the parent objects until I return to the original object. Then I'll have all the XML in java objects.
The method that I must implement as constructor in every object is similar to this:
public class Person{
final String[] SUBOBJETOS = {"Father", "Mother", "Brothers", "Education"};
private String name;
     private Father father;
     private Mother mother;
     private ArrayList brothers;
     private Education education;
     public Person(String xml){
       XmlUtil utilXml = new XmlUtil();
          String xmlFather = utilXml.textBetweenXmlTags(xml, SUBOBJETOS[0]);
          String xmlMother = utilXml.textBetweenXmlTags(xml, SUBOBJETOS[1]);
          String xmlBrothers = utilXml.textBetweenMultipleXmlTags(xml, SUBOBJETOS[2]);
          String xmlEducation = utilXml.textBetweenXmlTags(xml, SUBOBJETOS[3]);
          if (!xmlFather.equals("")){
               this.setFather(new Father(xmlFather));
          if (!xmlMother.equals("")){
               this.setMother(new Father(xmlMother));
          if (!xmlBrothers.equals("")){
            ArrayList aux = new ArrayList();
            String xmlBrother;
            while xmlBrothers != null && !xmlBrothers.equals("")){
              xmlBrother = utilXml.textBetweenXmlTags(xmlBrothers, SUBOBJETOS[2]);
              aux.add(new Brother(xmlBrother);
              xmlBrothers = utilXml.removeTagTreated(xmlBrothers, SUBOBJETOS[2]);
            this.setBrothers(aux);
          if (!xmlEducation.equals("")){
               this.setEducation(new Father(xmlEducation));
}If the object is a leaf object, the constructor will be like this:
public class Mother {
     //Elements
     private String name;
     private String age;
     public Mother(String xml){
          XmlUtil utilXml = new XmlUtil();
          HashMap objects = utilXml.parsearString(xml);
          ArraysList objectsList = new ArrayList();
          String[] Object = new String[2];
          this.setName((String)objects.get("Mother"));
          if (objects.get("attributes")!= null){
               objectsList = objects.get("attributes");
               for (int i = 0; i < objectsList.size();i++){
                 Object = objectsList.get(i);
                 if (object[0].equals("age"))
                   this.setAge(object[1]);
                 else
     }Each class will have its getter and setter but I do not have implemented in the examples.
Finally, the parser is as follows:
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;
public class XmlUtil {
     public HashMap parsearString(String contenido){
          HashMap objet = new HashMap();
          DocumentBuilderFactory factory;
          DocumentBuilder builder;
          Document document;
          try{
               if (content != null && !content.equals("")){
                    factory = DocumentBuilderFactory.newInstance();
                    builder = factory.newDocumentBuilder();
                    document = builder.parse(new ByteArrayInputStream(content.getBytes()));
                    object = visitNodes(document);
               }else{
                    object = null;
          } catch (ParserConfigurationException e) {
               e.printStackTrace();
               return null;
          } catch (SAXException e) {
               e.printStackTrace();
               return null;
          } catch (IOException e) {
               e.printStackTrace();
               return null;
          return object;
     private HashMap visitNodes (Node node){
          String nodeName = "";
          String nodeValue = "";
          ArrayList attributes = new ArrayList();
          HashMap object = new HashMap();
          Node childNode = node.getFirstChild();
          if (childNode.getNodeType() == Node.ELEMENT_NODE){
               nodeName = childNode.getNodeName();
               if (childNode.hasAttributes()){
                    attributes = visitAttributes(childNode.getAttributes());
               }else{
                    attributes = null;
               nodeValue = getNodeValue(childNode);
               object.put(nodeName, nodeValue);
               object.put("attributes", attributes);
          return object;
     private static String getNodeValue (Node node){
          if (node.hasChildNodes() && node.getFirstChild().getNodeType() == Node.TEXT_NODE && !node.getFirstChild().getNodeValue().contains("\n\t"))
               return node.getFirstChild().getNodeValue();
          else
               return "";
     private ArrayList visitAttributes(NamedNodeMap attributes){
          Node node;
          ArrayList ListAttributes = new ArrayList();
          String [] attribute = new String[2];
          for(int i = 0; i < attributes.getLength(); i++){
               atribute = new String[2];
               node = attributes.item(i);
               if (node.getNodeType() == Node.ATTRIBUTE_NODE){
                    attribute[0] = node.getNodeName();
                    attribute[1] = node.getNodeValue();
                    ListAttributes.add(attribute);
          return ListAttributes;
}This code functioning properly. However, as exist around 400 objects to the xml, I wanted to create a method for more easily invoking objects that are below other and that's what I can't get to do at the moment.
The code I use is:
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class UtilClasses {
     public Object UtilClasses(String package, String object, String xml){
          try {
            Class class = Class.forName(package + "." + object);
            //parameter types for methods
            Class[] partypes = new Class[]{Object.class};
            //Create method object . methodname and parameter types
            Method meth = class.getMethod(object, partypes);
            //parameter types for constructor
            Class[] constrpartypes = new Class[]{String.class};
            //Create constructor object . parameter types
            Constructor constr = claseObjeto.getConstructor(constrpartypes);
            //create instance
            Object obj = constr.newInstance(new String[]{xml});
            //Arguments to be passed into method
            Object[] arglist = new Object[]{xml};
            //invoke method!!
            String output = (String) meth.invoke(dummyto, arglist);
            System.out.println(output);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
          return null;
     }This is an example obtained from the Internet that I've wanted modified to my needs. The problem is that when the class calls this method to invoke the constructor and does not fail, this does not do what I expect, because it creates an empty constructor. If not, the parent class gives a casting error.
I hope that now have been more clear my intentions and that no one has fallen asleep reading this lengthy explanation.
greetings.

How to parse XML to Java object... please help really stuck

Thank you for reading this email...
If I have a **DTD** like:
<!ELEMENT person (name, age)>
<!ATTLIST person
     id ID #REQUIRED
>
<!ELEMENT name ((family, given) | (given, family))>
<!ELEMENT age (#PCDATA)>
<!ELEMENT family (#PCDATA)>
<!ELEMENT given (#PCDATA)>
the **XML** like:
<person id="a1">
<name>
     <family> Yoshi </family>
     <given> Samurai </given>
</name>
<age> 21 </age>
</person>
**** Could you help me to write a simple parser to parse my DTD and XML to Java object, and how can I use those objects... sorry if the problem is too basic, I am a beginner and very stuck... I am very confuse with SAXParserFactory, SAXParser, ParserAdapter and DOM has its own Factory and Parser, so confuse...
Thank you for your help, Yo

Hi, Yo,
Thank you very much for your help. And I Wish you are there...I'm. And I plan to stay - It's sunny and warm here in Honolulu and the waves are up :)
A bit more question for dear people:
In the notes, it's mainly focus on JAXB,
1. Is that mean JAXB is most popular parser for
parsing XML into Java object? With me, definitely. There are essentially 3 technologies that allow you to parse XML documents:
1) "Callbacks" (e.g. SAX in JAXP): You write a class that overrides 3 methods that will be called i) whenever the parser encounters a start tag, ii) an end tag, or iii) PCDATA. Drawback: You have to figure out where the heck in the document hierarchy you are when such a callback happens, because the same method is called on EACH start tag and similarly for the end tag and the PCDATA. You have to create the objects and put them into your own data structure - it's very tedious, but you have complete control. (Well, more or less.)
2) "Tree" (e.g. DOM in JAXP, or it's better cousin JDOM): You call a parser that in one swoop creates an entire hierarchy that corresponds to the XML document. You don't get called on each tag as with SAX, you just get the root of the resulting tree. Drawback: All the nodes in the tree have the same type! You probably want to know which tags are in the document, don't you? Well, you'll have to traverse the tree and ask each node: What tag do you represent? And what are your attributes? (You get only strings in response even though your attributes often represent numbers.) Unless you want to display the tree - that's a nice application, you can do it as a tree model for JTree -, or otherwise don't care about the individual tags, DOM is not of much help, because you have to keep track where in the tree you are while you traverse it.
3) Enter JAXB (or Castor, or ...): You give it a grammar of the XML documents you want to parse, or "unmarshall" as the fashion dictates to call it. (Actually the name isn't that bad, because "parsing" focuses on the input text while "unmarshalling" focuses on the objects you get, even though I'd reason that it should be marshalling that converts into objects and unmarshalling that converts objects to something else, and not vice versa but that's just my opinion.) The JAXB compiler creates a bunch of source files each with one (or now more) class(es) (and now interfaces) that correspond to the elements/tags of your grammar. (Now "compiler" is a true jevel of a misnomer, try to explain to students that after they run the "compiler", they still need to compile the sources the "compiler" generated with the real Java compiler!). Ok, you've got these sources compiled. Now you call one single method, unmarshall() and as a result you get the root node of the hierarchy that corresponds to the XML document. Sounds like DOM, but it's much better - the objects in the resulting tree don't have all the same type, but their type depends on the tag they represent. E.g if there is the tag <ball-game> then there will be an object of type myPackage.BallGame in your data structure. It gets better, if there is <score> inside <ball-game> and you have an object ballGame (of type BallGame) that you can simply call ballGame.getScore() and you get an object of type myPackage.Score. In other words, the child tags become properties of the parent object. Even better, the attributes become properties, too, so as far as your program is concerned there is no difference whether the property value was originally a tag or an attribute. On top of that, you can tell in your schema that the property has an int value - or another primitive type (that's like that in 1.0, in the early release you'll have to do it in the additional xjs file). So this is a very natural way to explore the data structure of the XML document. Of course there are drawbacks, but they are minor: daunting complexity and, as a consequence, very steep learning curve, documentation that leaves much to reader's phantasy - read trial and error - (the user's guide is too simplicistic and the examples too primitive, e.g. they don't even tell you how to make a schema where a tag has only attributes) and reference manual that has ~200 pages full of technicalities and you have to look with magnifying glas for the really usefull stuff, huge number of generated classes, some of which you may not need at all (and in 1.0 the number has doubled because each class has an accompanying interface), etc., etc. But overall, all that pales compared to the drastically improved efficiency of the programmer's efforts, i.e. your time. The time you'll spend learning the intricacies is well spent, you'll learn it once and then it will shorten your programming time all the time you use it. It's like C and Java, Java is order of magnitude more complex, but you'd probably never be sorry you gave up C.
Of course the above essay leaves out lots and lots of detail, but I think that it touches the most important points.
A word about JAXB 1.0 vs. Early Release (EA) version. If you have time, definitively learn 1.0, they are quite different and the main advantage is that the schema combines all the info that you had to formulate in the DTD and in the xjs file when using the EA version. I suggested EA was because you had a DTD already, but in retrospect, you better start from scratch with 1.0. The concepts in 1.0 are here to stay and once your surmounted the learning curve, you'll be glad that you don't have to switch concepts.
When parser job is done,
what kind of Java Object we will get? (String,
InputStream or ...)See above, typically it's an object whose type is defined as a class (and interface in 1.0) within the sources that JABX generates. Or it can be a String or one of the primitive types - you tell the "compiler" in the schema (xjs file in EA) what you want!
2. If we want to use JAXB, we have to contain a
XJS-file? Something like:In EA, yes. In 1.0 no - it's all in the schema.
I am very new to XML, is there any simpler way to get
around them? It has already take me 4 days to find a
simple parser which give it XML and DTD, then return
to me Java objects ... I mean if that kind of parser
exists....It'll take you probably magnitude longer that that to get really familiar with JAXB, but believe me it's worth it. You'll save countless days if not weeks once you'll start developing serious software with it. How long did it take you to learn Java and it's main APIs? You'll either invest the time learning how to use the software others have written, or you invest it writing it yourself. I'll take the former any time. But it's only my opinion...
Jan

Coding Preference ..Which is better for memory?

Hey all,
Javas garbage collection is sweet. However, I was reading somewhere that setting some objects to null after I'm done with them will actually help.
(help what .. I'm not sure.. my guess is memory used by the JVM)
Thus I have two ways to do the same thing and I'd like to hear peoples comments on which is "better" ... or will yield faster performance.
Task: I have a Vector of Strings (called paths) that hold absolute file paths. (Don't ask why I didn't use a String[]) I'd like to check and see if they exist, and if not, create them... I'll use the createNewFile() method for that.
Method A -- Here I'll reuse that File object
public void myMethod()throws Exception{
File file = null;
for(int i = 0; i < paths.size(); i++){
file = new File(paths.get(i).toString());
boolean made = file.createNewFile();
if(made){doSomething();}
file = null;
}Method B -- Here I'll use um... "dynamically made" ones that I won't eventually be set back to null
public void myMethod()throws Exception{
for(int i = 0; i < paths.size(); i++){
boolean made = (new File(paths.get(i).toString())).createNewFile();
if(made){doSomething();}
}So when the code eventually exists myMethod, the object "file" will be out of scope and trashed.... correct? If thats the case, then would there be any other differences between the two implementations?
Thanks

There's no real difference between the two. Choose the style you prefer,
although in the first one I'd lose the "file = null" statement since that
variable is about to disappear, and I'm move the definition into the loop
-- always give variables as small a scope as possible, mainly to
keep the logic simple:
public void myMethod()throws Exception{
    for(int i = 0; i < paths.size(); i++){
        File file= new File(paths.get(i).toString());
        boolean made = file.createNewFile();
         if(made){doSomething();}
}

Code generation: from resultset to Java Object

Hello all:
Is there any utilities that can convert the ResultSet to a list of Java objects? I think that's doable, since we can get the metadata from ResultSetMetaData anyway, which provide a means to construct the internal properties of a java object.
I just wonder if there is already something doing that out there... rather not to reinvent the wheel...
Thanks,
John

thanks to both.
You don't create data objects from data rather your data exists within the data objects. Thus the code that is going to use the data objects must already know the form so they can do something intelligent in the first place.So much better to start with a data model and then create code from that then populate from the database.
>
Here I just explore the idea and assess its viability. The project is using a cache solution, coherence as matter of fact. it seems the idea is to return a data strcture like a generic resultset from the cache. my understanding is that, when a user sends out a SQL, the database designer wouldn't know the POJOs the user uses from their side, still database is able to return a resultset from which the user will have enough info to populate their POJOs.
I will take another look at the design, but meanwhile I found BasicDynaBean from apache's bean utilities useful, and came out with the following code:
public List<BasicDynaBean> execute(final RequestObject ro) throws SQLException {
          List<BasicDynaBean> list = jdbcTemplate.execute(
                    new CallableStatementCreator(){
                         @Override
                         public CallableStatement createCallableStatement(Connection con)
                                   throws SQLException {
                              CallableStatement cs = con.prepareCall(spName);
                                         // code skipped
                                                                                                return cs;
                    new CallableStatementCallback<List<BasicDynaBean>>(){
                         @Override
                         public List<BasicDynaBean> doInCallableStatement(CallableStatement cs)
                                   throws SQLException, DataAccessException {
                              cs.execute();
                              ResultSet rs = (ResultSet) cs.getObject(outputPos);
                                                                                                //apache api to convert the rs to list of BasicDynaBean
                              RowSetDynaClass rsdc = new RowSetDynaClass(rs);
                              List<BasicDynaBean> rows = rsdc.getRows();
                              return rows;
          however, I noticed that each mean contains the column headers, seems to me it's quite a overhead!
thanks, John
Edited by: Johnny_hunter on Aug 1, 2011 10:49 AM
Edited by: Johnny_hunter on Aug 1, 2011 11:57 AM

Which is better ? Toplink Java objects or Toplink Entities ?

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