Persistent Bean framework

I am struggling with an architectural question, surrounding persistent beans. Here is the problem.
Supposed I have two classes, Group and Person. Obviously, Group contains some number of members. Thus, Group has a private HashMap (could have been Vector, but HashMap guarantees unique entries) listing all Person members. Finally, Group has get/set methods for its list of members.
I have a simple persistence framework, whereby a "manager" can Introspect a bean, find all its properties, then save them to a data store, commonly a JDBC store, but in this case LDAP (using JNDI).
The problem becomes how best to represent the Person members in the Group class. I could represent them as a Vector/HashMap/array of Person, but then persisting the Group becomes difficult, since when the manager Introspects the Group and finds the list of Person objects, it does not have basic elements to persist but rather complex user-defined Person objects. I do not want to store serialized objects, which make the data specific to my application, but rather the properties, so that the data can be used by other apps.
When my data store was an RDBMS, I simply stored IDs for the list of members, since this mapped nicely to a relational model. However, in the case of an LDAP store, the member attributes (representing the list) contain a DN rather than just the ID (which is inside the DN).
Here is my catch-22: if I store the serialized Person objects or even just the unique IDs of the Persons, then the underlying data in the LDAP directory become unique to my app; if I somehow get it to translate to the entire DN representing the Person, then my application objects become specific to my LDAP store and not reusable in other storage contexts.
Any ideas?

Hi Jhon,
Nothing like that exists for DB XML at the moment. Berkeley DB JE supports object persistence in Java using simple annotations, if that's what you need.
John

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Greetings,
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You cannot. You should either find the object by query or retrieve it
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Graham Cruickshanks wrote:
I have a persistent bean class with two Strings as member fields. (example
below)
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control the creation of the non persistant objects.
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On persist, How can I configuration JDO to detect that it's the same as an
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package foo;
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public String var1;
public String var2;
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return this.var1;
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this.var2 = var2Set
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<jdo>
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oneObject.setVar1("Value1");
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[email protected]
SolarMetric Inc.
http://www.solarmetric.com

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Regards
LJS Narayana

Hi Abrami,
Thank you for your reply. It is like this i am storing System.currentMillies() which gives Millis in long data type into a table having a number column with (14). Now i wrote a CMP bean which uses this table, for almost a year and half it is in production with no problem but from few days back when we try to use a finder method to query data SQL returns Exception telling that Number Overflow, a sample number for getting this overflow is 1046836194640L which represents 'Wed Mar 05 11:49:54 SGT 2003' this date. I found that the CMP which got generated is using oracle.sql.NUMBER.toLong(byte[] inputNumber) and thus giving the error. I try to use your suggested way, if we can directly work on the long it would be more convenient.
Regards
LJS Narayana

JNDI Lookup in JSP fails for EJB 3.0

I am new to Java technology. I read the EJB FAQ, NetBeans docs and may forum discussions and I am still confused with the error I am having.
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Virtual Interface generation bug with NetWeaver ?

I use the Web Service generation wizard to generate a virtual interface which exposes methods in an EJB. As one of the parameters I pass a simple java bean, lets say:
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When I look at the virtual interface generated, especially at the Types tab, my boolean attribute is not included.
If I change the getter to "getBuggy()", the attribute is included in the VI. The only problem is that the typical Java Bean framework, say from sun or ibm, always map 'boolean' getters to 'isSomething()' and not 'getSomething()'.
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Build id: 200407270250
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Regards,
Rich Heilman

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You'd end up with a single class that has both hibernate and JSF annotations on it.
Is that right?

There is a design forum.
I think you have a few too many keywords in there. Hopefully someone with experience end to end might clear that up.
You'd end up with a single class that has both hibernate and JSF annotations on it.Even if possible I suspect that no one is going to recommend that.

Error found in component h:selectOneMenu

Hi,
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     public Object getAsObject(FacesContext context, UIComponent component,
               String value) {
          if (value == null || value.equals(StringUtils.EMPTY)) {
               return null;
          long id;
          try {
               id = Long.parseLong(value);
          } catch (NumberFormatException e) {
               id = 0;
               e.printStackTrace();
          if (((UIInput) component).getValue() == null) {
               return createNewValue(context, component, id);
          } else {
               PersistentBean pk = (PersistentBean) ((UIInput) component)
                         .getValue();
               //To be sure the valueChangeListener is called
               if(pk.getId() != id){
                    return createNewValue(context, component, id);
               return pk;
     private Object createNewValue(FacesContext context, UIComponent component, long id){
          ValueExpression ve = component.getValueExpression("value");
          try {
               PersistentBean pk = (PersistentBean) ve.getType(context.getELContext())
                         .newInstance();
               pk.setId(id);
               return pk;
          } catch (Exception e) {
               e.printStackTrace();
               throw new RuntimeException(
                         "pbConverer error could not instanciate the assignable object of the persistent bean",
                         e);
     public String getAsString(FacesContext context, UIComponent component,
               Object value) {
          if (value == null || value.equals(StringUtils.EMPTY)) {
               return StringUtils.EMPTY;
          if (value instanceof PersistentBean) {
               return String.valueOf(((PersistentBean) value).getId());
          } else {
               throw new RuntimeException(
                         "The pbConverter required a value of PersistentBean");
}---------------------------------------- Expected result
I expect that the second value (Second value) of my listbox is selected.
----------------------------------------- Result
No value is selected
Strange I think, somebody knows why?
Thanks in advance,
Pieter
Belgium

I found a sollution by changing the core JSF libraries.
I changed the following:
--------------------- class javax.faces.component.UISelectOne starting at line 185
               Class type = value.getClass();
                Object newValue = getFacesContext().getApplication().
                    getExpressionFactory().coerceToType(item.getValue(), type);
                if (value.equals(newValue)) {
                    return (true);
                }.......................... in
                if(value.equals(item.getValue())){
                     return (true);
                }The second class i changed is the
--------------------- class com.sun.faces.renderkit.html_basic.MenuRenderer starting at line 580
          Object newValue = context.getApplication().getExpressionFactory().
              coerceToType(itemValue, type);
          isSelected = isSelected(newValue, valuesArray);.......................... in
isSelected = isSelected(itemValue, valuesArray);I'm not sure this is the correct way of handeling this error.
So my question is if somebody have some advice.
Thanks in advance,
Pieter

Why Threading is not allowed in EJB?

Hello,
I learnt that threading concepts is not allowed/used in EJB.
can u please post your view, regarding the above question.
Thanks

Good mourning...
EJB isn't used to web applications only, and also exist the Entity beans, the persistent beans and Message Driven Beans. EJB is a enterprise component that is deployed in Application Server. The AS harness the EJB instances amount. This amount is defined in ejb-jar.xml file. And, really, the EJB is thread-safety, thus only a client is connected in the specific time. For more and better information, read the Mastering EJB book, it's free download in theserverside.com, and this sections:
- Several Entity Bean Instances May Represent the Same Underlying Data (pag. 114);
- Entity Bean Instances Can Be Pooled (p�g 116).
treat this specific issue.
bye!

Instanciate an object depending on a variable value

Hi there,
I am developing a Web application based on a JSP+persistency MVC framework. In a number of classes, I have to be able to instanciate a "model" object (OO mapping from an RDBMS table) whose type depends on the value of a String variable. Currently, this is done this way:
if(Constants.CONSTANT1.equals(value)) {
    return new Type1Model(args);
} else if(Constants.CONSTANT2.equals(value)) {
    return new Type2Model(args);
} // else if...The Type1Model, Type2Model, etc. classes extend the same base class. But I find this code ugly - while quite efficient.
So I am trying to come to a design in which I call ModelFactory.getModel(value, args), period (more accurately, semi-colon). This factory holds a Hashtable, mapping possibles values for "value" to Class. Thus, each Type*Model class registrers itself in the ModelFactory for a given value, guaranteeing simple extensibility without modifying the factory nor the code that uses it.
Now, am I complicating a lot too much this task which is so easy to perform in C-style code ? Or is this the path to OO-enlightenment ?
Thanks and regards.

I would in general avoid the if's as doing a more flexible approach is just as easy to code and more flexible.
It is always best to first focus on the way you would like to call your code and then work on the details of what you need to do to get the code working (i.e. focus on the interface first).
You could use reflection and pass in the class name you would like to construct, and simply use the class name as your constant. This is very simple and flexible. The following is close although I didn't test it.
A sample invocation would be:
Model myModel=ModelFactory.getModel("com.ssouza.MyModel", args);
public class ModelFactory {
public static Model getModel(String className, Object[] args) {
   // this is more psuedo code and I don't know the exact syntax, but
   Class cls=Class.forName(className);
    Class[] argTypes=loop through args array getting the Class associated with each and put it into this Class array
   Constructor con=cls.getConstructor(argTypes);
    return (Model) con.newInstance(args);
}Steve http://www.jamonapi.com - JDBC/SQL monitoring in jamon 2.3!

Persistent Bean framework

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