Problem in using View Object for validation

Question

Hi,
I have defined a simple swing form to practice. It has one Entity Object and two View objects. One of these view objects is an updatable VO based on the EO and the other one has a simple "select count(*)" from a table. I defined a method validation on one of the EO attributes to see how can i use the VO for validation. On the other hand i defined the Application Module to use both of my views. As far as i undrestood, when i define a VO for AM, the AM will instantiate it the first time it starts running. Here is the code inside the method validation for FirstName attribute:
/**Validation method for FirstName
public boolean validateFirstName(String data) {
ViewObject vo = getDBTransaction().getRootApplicationModule().findViewObject("CountEmployeeInstance");
if (vo == null) {
System.out.println("vo is null");
else {
vo.executeQuery();
if (vo.hasNext()){
System.out.println("count = " + ((CountEmployeeRowImpl) vo.next()).getCount());
else {
System.out.println("vo has no next");
return true;
The problem is that vo.executeQuery() does not return any record. In fact the vo.hasNext() returns false and i get the message "vo has no next" on the console. Please pay attention that the VO's sql statement is SELECT COUNT(*) and it always returns a record. I found that if i use vo.closeRowSet() before vo.executeQuery() everything works fine.
Please tell me that what is my problem and why is it working like this?
Best Regards,
Alireza Vali

Answer 1

Chris,
1- Every thing is fine with the ADF model layer in this practice. I have tested it by using Test option on AM and it works. It works exactly the same as how it works throug swing UI that i use for it.
2- The VO is beeing found and as you see in the code, i have tested it by "if (vo == null)" just after the statement which finds it and vo is not null which means it has been instantiated by AM as it was supposed to.
3- The VO's SQL statement is "SELECT COUNT(*) FROM EMPLOYEE" with no where clause. I have 14 records in this table.
Every thing is OK with swing form. It runs and shows the records and all the binded operations like "next record", "previous record" and so on work perfectly on the records.
4- The code i used is a combination of two examples. Example 9-7 and 9-8 in pages 9-12 and 9-13 of mentioned document.
Now my findings:
I changed the code to the following:
    /**Validation method for FirstName
    public boolean validateFirstName(String  data) {
        ViewObject vo = getDBTransaction().getRootApplicationModule().findViewObject("MaxEmployeeIdInstance");
        if (vo == null) {
            System.out.println("vo is null");
        else {
            //vo.closeRowSet();
            vo.executeQuery();
            System.out.println("Row Count = " + vo.getRowCount());
            System.out.println("Default Slot = " + vo.getCurrentRowSlot());
            vo.next();
            System.out.println("Slot after next() = " + vo.getCurrentRowSlot());
            vo.reset();
            System.out.println("Slot after reset() = " + vo.getCurrentRowSlot());
            vo.first();
            System.out.println("Slot after first() = " + vo.getCurrentRowSlot());
            vo.last();
            System.out.println("Slot after last() = " + vo.getCurrentRowSlot());
            System.out.println("----------------------");
            vo.executeQuery();
            System.out.println("Deafault index = " + vo.getCurrentRowIndex());
            vo.next();
            System.out.println("Index after next() = " + vo.getCurrentRowIndex());
            vo.reset();
            System.out.println("Index after reset() = " + vo.getCurrentRowIndex());
            vo.first();
            System.out.println("Index after first() = " + vo.getCurrentRowIndex());
            vo.last();
            System.out.println("Index after last() = " + vo.getCurrentRowIndex());
            System.out.println("Slot Before First = " + vo.SLOT_BEFORE_FIRST);
            System.out.println("Slot Beyound Last = " + vo.SLOT_BEYOND_LAST);
        return true;
    }Here are the results :
Row Count = 1
Default Slot = 0
Slot after next() = 3
Slot after reset() = 0
Slot after first() = 0
Slot after last() = 0
Deafault index = 0
Index after next() = -1
Index after reset() = 0
Index after first() = 0
Index after last() = 0
Slot Before First = 2
Slot Beyound Last = 3
As you see, after the execution of the statement "vo.executeQuery()" the The RowIterrator pointer is not pointing to the slot before the first record but it is pointing to the first record itself. And that is why the statement "if (vo.hasNext()" returns false because we just have one record and RowIterrator Index is standing on that record and there is no next record present. The very important thing is that even reset() method does not set the index to the slot before the first record and it sends it to the first record.
After that, i took the statemet "vo.closeRowSet()" out of the comment and here are the results:
Row Count = 1
Default Slot = 2
Slot after next() = 0
Slot after reset() = 2
Slot after first() = 0
Slot after last() = 0
Deafault index = -1
Index after next() = 0
Index after reset() = -1
Index after first() = 0
Index after last() = 0
Slot Before First = 2
Slot Beyond Last = 3
These are the exact things that we expected from the first. After query execution, the pointer is set to the slot before first record and the reset() method does its defined job which is sending the pointer to the slot before the the first record.
My Assumptions:
The Rowset which is created by AM is somehow different from the RowSet which you create in your program. I am absolutely sure that this functionality is not a bug but a design decission. I look at my simple program and see that when it runs, the data is queried and shown on the screen which is all done by AM by instantiating my VO and executing the query on it. AM reasonably must put the RowSet pointer on the first record and not the slot before first record. And i am sure that if i use reset() method on the shown RowSet, the pointer goes to the first record and the data on the screen does not get cleared. Whe we use vo.closeRowSet() and execute the query again, the AM made RowSet is closed and a new one is created and the new RowSet is your's not AM's so it functions as you expect.
Best Regards,
Alireza Vali