View Object Exception -
VO extension is very useful, when need to add a new item to a region. Extend the VO and include the respective column in sql statement. Below are the steps need to follow in order to extend any VO.
1) Go to About This page and check the VO name being used for that region
2) FTP to JAVA_TOP to download the VO and dependent files.
3) De compile the class files and generate the source code
4) Create the same file structure in my projects under Jdeveloper folder
5) Create a new View Object in same structure under your custom path
6)  Include the new column in SQL query  and finish
7) Open the project properties and click on BC4J component
8) Select substitution and choose standard view as source and custom extended view as substitute
9) Project_Name.jpx file will be generated in myprojects
10) FTP back new extended view and subsequent class files to correct location on server
11) Also place the server.xml file
12) Run the JPXimporter
13) Go to Application and personalize the region
14) Create new item with viewSource = Standard VO Name and viewAttribute= newly added column name
Example - 
 
Requirement  – Introduce a new column in My Requisition Table Region to display the  Item number in comma separated concatenated format  This can be achieved by extending underlying VO, Below are the steps.
 
 
 Write a program unit to get required values. Input parameter must be in existing VO columns. 
 
CREATE OR REPLACE FUNCTION APPS.Sandeep_Test_prog(param IN VARCHAR2)  
 RETURN VARCHAR2 AS
         CURSOR cur_item_desc(p_segment1 IN VARCHAR2) IS
         SELECT NVL(item_description,'Sandeep') item_desc
         FROM po_requisition_lines_all a,po_requisition_headers_all b 
         WHERE a.requisition_header_id = b.requisition_header_id
         AND b.segment1=p_segment1;
         CURSOR cur_item_number(p_description IN VARCHAR2) IS
         SELECT DISTINCT NVL(segment1, 'Sandeep') itemNumber
         FROM mtl_system_items_b
         WHERE UPPER (description) = UPPER (p_description);
           p_item_number   VARCHAR2 (100) := null;
 
BEGIN
        FOR c1 in cur_item_desc(param) 
        LOOP
                           dbms_output.put_line('Outer Loop>>'||c1.item_desc);
                             FOR c2 in cur_item_number(c1.item_desc)
                             LOOP
                                          dbms_output.put_line('Inner Loop >>'||c2.itemNumber);
                               IF c2.itemNumber<>'Sandeep' THEN
                                    IF p_item_number IS NULL THEN 
                                              p_item_number := p_item_number ||c2.itemNumber ; 
                                    ELSE
                                                                        p_item_number :=   p_item_number||','|| c2.itemNumber ;  
                                    END IF;   
                                             ELSE
                                                        p_item_number := p_item_number ||',' ;
                               END IF;            
                      END LOOP;
             END LOOP;
          RETURN p_item_number;
EXCEPTION
           WHEN OTHERS  THEN
                  DBMS_OUTPUT.put_line ('Error');
                  RETURN 'Sandeep NULL';
END;
Check the VO name required to be extended.Click on About This Page 
VO being used for these beans values is MyReqsGlanceVO
Check the full path in Business Component References Details
oracle.apps.icx.por.reqmgmt.server.MyReqsGlanceVO
 
FTP VO and respective  VOImpl and VORowImpl class files. Create a similar package structure in  JDev myprojects forlder and place the all files and create a new view  object.




Modify the SQL and include custom column

 Some time you may encounter below  error message . To avoid it keep sql query as original and press next  till last page. Then come back to SQL page and do the your changes and  then press next. It won’t come again.

Press next till reach below page and click the checkbox Generate Java file for ViewRowClass and finish. 

This will generate VOImpl and VORowImpl java files also. Now open the Project Properties. 

Business Components  >>  Substitutions >> Available ( Choose the standard VO ) >>  Substitute (Pick the extended VO). 
If this is new substitution, ADD button will be enabled else UPDATE. 

This will generate a OAProject10.jpx and server.xml files. FTP all files at server and run JPX importer to upload the import.
Now Go to Application 
Click on Personalize “This Table display a list…..” link

Click create Item icon for Advanced Table  
 
Give the ID Name and Apply – It will create a new column in Advanced Table
Now  click new Item icon for TestColumn – It will create a new item for that  column. Also create a new item in columnHeader and give a prompt there,  to display the column  title. 
Select  the Item style and give the name of item.View Instance hold the name of  standard VO and view attribute is custom column name included by us.
Now return to application  New column ColumnHeader holding Item number appears.