Cursor as Stored Procedure out parameter mapped with JAVA ResultSet

In a recent project i need to write a very complex query that,depending on input parameters, have to compose itself. SELECT, FROM, WHERE and ORDER BY clauses were all builded dinamically. For this reason i chose to write a Stored Procedure that achieved this goal.
This one,basically, build the query choosing between a lot of conditions given by input parameters.
At the end of computing job, it open a cursor with the builded query and return it.
The question that this post try to answers is “How can i use a Cursor returned by a PL/SQL Stored Procedure in Java?”

The first step is to declare in PL/SQL a REF CURSOR Type.
I show you a small example of a sub-program that use a REF CURSOR Type

CREATE OR REPLACE
PACKAGE BODY TEST_CURSOR AS

TYPE REF_CUR_TYPE IS REF CURSOR;

PROCEDURE storeProcedureTest(
          INPUT_NUM IN NUMBER,
          REF_CUR_INSTANCE OUT REF_CUR_TYPE
         )
IS
  sqlString VARCHAR(100);
BEGIN
  sqlString := 'SELECT * FROM';
  IF INPUT_NUM=1 THEN
     sqlString := sqlString || ' table1';
  ELSE
     sqlString := sqlString || ' table2';
  ENDIF;

  OPEN REF_CUR_INSTANCE FOR sqlString;
END storeProcedureTest;

In this very basically stored procedure you have INPUT_NUM that specify on which table you will execute the query. This is a little example that shows a dynamically builded query.
At the TYPE DECLARATION section i define a REF CURSOR type. This say to Oracle that each REF_CUR_TYPE variable is a pointer to a CURSOR.
In the declaration i could make it strongly typed, explicitly defining which kind of rowtype the CURSOR have to return.

TYPE REF_CUR_TYPE IS REF CURSOR RETURN CURSOR_TABLE_TEST%ROWTYPE

At the end Stored Procedure opens REF_CUR_INSTANCE with the builded query. Explicitly note that i DON’T close CURSOR because i want to visit it on Java.

On Java i have to call stored procedure with CallableStatement, registering output Cursor variable. An Oracle Cursor is mapped in Java with java.sql.ResultSet class.

    Connection con = null;
    CallableStatement callableStmt = null;
    ResultSet rs = null;
        
        try {
            
             Class.forName("oracle.jdbc.driver.OracleDriver");
            
             con=DriverManager.getConnection(
                    "jdbc:oracle:thin:@address:1521:database_name",
                     "username",
                     "password");
            
            callableStmt = con.prepareCall("{ call TEST_CURSOR.storeProcedureTest(?,?) }");
            
            // set the INPUT_NUM parameter
            callableStmt.setInt(1, 1);
            // register the type of the out parameter for CURSOR
            callableStmt.registerOutParameter(2, OracleTypes.CURSOR);
            //execute stored procedure
            callableStmt.execute()
            //get cursor output
            rs = callableStmt.getObject(2);
                   
            while (rs.next){
             //do something useful on cursor
            }     
        
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        } catch (SQLException ex) {
            ex.printStackTrace();
        } finally {
            
            try {
                
                rs.close();
                callableStmt.close();
                con.close();
                
            } catch (SQLException ex) {
                ex.printStackTrace();
            }
            
        }