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///////////////////////////////////////////////////////////////////////////////
//                                                                             
// JTOpen (IBM Toolbox for Java - OSS version)                                 
//                                                                             
// Filename: AS400JDBCSavepoint.java
//                                                                             
// The source code contained herein is licensed under the IBM Public License   
// Version 1.0, which has been approved by the Open Source Initiative.         
// Copyright (C) 1997-2001 International Business Machines Corporation and     
// others. All rights reserved.                                                
//                                                                             
///////////////////////////////////////////////////////////////////////////////

package com.ibm.as400.access;

import java.sql.Savepoint;
import java.sql.SQLException;



// JDBC 3.0

/**

The AS400JDBCSavepoint class is the Toolbox JDBC driver's
representation of a savepoint.  A savepoint is a point within the current 
transaction that can be referenced from the 
{@link com.ibm.as400.access.AS400JDBCConnection#rollback(java.sql.Savepoint) Connection.rollback(savepoint)}
method. 
When a transaction is rolled back to a savepoint, all changes made 
after the savepoint was created are undone. 

Savepoints can be either named or unnamed. 
The DB2 for IBM i does not support unnamed savepoints 
so internally the Toolbox JDBC driver will create 
a name to send to the system.  The
format is T_JDBCINTERNAL_n where 'n' is a counter that is
incremented every time an unnamed savepoint is created.

Considerations:

Named savepoints must be unique.  A savepoint name cannot be reused until the savepoint is released, committed, or rolled back.
Savepoints are valid only if autocommit is off.  An exception is thrown is autocommit is enabled.
Savepoints are not valid across XA connections.  An exception is thrown if the connection is an XA connection.
Savepoints require OS/400 V5R2 or IBM i.  An exception is thrown if connecting to OS/400 V5R1 or earlier.
If the connection option is set to keep cursors open after a traditional rollback, cursors also remain open after a rollback to a savepoint.



OS/400 V5R2 or IBM i is required to use savepoints.  Savepoint support
is new in modification 5 of the Toolbox JDBC driver.


**/

public class AS400JDBCSavepoint
implements Savepoint
{
  static final String copyright = "Copyright (C) 1997-2001 International Business Machines Corporation and others.";

                                    
    // Counter for creating unique names.
    private static int counter_ = 1;      

    // So object can be serialized / de-serialized across releases    
    static final long serialVersionUID = 4L;


    // Savepoint ID.  Name is used if user named the savepoint, id is used if the user
    // did not name the save point.
    private String name_ = null;
    private int generatedId_ = 0;
    
    // State of savepoint.
    private int status_;
       static final int ACTIVE = 1;
       static final int CLOSED = 2;



    /**
    Constructs an AS400JDBCSavepoint object.  
    **/
    AS400JDBCSavepoint (String name, int id)
    {                            
       name_ = name;
       generatedId_ = id;                                         
       status_ = ACTIVE;
    }



    // The worker method in AS400JDBCConnection needs a method that gets the name
    // no matter how it is generated.  It cannot use the public getSavepointName()
    // method since that throws an exception if the savepoint is an unnamed savepoint.
    String getName()
    {
       return name_;
    }                               


    // Counter to help create unique name for unnamed savepoints.  Every savepoint
    // on the serve has a name.  We will create a name for unnamed savepoints to
    // send to the system.
    static synchronized int getNextId()
    {
       return counter_++;
    }                              
    
    


    /**
    *  Returns the generated ID for the savepoint that this Savepoint object represents.
    *  @return the numeric ID of this savepoint.
    *  @exception SQLException if this is a named savepoint.
    **/
    public int getSavepointId()
               throws SQLException 
    {                           
       if (generatedId_ == 0)
          JDError.throwSQLException(JDError.EXC_SAVEPOINT_DOES_NOT_EXIST);

       return generatedId_;
    } 


    /**
    *  Returns the name for the savepoint that this Savepoint object represents.
    *  @return the name of this savepoint.
    *  @exception SQLException if this is an un-named savepoint.
    **/
    public String getSavepointName()
               throws SQLException 
    {                           
       if (generatedId_ != 0)
          JDError.throwSQLException(JDError.EXC_SAVEPOINT_DOES_NOT_EXIST);

       return name_;
    } 


    // The worker method in AS400JDBCConnection can use this method to determine
    // if the savepoint is closed via the release or rollback methods.  Savepoints
    // that are no longer valid because of a commit will still show a status of 
    // active. 
    int getStatus()
    {
       return status_;
    }                               


    // Change the status of this savepoint.  Most likely use of this method is to 
    // change the status from active to closed after a release or rollback.
    void setStatus(int status)
    {
       status_ = status;
    }                               
                    
}