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setSavepoint and releaseSavepoint Example in Java

By: Vimala in JDBC Tutorials on 2007年10月13日 [フレーム]

The JDBC 3.0 API adds the method Connection.setSavepoint, which sets a savepoint within the current transaction. The Connection.rollback method has been overloaded to take a savepoint argument.

The example below inserts a row into a table, sets the savepoint svpt1, and then inserts a second row. When the transaction is later rolled back to svpt1, the second insertion is undone, but the first insertion remains intact. In other words, when the transaction is committed, only the row containing ?FIRST? will be added to TAB1:

Statement stmt = conn.createStatement();
int rows = stmt.executeUpdate("INSERT INTO TAB1 (COL1) VALUES " +
 "(?FIRST?)");
// set savepoint
Savepoint svpt1 = conn.setSavepoint("SAVEPOINT_1");
rows = stmt.executeUpdate("INSERT INTO TAB1 (COL1) " +
 "VALUES (?SECOND?)");
...
conn.rollback(svpt1);
...
conn.commit();

Releasing a Savepoint

The method Connection.releaseSavepoint takes a Savepoint object as a parameter and removes it from the current transaction.

Once a savepoint has been released, attempting to reference it in a rollback operation causes an SQLException to be thrown. Any savepoints that have been created in a transaction are automatically released and become invalid when the transaction is committed, or when the entire transaction is rolled back. Rolling a transaction back to a savepoint automatically releases and makes invalid any other savepoints that were created after the savepoint in question.

When to Call the Method rollback

As mentioned earlier, calling the method rollback aborts a transaction and returns any values that were modified to their previous values. If you are trying to execute one or more statements in a transaction and get an SQLException, you should call the method rollback to abort the transaction and start the transaction all over again. That is the only way to be sure of what has been committed and what has not been committed. Catching an SQLException tells you that something is wrong, but it does not tell you what was or was not committed. Since you cannot count on the fact that nothing was committed, calling the method rollback is the only way to be sure.

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