How to Correctly Close Resources

Question

As I was cleaning up some code, FindBugs pointed me to a bit of JDBC code that uses Connection, CallableStatement, and ResultSet objects. Here\'s a snippet from that code:

Answer 1

Use Lombok's cleanup, if you can:

@Cleanup
Connection c = ...
@Cleanup
statement = c.prepareStatement(...);
@Cleanup
rs = statement.execute(...);

This works translates to three nested try-finally blocks and works fine with exception. Never ever swallow an exception without a very good reason!

An alternative:

Write an own utility method like this:

public static void close(ResultSet rs, Statement stmt, Connection con) throws SQLException {
    try {
        try {
            if (rs!=null) rs.close();
        } finally {
            if (stmt!=null) stmt.close();
        }
    } finally {
        if (con!=null) con.close();
    }
}

and use it in

try {
    Connection con = ...
    Statement stmt = ...
    ResultSet rs = ...
} finally {
    close(rs, stmt, con);
}

and let the Exception bubble up or handle it as you want.