Correct way of reusing PreparedStatement instance?
What's the right way to create a PreparedStatement, reuse it a few times, then clean it up? I'm using the following pattern:
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = getConnection(...);
// first use
stmt = conn.prepareStatement("some statement ?");
stmt.setString(1, "maybe some param");
if (stmt.execute()) {
...
}
// second use
stmt = conn.prepareStatement("some statement ?");
stmt.setString(1, "maybe some param");
if (stmt.execute()) {
...
}
// third use.
stmt = conn.prepareStatement("some statement");
stmt.execute();
}
finally {
if (stmt != null) {
try {
stmt.close();
} catch (Exception sqlex) {
sqlex.printStackTrace();
}
stmt = null;
}
if (conn != null) {
try {
conn.close();
} catch (Exception sqlex) {
sqlex.printStackTrace();
}
conn = null;
}
}
Can we reuse the "stmt" object like that, or do we have to call stmt.close() between each query?
Thanks
---------- Update ------------------------
Ah ok I see, each of my statements will be different. So is this a more correct pattern?:
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = getConnection(...);
// first use
PreparedStatement stmt1 = null;
try {
stmt1 = conn.prepareStatement("some statement ?");
stmt1.setString(1, "maybe some param");
if (stmt1.execute()) {
...
}
}
finally {
if (stmt1 != null) {
try {
stmt1.close();
} catch (Exception ex) {}
}
}
// second use
PreparedStatement stmt2 = null;
try {
stmt2 = conn.prepa开发者_运维百科reStatement("some different statement ?");
stmt2.setString(1, "maybe some param");
if (stmt2.execute()) {
...
}
}
finally {
if (stmt2 != null) {
try {
stmt2.close();
} catch (Exception ex) {}
}
}
// third use
PreparedStatement stmt3 = null;
try {
stmt3 = conn.prepareStatement("yet another statement ?");
stmt3.setString(1, "maybe some param");
if (stmt3.execute()) {
...
}
}
finally {
if (stmt3 != null) {
try {
stmt3.close();
} catch (Exception ex) {}
}
}
}
finally {
if (conn != null) {
try {
conn.close();
} catch (Exception sqlex) {
sqlex.printStackTrace();
}
conn = null;
}
}
So each different statement will be closed individually before the next one executes.
It's the other way around -- you only need to prepare it once, and then reuse it.
I.E. This:
// second use
stmt = conn.prepareStatement("some statement ?");
stmt.setString(1, "maybe some param");
if (stmt.execute()) {
...
}
should become this:
// second use
stmt.setString(1, "maybe some param");
if (stmt.execute()) {
...
}
Your third use, which is a different statement, should either be a new variable, or close your prepared statement first. (Though usually with PreparedStatements, you keep them around and reuse them).
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