Thanks Alan, just to make the thing really clear. You propose code like
this:
public void execute() {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
Context envContext = null;
try {
Context initContext = new InitialContext();
envContext = (Context)
initContext.lookup("java:/comp/env");
DataSource ds = (DataSource)
envContext.lookup("jdbc/swex");
conn = ds.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery("some sql");
// iterate through the result set ...
} catch (SQLException e) {
e.printStackTrace();
} catch (NamingException e) {
e.printStackTrace();
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (envContext != null) {
try {
envContext.close();
} catch (NamingException e) {
e.printStackTrace();
}
}
}
For me this looks fine but I'm still confused, why they complicated
things in the example of "properly written code"
http://tomcat.apache.org/tomcat-6.0-doc/jndi-datasource-examples-howto.html?
Do I miss some important point here?
Stefan
Alan Chaney schrieb:
Hi Stefan
You don't need to repeat the stmt.close();conn.close() etc in the 'try'
body. The 'finally' by definition is ALWAYS called and that is where you
should do the tidy up...
Alan Chaney
Stefan Riegel wrote:
I guess I understood the point with the "Random Connection Closed
Exceptions" Problem.
See at the end of
http://tomcat.apache.org/tomcat-6.0-doc/jndi-datasource-examples-howto.html
As I understand, only the connection itself must be protected this
way. The statement and ResultSet must not. Is the following,
simplified code also correct?
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
conn = ... get connection from connection pool ...
stmt = conn.createStatement("select ...");
rs = stmt.executeQuery();
... iterate through the result set ...
// SUPERFLUsOUS
rs.close();
stmt.close();
conn.close(); // Return to connection pool
conn = null; // Make sure we don't close it twice
//SUPERFLUOUS
} catch (SQLException e) {
... deal with errors ...
} finally {
try {
rs.close();
} catch (SQLException e) {
// deal with errors
}
try {
stmt.close();
} catch (SQLException e) {
// deal with errors
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
// deal with errors
}
conn = null;
}
}
Thanks.
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