CODEWITHSUNDEEP
javajdbc
EricR
EricR

Reputation: 1497

Is this jdbc resource closed?

Looking back over my code I find that I occasionaly have written:

ResultSet rs = conn.createStatement().executeQuery("select * from main");
//snip
rs.close();

and sometimes I've written 

Statement st = conn.createStatement();
ResultSet rs = st.executeQuery("Select * from main");
//snip
rs.close();
st.close();

In the second code segment, it's more obvious that the Statement is closed, but is it also closed in the first one? conn.createStatement() returns a statement object, but when it's instantiated like that I don't see any easy way to close it after I'm done. Should I just rewrite the various bits of code to use method #2?

Upvotes: 3

Views: 113

Answers (3)

Marvo
Marvo

Reputation: 18133

A good practice is to put the rs.close() and st.close() in your finally clause.

Statement st;
ResultSet rs;

try {
   st = connection.createStatement(...);
   rs = st.executeQuery();
}
catch (JdbcErrorsExceptionsAndFoo exception) {
   // yadda yadda
}
finally {
    if (rs!= null) {
        rs.close();
    }
    if (st != null) {
        st.close();
    }
}

Upvotes: 2

Wayne
Wayne

Reputation: 60414

The Statement will be automatically closed when it is garbage collected, but you need to explicitly close it if you want to free the resources as soon as you're done with them.

Note, however, that the reverse actually does work. That is, closing a Statement also closes the ResultSet associated with it.

Upvotes: 1

Cem Güler
Cem Güler

Reputation: 635

if statement contains a resultset, gc does not collect it. you can use the second method or use aspects or filters to auto close them.

Upvotes: 1

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