CODEWITHSUNDEEP
javamysqlgwt
john
john

Reputation: 787

Proper way to do jdbc calls from GWT?

I am doing RPC's in GWT that query a database and I have a memory leak in my program and I have a strong suspicion its in the way I have the class set up. currently, I have to connect to the database within each method that I have and then close out that connection at the end of the method. Would doing it this way cause a memory leak? I feel like programming it this way leads to more code and is highly inefficient but I can't find many good samples to go off, can someone suggest a better way for this to work? names, IP's have been changed, and I've posted the connect method as a well as a sample of how the other method's are written. 

public class DatabaseServiceImpl extends RemoteServiceServlet implements DatabaseService {

private Connection con = null;
String database = "ioma";
String host = "localhost";
String password = "foo";
String url = "jdbc:mysql://" + host + "/" + database;
String user = "foo";

public String connect() {

    String connect = "";
    try {
        Class.forName("com.mysql.jdbc.Driver");
        con = DriverManager.getConnection(url, user, password);

    } catch (SQLException e) {
        for (Throwable t : e)
            System.err.println("Error connecting to the database: " + t);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    connect = "database connection aquired";
    return connect;

}

public int getAssemblerCount() {
    connect();
    try {
        int assemblerCount = 0;
        String query = "SELECT COUNT(*) FROM assemblers";
        PreparedStatement ps = con.prepareStatement(query);
        ResultSet rs = ps.executeQuery();
        rs.next();
        assemblerCount = rs.getInt(1);
        rs.close();
        ps.close();
        con.close();
        return assemblerCount;
    } catch (SQLException e) {
        for (Throwable t : e)
            System.err.println("Database error in getAssemblerCount " + e);
        return 0;
    }

}}

Upvotes: 0

Views: 723

Answers (1)

Don Roby
Don Roby

Reputation: 41127

You should always close in a "finally" block, so that the close happens in the event of an exception.

See the answers to this related question for help on doing that properly.

This is a common source of memory leaks and likely is your problem.

Upvotes: 1

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