How to troubleshoot problems when tomcat servlet connects to mysql - mysql

Question

Tomcat servlet gets connection to mysql with getConnection(). Just fetch data from db test table shop.Connection to mysql is successful, but browser doesn't still show any data from backend. JavaScript shows request.status is 200 and request.readyState is 2 or 3. How can I find the problem? I even don't see any exceptions in tomcat log file.
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/html");
response.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
out.println("ok");
try {
Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "***");
Statement statementQuery = connection.createStatement();
ResultSet set = statementQuery.executeQuery("select * from shop");
// connection.commit(); Error appears here(should be commented):
out.println("<div>");
while (set.next()) {
out.println("ok");
out.println(set.getInt(1) + " ");
out.println(set.getString(2) + " ");
out.println(set.getDouble(3));
}
} catch (Exception e) {
e.printStackTrace();
}
out.println("</div>");
out.flush();
out.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
doGet(request, response);
}
EDIT:
connection.commit() is wrong. Comment that line and it works.

Answer 1

Change Oracle driver to Mysql driver
Class.forName("com.mysql.jdbc.Driver");
SQL statements are executed sequentially. Change the order of execution to:
int ret = statement.executeUpdate("insert into shop values (53, 'fjd', 43.2)");
ResultSet s1 = statement.executeQuery("select * from shop");
Execute also a commit on the connection
connection.commit();
And add a finally to close statement and connection
}finally{
statement.close();
connection.close();
}