Checking database connectivity in JSP
How can I check the database connectivity in JSP. I want to print an error message if there is any problem occurs with the database connectivity.
I m using the following code:
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String connectionUrl = "jdbc:sqlserver://localhost;databaseName=dbname;user=username;password=password";
Connection conn = DriverManager.getConnection(connectionUrl);
Statement stmt = conn.createStatement();
After successfull connection, I want to insert data to the database. I also want to check the whether the data is inserted properly. Can anyoone help me on this...
Answer
The JSP is the wrong place for this. You need to create a standalone class which does the JDBC job and let each of the methods throw an exception whenever the SQL stuff fails.
Here's an example of a "DAO" class which does all the JDBC stuff on the User table:
public class UserDAO {
public User find(String username, String password) throws SQLException {
// ...
}
public void save(User user) throws SQLException {
// ...
}
public void delete(User user) throws SQLException {
// ...
}
}
Then, create a servlet which uses this class and handles the exception. Here's an example of a LoginServlet:
@WebServlet(urlPatterns={"/login"})
public class LoginServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
UserDAO userDAO = new UserDAO();
try {
User user = userDAO.find(username, password);
if (user != null) {
request.getSession().setAttribute("user", user); // Login.
response.sendRedirect("userhome");
} else {
request.setAttribute("message", "Unknown login, try again"); // Set error message.
request.getRequestDispatcher("/WEB-INF/login.jsp").forward(request, response); // Redisplay form with error.
}
} catch (SQLException e) {
throw new ServletException("Fatal database failure", e); // <-- Here
}
}
}
Let JSP submit to this servlet
<form action="login" method="post">
<input type="text" name="username" />
<input type="password" name="password" />
<input type="submit" />
${message}
</form>
You see, when the DAO class throws an SQLException, the servlet rethrows it as ServletException. It will by default end up in a container-default HTTP 500 error page. You can if necessary customize this with a JSP in your own look'n'feel as follows
<error-page>
<error-code>500</error-code>
<location>/error.jsp</location>
</error-page>