Can't connect or insert to database using ucanaccess method in applet

Question

While connecting one applet to an Access DB using the jdbc:ucanaccess method, I get the following error:

Firstdb.java:44: error: unreported exception SQLException; 
must be caught or declared to be thrown
stmt.executeUpdate(sql);   
                  ^

The code that I used for the applet is as follows (add() and setBounds() are removed from init()):

public class Firstdb extends Applet implements ActionListener {
    TextField t1, t2;
    Label l1;
    Button b1, b2;
    Connection con;
    Statement stmt;

    public void init() {
        try {
            con = DriverManager.getConnection("jdbc:ucanaccess://H:/test/db.mdb");
            stmt = con.createStatement();
        } catch (Exception e) {
        }
    }

    public void actionPerformed(ActionEvent ae) {
        String sql;

        if (ae.getSource() == b1) {
            sql = "insert into user (Uname) values(" + t1.getText() + ")"; 
            stmt.executeUpdate(sql);
        } else if (ae.getSource() == b2) {
            //do something
        }
    }
}

Note: java version "1.8.0_141"

Why am I getting this error?

Answer 1

Your code has two fatal flaws:

1. value is not a valid SQL keyword. It should be values. [Fixed in subsequent edit to question.]
2. Your dynamic SQL is generating command text with invalid syntax (unquoted string literal).

Also, user is a reserved word (function name), so if you need to use it as a table name you really should enclose it in square brackets.

The proper solution to issue #2 above is to use a parameterized query, e.g.,

sql = "insert into [user] ([Uname]) values (?)";
PreparedStatement ps = conn.prepareStatement(sql);
ps.setString(1, t1.getText());
ps.executeUpdate();

Answer 2

It is a compile error which means that you either need to surround your stmt.executeUpdate(sql); with try-catch statement, or your method should throw an SQLException:

 public void actionPerformed(ActionEvent ae) {
    try {
        String sql;

        if (ae.getSource() == b1) {
            sql="insert into user (Uname) values("+t1.getText()+")"; 
            stmt.executeUpdate(sql);
        } else if (ae.getSource() == b2) {
            //do something
        }
    catch (SQLException e) {
        // do something
    }
}

or

public void actionPerformed(ActionEvent ae) throws SQLException {
    String sql;

    if (ae.getSource() == b1) {
        sql="insert into user (Uname) values("+t1.getText()+")"; 
        stmt.executeUpdate(sql);
    } else if (ae.getSource() == b2) {
        //do something
    }
}

EDIT: By the way, I don't see if you are loading or registering Oracle JDBC driver class for UCanAccess before opening the database connection:

// Step 1: Loading or registering Oracle JDBC driver class
try {
     Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
} catch(ClassNotFoundException cnfex) {
     System.out.println("Problem in loading or "
            + "registering MS Access JDBC driver");
     cnfex.printStackTrace();
}

So do you have it or no? If no, you should add it before getting your connection: con = DriverManager.getConnection("jdbc:ucanaccess://H:/test/db.mdb");