如何在 Java 中使用准备好的语句进行选择查询？

Question

I had tried several times using prepared statements but it returns SQL exception. here is my code:

public ArrayList<String> name(String mobile, String password) {
    ArrayList<String> getdata = new ArrayList<String>();
    PreparedStatement stmt = null;
    try {
        String login = "select mobile, password from tbl_1 join tbl_2 on tbl_1.fk_id=2.Pk_ID where mobile=? and password=?";

        String data = "select * from tbl_2  where password='" + password + "'";

        PreparedStatement preparedStatement = conn.prepareStatement(login);

        preparedStatement.setString(1, mobile);
        preparedStatement.setString(1, password);

        ResultSet rs = preparedStatement.executeQuery(login);

        Statement stmts = (Statement) conn.createStatement();

        if (rs.next()) {
            System.out.println("Db inside RS");
            ResultSet data = stmts.executeQuery(data);

            while (data.next()) { /* looping through the resultset */

                getdata.add(data.getString("name"));
                getdata.add(data.getString("place"));
                getdata.add(data.getString("age"));
                getdata.add(data.getString("job"));
            }

        }

    } catch (Exception e) {
        System.out.println(e);
    }

    return getdata;
}

While running this, I got the following SQL exception:

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '? and password=?' at line 1.

Any suggestion to make this work? any piece of code is appreciated.

Answer 1

You need to use:

preparedStatement.executeQuery();

instead of

preparedStatement.executeQuery(login);

when you pass in a string to executeQuery() that query is executed literally and thus the ? is send to the database which then creates the error. By passing query string you are not execution the "cached" prepared statement for which you passed the values.

Answer 2

For both parameter you use preparedStatement.setString(1, ..); so the first parameter is set two times. but you never set the value for second parameter.

so change

preparedStatement.setString(1, mobile);
            preparedStatement.setString(1, password);

to

    preparedStatement.setString(1, mobile);
    preparedStatement.setString(2, password);