SQL，JDBC“无效列索引”错误，带有简单查询

Question

I'm new to STRUTS and JDBC, my application tries to connect to a simple DB that has 3 tables, right now all is doing is trying to query 1 table that only stores "first, last names and a Id field"

System.out.println("-------- Oracle JDBC Connection Testing ------");

            try {
                Class.forName("oracle.jdbc.driver.OracleDriver");
            } catch (ClassNotFoundException e) {
                System.out.println("Where is your Oracle JDBC Driver?");
                e.printStackTrace();
                return null;
            }

            System.out.println("Oracle JDBC Driver Registered!");

            try {
                connection = 
                    DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","david","changeit");
            } catch (SQLException e) {
                System.out.println("Connection Failed! Check output console");
                e.printStackTrace();
                return null;
            }

            if (connection != null) {
                System.out.println("You made it, take control your database now!");
            } else {
                System.out.println("Failed to make connection!");
            }

where I would like to get the result of 1 column if a match occurs:

            String sql = "SELECT S_ID FROM Students WHERE firstname=? AND lastname=?";

            PreparedStatement ps = connection.prepareStatement(sql);
            ps.setString(1, firstname);
            ps.setString(2, lastname);

            rs = ps.executeQuery();

            while (rs.next()) {
                studentid = rs.getString(1);
                ret = SUCCESS;
            }
        } catch (Exception e) { ...

As far as I can tell the connection is made, the SQL query

Select s_id from Students where firstname='first' and lastname='last';

when run on SQL Dev. works and gives me a single result.

I don't really get a stack trace the code just jumps from right before the 'while (rs.next()) {..' directly into the finally block

} catch (Exception e) {
        e.printStackTrace();
        ret = ERROR;
    } finally {
        if (connection != null) {
            try {
                connection.close();
            } catch (Exception e) {
            }
        }
    }

Answer 1

I'm not sure how Oracle drivers work. But below statement is what i see on Oracle site. Are you getting a non empty resultset ? As you are not getting a nullpointerexception on .next(), i'm wondering if Oracle drivers return an empty ResultSet, which may lead to this problem.

http://docs.oracle.com/cd/B28359_01/java.111/b31224/getsta.htm

In case of a standard JDBC driver, if the SQL string being executed does not return a ResultSet object, then the executeQuery method throws a SQLException exception. In case of an Oracle JDBC driver, the executeQuery method does not throw a SQLException exception even if the SQL string being executed does not return a ResultSet object.

Answer 2

Like I said I'm new at using this. The problem was that my schema didn't have the CONNECT role assigned to it.

Solution log in as 'SYSTEM' and grant the role to my schema

grant connect to MY_SCHEMA;