Question

The db tables that I am using are changing very often meaning new column can be add which will reflect my sql’s.

The solution that I was thinking is first “read” the meta data into some map and use it in order to retrieve the values something like this.

Read meta data:

public class Dynamic {
static public final Map<Integer, String> metadata = initMetaData();
HashMap<String, String> data = new HashMap<String, String>();

private static Map<Integer, String> initMetaData() {
    Map<Integer, String> tmpMap = new HashMap<Integer, String>();
    try {
        Connection connection = DBConnection.getConnection();
        try {
            Statement stmt = connection.createStatement();
            ResultSet result = stmt.executeQuery("SELECT * FROM TMP WHERE ROWNUM = 1");
            for (int i = 1; i <= result.getMetaData().getColumnCount(); i++) {
                tmpMap.put(new Integer(i), result.getMetaData().getColumnName(i));
            }
        } finally {
            connection.close();
        }
    } catch (SQLException ex) {
        …..
    }
    return Collections.unmodifiableMap(tmpMap);
}

public static String getColumnName(Integer index) {
    return metadata.get(index);
}

And when running the sql:

public static void test()        
    try {
        Connection connection = DBConnection.getConnection()
        try {
            Statement stmt = connection.createStatement();
            ResultSet result = stmt.executeQuery("SELECT * FROM TMP where idx = 'R5'");

            while (result.next()) {
            Dynamic d = new Dynamic()
                for (int i = 1; i <= Dynamic.metadata.size(); i++) {                        
                         d.setData(Dynamic.getColumnName(i),result.getString(Dynamic.getColumnName(i)));       
                }
            }

In this approach I have two problems(that I notice):

1) I need to execute two loops

2) I don’t know which get function to use via resultset since the type can also change.

How can I overcome those problems ?

I would also appreciate to get some other suggestion maybe there is a simple why

Thanks

Answer 1

1) What is your alternative to the inner loop? How would you get the field values? Do you think there is a lot of overhead in looping over small number of integers?
2) You can get extra information about field data type from the same metadata where you get the field name and map the method names accordingly.
3) You should really create a map for multiple tables – table/fieldSeq/fieldType/methodName and maybe few extra details – you don’t have to get them all dynamically all the time.