Mapping CLOB and Long in xml schema

Question

Hi,
I am creating an xml schema to map some user defined database objects. For example, for a column which is defined as VARCHAR2 in the database, I have the following xsd type mapping.
<xsd:element name="Currency" type="xsd:string" />
If the oracle column is CLOB or Long(Oracle datatype), could you please tell me how I can map it in the xml schema? I do not want to use Oracle SQL type like:
xdb:SQLType="CLOB" since I need a generic type mapping to CLOB. Would xsd:string still hold good for CLOB as well as Long(Oracle datatype) ?
Please help.
Thanks,
Vadi.

Answer 1

The problem is that LONGs are not buffered but are read from the wire in the order defined. The problem is the same as
rs = stmt.executeQuery("select myLong, myNumber from tab");
while (rs.next()) {
int n = rs.getInt(2);
String s = rs.getString(1);
The above will fail for the same reason. When the statement is executed the LONG is not read immediately. It is buffered in the server waiting to be read. When getInt is called the driver reads the bytes of the LONG and throws them away so that it can get to the NUMBER and read it. Then when getString is called the LONG value is gone so you get an exception.
Similar problem here. When the query is executed the CLOB and BLOB locators are read from the wire, but the LONG is buffered in the server waiting to be read. When Clob.getString is called, it has to talk to the server to get the value of the CLOB, so it reads the LONG bytes from the wire and throws them away. That clears the connection so that it can ask the server for the CLOB bytes. When the code reads the LONG value, those bytes are gone so you get an exception.
This is a long standing restriction on using LONG and LONG RAW values and is a result of the network protocol. It is one of the reasons that Oracle deprecates LONGs and recommends using BLOBs and CLOBs instead.
Douglas