Creating XML from Relational Tables using java

Question

I would like to create an XML document by querying relational tables in java
try {
        connection = getConnection();
        final String qryStr = "select XMLElement( foo, 'bar' ) from dual";
        final OracleXMLQuery qry = new OracleXMLQuery(connection, qryStr);
        final String xmlString = qry.getXMLString();
I would expect this to give the following result that I get from running the statement in SQL Developer
select XMLElement( foo, 'bar' ) from dual
<FOO>bar</FOO>
Instead I get
<?xml version = '1.0'?>
<ERROR>oracle.xml.sql.OracleXMLSQLException: Character ')' is not allowed in an XML tag name.</ERROR>
Is this the correct way to go about this?

Answer 1

Is this the correct way to go about this?
Not really.
OracleXMLQuery class is the Java-side implementation of DBMS_XMLQUERY APIs.
It's mostly designed to generate a canonical XML document out of a SQL query.
Assuming a query like "SELECT col1, col2 FROM my_table", the resulting XML should appear like this :
<ROWSET>
  <ROW>
    <COL1>123</COL1>
    <COL2>ABC</COL2>
  </ROW>
  <ROW>
    <COL1>456</COL1>
    <COL2>XYZ</COL2>
  </ROW>
</ROWSET>
So in your test, since the resulting column is not aliased (XMLElement), you're actually trying to generate something like this :
<ROWSET>
  <ROW>
    <XMLELEMENT(FOO,'BAR')>
      <FOO>bar</FOO>
    </XMLELEMENT(FOO,'BAR')>
  </ROW>
<ROWSET>
which of course is invalid, hence the error message.
If you want to generate only <FOO>bar</FOO> as output, just use a regular PreparedStatement with your query and access the document in the ResultSet with the proper getter.