ORA-30625: Method Dispatch on NULL SELF Argument Is Disallowed

Question:  I have a piece of code I am trying to run, but I keep getting an ORA-30625 error as follows: method dispatch on NULL SELF argument is disallowed.

ORA-30625: method dispatch on null self argument is disallowed
 

How can I get past this ORA-30625 error?

Answer:  Without seeing your full code listing or the contents of your whole error stack that includes the ORA-30625, it will be difficult to determine the specific problem with your code. 

The oerr utility should first be used to find the full content of the ORA-30625 error description from Oracle:

ORA-30625: method dispatch on NULL SELF argument is disallowed

Cause: A member method of a type is being invoked with a NULL SELF argument.

Action: Change the method invocation to pass in a valid self argument.

 In general terms, this is the PL/SQL equivalent of the Java Null Pointer Exception (NPE).  The implication is that you are invoking a method on a NULL object.

This commonly happens when attempting to extract XML data from a database that's of one type, perhaps CLOB, and converting it to another.  Check your XMLtype object to make sure it's not NULL before you attempt to invoke a method on it.

Also, it's possible that the NULL value is due to the specific tablespace not being identified in the extract statment.  A simple example would be:

...
SALES := x.extract('/Author/Last/text()');
price := SALES.getStringVal();  

dbms_output.put_line('Done');
dbms_output.put_line(price);

Even if the tablespace has been defined elsewhere in the code, the extract is not pointed at it.  The following snip does not return the ORA-30625 because it knows exactly where to look:

...
SALES := x.extract('//Author/Last/text()','xmlns="http://www.webserviceX.NET/"');
price := SALES.getStringVal();

dbms_output.put_line(price);