Create CLOB from long string using JDBC

I have the following query:

select id from table1 where some_func(?) = 1;

where some_func is a function which allows its arguments to be either VARCHAR2 or CLOB, and ? is some string, which could be really long.

I am trying to use the following code to bind variables:

stmt.setObject(i+1, obj);

but in case of string.length() > 4000 I get the following error:

java.sql.SQLException: ORA-01460: unimplemented or unreasonable conversion requested

for an obvious reason: the VARCHAR2 size limit is 4000 characters.

I then tried to use the following code:

if(obj instanceof String && ((String) obj).length() >= 4000) {
  String s = (String) obj;
  StringReader stringReader = new StringReader(s);
  stmt.setClob(i+1, stringReader, s.length());
} else {
  stmt.setObject(i+1, obj);
}

which gave a different error:

ORA-22922: nonexistent LOB value

The last idea I tried was to create a CLOB using oracle.sql.CLOB.createTemporary() method but it failed because of the following exception:

java.lang.ClassCastException:
  org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper 
  cannot be cast to oracle.jdbc.OracleConnection

What am I doing wrong? Are there any other possibilities to do this?

回答1:

The CLOB could be created in a simple manner:

if(obj instanceof String && ((String) obj).length() >= 4000) {
    Clob clob = connection.createClob();
    clob.setString(1, (String) obj);
    stmt.setClob(i+1, clob);
}

Then these clobs should be freed of course.

回答2:

From my experience setCharacterStream() is much more reliable than setClob()

String s = (String) obj;
StringReader stringReader = new StringReader(s);
stmt.setCharacterStream(i + 1, stringReader , s.length());

and it works without the need to create CLOB objects

回答3:

Have you tried the setCharacterStream method in PreparedStatement?