Here is a code example that shows how to implement a Java method for a UDF that maps an SQL INTEGER type parameter to the java.lang.Integer class. This method can handle NULL as an input argument and return NULL as a return value.
public class UDFExample {
public static Integer fact( Integer x ) {
if (x == null)
return null;
int x_t = x.intValue();
if (x_t < 0)
return new Integer(0);
int factResult = 1;
while (x_t > 1) {
factResult = factResult * x_t;
x_t = x_t - 1;
}
return new Integer(factResult);
}
...
}
If the JAR file for the UDFExample class is called UDFExample.jar, the following statement registers UDFExample.jar and the UDFExample class with the database, and creates an SQL identifier called JarUDF for the JAR file:
CALL SQLJ.INSTALL_JAR('CJ!udfsrc/UDFExample.jar','JarUDF',0);
The corresponding CREATE FUNCTION statement to define the UDF looks like this :
CREATE FUNCTION factorial (x INTEGER) RETURNS INTEGER LANGUAGE JAVA NO SQL PARAMETER STYLE JAVA CALLED ON NULL INPUT EXTERNAL NAME 'JarUDF:UDFExample.fact(java.lang.Integer) returns java.lang.Integer';