User Defined Java Expression

Description

This step allows you to enter User Defined Java Expressions as a basis for the calculation of new values.

If you have a Java expression like :

C=A+B

Then you can simply enter the right side of the expression in the dialog:

A+B

  The values are exposed to the expressions as the Java objects they are :

Examples

Add 2 integers, A and B

A+B

Concatenate 2 Strings : firstname and name and put a space in between

firstname+" "+name

or if you really care about performance, this might be faster:

new StringBuffer(firstname).append(" ").append(name).toString()

Set the first character of each word in upper-case: john dow --> John doe

org.pentaho.di.core.Const.initCap(name)

Use native Java and API functions

System.getProperty("os.name")

When the used method throws an exception, you need at minimum PDI 3.2.1, see PDI-2611

Business rules (If / Then / Else)

When a<c then return true else return false

a<c?true:false

This can be more complicated

a<c?(a==1?1:2):3

even with OR and AND and other operators and functions

Using Constants

If you use a constant, you may need to define the right type in some expressions otherwise it could throw:

Incompatible expression types "int" and "java.lang.Long"

To solve this, use:

test == null ? new Long(0) : test

In this case, it checks if test is null and replaces with zero. If it is not null, it will return test.

If the return value is a BigNumber (BigDecimal), you need at minimum PDI 3.2.3, see PDI-2910