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Groovy Expressions Implicit Type Conversions

This allows JDeveloper programmers to skip many trivial Java programming tasks with a shorthand Groovy expression

Under JDeveloper 11g, ADF Business Components introduced the support for Groovy expressions. Among other benefits this allows JDeveloper programmers to skip many trivial Java programming tasks with a shorthand Groovy expression. Grant Ronald's Introduction to Groovy Support in JDeveloper and Oracle ADF 11g provides a good compliment to the Fusion Guide on Groovy expressions.

The Groovy support includes the ability to reference attributes of Entity Objects and View Objects. For instance you may create a transient attribute TotalCost in an InvoiceLines Entity Object based on the Groovy expression "Cost * Quantity" referencing the same named Entity Object attributes:


As you become more familiar with the use of Groovy expressions you'll realize you can also call the functions of the underlying attribute type. For instance a String attribute FullName would support the Groovy expression "FullName.toLowerCase()".

However there is a catch. When calling functions of a specific attribute, say calling the oracle.jbo.domain.Number add() function on the Quantity Number attribute, at runtime you might discover a runtime error such as:

(oracle.jbo.JboException) JBO-29000: Unexpected exception caught: groovy.lang.MissingMethodException, msg=No signature of method: java.lang.Long.add() is applicable for argument types: (java.lang.Integer) values: [1]

This comes as a surprise as the Fusion Guide tells us the Number attribute type is backed by the oracle.jbo.domain.Number class supplied by Oracle.

What's happening is that the Groovy expression evaluator is undertaking some implicit datatype conversions/casts on our behalf with the underlying attributes. In order to make this easier to understand I've documented the type conversions for you. The following table gives you the Type Name as selected in the EO/VO attribute editor, the Java Type you'll see in the resulting EntityImpl and ViewRowImpl classes, and then the Groovy Type they'll be cast to during a Groovy expression evaluation.

Read the original blog entry...

More Stories By Chris Muir

Chris Muir, an Oracle ACE Director, senior developer and trainer, and frequent blogger at http://one-size-doesnt-fit-all.blogspot.com, has been hacking away as an Oracle consultant with Australia's SAGE Computing Services for too many years. Taking a pragmatic approach to all things Oracle, Chris has more recently earned battle scars with JDeveloper, Apex, OID and web services, and has some very old war-wounds from a dark and dim past with Forms, Reports and even Designer 100% generation. He is a frequent presenter and contributor to the local Australian Oracle User Group scene, as well as a contributor to international user group magazines such as the IOUG and UKOUG.

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