Thursday, July 23, 2009

Double in ActionScript, Java, and MS SQL

ActionScript 3

• There are three numeric data types in AS3: int, uint, and Number.
• They are not primitives because they can be instantiated using constructors.
• They are not "real" objects because they cannot be null, and they have default values:

myNumber.toString(); // No NPE thrown

• Default value for type Number is NaN (not zero).


• BlazeDS converts AS3 Number type to Java Double.
• NaN is idempotent of conversion:

NaN (Java) -> NaN (AS3) -> NaN (Java)

• null is not! Keep it in mind when you work with BlazeDS:

null (Java) -> 0 (AS3) -> 0.0 (Java)

If Java NaN doesn't have special meaning in your application, you can use it as a "replacement" for null in Java-Flex communication.


• Doesn't support NaN value for numeric columns.
• All NaN values should be replaced by null before saving entity in the database, otherwise you will get exception: The incoming tabular data stream (TDS) remote procedure call (RPC) protocol stream is incorrect. Parameter 24 (""): The supplied value is not a valid instance of data type real. Check the source data for invalid values. An example of an invalid value is data of numeric type with scale greater than precision.

In my current project I'm using all three languages, and I have to convert NaN to null back and forth for every object:

NaN (AS3) <-> NaN (Java) <-> null (Java) <-> null (MS SQL)

So I created small utility class that replaces all JavaBean properties of particular type from one value to another:

ExtendedPropertyUtils.replacePropertyValue(myBean, Double.NaN, null);
ExtendedPropertyUtils.replacePropertyValue(myBean, null, Double.NaN);

Feel free to use it if you have the same problem.


• Feature request to Adobe to introduce nullable Number type.
• Other solutions for similar issues in BlazeDS.

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