variable initialization bug?

[2001 JI Open Discussion]

By: Ryan Johnson - delscovich

variable initialization bug?

2002-06-26 15:12

Hi all,

 

I tried to optimize formatting of date fields by creating a variable containing a java.text.SimpleDateFormat based on a format string passed in as a parameter. That way, I wouldn't have to create a new one every time I formatted a date:

 

<variable name="dateFormatter" class="java.lang.Object" resetType="Report">

<initialValueExpression>

new java.text.SimpleDateFormat($P{dateFormat})

</initialValueExpression>

</variable>

 

My plan was to use the formatter in other variables to format them:

 

<variable name="formattedDate" class="java.lang.String" resetType="Report">

<initialValueExpression>

($P{reportDate} == null)? "No Date" : ((java.text.Format) $V{dateFormatter}).format($P{reportDate})

</initialValueExpression>

</variable>

 

This works great for parameters, but returns null for fields. Am I doing something wrong? Or does 'dateFormatter' not get initialized until after the fields are evaluated?

 

 

 

 

By: Ryan Johnson - delscovich

RE: variable initialization bug?

2002-06-26 15:36

BTW,

 

If I change the formatter variable to this:

 

<variable name="dateFormatter" class="java.lang.Object" resetType="Report">

<variableExpression>

new java.text.SimpleDateFormat($P{dateFormat})

</variableExpression>

</variable>

 

The fields start working and the params stop working. Very strange.

 

 

By: Teodor Danciu - teodord

RE: variable initialization bug?

2002-06-27 00:47

 

Hi,

 

Before talking about those variables,

I have a question:

Have you tried the "pattern" attribute available

in the "textField" element?

It allows you to format the content of your text field

when its values is a number or a date.

 

Anyway, lets get to your variables.

The problem with your formatting variable is that it

gets initialized with the SimpleDateFormat

object , but given the fact that

its "variableExpression" is not specified,

it is evaluated to null every time the engine

evaluates the variables (that is with every row in the

data source).

This is because the default calculation for a

variable is "Nothing" and this means that the

engine will use the "variableExpression" when

evaluating the variable.

You saw that when you switched

the "initialValueExpression" with

the "variableExpression".

 

The solution is to stick to

the "initialValueExpression" and choose

calculation="System" for your variable.

That will signal to the engine that for this variable

it should not perform any automatic evaluation

because the value of the variable should either

remain the same throughout the report, either it is

managed using scriptlets.

 

Attention:

Variables are evaluated in the order in which they

were declared in the report. So your formatting

variable should be declared first, for maximum

usability.

 

Thank you,

Teodor

 

 

 

By: Ryan Johnson - delscovich

RE: RE: variable initialization bug?

2002-06-27 08:49

Thanks!

 

The pattern attribute works fine when I know the pattern at design time, and your suggestion works perfectly for using the parameter to create a format variable.