BigDecimal and Locale in Grails

byMarcin Przeradzki
October 8, 2012
1 minute read

I was recently puzzled by strange behaviour of Grails application with web service interface. It resulted with rounding currency amount values when I sent request from my browser but it worked perfectly if another client application sent same request. After investigation it turned out that the HTTP requests were not exactly identical. The browser request contained header entry with Polish locale pl-PL for which coma is a decimal separator.

Request
http://localhost:8080/helloworld/amount/displayAmount?amount=12.22

Header
Accept-Language: pl-PL,pl;q=0.8,en-US;q=0.6,en;q=0.4

In order to reproduce this behaviour I created a simple Grails 2.1 HelloWorld app.

AccountController.groovy

package helloworld

class AmountController {

    def displayAmount(PaymentData paymentData) {
        render "Hello, this is your amount: " + paymentData.amount.toString()
    }
}

PaymentData.groovy:

    package helloworld

import grails.validation.Validateable

@Validateable
class PaymentData {
    BigDecimal amount

    static constraints = {
        amount(nullable: false, min: BigDecimal.ZERO, scale: 2)
    }
}

Starting this app we can observe rounding of cents in amount to 00 when sending request with dot in amount (http://localhost:8080/helloworld/amount/displayAmount?amount=12.22)

Whereas for amount with coma it gives a result with valid cent part (http://localhost:8080/helloworld/amount/displayAmount?amount=12,22)

Same behaviour might be expected in case of other locales that use coma as decimal separator, e.g. de_DE. Very not an obvious feature.

Tags:
groovy
java

Marcin Przeradzki

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Private fields and methods are not private in groovy

byTomasz Kalkosiński
July 12, 2012

I used to code in Java before I met groovy. Like most of you, groovy attracted me with many enhancements. This was to my surprise to discover that method visibility in groovy is handled different than Java!

Consider this example:

class Person {
private String name
public  String surname

private Person() {}

private String signature() { "${name?.substring(0, 1)}. $surname" }

public String toString() { "I am $name $surname" }
}

How is this class interpreted with Java?

Person has private constructor that cannot be accessed
Field "name" is private and cannot be accessed
Method signature() is private and cannot be accessed

Let's see how groovy interpretes Person:

public static void main(String[] args) {
def person = new Person()   // constructor is private - compilation error in Java
println(person.toString())

    person.@name = 'Mike'       // access name field directly - compilation error in Java
println(person.toString())

    person.name = 'John'        // there is a setter generated by groovy
println(person.toString())

    person.@surname = 'Foo'     // access surname field directly
println(person.toString())

    person.surname = 'Bar'      // access auto-generated setter
println(person.toString())

println(person.signature()) // call private method - compilation error in Java
}

I was really astonished by its output:

I am null null
I am Mike null
I am John null
I am John Foo
I am John Bar
J. Bar

As you can see, groovy does not follow visibility directives at all! It treats them as non-existing. Code compiles and executes fine. It's contrary to Java. In Java this code has several errors, pointed out in comments.

I've searched a bit on this topic and it seems that this behaviour is known since version 1.1 and there is a bug report on that: http://jira.codehaus.org/browse/GROOVY-1875. It is not resolved even with groovy 2 release. As Tim Yates mentioned in this Stackoverflow question: "It's not clear if it is a bug or by design". Groovy treats visibility keywords as a hint for a programmer.

I need to keep that lesson in mind next time I want to make some field or method private!

DDevelopment & Design