When i try execute the following code, which should just print a slashy string in groovy console version 1.7.4 i get a compilation error:
println /slashy string/
if i change this to:
def s = /slashy string/;
println s
everything is fine and the expected string is printed.
Any ideas what i am doing wrong?
The final gotcha (on the linked doc) says, a slashy string cannot be used with assert, because of a grammar limitation. Since println is also a part of the grammar (afaik, since its not a classical java function), I would guess this applies here, too.
It says to use braces around it:
println (/slashy string/)
This worked fine in my groovy shell.
Related
I found this in Groovy Syntax documentation at 4.6.1. Special cases:
As slashy strings were mostly designed to make regexp easier so a few
things that are errors in GStrings like $() or $5 will work with
slashy strings.
What $() syntax means? give some usage examples please
I also found it at Define the Contract Locally in the Repository of the Fraud Detection Service:
body([ // (4)
"client.id": $(regex('[0-9]{10}')),
loanAmount : 99999
])
but I don't understand what $() means when used with regex('[0-9]{10}').
It means nothing (or what you make of it). There are two places, you
are addressing, but they have nothing to do with each other.
The docs just mention this as "you can use slashy strings to write
things, that would give you an error with a GString" - the same is true
for just using '-Strings.
E.g.
"hello $()"
Gives this error:
unknown recognition error type: groovyjarjarantlr4.v4.runtime.LexerNoViableAltException
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
/tmp/x.groovy: 1: token recognition error at: '(' # line 1, column 9.
"hello $()"
The parser either wants a { or any char, that is a valid first char
for a variable (neither ( nor 5 is).
The other place you encountered $() (in Spring cloud contract), this
is just a function with the name $.
Form the docs 8. Contract DSL:
You can set the properties inside the body either with the value method or, if you use the Groovy map notation, with $()
So this is just a function, with a very short name.
E.g. you can try this yourself:
void $(x) { println x }
$("Hello")
I am fairly new to java programming and I am trying to learn groovy right now.
I am getting this weird error when I am entering a simple line of code of hello world.
I am buffered. I believe I have set the environment variables correctly
You have the method name wrong
It's println not printIn
If you look at the exception, it tells you what's wrong, and a list of possible solutions
I think that you are using the wrong letter:
println "hello"
with "L" lowercase
I try to create a small DSL, but i'm struggling with even simple stuff.
The following script gives me an error.
def DEMON(String input) {
['a': input]
}
DEMON 'Hello thingy' a
For some reasons, the parentheses around the parameters are not optional and i get an error.
This script runs fine:
def dEMON(String input) {
['a': input]
}
dEMON 'Hello thingy' a
Note: the only difference is the lowercase first char.
So what is going on here? Why are the scripts interpreted (compiled?) different? Is there some kind of method/class naming schemes i have to follow?
Update: The error message. I guess a Syntax error:
unexpected token: Hello thingy # line 4, column 7.
The groovy syntax is sometime complex, and the compiler use some rules to choose what it must do. One of this rule is simple : If a word starts with an uppercase, it's probably a class.
for example, f String is a syntax valid in groovy, and the compiler converts it to f(String.class).
you can use parenthesis to help groovy understand your DEMON is not a class but a method, DEMON('Hello thingy', a)
I need to obtain JAVA_HOME property from Groovy (Gradle), does anyone know how to achieve this? Only way I can think of is somehow executing this from cmd line via Exec.
Thanks
(I'm running Windows btw :))
System.properties.find { it.key == "java.home" }
A gotcha that bit me. Remember to use curly braces inside a gstring.
println "inside a gstring, java.home=$System.properties.'java.home' will be problematic
//dumps all system properties
but
println "inside a gstring, java.home=${System.properties.'java.home'} will be fine
Result: inside a gstring, java.home=C:\FAST\JDK64\1.7.0.79\jre will be fine
I am trying to test the overridden toString() in groovy (I know it is trivial but that is what you get after reading kent beck's TDD book).
I assertSame on the expected string and the actual
Here is the code block:
#Test void testToString(){
def study = new Study(identifier:"default-study", OID:"S_DEFAULTS1", name:"Default Study")
def expected = "org.foo.oc.model.bar(OID:S_DEFAULTS1, name:Default Study, identifier:default-study)"
assertSame "Should be equal", expected, study.toString()
}
Here is the stack trace for the failed test:
junit.framework.AssertionFailedError: Should be equal expected same:org.foo.oc.model.bar(OID:S_DEFAULTS1, name:Default Study, identifier:default-study) was not:org.foo.oc.model.bar(OID:S_DEFAULTS1, name:Default Study, identifier:default-study)
at junit.framework.Assert.fail(Assert.java:47)
at junit.framework.Assert.failNotSame(Assert.java:273)
at junit.framework.Assert.assertSame(Assert.java:236)
Just to add that assertEquals works well with the same parameters.
I know it is no biggie but I want to understand why it fails.
Thanks
Why aren't you using assertEquals which uses .equals()? assertSame compares object references (== operator). Even though the strings are the same, they are two different objects, hence the assertion is failing.
UPDATE: This is a very common mistake in Java: String.equals() and == operator work differently. This has been discussed several times:
How do I compare strings in Java?
Java String.equals versus ==
Difference between Equals/equals and == operator?
I know you are using Groovy which does not suffer this problem, but JUnit is written in Java and behaves according to the rules above.
UPDATE: actually, your string are different:
org.foo.oc.model.bar(OID:S_DEFAULTS1, name:Default Study, identifier:default-study)
org.foo.oc.model.bar(OID:S_DEFAULTS1, name:Default Study, identifier:default-study)
Your original uses lowercase d in "default Study" but your expected string does not.
EDIT: when comparing strings you should always use equals() rather than comparing references. Two strings that pass the equals() test may or may not also be the same object.
BTW, in Groovy == is the same as equals().