DDevelopment & Design

Rapid js + css development

BackgroundLast time I had some work to do in OSGi web module written in Spring MVC. If we have application splitted to well-designed modules, back-end development in this framework run in OSGi environment is quite fast because after some modification w…

Background

Last time I had some work to do in

OSGi web module written in Spring MVC. If we have application splitted to well-designed modules, back-end development in this framework run in OSGi environment is quite fast because after some modification we must update only one bundle (without dependencies). But programming in front-end is much less dynamic than in in modern frameworks like Ruby or Groovy. There is no build-in support to update resources “on the fly” after their modification (or I can’t find it).

There is many plugins to web browser which help you build front-end from scratch in wysiwyg mode. But I can’t find any which could modify resources of already ran application. Also it will be complicated to keep synchronized these modifications with our sources. Therefore I tried to use local links to my project in my application. I put code similar to this below in my page.
After redeploy I found in my Chromium console: Error::Not allowed to load local resource: file:///path/to/my/local/resource.js. After some googling I found solution: adding –allow-file-access-from-files switch to application. Unfortunately it doesn’t work on my Chromium v.18. I also checked other switches: –disable-web-security and –allow-file-access but with no effect. I also tried  LocalLinks plugin but with the same result.

Solution

I found out that the simplest walkaround to this problem is to link my local resources directory in Apache2 web root. So i did this:

After this inclusion of script looks like:

As you can see, it is only difference in port in new location of script. So maybe there is a tool which helps in automatic replace this string?

Tampermonkey script

In

Firefox I’ve been using Greasemonkey plugin which could do automatic code replacement like this on the fly. On Chrome there is Tampermonkey which is a port of Greasemonkey. I wrote script which do this thing for me:

What the script do?

It simply add on end of

script includes from location with replaced string from -> to. It also modify CSS link hrefs using the same approach. Both scripts and links are filtered using blacklist – it is helpful if our application using external resources.

Result

Now I can spend all of my time intended for development only writing a code. After any modification I only refresh a page in browser (I’m using

IntelliJ Idea so instant autosaving is working for me). And what solutions of this problem you are using?

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DDevelopment & Design

Private fields and methods are not private in groovy

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?

  1. Person has private constructor that cannot be accessed
  2. Field "name" is private and cannot be accessed
  3. 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!