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BobHanson merged 2 commits into from
May 10, 2019
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information about differences between SwingJS and Java #97

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5eefbf1
updated Differences.txt explaining how SwingJS is different from Java
May 10, 2019
eec2881
Merge branch 'hanson1' of https://github.com/BobHanson/java2script.gi…
May 10, 2019
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69 changes: 69 additions & 0 deletions sources/net.sf.j2s.java.core/doc/Differences.txt
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Expand Up @@ -66,6 +66,75 @@ they must allow full exit and re-entry of Thread.run(), not the typical while/sl
The key is to create a state-based run() that can be exited and re-entered in JavaScript.


Static fields
-------------

Final static primitive "constant" fields (String, boolean, int, etc.) such as

static final int TEST = 3;
static final String MY_STRING = "my " + "string";

are converted to their primitive form automatically by the Eclipse Java compiler
and do not appear in the JavaScript by their names.

Other static fields are properties of their class and can be used as expected.

Note, however, that SwingJS runs all "Java" code on a page in a common "jvm"
(like older versions of Java). So, like the older Java schema, the JavaScript
equivalents of both applets and applications will share all of their static
fields and methods. This includes java.lang.System.

Basically, SwingJS implementations of Java run in a browser page-based sandbox
instead of an applet-specific one.

In general, this is no problem. But if we are to implement pages with
multiple applets present, we must be sure to only have static references
that are "final" or specifically meant to be shared in a JavaScript
environment only (since they will not be shared in Java).

A simple solution, if static non-constant references are needed, is to attach the
field to Thread.currentThread.threadGroup(), which is an applet-specific reference.
Be sure, if you do this, that you use explicit setters and getters:

For example,

private static String myvar;

...

public void setMyVar(String x) {
ThreadGroup g = Thread.currentThread().threadGroup();
/**
* @j2sNative g._myvar = x;
*
*/
{
myvar = x;
}
}

public String getMyVar() {
ThreadGroup g = Thread.currentThread().threadGroup();
/**
* @j2sNative return g._myvar || null;
*
*/
{
return myvar;
}
}

in Java will get and set x the same in JavaScript and in Java.


A convenient way to do this in general is to supply a singleton class with
explicitly private-only constructors and then refer to it in Java and in JavaScript
instead of using static field, referring to myclass.getIntance().xxx instead of
myclass.xxx in Java (and JavaScript).

This was done extensively in the Jalview project. See jalview.bin.Instance.


Modal Dialogs
-------------

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