| 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> |
|---|
| 2 | |
|---|
| 3 | <html> |
|---|
| 4 | |
|---|
| 5 | <head> |
|---|
| 6 | <title>J User's Guide - Extending J</title> |
|---|
| 7 | <LINK REL="stylesheet" HREF="j.css" TYPE="text/css"> |
|---|
| 8 | </head> |
|---|
| 9 | |
|---|
| 10 | <body> |
|---|
| 11 | |
|---|
| 12 | <a href="contents.html">Top</a> |
|---|
| 13 | |
|---|
| 14 | <hr> |
|---|
| 15 | |
|---|
| 16 | <h1>Extending J</h1> |
|---|
| 17 | |
|---|
| 18 | <hr> |
|---|
| 19 | |
|---|
| 20 | <p> |
|---|
| 21 | |
|---|
| 22 | J provides a mechanism to support arbitrary user extensions. You can add a |
|---|
| 23 | line like this to your <a href="preferences.html">preferences</a> file: |
|---|
| 24 | <pre> |
|---|
| 25 | extension=SampleExtension |
|---|
| 26 | </pre> |
|---|
| 27 | where <code>SampleExtension</code> is the name of a class you've written, |
|---|
| 28 | compiled, and placed in <code>~/.j</code> or <code>C:\.j</code>. The class must |
|---|
| 29 | provide the method <code>public void run( )</code>, and the class itself must |
|---|
| 30 | be declared <code>public</code>. If these conditions are met, your class |
|---|
| 31 | will be loaded when the editor starts up and the <code>run</code> method will |
|---|
| 32 | be invoked. |
|---|
| 33 | <p> |
|---|
| 34 | One problem you're likely to run into with this is that any editor method or |
|---|
| 35 | member variable referenced in your extension class must be explicitly declared |
|---|
| 36 | <code>public</code> in the editor source; otherwise you'll get an |
|---|
| 37 | <code>IllegalAccessException</code>. The short-term solution to this is to |
|---|
| 38 | hack the editor source and make the thing <code>public</code>; the long-term |
|---|
| 39 | solution is to <a href="mailto:peter@armedbear.org">tell me about it</a> so |
|---|
| 40 | that I can make sure it stays <code>public</code> in the future. |
|---|
| 41 | <p> |
|---|
| 42 | The easiest way to write your extension class is to develop and debug it in the |
|---|
| 43 | j's top-level <code>src</code> directory; the loader will pick it up from |
|---|
| 44 | there, so you don't have to copy it into <code>~/.j</code> every time you |
|---|
| 45 | compile it. When you're done you should move it into <code>~/.j</code> and |
|---|
| 46 | delete any extraneous copies. |
|---|
| 47 | <p> |
|---|
| 48 | Strictly speaking, your extension class does not have to live in |
|---|
| 49 | <code>~/.j</code> or <code>C:\.j</code>. You can also specify the fully |
|---|
| 50 | qualified pathname of your extension's <code>.class</code> file in your |
|---|
| 51 | preferences file, like this: |
|---|
| 52 | <pre> |
|---|
| 53 | extension=/home/peter/SampleExtension.class |
|---|
| 54 | </pre> |
|---|
| 55 | In this case you must specifically append the <code>.class</code> extension, as |
|---|
| 56 | shown in the example. |
|---|
| 57 | |
|---|
| 58 | </body> |
|---|
| 59 | |
|---|
| 60 | </html> |
|---|
