Author: kohsuke
Date: Mon Aug 15 22:07:15 2005
New Revision: 232938
URL: http://svn.apache.org/viewcvs?rev=232938&view=rev
Log:
expanded the classloader section
Modified:
jakarta/commons/sandbox/javaflow/trunk/xdocs/tutorial.xml
Modified: jakarta/commons/sandbox/javaflow/trunk/xdocs/tutorial.xml
URL:
http://svn.apache.org/viewcvs/jakarta/commons/sandbox/javaflow/trunk/xdocs/tutorial.xml?rev=232938&r1=232937&r2=232938&view=diff
==============================================================================
--- jakarta/commons/sandbox/javaflow/trunk/xdocs/tutorial.xml (original)
+++ jakarta/commons/sandbox/javaflow/trunk/xdocs/tutorial.xml Mon Aug 15
22:07:15 2005
@@ -14,7 +14,7 @@
First, consider the following program:
</p>
<source>
-class MyRunnable implements Runnable, Continuable {
+class MyRunnable implements Runnable {
public void run() {
System.out.println("started!");
for( int i=0; i<10; i++ )
@@ -85,16 +85,14 @@
</section>
<section name="Preparation">
<p>
- For these to work, javaflow needs to enhance the byte
code of your program that runs inside the continuation-enabled environment. The
<tt>Continuable</tt> interface is used to mark those classes. Javaflow uses
this marker interface to decide which class to instrument.
(<tt>Continuable</tt> classes can be still executed normally outside the
environment, but it runs somewhat slower.)
- </p>
- <p>
- When the <tt>Continuation.suspend</tt> runs, all the
methods on the stack frames need to be on classes marked as
<tt>Continuable</tt>.
+ For these to work, javaflow needs to enhance the byte
code of your program that runs inside the continuation-enabled environment.
When the <tt>Continuation.suspend</tt> runs, all the methods on the stack
frames (up to <tt>Continuation.startWith</tt> or
<tt>Continuation.continueWith</tt>) need to be enhanced.
</p>
<p>
There are two ways to instrument bytecode. One way is
to do it statically. This means using the following Ant task as a part of your
build process:
</p>
<source><![CDATA[
-<taskdef name="javaflow"
classname="org.apache.commons.javaflow.ant.AntRewriteTask">
+<taskdef name="javaflow"
+ classname="org.apache.commons.javaflow.ant.AntRewriteTask">
<classpath>
...
</classpath>
@@ -105,11 +103,30 @@
</rewriteTask>
]]></source>
<p>
- This scans the build/classes directory for any class
file that needs instrumentation. For more details about this Ant task, see <a
href="javascript:window.alert('todo')">this document</a>.
+ This scans the build/classes directory and enhance all
the classes. For more details about this Ant task, see <a
href="javascript:window.alert('todo')">this document</a>. Since the byte-code
enhancement increases the class file size, you might want to consider avoiding
unnecessary class files enhancement.
</p>
<p>
- Alternatively, you can do this dynamically at runtime,
by using javaflow's custom class loader. *TODO*TODO*TODO*
+ Alternatively, you can do this dynamically at runtime,
by using javaflow's <tt>ContinuationClassLoader</tt>. This works like a
<tt>URLClassLoader</tt> with the byte-code enhancement. To use this, you need
to separate your application into two parts; one for classes that don't need
enhancement, and the other that do need enhancement. You can then configure the
first portion to be loaded by the system class loader, and then load the second
portion by a <tt>ContinuationClassLoader</tt>. The following code shows how to
do this:
+ </p>
+<source>
+// this class lives in the system class loader
+public class Foo {
+ public static void main(String[] args) {
+ ClassLoader cl = new ContinuationClassLoader(
+ new URL[]{new URL("latter.jar")},
+ Foo.class.getClassLoader()); // parent class loader
+ cl.loadClass(...);
+ }
+}
+</source>
+
+ <!-- One is <tt>ContinuationClassLoader</tt>, which
locates class files by using its ancestor class loaders, and then loads it
after the enhancement. This is convenient for a simple Java SE application,
where all the application classes are available in the default class loader.
The following code illustrates how to set up a <tt>ContinuationClassLoader</tt>.
</p>
+<source>
+</source>
+ <p>
+ The downside of this approach is that this model goes
against the default class loader delegation model, and therefore classes of the
same name are always available from two ClassLoaders. You need to carefully
think what class is loaded from where, or you'll get mysterious
<tt>ClassCastException</tt>, or some strange behavior when you suspend, etc.
+ </p-->
</section>
</body>
</document>
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