updates comments

git-svn-id: http://anonsvn.jboss.org/repos/javassist/trunk@186 30ef5769-5b8d-40dd-aea6-55b5d6557bb3

build.xml

@@ -52,9 +52,29 @@
            deprecation="on"
            optimize="off"
            includes="sample/**"
-           excludes="sample/hotswap/**">
+           excludes="sample/hotswap/**,sample/evolve/sample/**">
             <classpath refid="classpath"/>
     </javac>
+
+    <copy file="sample/vector/Test.j"
+          todir="${build.classes.dir}/sample/vector"/>
+
+    <javac srcdir="${basedir}/sample/evolve"
+           destdir="${build.classes.dir}/sample/evolve/"
+           debug="on"
+           deprecation="on"
+           optimize="off"
+           includes="sample/**">
+            <classpath refid="classpath"/>
+    </javac>
+    <copy todir="${build.classes.dir}/sample/evolve">
+      <fileset dir="sample/evolve"/>
+    </copy>
+    <copy file="${build.classes.dir}/sample/evolve/WebPage.class"
+          tofile="${build.classes.dir}/sample/evolve/WebPage.class.0"/>
+    <copy file="${build.classes.dir}/sample/evolve/sample/evolve/WebPage.class"
+          tofile="${build.classes.dir}/sample/evolve/WebPage.class.1"/>
+
     <javac srcdir="${basedir}/sample/hotswap"
            destdir="${build.classes.dir}"
            debug="on"
@@ -72,11 +92,6 @@
            includes="*">
             <classpath refid="classpath"/>
     </javac>
-    <copy file="sample/vector/Test.j"
-          todir="${build.classes.dir}/sample/vector"/>
-    <copy todir="${build.classes.dir}/sample/evolve">
-      <fileset dir="sample/evolve"/>
-    </copy>
     <echo>To run the sample programs without ant, change the current directory 
 to ${build.classes.dir}.</echo>
   </target>

sample/evolve/DemoServer.java

@@ -19,7 +19,8 @@
  * server overwrites WebPage.class (class file) and calls update()
  * in VersionManager so that WebPage.class is loaded into the JVM
  * again.  The new contents of WebPage.class are copied from
- * either WebPage.class.0 or WebPage.class.1.
+ * either sample/evolve/WebPage.class
+ * or sample/evolve/sample/evolve/WebPage.class.
  */
 public class DemoServer extends Webserver {
 

sample/evolve/WebPage.java

@@ -8,24 +8,10 @@
  * show() on the created object.
  */
 
-// WebPage.class.0
 public class WebPage {
     public void show(OutputStreamWriter out) throws IOException {
 	Calendar c = new GregorianCalendar();
 	out.write(c.getTime().toString());
 	out.write("<P><A HREF=\"demo.html\">Return to the home page.</A>");
     }
 }
-/*
-// WebPage.class.1
-public class WebPage {
-    public void show(OutputStreamWriter out) throws IOException {
-	out.write("<H2>Current Time:</H2>");
-	Calendar c = new GregorianCalendar();
-	out.write("<CENTER><H3><FONT color=\"blue\">");
-	out.write(c.getTime().toString());
-	out.write("</FONT></H3></CENTER><HR>");
-	out.write("<P><A HREF=\"demo.html\">Return to the home page.</A>");
-    }
-}
-*/

sample/evolve/demo.html

@@ -31,7 +31,8 @@ <H3>Source files</H3>
 
 <P>Web server: <A HREF="DemoServer.java"><code>DemoServer.java</code></A>
 
-<P>WebPage: <A HREF="WebPage.java"><code>WebPage.java</code></A>
+<P>WebPage: <A HREF="WebPage.java"><code>WebPage.java</code></A> and
+another  <A HREF="sample/evolve/WebPage.java"><code>WebPage.java</code></A>
 
 <P>Class loader: <A HREF="DemoLoader.java"><code>DemoLoader.java</code></A>,
 	<A HREF="Evolution.java"><code>Evolution.java</code></A>, and

sample/evolve/sample/evolve/WebPage.java

@@ -0,0 +1,20 @@
+package sample.evolve;
+
+import java.io.*;
+import java.util.*;
+
+/**
+ * Updatable class.  DemoServer instantiates this class and calls
+ * show() on the created object.
+ */
+
+public class WebPage {
+    public void show(OutputStreamWriter out) throws IOException {
+	out.write("<H2>Current Time:</H2>");
+	Calendar c = new GregorianCalendar();
+	out.write("<CENTER><H3><FONT color=\"blue\">");
+	out.write(c.getTime().toString());
+	out.write("</FONT></H3></CENTER><HR>");
+	out.write("<P><A HREF=\"demo.html\">Return to the home page.</A>");
+    }
+}

sample/evolve/start.html

@@ -1,14 +1,14 @@
 <h2>Instructions</h2>
 
 <p>1. Compile <code>sample/evolve/*.java</code>.
-	Copy <code>WebPage.class</code> to <code>WebPage.class.0</code>.
 
-<p>2. Edit <code>Webpage.java</code>, compile it,
-	and copy <code>WebPage.class</code> to <code>WebPage.class.1</code>.
-<br><code>WebPage.class.0</code> and
-	<code>WebPage.class.1</code> are used
-	for changing the contents of <code>WebPage.class</code> during
-	the demo.
+<p>2. change the current directory to <code>sample/evolve</code><br>
+and compile there <code>sample/evolve/WebPage.java</code><br>
+(i.e. compile <code>sample/evolve/sample/evolve/WebPage.java</code>).
+
+<p>The two versions of <code>WebPage.class</code> are used<br>
+for changing the contents of <code>WebPage.class</code> during
+the demo.
 
 <p>3. Run the server on the local host (where your web browser is running):
 

tutorial/tutorial.html

@@ -584,7 +584,8 @@ <h3>3.2 Class loading in Java</h3>
 version of that class during runtime.  Thus, you cannot alter
 the definition of a class after the JVM loads it.
 However, the JPDA (Java Platform Debugger Architecture) provides
-limited ability for reloading a class.  See "HotSwap" of JPDA for details.
+limited ability for reloading a class.
+See <a href="#hotswap">Section 3.6</a>.
 </ul>
 
 <p>If the same class file is loaded by two distinct class loaders,
@@ -999,6 +1000,24 @@ <h3>3.5 Modifying a system class</h3>
 
 <p><br>
 
+<a name="hotswap">
+<h3>3.6 Reloading a class at runtime</h3></a>
+
+<p>If the JVM is launched with the JPDA (Java Platform Debugger
+Architecture) enabled, a class is dynamically reloadable.  After the
+JVM loads a class, the old version of the class definition can be
+unloaded and a new one can be reloaded again.  That is, the definition
+of that class can be dynamically modified during runtime.  However,
+the new class definition must be somewhat compatible to the old one.
+<em>The JVM does not allow schema changes between the two versions.</em>
+They have the same set of methods and fields.
+
+<p>Javassist provides a convenient class for reloading a class at runtime.
+For more information, see the API documentation of
+<code>javassist.tool.HotSwapper</code>.
+
+<p><br>
+
 <a href="tutorial2.html">Next page</a>
 
 <hr>