path: root/docs/devGuideDB/ajdb.xml

<refentry>
  <refnamediv>
    <refname>ajdb</refname>
    <refpurpose>debugger for .class files produced by ajc (early-access)</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>ajdb</command>
      <arg>-classpath <replaceable>path</replaceable></arg>
      <arg>-D<replaceable>name</replaceable>=<replaceable>value</replaceable></arg>
      <arg>-help</arg>
      <arg>-gui</arg>
      <arg>-read <replaceable>file</replaceable></arg>
      <arg>-sourcepath <replaceable>dir</replaceable></arg>
      <arg>
        <group>
  	<arg>-v</arg>
  	<arg>-verbose</arg>
  	<group>
  	  <arg>:class</arg>
  	  <arg>:gc</arg>
  	  <arg>:jni</arg>
  	</group>
        </group>
      </arg>
      <arg>workingdir <replaceable>dir</replaceable></arg>
      <arg>-X<replaceable>option</replaceable></arg>
      <arg><replaceable>class</replaceable></arg>
      <arg><replaceable>arguments</replaceable>
      </arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>The command <command>ajdb</command> is used to debug AspectJ and
      Java programs. In addition to its command line interface,
      <command>adjb</command> also has a standalone, Swing-based GUI
      interface.
    </para>
    <para>
      Note: As of the 1.0.3 release, AspectJ supports JSR-45, which provides
      source-level debugging from many source files per class
      and non-Java source files. 
      JSR-45 is implemented in the J2SE 1.4 debugger support, so 
      you may be able to use your existing debugger to step through
      AspectJ source code if both the source and target VM's are
      running under Java 1.4 or later.  
      However, existing debuggers will display synthetic methods
      in the stack frame.
    </para> <!-- todo find docs on JSR-45 -->

    <simplelist>
      <member>-classpath <emphasis>path</emphasis></member>
      <member>Specify where to find user class files.</member>

      <member>
        -D<replaceable>name</replaceable>=<replaceable>value</replaceable>
      </member>
      <member>Define the property <literal>name</literal> to have the value
        <literal>value</literal>.</member>

      <member>-help</member>
      <member>Print out <command>ajdb</command>'s usage summary.</member>

      <member>-read <emphasis>file</emphasis></member>
      <member>Read this file for initializatoin commands.</member>

      <member>-sourcepath <emphasis>path</emphasis></member>
      <member>Search this directory for source files.</member>

      <member>-gui</member>
      <member></member>

      <member>-v | -verbose [:class | :gc | :jni]</member>
      <member>Print out class loading, garbage collection or dynamic library
        loading information. Defaults to class loading.
      </member>

      <member>-workingdir <emphasis>directory</emphasis></member>
      <member>Set <command>ajdb</command>'s working directory.</member>

      <member>-X<emphasis>option</emphasis></member>
      <member>Pass a non-standard option to the VM</member>
    </simplelist>

    <refsect2>
      <title>Capabilities</title>
      <para>
        The AspectJ debugger implements all of <command>jdb</command>'s
        commands. In addition, the command <literal>workingdir</literal>
        allow you to set the AspectJ working directory, and the breakpoint
        command, <literal>stop on</literal>, has been extended to allow the
        setting of breakpoint on a source file line.
      </para>
    </refsect2>

    <refsect2>
      <title>Examples</title>

      <example id="ajdbcommandline">
        <title>Command line use</title>

        <para>Suppose you want to debug the file spacewar/Ship.java found in
  	the examples directory.  At the command line start up the debugger:

  	<computeroutput>
  	  ajdb
  	</computeroutput>
        </para>


        <para>
  	The debugger will first look for initialization files in your
  	home or current directory called either
  	<filename>ajdb.ini</filename> or <filename>.ajdbrc</filename> and
  	execute the commands contained in them. A useful command to have
  	in this file is the <literal>source-path</literal> command which
  	tells the debugger where to find source files.
        </para>

        <para>For this example, we need to set the source path by:

  	<userinput>
  	  use C:\src
  	</userinput>
        </para>

        <para>To view the file to debug, type <userinput>list
  	  spacewar/Ship.java</userinput> which generates the following
  	output:
  	<programlisting>
  	  209 void fire() {
  	  210     // firing a shot takes energy
  	  211     if (!expendEnergy(BULLET_ENERGY))
  	  212     return;
  	  213
  	  214     //create a bullet object so it doesn't hit the ship that's firing it
  	  215     double xV = getXVel() + BULLET_SPEED * (Math.cos(orientation));
  	  216     double yV = getYVel() + BULLET_SPEED * (Math.sin(orientation));
  	  217
  	  218     // create the actual bullet
  	  219     new Bullet(
  	  220         getGame(),
  	  221         (getXPos() + ((getSize()/2 + 2) * (Math.cos(orientation))) + xV),
  	  222         (getYPos() + ((getSize()/2 + 2) * (Math.sin(orientation))) + yV),
  	  223         xV,
  	  224         yV);
  	  225 }
  	</programlisting>
        </para>
        <para>This is different from <command>jdb</command> because it allows
  	one to view files before the debugger has started.  The
  	<literal>list</literal>  command has the following syntax: </para>

        <simplelist>
  	<member><literal>list</literal></member>
  	<member>list the source containing the location at which we are
  	  currently stopped (can only be used with a running VM)</member>

  	<member><literal>list</literal>
  	  <emphasis><literal>source</literal></emphasis></member>
  	<member>list the entire file source</member>

  	<member><literal>list</literal> source line</member>
  	<member>list source line line of file source</member>

  	<member>
  	  list <emphasis><literal>source start-line
  	      end-line</literal></emphasis>
  	</member>
  	<member>
  	  list the lines from <emphasis>start-line</emphasis> to
  	  <emphasis>end-line</emphasis> of file
  	  <emphasis>source</emphasis>
  	</member>
        </simplelist>

        <para>
  	To set a breakpoint in the method <literal>Ship.fire</literal>, we
  	would could type <userinput>stop in spacewar.Ship.fire</userinput>.
        </para>

        <para>The following message appears notifying the user that the
  	breakpoint has been noted but will not be set until the class has
  	been loaded by the VM: </para>
        <programlisting>
  	Deferring breakpoint spacewar.Ship.fire()
  	It will be set after the class is loaded.
        </programlisting>

        <para>
  	To start Spacewar we type <userinput>run spacewar.Game</userinput>.
        </para>

        <para>
  	When the breakpoint is set, the following message appears:
  	<programlisting>
  	  Set deferred breakpoint spacewar.Ship.fire()
  	</programlisting>
        </para>

        <para> We are notified that we've hit the breakpoint:

  	<programlisting>
  	  Breakpoint hit: thread="Thread-2", spacewar.Ship.fire(), line=174, bci=0 209 void fire() {
  	</programlisting></para>

        <para>
  	The prompt changes to present the thread that has broken, and we
  	can view the current stack with the <literal>where</literal>
  	command, as follows:
  	<programlisting>
  	  Thread-2[1] where
  	  [1] fire (spacewar\Ship.java:209)
  	  [2] run (spacewar\Robot.java:100)
  	  [3] run [class java.lang.Thread]
  	</programlisting>
        </para>

        <para>
  	Next, to stop on line 216 we
  	type <userinput>stop on spacewar/Ship.java:216</userinput>
        </para>

        <para>
  	The following message tells us the breakpoint was set:
  	<programlisting>
  	  Set breakpoint Ship.java:216
  	</programlisting>
        </para>
        <para>
  	To continue execution, we type <userinput>cont</userinput> and the
  	breakpoint at line 216 is hit
  	<programlisting>
  	  Breakpoint hit: thread="Thread-2", spacewar.Ship.fire(), line=216, bci=28
  	  216 double yV = getYVel() + BULLET_SPEED * (Math.sin(orientation));
  	</programlisting></para>

        <para>
  	To view the visible local variables, we type
  	<userinput>locals</userinput> and ajdb responds with:
  	<programlisting>
  	  Local variables
  	  xV = 12.242462584304468
  	</programlisting></para>

        <para>
  	To change the value of the local variable i to 15, we type
  	<userinput>set xV = 16.1</userinput>

  	<programlisting>
  	  Changed 'xV' from '12.242462584304468' to '16.1'
  	</programlisting></para>

        <para>
  	To see our changes we can print the value of <literal>i</literal>
  	by the following:
  	<programlisting>
  	  print xV
  	  Value for printing 'xV' = 12.242462584304468
  	</programlisting></para>

        <para>We can now type exit or quit to leave the debugger, and we
  	receive the following message:

  	<programlisting>
  	  The application has exited.
  	</programlisting></para>
      </example>

    </refsect2>

    <refsect2>
      <title>The AspectJ debugger API</title>

      <para>
        The AspectJ debugger is implemented completely in Java and can be
        called as a Java class.  The only interface that should be
        considered public is the method
        <literal>org.aspectj.tools.debugger.Main.main(String[]
  	args)</literal> where <literal>args</literal> are the standard
        <command>ajc</command> command line arguments. This means that an
        alternative way to run the compiler is </para>

      <cmdsynopsis>
        <command>
  	<literal>java org.aspectj.tools.debugger.Main</literal>
        </command>
        <arg><replaceable>option</replaceable></arg>
        <arg><replaceable>class</replaceable></arg>
        <arg><replaceable>arguments</replaceable></arg>
      </cmdsynopsis>

<!--        <note> -->
        <para>
  	You must additionally include <filename>tools.jar</filename> from
  	your Java developer's kit in your classpath.
        </para>
<!--        </note> -->

    </refsect2>
  </refsect1>
</refentry>

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