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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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<title>Bind on Load</title>
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<body class="composite">
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<div class="app">
<div class="h3">
<h3><a name="onload">Binding classes at runtime</a></h3>
<p>JiBX also supports limited runtime binding of
class files. This adds runtime overhead as compared to using the binding
compiler directly during the build process, but can be convenient when you're
experimenting with different binding definitions or going through repeated
build-test cycles. At present, runtime binding only works with classes that are
present in the classpath as individual class files (not in jars). It's also not
designed for use in controlled environment such as servlet engines or application
servers.</p>
<p>To use the runtime binding support, you need to execute the
<code>org.jibx.binding.Run</code> class (from <i>/lib/jibx-bind.jar</i>) as the
main class when starting the JVM, in place of whatever main class you'd normally
give as the target. You can pass one or more binding definition files as command
line arguments to this class, along with the name of your application main class
and any command line arguments expected by your program. For example, if you
normally run your application using the command line:</p>
<div id="source"><pre>java -cp . com.myco.package.App arg1 arg2</pre></div>
<p>and your JiBX installation is at <i>/home/dennis/jibx</i>, you'd run the
application using runtime binding as follows (in a single line, shown
split here only for formatting):</p>
<div id="source"><pre>java -cp .:/home/dennis/jibx/lib/jibx-bind.jar org.jibx.binding.Run
-b binding.xml com.myco.package.App arg1 arg2</pre></div>
<p>This tells the JVM to start execution with the <code>org.jibx.binding.Run</code>
class, which will then use its own classloader to load your application classes,
after first modifying the classes read from disk to reflect the <i>binding.xml</i>
binding definition. Once the binding has been processed, JiBX will transfer
control to your application main class (in this case,
<code>com.myco.package.App</code>), passing the command line arguments just as
if your application were executed directly from the command line. Note that
this is the Unix/Linux version of the command line; if you're running
Windows you'll need to reverse the slashs and use ';' instead of ':' as a path
separator character.</p>
</div>
<div class="h3">
<h3><a name="loaddefs">Specifying the binding definitions</a></h3>
<p>The runtime binding code supports several different ways of specifying the
binding definition file or files to be used for your application. The first, and most
direct, approach is to supply one or more <i>-b file-path</i> argument pairs
before your application main class name on the command line. This is the
approach used in the above example, with a single binding definition. To use
multiple binding definitions this way, you need to give the <i>-b</i> argument
before each individual file path.</p>
<p>The second approach is to give the path to a simple text file (not an XML
file) that gives a list of binding definition file paths, with one binding file
per line. This uses the <i>-l</i> argument as a flag, so if the binding file
list is in a file named <i>bindings.txt</i> you could use the following command
line to run your application with the named bindings (on Unix/Linux; if you're
using Windows or MS-DOS you'll need to reverse the slashs and use ';' instead of
':' as a path separator character):</p>
<div id="source"><pre>java -cp .:/home/dennis/jibx/lib/jibx-bind.jar org.jibx.binding.Run
-l bindings.txt com.myco.package.App arg1 arg2</pre></div>
<p>The third way is to give the binding definition(s) as resources loaded from
the classpath, rather than as actual file paths. The advantage of doing things
this way is that the binding definition(s) can be kept with your actual class
files (or with the source files, and copied during build to the same directory
as your class files). This uses the <i>-r</i> argument as a flag for each
binding definition to be loaded as a resource, followed by the actual resource
path. For example, if your binding file is kept with your main class you could
use a command line of this form to run it:</p>
<div id="source"><pre>java -cp .:/home/dennis/jibx/lib/jibx-bind.jar org.jibx.binding.Run
-r /com/myco/package/binding.xml com.myco.package.App arg1 arg2</pre></div>
<p>All three of the above techniques can be used in any combination on the
command line (though it's difficult to imagine actually needing to do so!).</p>
<p>Finally, you can instead use implicit binding definition resources. When
you do this you don't need any command line arguments for JiBX (though you still
need to specify the <code>org.jibx.binding.Run</code> as your main class) except
for the application main class name and any arguments to be passed to that
class:</p>
<div id="source"><pre>java -cp .:/home/dennis/jibx/lib/jibx-bind.jar org.jibx.binding.Run
com.myco.package.App arg1 arg2</pre></div>
<p>In this case JiBX goes through the following sequence of steps to find the
binding definition resource(s) to be applied:</p>
<ol>
<li>Look for a resource named <i>jibx_bindings.txt</i> that gives a list of
bindings (one per line) to be loaded as resources,</li>
<li>If not found, construct a resource path by using the package path for your
application main class and appending <i>_jibx_bindings.txt</i> to the main class
name. For the sample I've been using throughout this description the resulting
path would be <i>/com/myco/package/App_jibx_bindings.txt</i>. If this resource
is found, it's interpreted as a list of bindings (one per line) to be loaded as
resources,</li>
<li>If not found, look for a single binding definition file named
<i>jibx_binding.xml</i> and use that binding,</li>
<li>If not found, construct a resource path by using the package path for your
application main class and appending <i>_jibx_binding.xml</i> to the main class
name, and use that binding. For the sample application this path would
be <i>/com/myco/package/App_jibx_binding.xml</i>.</li>
</ol>
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