plugins/org.eclipse.objectteams.otdt.doc/guide/weavingscheme.html - objectteams/org.eclipse.objectteams - Git at Google

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     <h1>Selecting the target weaving scheme</h1>
 	<p>Running an OT/J application requires a byte code weaver for binding roles into their bases.
 		Since version 2.3, the OTDT ships with two distinct weavers with
 		the following properties:
 	</p>
 	<dl>
 		<dt><strong>OTRE</strong>:</dt>
 		<dd>This is the traditional <strong>load-time</strong>
 			weaver. This weaver has <strong>matured</strong> over many years, but
 			unfortunately, the underlying library <strong>BCEL</strong> is no
 			longer maintained and thus cannot handle class files from recent Java
 			versions. Up-to Java 7 this could be worked around, but Java 8 class
 			files contain several elements that this BCEL-based weaver cannot
 			handle.</dd>
 		<dt><strong>OTDRE</strong>:<dt>
 		<dd>The newer Object Teams Dynamic Runtime Environment has been developed
 			to enable even <strong>runtime weaving</strong>.
 			To make this work despite the fact that the JVM doesn't allow runtime-addition of new
 			fields or methods, this weaver inserts a few general hooks into every weavable class (at load-time).<br/>
 			This weaver is also interesting for weaving into <strong>Java 8</strong> class
 			files, as it is based on the library <strong>ASM</strong>, for which
 			a Java-8-enabled version already exists. It should be noted, however,
 			that the OTDRE is not as mature as the OTRE, both in terms of
 			complete coverage of all combinations of language features as well as
 			in terms of performance measurement (we simply have no large-scale
 			experience with the OTDRE, yet).</dd>
 	</dl>
 	<p>In short: for the time being the traditional OTRE is still the default weaver,
 		recommended for all productive use. For now the new OTDRE is needed only
 		when working with Java 8. It will be further improved in the near future
 		and may fully replace the OTRE in a future version.</p>

 	<h2>Configuration</h2>
 	<p>
 		Initial configuration of the target weaving scheme happens in the
 		<a href="project.html#settings">New Object Teams Project Wizard</a>.
 		The corresponding compiler option is intentionally <em>not</em> yet
 		surfaced in the project preferences, because for productive use
 		it is strongly encouraged to still use the traditional OTRE.
 		For experiments requiring to switch the target weaving scheme, please
 		open the file <code>.settings/org.eclipse.jdt.core.prefs</code>
 		in your project and edit/add the following line:
 	</p>
 		<pre>    org.eclipse.objectteams.otdt.compiler.option.weaving_scheme=OTDRE</pre>
 	<p>
 		The above line enables the new OTDRE, whereas a value of "OTRE" switches back
 		to the traditional OTRE.
 	</p>
 	<p>This configuration is evaluated by the compiler and when launching an OT/J application.
 		Since the <strong>OT/J compiler</strong> performs some preparation for the respective weaver,
 		it has to generate different byte code formats, depending on the targeted weaving scheme.
 		As a consequence, switching from one weaving scheme to the other requires a full
 		recompilation of all OT/J code involved. The runtime will detect if it encounters
 		any class files compiled for an incompatible weaving scheme, signaled by throwing
 		<code>UnsupportedClassVersionError</code>.
 	</p>
 </body>
 </html>
	<html>
	<head>
	<meta name="copyright" content="Copyright Stephan Herrmann 2014. This page is made available under the Eclipse Public License v1.0. For full details see http://www.eclipse.org/legal/epl-v10.html" />
	<link rel=stylesheet type="text/css" href="../css/book.css">
	<link rel=stylesheet type="text/css" href="otguide.css">
	<title>Running Object Teams programs</title>
	<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
	</head>
	<body>
	<h1>Selecting the target weaving scheme</h1>
	<p>Running an OT/J application requires a byte code weaver for binding roles into their bases.
	Since version 2.3, the OTDT ships with two distinct weavers with
	the following properties:
	</p>
	<dl>
	<dt><strong>OTRE</strong>:</dt>
	<dd>This is the traditional <strong>load-time</strong>
	weaver. This weaver has <strong>matured</strong> over many years, but
	unfortunately, the underlying library <strong>BCEL</strong> is no
	longer maintained and thus cannot handle class files from recent Java
	versions. Up-to Java 7 this could be worked around, but Java 8 class
	files contain several elements that this BCEL-based weaver cannot
	handle.</dd>
	<dt><strong>OTDRE</strong>:<dt>
	<dd>The newer Object Teams Dynamic Runtime Environment has been developed
	to enable even <strong>runtime weaving</strong>.
	To make this work despite the fact that the JVM doesn't allow runtime-addition of new
	fields or methods, this weaver inserts a few general hooks into every weavable class (at load-time).<br/>
	This weaver is also interesting for weaving into <strong>Java 8</strong> class
	files, as it is based on the library <strong>ASM</strong>, for which
	a Java-8-enabled version already exists. It should be noted, however,
	that the OTDRE is not as mature as the OTRE, both in terms of
	complete coverage of all combinations of language features as well as
	in terms of performance measurement (we simply have no large-scale
	experience with the OTDRE, yet).</dd>
	</dl>
	<p>In short: for the time being the traditional OTRE is still the default weaver,
	recommended for all productive use. For now the new OTDRE is needed only
	when working with Java 8. It will be further improved in the near future
	and may fully replace the OTRE in a future version.</p>

	<h2>Configuration</h2>
	<p>
	Initial configuration of the target weaving scheme happens in the
	<a href="project.html#settings">New Object Teams Project Wizard</a>.
	The corresponding compiler option is intentionally <em>not</em> yet
	surfaced in the project preferences, because for productive use
	it is strongly encouraged to still use the traditional OTRE.
	For experiments requiring to switch the target weaving scheme, please
	open the file <code>.settings/org.eclipse.jdt.core.prefs</code>
	in your project and edit/add the following line:
	</p>
	<pre> org.eclipse.objectteams.otdt.compiler.option.weaving_scheme=OTDRE</pre>
	<p>
	The above line enables the new OTDRE, whereas a value of "OTRE" switches back
	to the traditional OTRE.
	</p>
	<p>This configuration is evaluated by the compiler and when launching an OT/J application.
	Since the <strong>OT/J compiler</strong> performs some preparation for the respective weaver,
	it has to generate different byte code formats, depending on the targeted weaving scheme.
	As a consequence, switching from one weaving scheme to the other requires a full
	recompilation of all OT/J code involved. The runtime will detect if it encounters
	any class files compiled for an incompatible weaving scheme, signaled by throwing
	<code>UnsupportedClassVersionError</code>.
	</p>
	</body>
	</html>