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 = DevFaqModuleDependencies
 :jbake-type: wiki
 :jbake-tags: wiki, devfaq, needsreview
 :jbake-status: published
 :keywords: Apache NetBeans wiki DevFaqModuleDependencies
 :description: Apache NetBeans wiki DevFaqModuleDependencies
 :toc: left
 :toc-title:
 :syntax: true

 === How do module dependencies and class loading work?

 The nuts and bolts of module dependencies are as follows:

 * Modules can load classes from modules they depend on.   They have to declare a dependency on them.
 * NetBeans does not care about things like the `CLASSPATH` environment variable - it knows how to find modules in an installation of NetBeans, and enforces dependencies between them.

 What this means is that if

 * Module B tries to use a class from module A, but module B does not _explicitly state_ that it depends on A, or...
 * Module B tries to use a class from module A, and it _does_ declare a dependency on Module A, _but_ the package that class is in is not in the list of packages A says other modules can touch...

 then a `NoClassDefFoundException` will be thrown at runtime.
 (If you even get that far - the module build harness will refuse to even compile module B in such cases.)

 An exception to the second item is that if Module B declares an _implementation dependency_ on module A, then it will have access to the full set of classes.
 Normally you should not need to do this,
 and anyway it will then be hard to upgrade B independently of A.

 Modules can also load classes from libraries - JAR files that are packaged with the module (see link:DevFaqHowPackageLibraries.asciidoc[DevFaqHowPackageLibraries]).
 Some points to remember about libraries:

 * They are delivered to the user inside the NBM file if they are not part of a full application based on NetBeans.
 * When unpacked, the module will end up in `$SOMECLUSTER/modules/` and any libraries will end up in `$SOMECLUSTER/modules/ext/`.
 * The module will use the library by having an entry in its manifest `Class-Path: ext/someLibrary.jar` the same way any JAR would.

 If you are using the IDE's module development support,
 you will manage module dependencies in the properties dialog for your module
 (or the *Libraries* node in the *Projects* tab).
 This just modifies `yourmodule/nbproject/project.xml`.
 The data saved there is then used to generate the appropriate manifest entries for you.

 If you are writing a module that will use some third party libraries,
 you probably want to read link:DevFaqWrapperModules.asciidoc[DevFaqWrapperModules] and also link:DevFaqWhenUseWrapperModule.asciidoc[DevFaqWhenUseWrapperModule].

 For more details, see the link:http://bits.netbeans.org/dev/javadoc/org-openide-modules/org/openide/modules/doc-files/classpath.html[reference documentation about classloading in NetBeans].

 <hr/>

 Applies to: NetBeans 6.8 and above

 === Apache Migration Information

 The content in this page was kindly donated by Oracle Corp. to the
 Apache Software Foundation.

 This page was exported from link:http://wiki.netbeans.org/DevFaqModuleDependencies[http://wiki.netbeans.org/DevFaqModuleDependencies] ,
 that was last modified by NetBeans user Rmichalsky
 on 2009-12-02T13:40:56Z.


 *NOTE:* This document was automatically converted to the AsciiDoc format on 2018-02-07, and needs to be reviewed.
	//
	// Licensed to the Apache Software Foundation (ASF) under one
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	// to you under the Apache License, Version 2.0 (the
	// "License"); you may not use this file except in compliance
	// with the License. You may obtain a copy of the License at
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	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing,
	// software distributed under the License is distributed on an
	// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	// KIND, either express or implied. See the License for the
	// specific language governing permissions and limitations
	// under the License.
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	= DevFaqModuleDependencies
	:jbake-type: wiki
	:jbake-tags: wiki, devfaq, needsreview
	:jbake-status: published
	:keywords: Apache NetBeans wiki DevFaqModuleDependencies
	:description: Apache NetBeans wiki DevFaqModuleDependencies
	:toc: left
	:toc-title:
	:syntax: true

	=== How do module dependencies and class loading work?

	The nuts and bolts of module dependencies are as follows:

	* Modules can load classes from modules they depend on. They have to declare a dependency on them.
	* NetBeans does not care about things like the `CLASSPATH` environment variable - it knows how to find modules in an installation of NetBeans, and enforces dependencies between them.

	What this means is that if

	* Module B tries to use a class from module A, but module B does not _explicitly state_ that it depends on A, or...
	* Module B tries to use a class from module A, and it _does_ declare a dependency on Module A, _but_ the package that class is in is not in the list of packages A says other modules can touch...

	then a `NoClassDefFoundException` will be thrown at runtime.
	(If you even get that far - the module build harness will refuse to even compile module B in such cases.)

	An exception to the second item is that if Module B declares an _implementation dependency_ on module A, then it will have access to the full set of classes.
	Normally you should not need to do this,
	and anyway it will then be hard to upgrade B independently of A.

	Modules can also load classes from libraries - JAR files that are packaged with the module (see link:DevFaqHowPackageLibraries.asciidoc[DevFaqHowPackageLibraries]).
	Some points to remember about libraries:

	* They are delivered to the user inside the NBM file if they are not part of a full application based on NetBeans.
	* When unpacked, the module will end up in `$SOMECLUSTER/modules/` and any libraries will end up in `$SOMECLUSTER/modules/ext/`.
	* The module will use the library by having an entry in its manifest `Class-Path: ext/someLibrary.jar` the same way any JAR would.

	If you are using the IDE's module development support,
	you will manage module dependencies in the properties dialog for your module
	(or the Libraries node in the Projects tab).
	This just modifies `yourmodule/nbproject/project.xml`.
	The data saved there is then used to generate the appropriate manifest entries for you.

	If you are writing a module that will use some third party libraries,
	you probably want to read link:DevFaqWrapperModules.asciidoc[DevFaqWrapperModules] and also link:DevFaqWhenUseWrapperModule.asciidoc[DevFaqWhenUseWrapperModule].

	For more details, see the link:http://bits.netbeans.org/dev/javadoc/org-openide-modules/org/openide/modules/doc-files/classpath.html[reference documentation about classloading in NetBeans].

	<hr/>

	Applies to: NetBeans 6.8 and above

	=== Apache Migration Information

	The content in this page was kindly donated by Oracle Corp. to the
	Apache Software Foundation.

	This page was exported from link:http://wiki.netbeans.org/DevFaqModuleDependencies[http://wiki.netbeans.org/DevFaqModuleDependencies] ,
	that was last modified by NetBeans user Rmichalsky
	on 2009-12-02T13:40:56Z.


	NOTE: This document was automatically converted to the AsciiDoc format on 2018-02-07, and needs to be reviewed.