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Posted to dev@maven.apache.org by tr...@apache.org on 2005/08/09 02:20:34 UTC
svn commit: r230934 -
/maven/components/trunk/maven-site/src/site/xdoc/dependency-mechanism.xml
Author: trygvis
Date: Mon Aug 8 17:20:31 2005
New Revision: 230934
URL: http://svn.apache.org/viewcvs?rev=230934&view=rev
Log:
o Adding a piece about dependency management.
Modified:
maven/components/trunk/maven-site/src/site/xdoc/dependency-mechanism.xml
Modified: maven/components/trunk/maven-site/src/site/xdoc/dependency-mechanism.xml
URL: http://svn.apache.org/viewcvs/maven/components/trunk/maven-site/src/site/xdoc/dependency-mechanism.xml?rev=230934&r1=230933&r2=230934&view=diff
==============================================================================
--- maven/components/trunk/maven-site/src/site/xdoc/dependency-mechanism.xml (original)
+++ maven/components/trunk/maven-site/src/site/xdoc/dependency-mechanism.xml Mon Aug 8 17:20:31 2005
@@ -2,16 +2,29 @@
<properties>
<title>Dependency Mechanism</title>
<author email="brett@apache.org">Brett Porter</author>
+ <author email="trygvis@apache.org">Trygve Laugstol </author>
</properties>
<body>
<section name="Dependency Mechanism">
<p>
There are many aspects to working with dependencies in Maven. While it is not the sole focus of Maven, it
- does comprise a large and important part of the system.
+ does comprise a large and important part of the system. Learn more about:
+ <ul>
+ <li>
+ <a href="#transitive_dependencies">Transitive Dependencies</a>
+ </li>
+ <li>
+ <a href="#dependency_scope">Dependency Scope</a>
+ </li>
+ <li>
+ <a href="#dependency_management">Dependency Management</a>
+ </li>
+ </ul>
</p>
<p>
- This document is currently in the process of being written, so not all facets are covered.
+ <i>This document is currently in the process of being written, so not all facets are covered.</i>
</p>
+ <a name="transitive_dependencies"/>
<subsection name="Transitive Dependencies">
<p>
Transitive dependencies are a new feature in Maven 2.0. This allows you to avoid needing to discover and
@@ -33,12 +46,14 @@
</p>
<ul>
<li>
- <i>Dependency mediation</i>- this determines what version of a dependency will be used when multiple
+ <i>Dependency mediation</i>
+ - this determines what version of a dependency will be used when multiple
different ones are encountered. Currently, Maven 2.0 only supports using the "nearest definition" - so
you can always guarantee a version by declaring it explicitly in the project's POM.
</li>
<li>
- <i>Dependency scope</i>- this allows you to only include dependencies appropriate for the current stage
+ <i>Dependency scope</i>
+ - this allows you to only include dependencies appropriate for the current stage
of the build. This is described in more detail below.
</li>
</ul>
@@ -49,6 +64,7 @@
</p>
</subsection>
<subsection name="Dependency Scope">
+ <a name="dependency_scope"/>
<p>
Dependency scope is used to limit the transitivity of a depedency, and also to affect the classpath used for
various build tasks.
@@ -58,20 +74,24 @@
</p>
<ul>
<li>
- <b>compile</b>- this is the default scope, used if none is specified. Compile dependencies are available
+ <b>compile</b>
+ - this is the default scope, used if none is specified. Compile dependencies are available
in all classpaths.
</li>
<li>
- <b>provided</b>- this is much like compile, but indicates you expect the JDK or a container to provide it.
+ <b>provided</b>
+ - this is much like compile, but indicates you expect the JDK or a container to provide it.
It is only available on the compilation classpath, and is not transitive.
</li>
<li>
- <b>runtime</b>- this scope indicates that the dependency is not required for compilation, but is for
+ <b>runtime</b>
+ - this scope indicates that the dependency is not required for compilation, but is for
execution.
It is in the runtime and test classpaths, but not the compile classpath.
</li>
<li>
- <b>test</b>- this scope indicates that the dependency is not required for normal use of the application, and
+ <b>test</b>
+ - this scope indicates that the dependency is not required for normal use of the application, and
is only available for the test compilation and execution phases.
</li>
</ul>
@@ -119,13 +139,140 @@
</tr>
</table>
<p>
- <b>(*) Note:</b>it is intended that this should be runtime instead, so that all compile dependencies must
+ <b>(*) Note:</b>
+ it is intended that this should be runtime instead, so that all compile dependencies must
be explicitly listed - however, there is the case where the library you depend on extends a class from another
library, forcing you to have available at compile time. For this reason, compile time dependencies remain
as compile scope even when they are transitive.
</p>
</subsection>
+ <a name="dependency_management"/>
+ <subsection name="Dependency Management">
+ <p>
+ The dependency management section is a mechanism for centralizing dependency information. When you have
+ a set of projects that inherits a common parent it's possible to put all information about the dependency
+ in the common POM and have simpler references to the artifacts in the child POMs. The mechanism is best
+ illustrated through some examples. Given these two POMs which extend the same parent:
+ </p>
+ <p>
+ Project A:
+ <source><![CDATA[
+<project>
+ ...
+ <dependencies>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-a</artifactId>
+ <version>1.0</version>
+ <exclusions>
+ <exclusion>
+ <groupId>group-c</groupId>
+ <artifactId>excluded-artifact</artifactId>
+ </exclusion>
+ </exclusions>
+ </dependency>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-b</artifactId>
+ <version>1.0</version>
+ <type>bar</type>
+ <scope>runtime</scope>
+ </dependency>
+ </dependencies>
+</project>]]></source>
+ Project B:
+ <source><![CDATA[
+<project>
+ ...
+ <dependencies>
+ <dependency>
+ <groupId>group-c</groupId>
+ <artifactId>artifact-b</artifactId>
+ <version>1.0</version>
+ <type>war</type>
+ <scope>runtime</scope>
+ </dependency>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-b</artifactId>
+ <version>1.0</version>
+ <type>bar</type>
+ <scope>runtime</scope>
+ </dependency>
+ </dependencies>
+</project>]]></source>
+ </p>
+ <p>
+ These two example POMs share a common dependencies and each one non-trivial dependency. This information
+ can be put in the parent POM like this:
+ <source><![CDATA[
+<project>
+ ...
+ <dependencies>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-a</artifactId>
+ <version>1.0</version>
+ <exclusions>
+ <exclusion>
+ <groupId>group-c</groupId>
+ <artifactId>excluded-artifact</artifactId>
+ </exclusion>
+ </exclusions>
+ </dependency>
+ <dependency>
+ <groupId>group-c</groupId>
+ <artifactId>artifact-b</artifactId>
+ <version>1.0</version>
+ <type>war</type>
+ <scope>runtime</scope>
+ </dependency>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-b</artifactId>
+ <version>1.0</version>
+ <type>bar</type>
+ <scope>runtime</scope>
+ </dependency>
+ </dependencies>
+</project>]]></source>
+ And then the two child poms would become much simpler:
+ </p>
+ <p>
+ <source><![CDATA[
+<project>
+ ...
+ <dependencies>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-a</artifactId>
+ </dependency>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-b</artifactId>
+ </dependency>
+ </dependencies>
+</project>]]></source>
+ <source><![CDATA[
+<project>
+ ...
+ <dependencies>
+ <dependency>
+ <groupId>group-c</groupId>
+ <artifactId>artifact-b</artifactId>
+ </dependency>
+ <dependency>
+ <groupId>group-a</groupId>
+ <artifactId>artifact-b</artifactId>
+ </dependency>
+ </dependencies>
+</project>]]></source>
+ </p>
+ <p>
+ The reference information about the dependency management tags is available from the
+ <a href="maven-model/maven.html#class_DependencyManagement">project descriptor reference</a>.
+ </p>
+ </subsection>
</section>
</body>
</document>
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