Apache
/
maven
mirror of https://github.com/apache/maven.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

o Adding a piece about dependency management. 

git-svn-id: https://svn.apache.org/repos/asf/maven/components/trunk@230934 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Trygve Laugstol 2005-08-09 00:20:31 +00:00
parent 80c945fd82
commit 16bbbbdd91
1 changed files with 157 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

167
maven-site/src/site/xdoc/dependency-mechanism.xml
View File

@ -2,16 +2,29 @@
<properties> <properties>
<title>Dependency Mechanism</title> <title>Dependency Mechanism</title>
<author email="brett@apache.org">Brett Porter</author> <author email="brett@apache.org">Brett Porter</author>
<author email="trygvis@apache.org">Trygve Laugstol </author>
</properties> </properties>
<body> <body>
<section name="Dependency Mechanism"> <section name="Dependency Mechanism">
<p> <p>
There are many aspects to working with dependencies in Maven. While it is not the sole focus of Maven, it 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>
<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> </p>
<a name="transitive_dependencies"/>
<subsection name="Transitive Dependencies"> <subsection name="Transitive Dependencies">
<p> <p>
Transitive dependencies are a new feature in Maven 2.0. This allows you to avoid needing to discover and Transitive dependencies are a new feature in Maven 2.0. This allows you to avoid needing to discover and
@ -33,12 +46,14 @@
</p> </p>
<ul> <ul>
<li> <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 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. you can always guarantee a version by declaring it explicitly in the project's POM.
</li> </li>
<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. of the build. This is described in more detail below.
</li> </li>
</ul> </ul>
@ -49,6 +64,7 @@
</p> </p>
</subsection> </subsection>
<subsection name="Dependency Scope"> <subsection name="Dependency Scope">
<a name="dependency_scope"/>
<p> <p>
Dependency scope is used to limit the transitivity of a depedency, and also to affect the classpath used for Dependency scope is used to limit the transitivity of a depedency, and also to affect the classpath used for
various build tasks. various build tasks.
@ -58,20 +74,24 @@
</p> </p>
<ul> <ul>
<li> <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. in all classpaths.
</li> </li>
<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. It is only available on the compilation classpath, and is not transitive.
</li> </li>
<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. execution.
It is in the runtime and test classpaths, but not the compile classpath. It is in the runtime and test classpaths, but not the compile classpath.
</li> </li>
<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. is only available for the test compilation and execution phases.
</li> </li>
</ul> </ul>
@ -119,13 +139,140 @@
</tr> </tr>
</table> </table>
<p> <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 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 library, forcing you to have available at compile time. For this reason, compile time dependencies remain
as compile scope even when they are transitive. as compile scope even when they are transitive.
</p> </p>
</subsection> </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> </section>
</body> </body>
</document> </document>