What is the point of having a version in a Maven aggregate (multi-module) POM? What is it used for? What would be affected if I change it?
For example:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>foobar</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
…
Where is the 1.0-SNAPSHOT used? What artifacts are affected?
On a related note, what semantics does it have? Is it the version of my combined project? Or is it the version solely of the aggregation (which may remain constant through many release versions of the individual modules)?
Related
I am trying to make a new multi-module Spring project with Maven. I have one main Pom.xml, and to other modules.
This is the main pom.xml :
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.ev</groupId>
<artifactId>multi</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<modules>
<module>main</module>
<module>user</module>
</modules>
And this is the module1 pom.xml :
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>multi</artifactId>
<groupId>org.ev</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>user</artifactId>
</project>
Where should i add the dependencies? When i put them into main pom.xml , i get an error "cant resolve pom" .
Do you have any idea about this issue? Because its very hard to create multi module project for me.
try to change main/pom.xml
<artifactId>multi</artifactId>
to
<artifactId>main</artifactId>
Once you set packaging equal to pom, do you need the groupID, artifactId and version tags and if so, what purpose do they serve? Are there any tags you should use (after all groupID is clearly intended for java so I wouldn't be surprised if there are other language or artifact type specific tags that should be used). Samples:
Simple parent pom:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.company</groupId>
<artifactId>project_name</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<properties>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
<modules>
<module>hosts</module>
</modules>
</project>
Simple child pom:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.company</groupId>
<artifactId>hosts</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<properties>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
</project>
Then sub children are various projects of many types, java, C++, angular, python, more poms.
You need all those tags.
The POMs are deployed along with the JARs, WARs etc. with their respective Maven coordinates (GroupId, ArtifactId, Version). They are resolved if anybody uses e.g. a dependency with your parent.
Suppose there are two 3rd-party Maven artifacts with the following POM.XMLs:
artifact1 POM.XML:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>group1</groupId>
<artifactId>artifact1</artifactId>
<version>${artifact1.version}</version>
<packaging>pom</packaging>
<properties>
<artifact1.version>0.0.1-SNAPSHOT</artifact1.version>
</properties>
<modules>
<module>../artifact2</module>
</modules>
artifact2 POM.XML:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>artifact2</artifactId>
<parent>
<groupId>group1</groupId>
<artifactId>artifact1</artifactId>
<version>${artifact1.version}</version>
<relativePath>../artifact1</relativePath>
</parent>
They are built normally using
mvn clean install
Now, if I try to reuse artifact2 in a 3rd POM.XML:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>group2</groupId>
<artifactId>artifact3</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>group1</groupId>
<artifactId>artifact2</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
After executing...
mvn clean install
...the build fails trying to locate group1:artifact1:pom:${artifact1.version}
[ERROR] Failed to execute goal on project artifact3: Could not resolve dependencies for project group2:artifact3:jar:0.0.1-SNAPSHOT: Failed to collect dependencies at group1:artifact2:jar:0.0.1-SNAPSHOT: Failed to read artifact descriptor for group1:artifact2:jar:0.0.1-SNAPSHOT: Could not find artifact group1:artifact1:pom:${artifact1.version} in central (https://repo.maven.apache.org/maven2) -> [Help 1]
And setting the property in the command-line doesn't work either:
mvn clean install -Dartifact1.version=0.0.1-SNAPSHOT
How can I use artifact2 as a dependency?
<parent> doesn't allow variables. Because in order to get a list of variables Maven first has to build Effective POM and for this it needs to resolve parents.
Even if there is some version of Maven that allowed such module to be installed it's not a working solution in general. Maven's ideology is that all the dependencies (including parent) could be downloaded from a repo and are not necessarily present on local FS/in the reactor. With properties in the parent dependency definition you violate this rule.
I have a project Structure like below
P1 |trunk
|branches
|tags
P2 |trunk
|branches
|tags
P3 |trunk
|branches
|tags
p1 is an individual jar project. P2 is also a jar project but dependant on p1 and p3 requires both p1 and p2. P3 is basically a war file that has both p1 and p2 in it.
Till now i was trying to use a parent pom with these projects added as child modules and trying to perform a version upgrade, tag and release.Each of these projects inherit the parent pom However i see that the tagging is failing for individual projects.
So my question is
is it possible for me to use release plugin to upgrade the version and perform a tag update to individual projects like this?.
If not possible what is the best way to perform an automated release for an individual project structure like this?.
These are legacy code and the branches folder has a lot of branches checked in there. can't easily re factor it to plain parent - child model in maven.
Thanks in Advance
This should be possible. Could you show the relevant parts of your pom.xml and describe why the tagging is failing? And by the way, this is Subversion, right?
I would try with a POM structure like this. Parent:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>...</groupId>
<artifactId>parent</artifactId>
<version>1.0</version>
<packaging>pom</packaging>
<modules>
<module>../child1/</module>
<module>../child2/</module>
</modules>
</project>
Child:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>...</groupId>
<artifactId>parent</artifactId>
<version>1.0</version>
<relativePath>../parent/pom.xml</relativePath>
</parent>
<groupId>...</groupId>
<artifactId>child-1</artifactId>
<version>1.1</version>
...
</project>
I am creating multimodule project using maven in eclipse.After configuring parent in that configuration tab,to add modules I have selected Add and selected the modules to be added and I have checked the 'Update POM parent section in selected projects'.But it doesnot include the parent information in the selected modules.
I was not aware that such a feature exists, but you can do it by your own, with more reliability adding those lines to your parent pom :
parent pom.xml
Here put your modules configuration
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.company.bla.bla</groupId>
<artifactId>you-parent-artifact</artifactId>
<version>1.0</version>
<modules>
<module>module-child-1</module>
<module>module-child-2</module>
</modules>
childs pom.xml
Here put you parent reference and ommit version
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.company.bla.bla</groupId>
<artifactId>you-parent-artifact</artifactId>
<version>1.0</version>
</parent>
<artifactId>child-1</artifactId>
More information here : http://www.sonatype.com/books/mvnex-book/reference/multimodule.html