问题
Since I updated to Maven 3 I get the following warning messages at each build :
How can I get rid of these warnings?
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for proj:id:jar:3.1
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-javadoc-plugin is missing. @ line 195, column 15
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ line 204, column 15
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-surefire-plugin is missing. @ line 227, column 15
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-jar-plugin is missing. @ line 215, column 15
[WARNING] 'reporting.plugins.plugin.version' for org.codehaus.mojo:jdepend-maven-plugin is missing. @ line 271, column 15
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
回答1:
Add a <version> element after the <plugin> <artifactId> in your pom.xml file. Find the following text:
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
Add the version tag to it:
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
The warning should be resolved.
Regarding this:
'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing
Many people have mentioned why the issue is happening, but fail to suggest a fix. All I needed to do was to go into my POM file for my project, and add the <version> tag as shown above.
To discover the version number, one way is to look in Maven's output after it finishes running. Where you are missing version numbers, Maven will display its default version:
[INFO] --- maven-compiler-plugin:2.3.2:compile (default-compile) @ entities ---
Take that version number (as in the 2.3.2 above) and add it to your POM, as shown.
回答2:
Run like:
$ mvn help:describe -DartifactId=maven-war-plugin -DgroupId=org.apache.maven.plugins
for plug-in that have no version. You get output:
Name: Maven WAR Plugin Description: Builds a Web Application Archive (WAR) file from the project output and its dependencies. Group Id: org.apache.maven.plugins Artifact Id: maven-war-plugin Version: 2.2 Goal Prefix: war
Use version that shown in output.
UPDATE If you want to select among list of versions, use http://search.maven.org/ or http://mvnrepository.com/ Note that your favorite Java IDE must have Maven package search dialog. Just check docs.
SUPER UPDATE I also use:
$ mvn dependency:tree
$ mvn dependency:list
$ mvn dependency:resolve
$ mvn dependency:resolve-plugins # <-- THIS
Recently I discover how to get latest version for plug-in (or library) so no longer needs for googling or visiting Maven Central:
$ mvn versions:display-dependency-updates
$ mvn versions:display-plugin-updates # <-- THIS
回答3:
Maven 3 is more restrictive with the POM-Structure. You have to set versions of Plugins for instance.
With maven 3.1 these warnings may break you build. There are more changes between maven2 and maven3: https://cwiki.apache.org/confluence/display/MAVEN/Maven+3.x+Compatibility+Notes
回答4:
I'm using a parent pom for my projects and wanted to specify the versions in one place, so I used properties to specify the version:
parent pom:
<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">
....
<properties>
<maven-compiler-plugin-version>2.3.2</maven-compiler-plugin-version>
</properties>
....
</project>
project pom:
<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">
....
<build>
<finalName>helloworld</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin-version}</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
See also: https://www.allthingsdigital.nl/2011/04/10/maven-3-and-the-versions-dilemma/
回答5:
get the latest version information from:
https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin
click on the latest version (or the one you'd like to use) and you'll see the the dependency info (as of 2019-05 it's 3.8.1):
<!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin -->
<dependency>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
</dependency>
you might want to use the version tag and the comment for your plugin tag.
<!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin -->
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source />
<target />
</configuration>
</plugin>
if you like you can modify your pom to have the version information in the properties tag as outlined in another answer.
回答6:
It's great answer in here. And I want to add 'Why Add a element in Maven3'.
In Maven 3.x Compatibility Notes
Plugin Metaversion Resolution
Internally, Maven 2.x used the special version markers RELEASE and LATEST to support automatic plugin version resolution. These metaversions were also recognized in the element for a declaration. For the sake of reproducible builds, Maven 3.x no longer supports usage of these metaversions in the POM. As a result, users will need to replace occurrences of these metaversions with a concrete version.
And I also find in maven-compiler-plugin - usage
Note: Maven 3.0 will issue warnings if you do not specify the version of a plugin.
回答7:
Search "maven-jar-plugin" in pom.xml and add version tag maven version
来源：https://stackoverflow.com/questions/4123044/maven-3-warnings-about-build-plugins-plugin-version