Intellij version : Community 2019.2.3
Maven : 3.6.2
Spring : 2.2.0
I am trying to create a very simple Spring maven project with two sub-modules (one independent and another one dependent on independent one).
Root module - testmultimodule
Independent module - independent
Dependent module - dependent
testmultimodule pom.xml has all Spring related declaration and module definition
<modules>
<module>independent</module>
<module>dependant</module>
</modules>
Independent poom.xml is simplest and . only has parent maven declaration
<parent>
<artifactId>testmultimodule</artifactId>
<groupId>in.org.app</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
dependent module pom.xml has the dependency declaration as below to independent module
<dependencies>
<dependency>
<groupId>in.org.app</groupId>
<artifactId>independent</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
</dependencies>
I have created a Test class under dependent module and using a User object from independent module. Initially, without the above dependency declaration, asa usual there was compilcation error.
As soon as I add the dependency and builld the project within Intellij IDE with the option "Build Prooject" option from "Build" menu, it successfully builds.
However, if I try to use Maven install option within Intellij right side window option. It always fails stating Error:(3,33) java: package in.org.app.independent.bo does not exist .
I am providing the GitHub URL for the test project , if you want to take a look and test by yourself.
GIT URL:
https://github.com/DhruboB/testmultimodule
I have tried all sort of tweaking found in internet so far e.g.
clearing Intellij Cache & restarting, mvn -U clean install, mvn scope verification, proxy etc.
Any further idea to resolve this? I need to solve this in the Community version of Intellij.
Your parent project includes the definition for the spring-boot-maven-plugin. This leads to each project defining this as a parent to be repacked to an executable JAR by this plugin. This repackaged JAR isn't useable as a dependency in another project.
Either you need to change the configuration of the spring-boot-maven-plugin for the project you want to use as a dependency. This is explained here in the Spring Boot Reference Guide. You now basically have 2 jars from this project, one plain and one executable.
If you don't need that project to be an executable JAR file then just move the spring-boot-maven-plugin to the project that needs to be. All other projects will no be basic JAR files again.
See also How to add a dependency to a Spring Boot Jar in another project?
Please do you know if it's possible to automatically replace one Maven plugin with another in the POM files for a project?
The context is that I'm trying to intercept a Scala build using a Scala compiler plugin, for which I want to be able to specify the Scala compiler plugin as an argument to scalac from the command-line (i.e. not within the POM files). This is possible using the latest version of the Scala Maven plugin (known as scala-maven-plugin) by using its addScalacArgs flag - see here: http://davidb.github.com/scala-maven-plugin/apidocs/scala_maven/ScalaMojoSupport.html. However, it's not possible for the old version of the plugin (known as maven-scala-plugin), and I'd need to add the argument in all the various POM files (not an attractive proposition when dealing with a large, third-party project).
My thinking is that if I can automatically replace the old version of the plugin with the new version in the POM files, then I can use addScalacArgs and everything will work out well. I can probably cook up some code to do this (evidently doing it manually would be no better than going through and adding the argument), but it seems like the sort of thing that might be a supported Maven use-case.
Being specific, I'm trying to replace this plugin:
<plugin>
<groupId>org.scala-tools</groupId>
<artifactId>maven-scala-plugin</artifactId>
...
</plugin>
with this one:
<plugin>
<groupId>net.alchim31.maven</groupId>
<artifactId>scala-maven-plugin</artifactId>
...
</plugin>
You can do this with two profiles in your pom. One activate by default the other not. Then you can easily select which to use accordingly which profile you choose.
For exemple, here is a older post in the same spirit : How do I exclude a dependency in provided scope when running in Maven test scope?
Created project with Spring, Hibernate & Maven. My question is what is the logic behind plugin versus dependency ?
Both plugins and dependencies are Jar files.
But the difference between them is, most of the work in maven is done using plugins; whereas dependency is just a Jar file which will be added to the classpath while executing the tasks.
For example, you use a compiler-plugin to compile the java files. You can't use compiler-plugin as a dependency since that will only add the plugin to the classpath, and will not trigger any compilation. The Jar files to be added to the classpath while compiling the file, will be specified as a dependency.
Same goes with your scenario. You have to use spring-plugin to execute some spring executables [ I'm not sure what spring-plugins are used for. I'm just taking a guess here ]. But you need dependencies to execute those executables. And Junit is tagged under dependency since it is used by surefire-plugin for executing unit-tests.
So, we can say, plugin is a Jar file which executes the task, and dependency is a Jar which provides the class files to execute the task.
Hope that answers your question!
Maven itself can be described as food processor which has many different units that can be used to accomplish different tasks. Those units are called plugins. For example, to compile your project maven uses maven-compiler-plugin, to run tests - maven-surefire-plugin and so on.
Dependency in terms of maven is a packaged piece of classes that your project depends on. It can be jar, war etc. For example, if you want to be able to write JUnit test, you'll have to use JUnit annotations and classes thus you have to declare that your project depends on JUnit.
Plugins and dependencies are very different things and these are complementary.
What plugins are ?
Plugins perform tasks for a Maven build. These are not packaged in the application.
These are the heart of Maven.
Any task executed by Maven is performed by plugins.
There are two categories of plugins : the build and the reporting plugins :
Build plugins will be executed during the build and they should be configured in the <build/> element from the POM.
Reporting plugins will be executed during the site generation and they should be configured in the <reporting/> element from the POM.
According to the maven goal specified in the command line (for example mvn clean, mvn clean package or mvn site) , a specific lifecyle will be used and a specific set of plugins goals will be executed.
There are three built-in build lifecycles: default, clean and site. The default lifecycle handles your project deployment, the clean lifecycle handles project cleaning, while the site lifecycle handles the creation of your project's site documentation.
A plugin goal may be bound to a specific phase of a specific lifecyle.
For example the maven-compiler-plugin binds by default the compile goal to the lifecycle phase: compile.
Most of maven plugins (both core plugins and third party plugins) favor convention over configuration. So these generally bound a plugin goal to a specific phase to make their usage simpler.
That is neater and less error prone :
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
</plugin>
than :
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<executions>
<execution>
<phase>compile</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
What dependencies are ?
Dependencies are Maven artifacts/components required for the project.
Concretely most of dependencies are jar (that is libraries) but these may also be other kinds of archives : war, ear, test-jar, ejb-client ... or still POM or BOM.
In a pom.xml, dependencies may be specified at multiple places : the <build><dependencies> part , the dependencies management part or still in a plugin declaration ! Indeed some plugins may need to have some dependencies in the classpath during their execution. That is not common but that may happen.
Here is an example from the documentation that shows that plugin and dependency may work together :
For instance, the Maven Antrun Plugin version 1.2 uses Ant version
1.6.5, if you want to use the latest Ant version when running this plugin, you need to add <dependencies> element like the following:
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-antrun-plugin</artifactId>
<version>1.2</version>
...
<dependencies>
<dependency>
<groupId>org.apache.ant</groupId>
<artifactId>ant</artifactId>
<version>1.7.1</version>
</dependency>
<dependency>
<groupId>org.apache.ant</groupId>
<artifactId>ant-launcher</artifactId>
<version>1.7.1</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
...
</project>
In Maven, dependencies are referenced in a specific format :
groupId:artifactId:packaging:classifier:version.
The classifier (that is optional) and the packaging (JAR by default) are not commonly specified. So the common format in the dependency declaration is rather : groupId:artifactId:version.
Here is an example of dependency declared in the <build><dependencies> part :
<build>
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.2.14.Final</version>
</dependency>
<dependencies>
</build>
Dependency doesn't have a phase binding as plugins to address the "when" question.
But it has a counterpart : the scope.
Indeed declared dependencies are usable by the application at a specific time according to the scope we defined for these.
The scope is a central concept about how a dependency will be visible for the project.
The default scope is compile. That is the most commonly needed scope (convention over configuration again).
The compile scope means that the dependency is available in all classpaths of a project.
The scope defines in which classpaths the dependency should be added.
For example do we need it at compile and runtime, or only for tests compilation and execution ?
For example we previously defined Hibernate as a compile dependency as we need it everywhere : source compilation, test compilation, runtime and so for....
But we don't want that testing libraries may be packaged in the application or referenced in the source code. So we specify the test scope for them :
<build>
<dependencies>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<version>5.1.0</version>
<scope>test</scope>
</dependency>
<dependencies>
</build>
One line answer - basic understanding
Plugin is a tool you use at the execution of your maven build
Dependency means kind of any library which you will use in your code
If you're coming from a front-end background like me, and are familiar with Grunt and npm, think of it like this:
First you would run, say, npm install grunt-contrib-copy --save-dev. This is like maven's <dependency></dependency>. It downloads the files needed to execute a build task.
Then you would configure the task in Gruntfile.js
copy: {
main: {
src: 'src/*',
dest: 'dest/',
},
}
This is like maven's <plugin>/<plugin>. You are telling the build tool what to do with the code downloaded by npm/<dependency></dependency>.
Of course this is not an exact analogy, but close enough to help wrap your head around it.
Plug-ins are used for adding functionalities to Maven itself (like adding eclipse support or SpringBoot support to Maven etc.). Dependencies are needed by your source code to pass any Maven phase (compile or test for example). In case of JUnit since the test code is basically part of your code base and you call JUnit specific commands inside test suites and those commands are not provided by Java SDK therefore JUnit must be present at the time Maven is in the test phase and this is handled by mentioning JUnit as a dependency in your pom.xml file.
In simple words:
Plugins are used to add some additonal features to the software/tools(like Maven). Maven will use the added plugins at the time of building when we use the build command.
Dependecies are used to add some addtional code to your source code, so a dependency will make some extra code (like Classes in Java) in the form of library available for your source code.
Maven at its heart is a plugin execution framework -- as per formal and standard compact definition. To make it more clear, the commands you use like maven-install/clean/compile/build etc for creating/executing jars, which we sometimes manually run too. So, the things which you want to run (or configure or execute) you basically put them in dependency tag of mavens pom and the answer so as to who will run these dependencies (required for environment setup) be the plugins.
javac (compiler) dependency.java (dependency)
A plugin is an extension to Maven, something used to produce your artifact (maven-jar-plugin for an example, is used to, you guess it, make a jar out of your compiled classes and resources).
A dependency is a library that is needed by the application you are building, at compile and/or test and/or runtime time.
I dont know if this is a question or suggestion. But I am going to ask it as a question cos may be i am doing something wrong.
My problem was that I wanted to skip tests in maven build, In eclipse plugin I checked the Skip Test option in configuration when running maven. It was still failing on the Test surefire plugin as it couldn't download the version 2.4.3 (even though my previous maven project used a 2.7.2 and it was already there in my repo) So i tried with skipping tests and it still failed.
I configured my POM to use the 2.7.3 plugin of surefire which i already had and it went forward only to say Skipping Tests. Now, my confusion is that when it was already going to SKIP the test part why bother going into the download and confirming if the plugin for surefire is there or not. Just Skip it I say..
well, Is that the normal behavior of maven that when you skip something the plugin is still downloaded as if you are going to use it. Or was I doing it wrongly that made it download it.
May be because there was something new called "Effective POM" and it contained a listing of surefire plugin 2.4.2 in the plugin management area, when i imported my maven project in eclipse using the m2eclipse and i couldnt edit the Effective POM. I had not seen this before in the NetBeans when making the maven project.
In order to work i added an unnecessary surefire plugin entry in my build profile and skipped the tests there as well and added the version that I had in my repo already. I only did this so that my project can be built under eclipse as well. other wise my project works in NetBeans and simple command line without any issues.
Any comments!!
I think maven should be able to see first the SKIP part and then proceed into the usage of the plugin.
Syed..
Based on what you mentioned you didn't understand the difference between using a plugin and configuring the plugin. In this case you are using the plugin (it's in your build area or as you already figured out coming via super-pom). Furthermore you are trying to skip the tests despite the fact that maven-surefire-plugin in version 2.7.3 does not exist.
The configuration parameter skip will not execute the tests as well as not compile them. If you wan't just ignore the tests for a limited time you can use the "skipTest" parameter which in contradiction to skip will continue to compile the tests.
I would recommend to use a pluginManagement section of your project or your parent pom to define the version of the maven-surefire-plugin (which in the meantime exists in version 2.12)...
The following snippet add the pluginManagement part to a pom which controls which version of the maven-surefire plugin will be used.
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.11</version>
</plugin>
</plugins>
</pluginManagement>
<plugins>
..
</build>
After you inserted that into your project pom the output effective pom should give you the version...otherwise you might need to update the project configuration first.
Compiling and running tests is part of the default lifecycle of maven. Since maven uses surefire to do run tests, it needs to download surefire. skipTests is not a maven configuration, but a surefire plugin configuration. The plugin determines that maven needs to skip tests.
As for 2.4.3 of surefire plugin, it is a valid version, but will work with 2.0.6 version of maven. Most likely you are using a newer maven, but, for some reason have the super pom of the older maven version on your system.
skipTest doesn't tell maven to skip the test lifecycle, it tells the surefire plugin not to run them. The plugin is still part of the lifecycle (it just does nothing when it's called). Hence your error.
If you want to NOT have surefire at all, you need to define your own packaging (since surefire is part of the standard jar packaging lifecycle) - which is a lot more work than just choosing a version of surefire that works for you (add a section with the right in your section).
I'm trying to convert a project from ant to maven.
The unit tests depend on a third party binary jar, which is not available in any public maven repositories.
How do I make maven handle this situation? I have found two solutions, neither of which are acceptable. First is to use a system dependency; this doesn't work because a) the dependency should only be for the tests, and b) the dependency is not found by eclipse after generating an eclipse project.
Second is to manually install the dependency in a local repository. This seems to be the recommended way. I don't want to do this because I want users to be able to build and test with a simple 'mvn test'. If users have to read a document and copy/paste some shell commands to be able to build and test, then something's wrong.
I suppose it would be OK if maven itself installed the dependency in the local repository as part of the build - is this possible, and if so, how?
Aled.
You may want to look at install:install-file. You can make it execute in the early phase of your project (validate or initialize) via standard means.
On the second thought, if it fails because of missing dependency in the same project, there are couple more options. One is to call ant script via antrun plugin to install artifact.
Or create additional module not dependent on your artifact to be executed prior to main module and have that module install artifact as described earlier.
First of all my way would be using a repository manager such as nexus and installing this dependency to there.
However there is another solution. You can include this 3rd party jar to your project and with test plugin you can configure to include it in classpath such this:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.10</version>
<configuration>
<additionalClasspathElements>
<additionalClasspathElement>path/to/additional/resources</additionalClasspathElement>
<additionalClasspathElement>path/to/additional/jar</additionalClasspathElement>
</additionalClasspathElements>
</configuration>
</plugin>
By the way, I hope that you are aware of that maven is executing surefire plugin in order to run tests by default lifecycle.