What is the difference between mvn clean install and mvn install?
clean is its own build lifecycle phase (which can be thought of as an action or task) in Maven. mvn clean install tells Maven to do the clean phase in each module before running the install phase for each module.
What this does is clear any compiled files you have, making sure that you're really compiling each module from scratch.
Maven lets you specify either goals or lifecycle phases on the command line (or both).
clean and install are two different phases of two different lifecycles, to which different plugin goals are bound (either per default or explicitly in your pom.xml)
The clean phase, per convention, is meant to make a build reproducible, i.e. it cleans up anything that was created by previous builds. In most cases it does that by calling clean:clean, which deletes the directory bound to ${project.build.directory} (usually called "target")
You can call more than one target goal with maven. mvn clean install calls clean first, then install. You have to clean manually, because clean is not a standard target goal and not executed automatically on every install.
clean removes the target folder - it deletes all class files, the java docs, the jars, reports and so on. If you don't clean, then maven will only "do what has to be done", like it won't compile classes when the corresponding source files haven't changed (in brief).
we call it target in ant and goal in maven
To stick with the Maven terms:
"clean" is a phase of the clean
lifecycle
"install" is a phase of the
default lifecycle
http://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html#Lifecycle_Reference
Ditto for #Andreas_D, in addition if you say update Spring from 1 version to another in your project without doing a clean, you'll wind up with both in your artifact. Ran into this a lot when doing Flex development with Maven.
Related
I have a question which is pretty straight forward, but hard to find an exact answer.
When we are using mvn build, what are the exact situation where we must go for clean install in order to see latest code changes in our built artifact. i.e. just install would not do that for us.
Thanks in advance.
Basically
mvn clean install
is same as
mvn clean && mvn install
so as to answer your question, its required when cleaning the files and directories generated by Maven is the primary requirement prior to doing another install.
Related to the changes in code, I would assume this is more of cleaning the target folder generated by Maven, hence mostly the files compiled would be overwritten when there is not much of a change.
In cases where one has removed/refactored a class from the previous build. There might be references still left if you don't clean and that would get packaged into the jar created thereafter.
From the official documentation(formatting mine) shared by ernest,
But if we try to build the project with mvn install without any clean lifecycle, then we see 2 bugs
the maven build still succeeds to compile the project maven even
generates a jar which contains broken classes
moduleB does not get recompiled and is thus broken as well.
Also, a preferably suggested way is to instead use
mvn verify
I want to execute a maven plugin during mvn clean install whenever a file is changed since the last build. If the file is not changed since the last build then plugin execution should be skipped during mvn clean install.
Is it possible to achieve this in maven 3.5.0?
Maven doesn't keep record of all modules it ever built. However, this would be necessary if Maven would have to know if some (source) files changed.
Some plugins, like the maven-compiler-plugin, compare timestamps of source-files with timestamps of corresponding, generated class-files, which allows to skip compilation if classfile is newer. However, if you execute mvn clean (as mentioned in the question), class files are removed and compilation thus has to be executed anyway.
So to conculde: your request cannot be fulfilled by maven without major changes in maven itself.
I just starting using maven in my new project.
I am trying to create artifacts(java files) of a project A into another project B in order to resolve their cyclic dependency.
If I run the whole build for the first time,its working fine. The jar of B contains classes of both project A and B.
However, if I make changes to only project B , and run the build, only project B is running and build is failing . Thats because sine no changes are done to project A, maven is not running it and the artifacts are also not getting generated.
Can anyone advise how can I trigger the build of a project even though no changes are done to it.
exec mvn with clean phase! i.e.
mvn clean package
Phases are actually mapped to underlying goals. The specific goals executed per phase is dependant upon the packaging type of the project. For example, package executes jar:jar if the project type is a JAR, and war:war if the project type is - you guessed it - a WAR.
An interesting thing to note is that phases and goals may be executed in sequence.
mvn clean dependency:copy-dependencies package
This command will clean the project, copy dependencies, and package the project
mvn site
This phase generates a site based upon information on the project's pom. You can look at the documentation generated under target/site.
official documentation http://docs.sonarqube.org/display/SONAR/Analyzing+with+Maven says that the proper way of invoking sonar is:
mvn clean install -DskipTests=true
mvn sonar:sonar
but doesn't say why. how does sonar work? does it need compiled classes? so why not just mvn clean compile? or does it need a jar file? so why not just mvn clean package? what exactly does sonar plugin?
Explanation from a SonarSource team member:
In a multi-module build an aggregator plugin can't resolve dependencies from target folder. So you have two options:
mvn clean install && mvn sonar:sonar as two separate processes
mvn clean package sonar:sonar as a single reactor
I was surprised too, so I made a tweet an received the following answer from the official Maven account:
If the plugin is not designed to use the target/classes folder as a substitute, then yes you would need to have installed to get the jar when running *in a different session*. Complain to the plugin author if they force you to use install without foo reason [ed - #connolly_s]
The SonarQube analyzer indeed needs compiled classes (e.g for Findbugs rules, coverage). And since by default it executes tests itself, the compile phase can skip tests.
You can run SonarQube as part of a single Maven command if you meet some requirements:
As Mithfindel mentions, some SonarQube plugins need to analyze .class files. And if you run unit tests outside of SonarQube, then of course the testing plugins must read output from the test phase.
Got integration tests? Then you need to run after the integration-test phase.
If you want to run SonarQube as a true quality gate then you absolutely must run it before the deploy phase.
One solution is to just attach SonarQube to run after the package phase. Then you can get a full build with a simple clean install or clean deploy. Most people do not do this because SonarQube is time-consuming, but the incremental mode added in 4.0 and greatly improved in the upcoming 4.2 solves this.
As far as the official documentation goes, it's a lot easier to say "build and then run sonar:sonar" then it is to say, "open your POM, add a build element for the sonar-maven-plugin, attach it to verify, etc".
One caveat. SonarQube requires Java 6, so if you're building against JDK 1.5 (still common in large organizations), the analysis will have to happen in a separate Maven invocation with a newer JDK selected. We solved this issue with custom Maven build wrapper.
If I have 6 modules in my project is it possible to build only one out of six ? without commenting out others ?
EDIT
Submodule will not work itselft because or parent tags. I need to install the parent first to make it build. how can I do it without installing parent
is it possible to build only one out of six ? without commenting out others ?
My understanding is that you want to launch maven from the aggregating project (i.e. a reactor build) but only build one module. This is possible using the -pl, --projects project list option (see advanced reactor options):
mvn --projects my-submodule install
This is a very powerful option, especially when combined with --aslo-make (to also build the projects on which the listed modules depend) or the --also-make-dependents (to also build the projects that depends on the listed modules). On the basis of your update, you might want this actually:
mvn --projects my-submodule --also-make install
Launching Maven from the directory of the module you want to build is of course an option but this won't allow you to do the things mentioned above nor to build a subset of all modules. For such use cases, the advanced reactor options are the way to go.
Opening a command shell, navigating to the submodule directory and executing mvn install (or whatever your preferred lifecycle is) should do the trick.
You can simply build the module by going in this module directory and run the mvn clean install.
However, note that with this method, the dependencies with the others modules will be taken from your local repository (or the entreprise repository).
Let's take a simple example:
project
+ commons
+ business
Now, imagine that you build, on the root directory the whole project, using the mvn clean install command. Consider that all your modules are in version 1.0.
Now, you move to version 1.1. If you run the mvn clean install on the business project only, it will try to get the 1.1 of module commons. You will then have an error, as Maven will not find any version 1.1 in your local repository.
Within Eclipse, assuming you have m2eclipse installed: Right-click on the module in question and choose Run As -> Maven package.