Улучшение Maven проектов
В течение долгого времени Maven был инструментом сборки defacto и управления зависимостями для проектов Java. Плагины добавили некоторые интересные вещи, но теперь Maven пополнился новыми функциями, улучшающими другие:
- Maven Lifecycle
- Мавен Полиглот
- Maven Wrapper
Все эти новые функции благодаря Такири , который возглавляет Джейсон ван Зил ( @jvanzyl ), отец Maven.
Maven Lifecycle
Избегайте повторной компиляции, если в исходном коде нет изменений. Вам просто нужно выполнить два простых шага, чтобы включить эту удивительную функцию. Экономьте свое время!
1. Добавьте плагин ниже:
io.takari.maven.plugins takari-lifecycle-plugin true 2. Переключите ваш ток packaging с jar на takari-jar .
В журнале видно, что плагин вступил в силу. Теперь, если вы уже скомпилировали, вам не придется снова компилировать, если вы не внесете изменения в свой исходный код.
Мавен Полиглот
Создание pom файла в формате XML является многословным. Теперь вы можете создавать свой pom на разных языках: Atom, Clojure, Groovy, Ruby, Scala, Yaml. И воспользоваться каждым из них.
- Внутри проекта создайте .mvn/extensions.xml файл, где будет иметь место языковая зависимость:
Атом:
io.takari.polyglot polyglot-atom 0.1.6 Clojure:
io.takari.polyglot polyglot-clojure 0.1.6 Groovy:
io.takari.polyglot polyglot-groovy 0.1.6 Рубин:
io.takari.polyglot polyglot-ruby 0.1.6 Scala:
io.takari.polyglot polyglot-scala 0.1.6 YAML:
io.takari.polyglot polyglot-yaml 0.1.6 Вы хотите перенести xml на любой другой язык? Вы можете сделать это, выполнив команду ниже:
mvn io.takari.polyglot:polyglot-translate-plugin:translate -Dinput=pom.xml -Doutput=pom.
Где format может быть atom , clj , groovy , rb , scala и yml .
Maven Wrapper
Совместное использование проектов является распространенным явлением, и иногда у нас есть конкретные версии из нашего инструмента сборки Теперь вам не нужно спрашивать вашего друга, какая версия maven вам нужна, если используется проект maven maven-wrapper . Для этого вам просто нужно запустить:
mvn -N io.takari:maven:wrapperТеперь вы можете сделать сборку mvnw clean install . Если вы хотите посмотреть, какую версию Maven вы скачаете, загляните .mvn/wrapper/maven-wrapper.properties внутрь своего проекта.
Maven Wrapper
The Maven Wrapper is an easy way to ensure a user of your Maven build has everything necessary to run your Maven build.
Why might this be necessary? Maven to date has been very stable for users, is available on most systems or is easy to procure: but with many of the recent changes in Maven it will be easier for users to have a fully encapsulated build setup provided by the project. With the Maven Wrapper, this is very easy to do and it’s a great idea and initial implementation borrowed from Gradle.
The easiest way to setup the Maven Wrapper for your project is to use the Maven Wrapper Plugin with its provided wrapper goal. To add or update all the necessary Maven Wrapper files to your project execute the following command:
mvn wrapper:wrapper Normally you instruct users to install a specific version of Apache Maven, put it on the PATH and then run the mvn command like the following:
mvn clean install But now, with a Maven Wrapper setup, you can instruct users to run wrapper scripts:
./mvnw clean install mvnw.cmd clean install A normal Maven build will be executed, with the one important change that if the user doesn’t have the necessary version of Maven specified in .mvn/wrapper/maven-wrapper.properties it will be downloaded for the user first, installed and then used.
Subsequent uses of mvnw / mvnw.cmd use the previously downloaded, specific version as needed.
Supported Systems
The wrapper should work on various operating systems including
- Linux (numerous versions, tested on Ubuntu and CentOS)
- OSX / macOS
- Windows (various newer versions)
- Solaris (10 and 11)
- BSD
A POSIX-compatible Bourne shell is required to run the wrapper script.
In terms of Apache Maven versions itself, the wrapper should work with any Maven 3.x version and it defaults to the release used when setting up the wrapper. We do NOT plan to support the deprecated, EOL’ed Maven 2.x.
The maven-wrapper.jar (to download and install target Maven version required by mvnw ) and the Maven Wrapper Plugin (to inject Wrapper into a project) use Java 7.
Verbose Mode
The wrapper supports a verbose mode in which it outputs further information. It is activated by setting the MVNW_VERBOSE environment variable to true .
By default it is off.
Usage without Binary JAR
By default, the Maven Wrapper JAR archive is added to the using project as small binary file .mvn/wrapper/maven-wrapper.jar . It is used to bootstrap the download and invocation of Maven from the wrapper shell scripts.
If your project is not allowed to contain binary files like this, you can use the source distribution of the maven wrapper which adds a file .mvn/wrapper/MavenWrapperDownloader.java file instead:
# defaults to bin mvn wrapper:wrapper -Dtype=source You can also chose to opt out of all additional resources except the wrapper scripts:
mvn wrapper:wrapper -Dtype=script Another type is the lite implementation of mvnw / mvnw.cmd scripts which download the maven directly via wget or curl on *nix, or PowerShell on Windows, then call the original mvn / mvn.cmd scripts of the downloaded maven distribution. This type does not use maven-wrapper.jar nor MavenWrapperDownloader.java , only the wrapper scripts are required.
mvn wrapper:wrapper -Dtype=only-script If the JAR is not found to be available by the scripts they will attempt to download the file from the URL specified in .mvn/wrapper/maven-wrapper.properties under wrapperUrl and put it in place. The download is attempted via curl, wget and, as last resort, by compiling the .mvn/wrapper/MavenWrapperDownloader.java file and executing the resulting class.
If your Maven repository is password protected you can specify your username via the environment variable MVNW_USERNAME and the password via the environment variable MVNW_PASSWORD .
Using a Different Version of Maven
To switch the version of Maven used to build a project, you can initialize it using:
mvn wrapper:wrapper -Dmaven=3.5.4 which works for any version except snapshots. Once you have a wrapper you can change its version by setting the distributionUrl in .mvn/wrapper/maven-wrapper.properties , e.g.
distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.5.4/apache-maven-3.5.4-bin.zip Using Basic Authentication for Distribution Download
To download Maven from a location that requires Basic Authentication you have 2 options:
- Set the environment variables MVNW_USERNAME and MVNW_PASSWORD or
- add user and password to the distributionUrl like that: distributionUrl=https://username:password@/maven2/org/apache/maven/apache-maven/3.2.1/apache-maven-3.2.1-bin.zip
Specifying Maven Distribution Base Path
This is a feature of Maven itself and the wrapper just happens to take it into account. Simply set MAVEN_USER_HOME to the desired path and the wrapper uses it as the base of the Maven distro installation.
Using a Maven Repository Manager
When using an internal Maven repository manager, you have two options:
- Just set the correct URL to wrapper jar and Maven distro in maven-wrapper.properties in your project
- Leave the default URL in the project pointing to Maven Central and set the environment variable MVNW_REPOURL to your repo manager URL such as https://repo.example.com/central-repo-proxy .
If MVNW_REPOURL is set during the wrapper installation with the maven-wrapper-plugin, the URL is used in the maven-wrapper.properties file.
If not set, but your mirror URL in your settings.xml is configured, it will be used.
Checksum verification of downloaded binaries
To avoid supply-chain-attacks by downloading a corrupted artifact, it is possible to specify checksums for both the maven-wrapper.jar and the downloaded distribution. To apply verification, add the expected file’s SHA-256 sum in hex notation, using only small caps, to maven-wrapper.properties . The property for validating the maven-wrapper.jar file is named wrapperSha256Sum whereas the distribution file property is named distributionSha256Sum .
Internals
Maven Wrapper is composed of 3 pieces:
- maven-wrapper, providing the maven-wrapper.jar that downloads, installs and runs target Maven distribution,
- maven-wrapper-distribution, that provides mvnw / mvnw.cmd scripts distributions,
- maven-wrapper-plugin, the wrapper plugin to ease installing Wrapper into a project.
What is the purpose of mvnw and mvnw.cmd files?
When I created a Spring Boot application I could see mvnw and mvnw.cmd files in the root of the project. What is the purpose of these two files?
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asked Aug 2, 2016 at 14:53
shaunthomas999 shaunthomas999
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6 Answers 6
These files are from Maven wrapper. It works similarly to the Gradle wrapper.
This allows you to run the Maven project without having Maven installed and present on the path. It downloads the correct Maven version if it’s not found (as far as I know by default in your user home directory).
The mvnw file is for Linux (bash) and the mvnw.cmd is for the Windows environment.
To create or update all necessary Maven Wrapper files execute the following command:
mvn -N io.takari:maven:wrapper To use a different version of maven you can specify the version as follows:
mvn -N io.takari:maven:wrapper -Dmaven=3.3.3 Both commands require maven on PATH (add the path to maven bin to Path on System Variables) if you already have mvnw in your project you can use ./mvnw instead of mvn in the commands.
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answered Aug 2, 2016 at 14:57
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Thanks for the answer. Can you explain when this gets generated, like is it when you initially create a project? Will it gets updated along the line when you do changes to your pom like add remove dependencies/plugins ?
Sep 20, 2017 at 23:20
and, should you add/commit the mvnw.cmd files?
Jan 15, 2019 at 3:26
yes, of course. it allows you to quickly run your maven build without the need to extra install maven or having it on PATH.
Jan 15, 2019 at 19:04
So many thanks for the answer, it’s very helpful ¿Could you tell us something about the portability of the maven settings files when we working in that way? Saludos and thanks again.
Sep 13, 2019 at 4:49
@DanielHernández the maven wrapper uses the default settings.xml on the users system. and according to this issue there are some tricks how you could add a custom settings.xml to the repo but it seems then it ignores the user settings on system.
Sep 13, 2019 at 6:30
Command mvnw uses Maven that is by default downloaded to ~/.m2/wrapper on the first use.
URL with Maven is specified in each project at .mvn/wrapper/maven-wrapper.properties :
distributionUrl=https://repo1.maven.org/maven2/org/apache/maven/apache-maven/3.3.9/apache-maven-3.3.9-bin.zip To update or change Maven version invoke the following (remember about —non-recursive for multi-module projects):
./mvnw io.takari:maven:wrapper -Dmaven=3.3.9 or just modify .mvn/wrapper/maven-wrapper.properties manually.
To generate wrapper from scratch using Maven (you need to have it already in PATH run:
mvn io.takari:maven:wrapper -Dmaven=3.3.9 answered Dec 20, 2016 at 10:01
Michal Kordas Michal Kordas
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The Maven Wrapper is an excellent choice for projects that need a specific version of Maven (or for users that don’t want to install Maven at all). Instead of installing many versions of it in the operating system, we can just use the project-specific wrapper script.
mvnw: it’s an executable Unix shell script used in place of a fully installed Maven
mvnw.cmd: it’s for Windows environment
Use Cases
The wrapper should work with different operating systems such as:
After that, we can run our goals like this for the Unix system:
./mvnw clean install And the following command for Batch:
./mvnw.cmd clean install If we don’t have the specified Maven in the wrapper properties, it’ll be downloaded and installed in the folder $USER_HOME/.m2/wrapper/dists of the system.
Maven Wrapper plugin
Maven Wrapper plugin to make auto installation in a simple Spring Boot project.
First, we need to go in the main folder of the project and run this command:
mvn -N io.takari:maven:wrapper We can also specify the version of Maven:
mvn -N io.takari:maven:wrapper -Dmaven=3.5.2 The option -N means –non-recursive so that the wrapper will only be applied to the main project of the current directory, not in any submodules.
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answered Nov 13, 2019 at 15:26
Romil Patel Romil Patel
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Maybe you should mention that part of the text is extracted from baeldung.com/maven-wrapper
Sep 15, 2020 at 11:20
short answer: to run Maven and Gradle in the terminal without following manual installation processes.
./gradlew clean build ./gradlew bootRun ./mvnw clean install ./mvnw spring-boot:run «The recommended way to execute any Gradle build is with the help of the Gradle Wrapper (in short just “Wrapper”). The Wrapper is a script that invokes a declared version of Gradle, downloading it beforehand if necessary. As a result, developers can get up and running with a Gradle project quickly without having to follow manual installation processes saving your company time and money.«
Gradle would also add some specific files corresponding to the Maven files Gradlew and Gradle.bat
A Quick Guide to Maven Wrapper
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