Файл: Gradle.pdf

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44.5. More about project libraries

If your project is supposed to be used as a library, you need to define what are the artifacts of this library and what are the dependencies of these artifacts. The Java plugin adds a runtime configuration for this purpose, with the implicit assumption that the runtime dependencies are the dependencies of the artifact you want to publish. Of course this is fully customizable. You can add your own custom configuration or let the existing configurations extend from other configurations. You might have different group of artifacts which have a different set of dependencies. This mechanism is very powerful and flexible.

If someone wants to use your project as a library, she simply needs to declare on which configuration of the dependency to depend on. A Gradle dependency offers the configuration property to declare this. If this is not specified, the default configuration is used (see Section 43.4.9, “Dependency configurations”). Using your project as a library can either happen from within a multi-project build or by retrieving your project from a repository. In the latter case, an ivy.xml descriptor in the repository is supposed to contain all the necessary information. If you work with Maven repositories you don't have the flexibility as described above. For how to publish to Maven repository, see the section Section 45.6, “Interacting with Maven repositories”.

[16] To be exact, the Base plugin provides those tasks. This plugin is automatically applied if you use the Java plugin.

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45

The Maven Plugin

This chapter is a work in progress

The Maven plugin adds support for deploying artifacts to Maven repositories.

45.1. Usage

To use the Maven plugin, include in your build script:

Example 45.1. Using the Maven plugin

build.gradle

apply plugin: 'maven'

45.2. Tasks

The Maven plugin defines the following tasks:

Table 45.1. Maven plugin - tasks

45.3. Dependency management

The Maven plugin does not define any dependency configurations.

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45.4. Convention properties

The Maven plugin defines the following convention properties:

Table 45.2. Maven plugin - properties

See

Section 45.6. “Dependen mapping”.

These properties are provided by a MavenPluginConvention convention object.

45.5. Convention methods

The maven plugin provides a factory method for creating a POM. This is useful if you need a POM without the context of uploading to a Maven repo.

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Example 45.2. Creating a stand alone pom.

build.gradle

task writeNewPom << { pom {

project {

inceptionYear '2008' licenses {

license {

name 'The Apache Software License, Version 2.0'

url 'http://www.apache.org/licenses/LICENSE-2.0.txt' distribution 'repo'

}

}

}

}.writeTo("$buildDir/newpom.xml")

}

Amongst other things, Gradle supports the same builder syntax as polyglot Maven. To learn more about the Gradle Maven POM object, see MavenPom. See also: MavenPluginConvention

45.6. Interacting with Maven repositories

45.6.1. Introduction

With Gradle you can deploy to remote Maven repositories or install to your local Maven repository. This includes all Maven metadata manipulation and works also for Maven snapshots. In fact, Gradle's deployment is 100 percent Maven compatible as we use the native Maven Ant task under the hood.

Deploying to a Maven repository is only half the fun if you don't have a POM. Fortunately Gradl can generate this POM for you using the dependency information it has.

45.6.2. Deploying to a Maven repository

Let's assume your project produces just the default jar file. Now you want to deploy this jar file to remote Maven repository.

Example 45.3. Upload of file to remote Maven repository

build.gradle

apply plugin: 'maven'

uploadArchives { repositories {

mavenDeployer {

repository(url: "file://localhost/tmp/myRepo/")

}

}

}

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That is all. Calling the uploadArchives task will generate the POM and deploys the artifact and the pom to the specified repository.

There is some more work to do if you need support for other protocols than file. In this case the native Maven code we delegate to needs additional libraries. Which libraries depend on the protocol you need. The available protocols and the corresponding libraries are listed in Table 45.3, “Protocol jars for Maven deployment”(those libraries have again transitive dependencies which

have transitive dependencies). For example to use the ssh protocol you can do:

Example 45.4. Upload of file via SSH

build.gradle

configurations { deployerJars

}

repositories { mavenCentral()

}

dependencies {

deployerJars "org.apache.maven.wagon:wagon-ssh:1.0-beta-2"

}

uploadArchives { repositories.mavenDeployer {

name = 'sshDeployer' // optional configuration = configurations.deployerJars

repository(url: "scp://repos.mycompany.com/releases") { authentication(userName: "me", password: "myPassword")

}

}

}

There are many configuration options for the Maven deployer. The configuration is done via a Groovy builder. All the elements of this tree are Java beans. To configure the simple attributes you pass a map to the bean elements. To add another bean elements to its parent, you use a closure. In the example above repository and authentication are such bean elements. Table 45.4, “Configuration elements of the MavenDeployer”lists the available bean elements and a link to the javadoc of the corresponding class. In the javadoc you can see the possible attributes you can set for a particular element.

In Maven you can define repositories and optionally snapshot repositories. If no snapshot repository is defined, releases and snapshots are both deployed to the repository element. Otherwise snapshots are deployed to the snapshotRepository element.

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Table 45.3. Protocol jars for Maven deployment

snapshotRepository org.apache.maven.artifact.ant.RemoteRepository

45.6.3. Installing to the local repository

The Maven plugin adds an install task to your project. This task depends on all the archives task of the archives configuration. It installs those archives to your local Maven repository. If the default location for the local repository is redefined in a Maven settings.xml, this is considered by this task.

45.6.4. Maven POM generation

The Maven POMs for uploading are automatically generated by Gradle. The groupId, artifactId, version and packaging values are taken from the project object. The dependency elements are created from the Gradle dependency declarations. You can find the generated POMs in the directory <buildDir>/poms. You can further customize the POM via the API of the MavenPom object.

You might want the artifact deployed to the maven repository to have a different version or name than the artifact generated by Gradle. To customize these you can do:

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Example 45.5. Customization of pom

build.gradle

uploadArchives { repositories {

mavenDeployer {

repository(url: "file://localhost/tmp/myRepo/") pom.version = '1.0Maven'

pom.artifactId = 'myMavenName'

}

}

}

Or you want to add new elements like license information.

Example 45.6. Builder style customization of pom

build.gradle

uploadArchives { repositories {

mavenDeployer {

repository(url: "file://localhost/tmp/myRepo/") pom.project {

licenses { license {

name 'The Apache Software License, Version 2.0'

url 'http://www.apache.org/licenses/LICENSE-2.0.txt' distribution 'repo'

}

}

}

}

}

}

We use a builder here. You could also add the artifactId and groupId via the builder.

The pom object offers a whenConfigure method, if you need to modify the autogenerated content.

Example 45.7. Modifying auto-generated content

build.gradle

[installer, deployer]*.pom*.whenConfigured {pom ->

pom.dependencies.find {dep -> dep.groupId == 'group3' && dep.artifactId ==

}

If you have more than one artifact to publish, things work a little bit differently. SeeSection 45.6.4.1, “Multiple artifacts per projec.t”

To customize the settings for the Maven installer (seeSection 45.6.3, “Installing to the loc

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repository”), you can do:

Example 45.8. Customization of Maven installer

build.gradle

configure(install.repositories.mavenInstaller) { pom.project {

version '1.0Maven' artifactId 'myName'

}

}

In contrast to the example above we use the builder here for changing groupId and artifactId.

45.6.4.1. Multiple artifacts per project

Maven can only deal with one artifact per project. This is reflected in the structure of the Maven POM. We think there are many situations where it makes sense to have more than one artifact per project. In such a case you need to generate multiple POMs. In such a case you have to explicitly declare each artifact you want to publish to a Maven repository. The MavenDeployer and the MavenInstaller both provide an API for this:

Example 45.9. Generation of multiple poms

build.gradle

uploadArchives { repositories {

mavenDeployer {

repository(url: "file://localhost/tmp/myRepo/") addFilter('api') {artifact, file ->

artifact.name == 'api'

}

addFilter('service') {artifact, file -> artifact.name == 'service'

}

pom('api').version = 'mySpecialMavenVersion'

}

}

}

You need to declare a filter for each artifact you want to publish. This filter defines a boolean expression for which Gradle artifact it accepts. Each filter has a POM associated with it which you can configure. To learn more about this have a look at PomFilterContainer and its associated classes.

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45.6.4.2. Dependency mapping

The Maven plugin configures the default mapping between the Gradle configurations added by the Java and War plugin and the Maven scopes. Most of the time you don't need to touch this and yo can safely skip this section. The mapping works like the following. You can map a configuration to one and only one scope. Different configurations can be mapped to one or different scopes. One can assign also a priority to a particular configuration-to-scope mapping. Have a look at Conf2ScopeMappingContainer to learn more. To access the mapping configuration you can

say:

Example 45.10. Accessing a mapping configuration

build.gradle

task mappings << {

println conf2ScopeMappings.mappings

}

Gradle exclude rules are converted to Maven excludes if possible. Such a conversion is possible if in the Gradle exclude rule the group as well as the module name is specified (as Maven needs both in contrast to Ivy). Per-configuration excludes are also included in the Maven POM, if they are convertible.

[17] It is planned for a future release to provide out-of-the-box support for this

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