Problem
I have a setup of various distinct repos/projects (i.e. app1, app2, app3) that all depend on shared functionality in my base package.
The projects also use various other third-party dependencies (i.e. app1 and app3 use spring, all of them use kotlinx-serialization).
I want to synchronise the versions of all third-party dependencies, so that any project using my base package uses the same version of every third-party dependency. However, I don't want to introduce new dependencies to projects that do not use them (i.e. app2 does not use spring)
Solution attempts
For libraries, I have been able to solve this with the help of a gradle platform, which does exactly what I want - I specify the versions in my base package, then add the platform as a dependency to my projects and can then simply add dependencies by name (i.e. implementation("org.springframework.boot:some-package")) without having to specify a version number, because it uses the provided value from my platform.
However, for plugins, I have not been able to do this. Many libraries come with plugins and naturally the plugin should be at the same version as the library. I have tried various approaches, including writing a standalone plugin, but none have worked.
Current best idea
I added implementation("org.springframework.boot:spring-boot-gradle-plugin:3.0.2") to the dependencies of my standalone plugin. Then, I added the following code to my standalone plugin:
class BasePlugin : Plugin<Project> {
override fun apply(target: Project) {
target.plugins.apply("org.springframework.boot")
}
}
This works and applies the plugin to my main project at the correct version. However, there are 2 major problems with this:
a) Now every project applies the spring plugin, including app2 (which does not use spring).
b) I have many plugins to manage and no idea how to get the long implementation-string for most of them. I found the "org.springframework.boot:spring-boot-gradle-plugin:3.0.2" by looking up the plugin-id on https://plugins.gradle.org/ and then looking at the legacy plugin application section, which sounds like I am on the wrong track.
I just want to manage the versions of plugins and libraries of multiple projects/repos in a central place - this feels like a fairly basic use case - why is this so hard?
There are some great and detailed answers about dependency management, but unfortunately none worked to perform cross-project version management for plugins.
It seems that there is no gradle functionality to do this, but I got it working with a bit of a workaround. Here is my (working) approach, in hope that it helps someone else with this:
Create a Standalone gradle Plugin
In the build.gradle.kts of the plugin, include the maven coordinates (not its ID) of every other plugin whose version you want to manage in any of your projects in the dependency block with the api keyword. i.e. api("org.springframework:spring-web:6.0.2")
In the main projects, remove every other plugin from the plugins block, so that your custom standalone plugin is the only one remaining.
Create a file (i.e. a plugins.json or whatever you want) in the project root directory of all main projects and in there supply the plugin IDs of the plugins that you actually intend to use in that project. Just the IDs, no version numbers, i.e. "org.springframework.boot" for Spring's plugin. (Keep in mind that for plugins declared as kotlin("abc") you will have to add the prefix "org.jetbrains.com.", as the kotlin method is just syntactic sugar for that)
In your plugin source code, in the overriden apply method, look for. a file named plugins.json (or whatever you chose) in the project.buildFile.parent directory (which will be the directory of the project using this plugin, NOT of the plugin itself). From this file, read the plugin IDs
for every pluginID in the file, call project.plugins.apply(id)
How/Why it works:
The main project build.gradle.kts is executed, looks at the plugin block and applies your standalone plugin (which is the only one), which calls its apply method.
This plugin then applies other plugins based on their ID from the file.
Normally, this will throw an error because these plugins are not found, but because we defined them as dependencies with the api keyword in our standalone plugin, they are now available on the classpath and in exactly the version of that import statement.
Hope it helps someone!
I use version numbers in a gradle.properties file for this purpose. Since the introduction of Gradle version catalogs, my approach is probably a bit out of date, but I'll share it here anyway. It's based on the fact that plugin versions can be managed in settings.gradle.kts by reading values from the properties file.
In gradle.properties:
springBootVersion=3.0.2
In settings.gradle.kts:
pluginManagement {
val springBootVersion: String by settings
plugins {
id("org.springframework.boot") version springBootVersion
}
}
And finally in build.gradle.kts:
plugins {
id("org.springframework.boot")
}
dependencies {
val springBootVersion: String by project
implementation(platform("org.springframework.boot:spring-boot-dependencies:$springBootVersion"))
}
Notice that the plugin version is omitted in the build script because it is already specified in the settings file.
And note also that the method for accessing the property in the settings script is slightly different from that in the build script.
a) Now every project applies the spring plugin, including app2 (which does not use spring).
It is indeed better to avoid applying too many plugins - and that's why Gradle encourages reacting to plugins.
import org.gradle.api.Plugin
import org.gradle.api.Project
import org.gradle.kotlin.dsl.*
import org.springframework.boot.gradle.plugin.SpringBootPlugin
class BasePlugin : Plugin<Project> {
override fun apply(target: Project) {
// don't apply
//target.plugins.apply("org.springframework.boot")
// instead, react!
target.plugins.withType<SpringBootPlugin>().configureEach {
// this configuration will only trigger if the project applies both
// BasePlugin *and* the Spring Boot pluging
}
// you can also react based on the plugin ID
target.pluginManager.withPlugin("org.springframework.boot") {
}
}
}
Using the class is convenient if you want to access the plugin, or the plugin's extension, in a typesafe manner.
You can find the Plugin's class by
looking in the source code for the class that implements Plugin<Project>,
in the plugin's build config for the implementationClass,
or in the published plugin JAR - in the META-INF/gradle-plugins directory there will be a file that has the implementationClass.
This doesn't help your version alignment problem - but I thought it was worth mentioning!
b) I have many plugins to manage and no idea how to get the long implementation-string for most of them. I found the "org.springframework.boot:spring-boot-gradle-plugin:3.0.2" by looking up the plugin-id on https://plugins.gradle.org/ and then looking at the legacy plugin application section, which sounds like I am on the wrong track.
You're on the right track with the "long implementation string" as you call it. I'll refer to those as the 'Maven coordinates' of the plugin.
Gradle Plugin Maven Coordinates
The plugin id of the Kotlin JVM plugin is org.jetbrains.kotlin.jvm, but the Maven coordinates are org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.0 .
The 'legacy' part refers to how the plugins are applied, using the apply(plugin = "...") syntax. The new way uses the plugin {} block, but under the hood, both methods still use the Maven coordinates of the plugin.
If you add those Maven coordinates (with versions) to your Java Platform, then you can import the platform into your project. But where?
Defining plugin versions
There are a lot of ways to define plugins, so I'll only describe one, and coincidentally it will be compatible with defining the version using a Java Platform.
If you're familiar with buildSrc convention plugins, you'll know that they can apply plugins, but they can't define versions.
// ./buildSrc/src/main/kotlin/kotlin-jvm-convention.gradle.kts
plugins {
kotlin("jvm") version "1.8.0" // error: pre-compiled script plugins can't set plugin versions!
}
Instead, plugin versions must be defined in the build config for buildSrc
// ./buildSrc/build.gradle.kts
plugins {
`kotlin-dsl`
}
dependencies {
// the Maven coordinates of the Kotlin JVM plugin - including the version
implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.0")
}
This looks a lot more traditional, and so I hope the next step is clean: use your Java Platform!
Applying a Java Platform to buildSrc
// ./buildSrc/build.gradle.kts
plugins {
`kotlin-dsl`
}
dependencies {
// import your Java Platform
implementation(platform("my.group:my-platform:1.2.3"))
// no version necessary - it will be supplied by my.group:my-platform
implementation("org.jetbrains.kotlin:kotlin-gradle-plugin")
}
Note that this same method will also apply if your projects an 'included build' instead of buildSrc.
Once the plugin versions are defined in ./buildSrc/build.gradle.kts, you can use them throughout your project (whether in convention plugins, or in subprojects), they will be aligned.
// ./subproject-alpha/build.gradle.kts
plugins {
kotlin("jvm") // no version here - it's defined in buildSrc/build.gradle.kts
}
I'm building a Kotlin multiplatform library. One of the targets in this project is javascript. In the source set I have added a dependency like this:
val jsMain by getting {
dependencies {
implementation(npm("libphonenumber-js", "1.10.13"))
}
}
The gradle sync was successful, now I want to import the files in jsMain directory. How can I achieve this?
Add npm dependency with generateExternals as you already did
implementation(npm("libphonenumber-js", "1.10.13", generateExternals = true))
generateExternals = true triggers a tool called Dukat that generates Kotlin external declarations from the Typescript definition file of that npm module.
Once your project syncs, it would have externals folder under your shared module's build folder like shown below,
(Ignore kmp-lib-1621 in above image. That would be your module/library name instead)`
Now copy and paste these files in your project (jsMain source set) and remove generateExternal = true from your dependency otherwise it would generate this files everytime. (1) you would lose any manual change (2) if you update the library version then it can potentially break your project
You should be able to call generated external code from Kotlin code, whether you keep it in build folder or you pasted it in your project code.
Important Note: Dukat tool is experiemental and known to create externals that may not work 100% times. So remove all unnecessary code from external generated code so you only end up having few references of classes you want to use from the npm library. Do some trial and error and you would be fine.
Hope this helps!
You have to use js(IR) backend and generate externals
implementation(npm("libphonenumber-js", "1.10.13", generateExternals = true)).
I am using Kotlin to share logic between my back end (Java Spring Web) and front end. Getting the Java back end to call the Kotlin logic is easy: I made both part of the same Gradle Multiproject build and have the server project depend on the Kotlin project.
Now I need to get the generated JavaScript out of Kotlin and into a format where the server can serve it. Looking through the Gradle output jar for the server, it only has the jvm jar and not the js jar.
I had a similar problem in this GitHub project with a Spring Boot backend and a Kotlin/JS frontend + common code.
If everything is in the same repo in multiple Gradle subprojects, you can use the following in the server subproject to bundle the produced JS as resources into your server's jar:
tasks.processResources {
// make sure we build the frontend before creating the jar
dependsOn(":frontend:assemble")
// package the frontend app within the jar as static
val frontendBuildDir = project(":frontend").buildDir
val frontendDist = frontendBuildDir.toPath().resolve("distributions")
from(frontendDist) {
include("**/*")
into("static")
}
}
It's not ideal (I don't like inter-project dependencies like this), but it does the job.
Spring Boot then automatically serves the static files from this place in the jar (/static).
I am trying to build a kotlin library for discord bots, which can be found at https://github.com/TheDrone7/discord-kt , published to jcenter (bintray link - https://bintray.com/thedrone7/discordKt/discord-kt). The library has a few dependencies of it's own as well.
When I add my own library to my test app, the library's dependencies were not installed and I started getting some errors. Is there a way to specify the library's dependencies so that they get automatically installed when a user uses my library?
EDIT: -
So basically my test app's build.gradle.kts file's dependencies section is given below
dependencies {
// Use the Kotlin JDK 8 standard library.
implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
implementation("org.theDrone:discordKt:0.0.1a")
// Use the Kotlin test library.
testImplementation("org.jetbrains.kotlin:kotlin-test")
// Use the Kotlin JUnit integration.
testImplementation("org.jetbrains.kotlin:kotlin-test-junit")
}
And my library is dependent on the following packages: -
org.jetbrains.kotlinx:kotlinx-coroutines-core:1.1.0
org.java-websocket:Java-WebSocket:1.4.0
com.beust:klaxon:5.0.5
org.slf4j:slf4j-jdk14:1.7.26
now when I run my test app, it shows gives error that there is no class named WebSocketClient which is a part of the org.java-websocket:Java-WebSocket:1.4.0 package and is also the base of my entire library.
When I add the listed packages to my test app's dependencies, it works perfectly fine. So is there a way that I could define in my library that the apps using it will also automatically depend on the packages my library depends on?
You declared the Java-WebSocket library as a dependency of your library using the implementation configuration.
This configuration means: I need that for my code to work, but it's an implementation detail and it's thus not part of my public API, so users of my library won't have access to it in their compile classpath.
So Gradle, when it generates the pom.xml file for your library, adds Java-WebSocket as a runtime dependency, and not as a compile dependency.
Read the java-library plugin documentation, which explains all of that in details. Once you have understood it, use api instead of implementation in your library's build.gradle.kts file for the dependencies that are part of your API, and should thus be compile dependencies and not runtime dependencies:
api("org.java-websocket:Java-WebSocket:1.4.0")
I am thinking to use Gradle to manipulate with mysql database. It will read some files from filesystem, analyse them and populate database accordingly.
Such project will not produce any project code, because all output will go to database tables. On the other hand, gradle script should access some custom java or groovy classes to facilitate working with source data.
Is this a possible Gradle usage? Where to put gradle-accessible classes then? I don't want to have separate project, producing JAR for this project. I wan't single project, so that Gradle first compiles classes and the utilizes them in the script.
Is this possible?
Gradle is extensible, so you can utilize buildSrc for such scenarios. It works in the following way:
along build.gradle in the project there is buildSrc dir with custom build.gradle
in buildSrc/build.gradle you can define the script dependencies itself, implement plugins and tasks
finally you can apply a plugin from buildSrc to build.gradle.
It's quite handy, since e.g. IntelliJ can import such project and provide code completion for instance.
Another way is to put all the necessary stuff in build.gradle itself.
Such buildSrc project can be compiled to a jar, published and provided as a plugin, or it can be a separate project on github to be downloaded and used to manipulate data. Also, there no need to implement Plugin, you can use static methods e.g. Have a look at the demo.