Develop Reference

How to use Kotlin with a Bukkit/Spigot plugin and Gradle

I am trying to use Kotlin for a Spigot plugin (for version 1.8.8), as I find Kotlin a lot more efficient to use. But, whenever I try and run the plugin, I get this error:
Caused by: java.lang.ClassNotFoundException: kotlin.jvm.internal.Intrinsics
I have looked online, and it seems I need to shade the Kotlin jar file into my plugin, could anyone advise me how I would do that?
UPDATE After trying what was suggested below I still get the same error.
Here is my build.gradle:
plugins {
id 'java'
id 'org.jetbrains.kotlin.jvm' version '1.3.31'
id 'com.github.johnrengelman.shadow' version '4.0.2'
}
group 'me.graphicalcake95'
version '1.0.0'
sourceCompatibility = 1.8
repositories {
mavenCentral()
maven {
url 'https://hub.spigotmc.org/nexus/content/repositories/snapshots/'
}
}
shadowJar {
baseName = 'shadow'
classifier = null
version = null
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.12'
compileOnly 'org.bukkit:bukkit:1.8.8-R0.1-SNAPSHOT'
shadow "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
}
compileKotlin {
kotlinOptions {
jvmTarget = "1.8"
}
}
compileTestKotlin {
kotlinOptions {
jvmTarget = "1.8"
}
}

You indeed need to Shadow the Kotlin standard library into your plugin. Since you are using Gradle it can do this by using the Shadow Plugin which is similar to Shade but Shade is only for Maven so it won't be useful for you.
Using the Shadow plugin is straightforward. First you apply the plugin itself:
plugins {
id 'com.github.johnrengelman.shadow' version '5.0.0'
}
then you can configure Shadow:
shadowJar {
baseName = 'shadow'
classifier = null
version = null
}
This will create a shadow.jar in your build folder when you build the project. After applying the shadow plugin you can shadow dependencies to be included in the fat jar:
dependencies {
shadow "org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
}

Install this plugin on your spigot server
download the jar and place it in the plugins folder,
then follow the documentation

Is there any way of making IntelliJ IDEA recognizing Dagger 2 generated classes in a Java project?

Context
I have started a personal project in java with Gradle as the build system and I want to use Dagger 2 as a DI. The main reason of doing that is to get used to that library and be able to use it easily in bigger projects.
What have I tried
I've managed to make the Google sample runs on IntelliJ IDEA
Problem
IntelliJ IDEA keeps telling me that it cannot resolve the generated class (in this case DaggerCoffeeApp_Coffee). It's a bit annoying not to know if the written code is correct (specially when you are learning to use Dagger 2).
All java classes are the same as the Google sample. Here is my build.gradle file:
apply plugin: 'java'
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.12'
compile 'com.google.dagger:dagger:2.0.1'
compile 'com.google.dagger:dagger-compiler:2.0.1'
}
Question
Is there any way to make IntelliJ IDEA recognize DaggerCoffeeApp_Coffee as a generated class (and so make it possible to go to its implementation by `ctrl + left click)?

Simplest way I found:
Add idea plugin and add Dagger2 dependency like below:
plugins {
id "net.ltgt.apt" version "0.10"
}
apply plugin: 'java'
apply plugin: 'idea'
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.12'
compile 'com.google.dagger:dagger:2.11'
apt 'com.google.dagger:dagger-compiler:2.11'
}
Turn on Annotation Processing for IntelliJ: Go to Settings and search for Annotation Processors, check Enable annotation processing like below image:

Finally I made it!
I had to add the apt and the idea plugin so right now my build.gradle file look like this:
buildscript {
repositories {
maven {
url "https://plugins.gradle.org/m2/"
}
}
dependencies {
classpath "net.ltgt.gradle:gradle-apt-plugin:0.4"
}
}
apply plugin: "net.ltgt.apt"
apply plugin: 'java'
apply plugin: 'idea'
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.12'
compile 'com.google.dagger:dagger:2.0.1'
apt 'com.google.dagger:dagger-compiler:2.0.1'
}

you must manually enable the annotation processing in IntelliJ.
From: Settings --> Build, Execution, Deployment --> Compiler --> Annotation Processors --> Enable annotation processing and Obtain processors from project classpath
then rebuild the project and you will find the generated classes in the project.
Please note that I have used this solution in a (java) android project.

I'm using version 2017.3.3 of IntelliJ IDEA, version 0.14 of the net.ltgt.apt plugin and version 2.14.1 of Dagger and as well as applying the idea plugin in the build.gradle file (as in Pelocho's answer) I found I also had to tell IntelliJ where it can find the sources generated by Dagger, as follows:
apply plugin: 'idea'
idea {
module {
sourceDirs += file("$buildDir/generated/source/apt/main")
testSourceDirs += file("$buildDir/generated/source/apt/test")
}
}

This is what I had to do in order to get Idea to work with Dagger2 and gradle.
Turn on annotation processing as shown in the answers above.
Add the following to the build.gradle file in order for Idea to see the generated classes as sources.
sourceDirs += file("$projectDir/out/production/classes/generated/")
Here's the full listing of my build.gradle
plugins {
id 'java'
id 'idea'
id "net.ltgt.apt" version "0.10"
}
idea {
module {
sourceDirs += file("$projectDir/out/production/classes/generated/")
}
}
repositories {
mavenCentral()
}
dependencies {
compile 'com.google.dagger:dagger:2.16'
apt 'com.google.dagger:dagger-compiler:2.16'
}
sourceCompatibility = 1.8
Also, I had to add the following gradle task (to my build.gradle file) to clear out my out directory. When I moved some files around and Dagger2 regenerated the source files, the out directory wasn't being cleared out :(. I also included this task in my run configuration, so that it gets triggered before I rebuild my project.
task clearOutFolder(type: Delete) {
delete 'out'
}

Here's the solution that worked for me:
File -> Project Structure -> (select your project under list of modules) -> Open 'Dependencies' tab
Then, click on green '+' sign, select 'JARs or directory' and select 'build/classes/main' folder.
Another solution would be to link folder with build class files using 'dependencies' block inside build.gradle:
https://stackoverflow.com/a/22769015/5761849

Using IntelliJ IDEA 2019.1 and Gradle 5.4.1, this seems to be enough:
plugins {
id 'java'
}
version '1.0-SNAPSHOT'
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
testImplementation group: 'junit', name: 'junit', version: '4.12'
implementation 'com.google.dagger:dagger:2.23.1'
annotationProcessor 'com.google.dagger:dagger-compiler:2.23.1'
}
I don't know the minimal versions for which this solution works, though.

I had a similar problem, I could not find out the cause for a long time.
Just launched and the result surprised me.
Intellij Idea 2018.3.6 -
build.gradle:
plugins {
id "java"
}
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.12'
compile 'com.google.dagger:dagger:2.11'
apt 'com.google.dagger:dagger-compiler:2.11'
}

The following worked for me on IntelliJ 2021.3.3 (UE)
plugins {
id 'java'
id 'idea'
id("com.github.johnrengelman.shadow") version "7.1.2"
}
idea {
module {
sourceDirs += file("$projectDir/build/generated/sources/annotationProcessor/java/main")
testSourceDirs += file("$projectDir/build/generated/sources/annotationProcessor/java/test")
}
}
group 'com.codigomorsa'
version '1.0-SNAPSHOT'
repositories {
mavenCentral()
}
dependencies {
annotationProcessor 'com.google.dagger:dagger-compiler:2.44'
implementation 'com.google.code.gson:gson:2.9.1'
implementation 'com.google.dagger:dagger:2.44'
testAnnotationProcessor 'com.google.dagger:dagger-compiler:2.44'
testImplementation 'org.junit.jupiter:junit-jupiter-api:5.9.0'
testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.9.0'
}
test {
useJUnitPlatform()
}

Which is the proper Gradle plugin to support 'provided' method?

I'm currently trying to include Project Lombok helper into my Gradle project, but while following their instructions for Gradle within my build.gradle, I'm getting the following error:
Error:(11, 0) Build script error, unsupported Gradle DSL method found: 'provided()'!
Possible causes could be:
you are using Gradle version where the method is absent
you didn't apply Gradle plugin which provides the method
or there is a mistake in a build script
My current build.gradle file:
apply plugin: 'java'
sourceCompatibility = 1.5
version = '1.0'
repositories {
mavenCentral()
}
dependencies {
provided "org.projectlombok:lombok:1.14.4"
testCompile group: 'junit', name: 'junit', version: '4.11'
}

As of release 2.12, provided scope is called compileOnly
Old answer:
Provided scope is available in 'war' plugin (http://www.gradle.org/docs/current/userguide/war_plugin.html , providedCompile ) If You don't want to use the 'war' plugin, there is also an opened JIRA issue regarding 'provided' scope http://issues.gradle.org/browse/GRADLE-784 , suggested workaround is to create Your own cofiguration:
configurations {
provided
}
and set it to be used with your compilation classpath:
sourceSets {
main {
compileClasspath += configurations.provided
}
}

Check your app level gradle file. If any line looks like this:
compile dependency.gson provided dependency.javaxAnnotation
Edit it like this:
compile dependency.gson
provided dependency.javaxAnnotation
It should work.

Gradle: JDBC driver not compiled into JAR

I have a module build.gradle file that looks like this:
apply plugin: 'java'
sourceCompatibility = 1.5
version = '1.0'
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.11'
compile 'mysql:mysql-connector-java:5.1.6'
}
I also have an artefact set up like this:
When I build this artifact, my classes are included but MySQL driver is not. When executed, MySQL driver class is not found. How do I build so that my JAR artifact (used as a library)
ccontains MySQL JDBC driver?

Configuring this in Gradle and IntelliJ is two different things. The most direct way to create a fat Jar in Gradle is:
jar {
from { configurations.runtime.collect { it.directory ? it : zipTree(it) } }
}
PS: Merging Jars can cause problems. In most cases it should not be done, in particular for a library.

Gradle with IntelliJ not loading PostgreSQL JDBC as a dependency

I am trying to setup IntelliJ alongwith Gradle and JOOQ for my next project. As of now, this is how my Gradle file looks like:
apply plugin: 'java'
apply plugin: 'jooq'
sourceCompatibility = 1.5
version = '1.0'
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.11'
}
dependencies {
compile 'org.jooq:jooq:3.1.0'
compile 'com.google.guava:guava:14.0'
compile 'postgresql:postgresql:9.1-901-1.jdbc4'
}
buildscript {
repositories {
mavenLocal()
mavenCentral()
}
dependencies {
classpath 'postgresql:postgresql:9.1-901-1.jdbc4'
classpath 'com.github.ben-manes:gradle-jooq-plugin:0.5'
}
}
jooq {
... snip ...
}
And this is how my external dependencies (in IntelliJ) show up:
.
Somehow, Gradle is downloading and IntelliJ is recognizing the jooq and guava as part of my dependencies, but postgresql does not show up. So, while doing this works (using Guava, a dependency loaded from Gradle):
List<String> stringList = Lists.newArrayList();
This fails with a ClassNotFoundException:
Class.forName("org.postgresql.Driver").newInstance();
While doing a ./gradlew build, I have seen gradle output the fact that it did download thr postgresql-9.1-901 jar from Maven Central, but I don't know where it keeps it. Any help is greatly appreciated.

Apparently, I really need to RTFM. I hadn't refreshed the dependencies from the Gradle tool window in IntelliJ after making changes to the Gradle script. Got it from here: https://www.jetbrains.com/idea/webhelp/synchronizing-changes-in-gradle-project-and-intellij-idea-project.html