There's a strange issue I've never seen.
Adding a compile 'org.locationtech.spatial4j:spatial4j:0.7' to the dependencies list in my gradle project leads to a corrupt classpath. When I comment out that library and run java -verbose:class -jar sol_backend_full.jar > ok.log it outputs 4399 lines of class entries. However, with that library in classpath, java -verbose:class -jar sol_backend_full.jar > failed.log outputs only 953 lines, most of which are java.lang.* or sun.*.
It obviously results in Error: Could not find or load main class.
➥ Has anyone ever encountered that strange behaviour?
Of course, I can substitute that library with another spatial library, but what's happening is simply strange. It happens only with this library, removing/adding any other is fine.
Gradle version in question is 5.5.1, and that library manifest looks a bit long, but not suspicious at all. Falling back to 4.8 also reproduces it.
Here is the build script:
task customFatJar(type: Jar) {
manifest {
attributes 'Main-Class': 'ru.rxproject.sol.backend.BackendApplication',
'Implementation-Version': version + System.getenv('BUILD_NUMBER').toString(),
'Commit-Hash': 'git-' + System.getenv('GIT_COMMIT'),
'Build-Date': java.time.LocalDateTime.now().toString()
}
archiveName = 'sol_backend_full.jar'
from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
with jar
}
The JAR dependancy org.locationtech.spatial4j:spatial4j:0.7 is a signed jar. When you create a fat jar, java Classloader is not able to load the other classes from your fat jar because these are not signed.
So, you can't create a fat jar with that dependancy without excluding the signatures.
Please refer - Gradle - FatJar - Could not find or load main class
Like mentioned in the above post, you may exclude the signatures like -
jar {
manifest {
attributes "Main-Class": mainClassName
}
from {
configurations.compile.collect { it.isDirectory() ? it : zipTree(it) }
}
exclude 'META-INF/*.RSA'
exclude 'META-INF/*.SF'
exclude 'META-INF/*.DSA'
}
But, I would suggest to keep the jar dependancy out of the fat jar.
I have started on gradle today itself. So I am trying out random things. I have below build.gradle file:
apply plugin: 'java'
repositories {
mavenCentral()
}
dependencies {
testImplementation('org.junit.jupiter:junit-jupiter-api:5.4.2')
testRuntime('org.junit.jupiter:junit-jupiter-engine:5.4.2')
compile 'com.googlecode.json-simple:json-simple:1.1.1'
}
test {
useJUnitPlatform()
}
jar {
manifest {
attributes(
'Main-Class': 'src.main.java.demo.Hello'
)
}
from {
configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it)}
}
}
I have read somewhere that the method that I am using inside from block will create fat jar, which is not a good practice. As I am fairly new to this, I humbly want to ask the alternative to this. Is it adding classpath to manifest or something else??
The primary purpose is to bundle third party dependency jar files that will be used on runtime.
Thank You!
You could put all your dependencies into a ZIP file together with your own JAR and possibly external resources, or build an installer, or (if you're building a web app) build a WAR or EAR file. Gradle will take care of the manifest for you in any case.
(Also, there is nothing really wrong with fat JARs, they are fairly common these days and they do work.)
I have a Gradle project which depends on sub-projects. I would like to create a "fat jar" containing all my sub-projects, and externel dependencies as external jars.
build.gradle:
dependencies {
compile project(':MyDep1')
compile project(':MyDep2')
compile 'com.google.guava:guava:18.0'
}
I would like to be able to generate the following output:
MyProject.jar -> Includes MyDep1 & MyDep2
libs/guavaXXX.jar -> Guava as external lib
I don't know how I could do this.
Use different configurations to hold your internal and external dependencies and package only one of those configurations into your project artifact.
configurations{
internalCompile
externalCompile
}
//add both int and ext to compile
configurations.compile.extendsFrom(internalCompile)
configurations.compile.extendsFrom(externalCompile)
dependencies{
internalCompile project(':MyDep1')
internalCompile project(':MyDep2')
externalCompile 'com.google.guava:guava:18.0'
}
in your fat jar task, include only from internalCompile
I finally made it work with this solution:
jar {
subprojects.each {
from files(it.sourceSets.main.output)
}
}
distributions {
main {
contents {
exclude subprojects.jar.archivePath.name
}
}
}
In my project's jar, I include the content of all subprojects ouputs. In the distribution, I exclude the jar from subprojects (so it only contains dependencies). This is probably not the best way, but it's simple and it works.
I have a task that looks like this (this is not the main jar this module kicks out, there is another one I can't show)
task interfaceJar(type: Jar) {
classifier = 'interface'
from "$buildDir/classes/main/"
include 'x/y/z/stuff.class'
}
And some dependencies like this
dependencies {
/* lots of dependencies */
compile 'com.esotericsoftware:kryo:3.0.3'
}
How can I include that one specific dependency in my interfaceJar task?
To include dependency jar without unpacking it first: (Note: if you use this, you may want to add a Class-Path entry to your manifest)
task interfaceJar(type: Jar) {
classifier = 'interface'
from "$buildDir/classes/main/"
from configurations.compile.findAll{it.name.contains('kryo')}
include 'x/y/z/stuff.class'
include '*.jar'
}
Edit: to unpack your dependency jar and include the contents in your interface jar:
task interfaceJar(type: Jar) {
classifier = 'interface'
from("$buildDir/classes/main/"){
include 'stuff.class'
}
configurations.compile.findAll{it.name.contains('kryo')}.each{
from(it.isDirectory() ? it : zipTree(it))
}
}
Until now I created runnable JAR files via the Eclipse "Export..." functionallity but now I switched to IntelliJ IDEA and Gradle for build automation.
Some articles here suggest the "application" plugin, but this does not entirely lead to the result I expected (just a JAR, no start scripts or anything like this).
How can I achieve the same result Eclipse does with the "Export..." dialog?
An executable jar file is just a jar file containing a Main-Class entry in its manifest. So you just need to configure the jar task in order to add this entry in its manifest:
jar {
manifest {
attributes 'Main-Class': 'com.foo.bar.MainClass'
}
}
You might also need to add classpath entries in the manifest, but that would be done the same way.
See http://docs.oracle.com/javase/tutorial/deployment/jar/manifestindex.html
If you already have defined an application context, you can re-use the definition rather than duplicate it:
application {
// Define the main class for the application.
mainClass = 'com.foo.bar.MainClass'
}
jar {
manifest {
attributes 'Main-Class': application.mainClass
}
}
Both JB Nizet and Jorge_B's answers are correct.
In its simplest form, creating an executable JAR with Gradle is just a matter of adding the appropriate entries to the manifest. However, it's much more common to have dependencies that need to be included on the classpath, making this approach tricky in practice.
The application plugin provides an alternate approach; instead of creating an executable JAR, it provides:
a run task to facilitate easily running the application directly from the build
an installDist task that generates a directory structure including the built JAR, all of the JARs that it depends on, and a startup script that pulls it all together into a program you can run
distZip and distTar tasks that create archives containing a complete application distribution (startup scripts and JARs)
A third approach is to create a so-called "fat JAR" which is an executable JAR that includes not only your component's code, but also all of its dependencies. There are a few different plugins that use this approach. I've included links to a few that I'm aware of; I'm sure there are more.
shadow
one-jar
spring-boot
capsule
Least effort solution for me was to make use of the gradle-shadow-plugin
Besides applying the plugin all that needs to be done is:
Configure the jar task to put your Main class into manifest
jar {
manifest {
attributes 'Main-Class': 'com.my.app.Main'
}
}
Run the gradle task
./gradlew shadowJar
Take the app-version-all.jar from build/libs/
And finally execute it via:
java -jar app-version-all.jar
As others have noted, in order for a jar file to be executable, the application's entry point must be set in the Main-Class attribute of the manifest file. If the dependency class files are not collocated, then they need to be set in the Class-Path entry of the manifest file.
I have tried all kinds of plugin combinations and what not for the simple task of creating an executable jar and somehow someway, include the dependencies. All plugins seem to be lacking one way or another, but finally I got it like I wanted. No mysterious scripts, not a million different mini files polluting the build directory, a pretty clean build script file, and above all: not a million foreign third party class files merged into my jar archive.
The following is a copy-paste from here for your convenience..
[How-to] create a distribution zip file with dependency jars in subdirectory /lib and add all dependencies to Class-Path entry in the manifest file:
apply plugin: 'java'
apply plugin: 'java-library-distribution'
repositories {
mavenCentral()
}
dependencies {
compile 'org.apache.commons:commons-lang3:3.3.2'
}
// Task "distZip" added by plugin "java-library-distribution":
distZip.shouldRunAfter(build)
jar {
// Keep jar clean:
exclude 'META-INF/*.SF', 'META-INF/*.DSA', 'META-INF/*.RSA', 'META-INF/*.MF'
manifest {
attributes 'Main-Class': 'com.somepackage.MainClass',
'Class-Path': configurations.runtime.files.collect { "lib/$it.name" }.join(' ')
}
// How-to add class path:
// https://stackoverflow.com/questions/22659463/add-classpath-in-manifest-using-gradle
// https://gist.github.com/simon04/6865179
}
Hosted as a gist here.
The result can be found in build/distributions and the unzipped contents look like this:
lib/commons-lang3-3.3.2.jar
MyJarFile.jar
Contents of MyJarFile.jar#META-INF/MANIFEST.mf:
Manifest-Version: 1.0
Main-Class: com.somepackage.MainClass
Class-Path: lib/commons-lang3-3.3.2.jar
This is for Kotlin DSL (build.gradle.kts).
Method 1 (no need for application or other plugins)
tasks.jar {
manifest.attributes["Main-Class"] = "com.example.MyMainClass"
// OR another notation
// manifest {
// attributes["Main-Class"] = "com.example.MyMainClass"
// }
}
If you use any external libraries, use below code. Copy library JARs in libs sub-directory of where you put your result JAR. Make sure your library JAR files do not contain space in their file name.
tasks.jar {
manifest.attributes["Main-Class"] = "com.example.MyMainClass"
manifest.attributes["Class-Path"] = configurations
.runtimeClasspath
.get()
.joinToString(separator = " ") { file ->
"libs/${file.name}"
}
}
Note that Java requires us to use relative URLs for the Class-Path attribute. So, we cannot use the absolute path of Gradle dependencies (which is also prone to being changed and not available on other systems). If you want to use absolute paths, maybe this workaround will work.
Create the JAR with the following command:
./gradlew jar
The result JAR will be created in build/libs/ directory by default.
Method 2: Embedding libraries (if any) in the result JAR (fat or uber JAR)
tasks.jar {
manifest.attributes["Main-Class"] = "com.example.MyMainClass"
val dependencies = configurations
.runtimeClasspath
.get()
.map(::zipTree) // OR .map { zipTree(it) }
from(dependencies)
duplicatesStrategy = DuplicatesStrategy.EXCLUDE
}
Creating the JAR is exactly the same as the previous method.
Method 3: Using the Shadow plugin (to create a fat or uber JAR)
plugins {
id("com.github.johnrengelman.shadow") version "6.0.0"
}
// Shadow task depends on Jar task, so these will be reflected for Shadow as well
tasks.jar {
manifest.attributes["Main-Class"] = "org.example.MainKt"
}
Create the JAR with this command:
./gradlew shadowJar
See Shadow documentations for more information about configuring the plugin.
Running the created JAR
java -jar my-artifact.jar
The above solutions were tested with:
Java 17
Gradle 7.1 (which uses Kotlin 1.4.31 for .kts build scripts)
See the official Gradle documentation for creating uber (fat) JARs.
For more information about manifests, see Oracle Java Documentation: Working with Manifest files.
Note that your resource files will be included in the JAR file automatically (assuming they were placed in /src/main/resources/ directory or any custom directory set as resources root in the build file). To access a resource file in your application, use this code (note the / at the start of names):
Kotlin
val vegetables = MyClass::class.java.getResource("/vegetables.txt").readText()
// Alternative ways:
// val vegetables = object{}.javaClass.getResource("/vegetables.txt").readText()
// val vegetables = MyClass::class.java.getResourceAsStream("/vegetables.txt").reader().readText()
// val vegetables = object{}.javaClass.getResourceAsStream("/vegetables.txt").reader().readText()
Java
var stream = MyClass.class.getResource("/vegetables.txt").openStream();
// OR var stream = MyClass.class.getResourceAsStream("/vegetables.txt");
var reader = new BufferedReader(new InputStreamReader(stream));
var vegetables = reader.lines().collect(Collectors.joining("\n"));
You can use the SpringBoot plugin:
plugins {
id "org.springframework.boot" version "2.2.2.RELEASE"
}
Create the jar
gradle assemble
And then run it
java -jar build/libs/*.jar
Note: your project does NOT need to be a SpringBoot project to use this plugin.
Have you tried the 'installApp' task? Does it not create a full directory with a set of start scripts?
http://www.gradle.org/docs/current/userguide/application_plugin.html
Thank you Konstantin, it worked like a charm with few nuances. For some reason, specifying main class as part of jar manifest did not quite work and it wanted the mainClassName attribute instead. Here is a snippet from build.gradle that includes everything to make it work:
plugins {
id 'java'
id 'com.github.johnrengelman.shadow' version '1.2.2'
}
...
...
apply plugin: 'application'
apply plugin: 'com.github.johnrengelman.shadow'
...
...
mainClassName = 'com.acme.myapp.MyClassMain'
...
...
...
shadowJar {
baseName = 'myapp'
}
After running gradle shadowJar you get myapp-{version}-all.jar in your build folder which can be run as java -jar myapp-{version}-all.jar.
You can define a jar artifact in the module settings (or project structure).
Right click the module > Open module settings > Artifacts > + > JAR > from modules with dependencies.
Set the main class.
Making a jar is then as easy as clicking "Build artifact..." from the Build menu. As a bonus, you can package all the dependencies into a single jar.
Tested on IntelliJ IDEA 14 Ultimate.
I checked quite some links for the solution, finally did the below mentioned steps to get it working. I am using Gradle 2.9.
Make the following changes in your build,gradle file :
Mention plugin:
apply plugin: 'eu.appsatori.fatjar'
Provide the Buildscript:
buildscript {
repositories {
jcenter()
}
dependencies {
classpath "eu.appsatori:gradle-fatjar-plugin:0.3"
}
}
Provide the Main Class:
fatJar {
classifier 'fat'
manifest {
attributes 'Main-Class': 'my.project.core.MyMainClass'
}
exclude 'META-INF/*.DSA', 'META-INF/*.RSA', 'META-INF/*.SF'
}
Create the fatjar:
./gradlew clean fatjar
Run the fatjar from /build/libs/ :
java -jar MyFatJar.jar
Here is the solution I tried with Gradle 6.7
Runnable fat Jar (with all dependent libraries copied to the jar)
task fatJar(type: Jar) {
manifest {
attributes 'Main-Class': 'com.example.gradle.App'
}
from {
configurations.compile.collect { it.isDirectory() ? it : zipTree(it) }
} with jar
}
Runnable jar with all dependencies copied to a directory and adding the classpath to the manifest
def dependsDir = "${buildDir}/libs/dependencies/"
task copyDependencies(type: Copy) {
from configurations.compile
into "${dependsDir}"
}
task createJar(dependsOn: copyDependencies, type: Jar) {
manifest {
attributes('Main-Class': 'com.example.gradle.App',
'Class-Path': configurations.compile.collect { 'dependencies/' + it.getName() }.join(' ')
)
}
with jar
}
How to use ?
Add the above tasks to build.gradle
Execute gradle fatJar //create fatJar
Execute gradle createJar // create jar with dependencies copied.
More details : https://jafarmlp.medium.com/a-simple-java-project-with-gradle-2c323ae0e43d
Configure Main Class to your Manifest
If you are using gradle project, just add the following into your build.gradle
jar {
manifest {
attributes(
'Main-Class': 'pokerhandscorer.PokerHandScorer'
)
}
}
Where 'pokerhandscorer' is the name of the package name,
and PokerHandScorer is the main class name
This creates a jar file into your \build\libs{jarFilename}.jar
Run jar file using java -jar /{path}/{jarFileName.jar}
java -jar /{path}/{jarFileName.jar}