问题
I try to run a very simple gradle project which uses java 9 modules, but i receive the following error.
/home/vadim/IdeaProjects/test_modules/src/main/java/module-info.java:2: error: module not found: HdrHistogram
requires HdrHistogram;
^
Here is it https://github.com/vad0/test_modules. The main class does basically nothing.
package app;
import org.HdrHistogram.Histogram;
public class RunHdr {
public static void main(String[] args) {
final Histogram histogram = new Histogram(5);
System.out.println(histogram);
}
}
It uses only one dependency: HdrHistogram. I included this magic command in build.gradle according to official gradle tutorial https://docs.gradle.org/current/samples/sample_java_modules_multi_project.html.
java {
modularity.inferModulePath = true
}
The whole build.gradle looks like this.
plugins {
id 'java'
}
group 'org.example'
version '1.0-SNAPSHOT'
repositories {
mavenCentral()
}
java {
modularity.inferModulePath = true
}
dependencies {
compile group: 'org.hdrhistogram', name: 'HdrHistogram', version: '2.1.12'
testCompile group: 'junit', name: 'junit', version: '4.12'
}
module.info looks like this
module test.modules.main {
requires HdrHistogram;
}
I have already read a number of tutorials on Jigsaw and a whole bunch of stackoverflow questions related to it, but still can't make this simple example work. How do i fix it?
Thank you
回答1:
Unfortunately, gradle
does not treat every jar as a module (in simple words). If you want to find out how exactly is gradle
building the module-path
(as opposed to class-path
), you probably want to start from here, specifically at the isModuleJar method. It's pretty easy to understand (though it took me almost two days to set-up gradle and debug the problem out) that the dependency that you are trying to use : gradle says that it is not a module (it isn't wrong, but I am not sure it is correct either). To make it very correct, gradle
will add your dependency to the CLASSPATH, but in the very next line: it will not add your dependency to the module-path
, because if fails the filter in isModuleJar
.
I do not know if this is a bug or not, or may be this is on purpose, but the solution is easy:
plugins.withType(JavaPlugin).configureEach {
java {
modularity.inferModulePath = true
}
tasks.withType(JavaCompile) {
doFirst {
options.compilerArgs = [
'--module-path', classpath.asPath,
]
classpath = files()
}
}
you add it to the path, on purpose. I will flag this as a defect and let's see what they have to say.
EDIT
Even better, use a plugin that is written by a gradle commiter:
plugins {
id 'java'
id 'de.jjohannes.extra-java-module-info' version "0.1"
}
And the easiest option on your case is to do :
extraJavaModuleInfo {
automaticModule("HdrHistogram-2.1.12.jar", "HdrHistogram")
}
来源:https://stackoverflow.com/questions/63204044/gradle-jigsaw-module-not-found