英文:
Compiling a Gradle Java project with Java 8 but running tests with Java 11
问题
作为我项目转换过程的第一部分，我希望在保持使用JDK-8编译器的情况下，使用JDK-11运行时执行测试。
我的项目是Gradle项目（如果有影响则为6.+版本），使用了java插件或java-library插件。
我无法找到使用Gradle选项来实现这一目标的方法。
我尝试了在一个终端中使用JDK-8进行编译（gradlew build），然后切换到另一个终端使用JDK-11运行测试（gradlew test），但它重新编译了代码。
正确的做法是什么？
英文:
As the first part of a transition process of my projects, I would like to keep compile with JDK-8 compiler, but execute tests with JDK-11 runtime.
My projects are Gradle projects (6.+ if it matters), using the java plugin or java-library plugins.
I could not find a way to do it with Gradle options.
I tried to compile (gradlew build) in one terminal with JDK-8, and then switch to another terminal with JDK 11 and run the tests (gradlew test), but it re-compiled the code.
What is the correct way to do it?
答案1
得分: 2
你可以使用不同于运行Gradle的JDK的配置来处理所有与Java相关的任务（编译、测试、JavaExec、JavaDoc等）。用户指南中有一章节提供了一个示例，说明如何在使用Java 8运行Gradle的情况下，让所有任务使用Java 7。同样适用于Java 11。
对于你的项目，你可以继续使用Java 8运行Gradle，但是为了使用不同的版本运行测试，可以添加以下内容：
// Gradle <= 6.6 (Groovy DSL)
tasks.withType(Test) {
executable = new File("/my/path/to/jdk11/bin/java")
}
用户指南中提供了一个更可配置的解决方案，但这是其中的要点。
Gradle即将发布的版本6.7中的一个很酷的功能是支持JVM工具链。目前情况下，你必须自己下载JDK 11分发版并配置其路径。新版本将允许你声明所需版本，并在缺失时让Gradle为你下载（从AdoptOpenJDK）：
// Gradle >= 6.7 (Groovy DSL)
// 此刻尚未发布，在写作时语法可能会有所变化
test {
javaLauncher = javaToolchains.launcherFor {
languageVersion = JavaLanguageVersion.of(11)
}
}
最后一个选项是使用Java 11运行Gradle，并使用release选项将编译器目标设置为Java 8：
// 使用Java 11运行Gradle
compileJava {
options.release = 8
}
英文:
You can configure all Java-related tasks (compilations, tests, JavaExec, JavaDoc, etc) with a different JDK than what is used to run Gradle. There is a chapter in the user guide that gives an example of how to run Gradle with Java 8 but use Java 7 in all tasks. It works the same with Java 11.
For your project, you can continue running Gradle with Java 8 but add the following for running tests with a different version:
// Gradle <= 6.6 (Groovy DSL)
tasks.withType(Test) {
executable = new File("/my/path/to/jdk11/bin/java")
}
The user guide has a more configurable solution, but this is the gist of it.
A cool feature that is part of the upcoming version 6.7 of Gradle is support for JVM toolchains. As it is now, you have to download a JDK 11 distribution yourself and configure the path to it. Newer versions will allow you to declare the version and let Gradle download it for you (from AdoptOpenJDK) if missing:
// Gradle >= 6.7 (Groovy DSL)
// Unreleased at the time of this writing and the syntax is therefore subject to change
test {
javaLauncher = javaToolchains.launcherFor {
languageVersion = JavaLanguageVersion.of(11)
}
}
A final option is to run Gradle with Java 11 and make the compiler target Java 8 using the release option:
// Run Gradle with Java 11
compileJava {
options.release = 8
}
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