为什么不将所有JavaFX deps放在类路径中而又不用担心Java模块呢? [英] Why isn't it enough put all JavaFX deps in the classpath w/o bothering about Java modules?

问题描述

我一直在尝试编写Hello JavaFX应用程序，面对着有关启动该应用程序的Java模块的必要考虑.

I've been trying to write Hello JavaFX app and faced with necessity consider about Java modules for starting the app.

F.e. javafx-maven-plugin 的 run 目标产生这样的启动命令:

F.e. javafx-maven-plugin's run goal produce such startup command:

[DEBUG] Executing command line: [C:\java\zulu14.29.23-ca-jdk14.0.2-win_x64\bin\java.exe, 
--module-path, C:\.m2\repository\org\openjfx\javafx-base\14\javafx-base-14-win.jar;
C:\.m2\repository\org\openjfx\javafx-base\14\javafx-base-14.jar;
C:\.m2\repository\org\openjfx\javafx-controls\14\javafx-controls-14-win.jar;
C:\.m2\repository\org\openjfx\javafx-controls\14\javafx-controls-14.jar;
C:\.m2\repository\org\openjfx\javafx-graphics\14\javafx-graphics-14-win.jar;
C:\.m2\repository\org\openjfx\javafx-graphics\14\javafx-graphics-14.jar, 
--add-modules, javafx.base,javafx.controls,javafx.graphics, 
-classpath, D:\project\target\classes, org.pkg.pkg.App]

但是我项目的结构没有提到Java模块功能-我没有 module-info.java 文件.
为什么我不能将所有JAR放在应用程序的类路径中并感到高兴?
F.e.:

But my project's structure doesn't mention Java module functionality - I didn't have module-info.java file.
Why can't I put all above JARs in the app classpath and be happy?
F.e.:

C:\java\zulu14.29.23-ca-jdk14.0.2-win_x64\bin\java.exe 
"-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2019.3.4\lib\idea_rt.jar=59556:C:\Program Files\JetBrains\IntelliJ IDEA 2019.3.4\bin" 
-Dfile.encoding=UTF-8 
-classpath D:\project\target\classes;
C:\.m2\repository\org\openjfx\javafx-controls\14\javafx-controls-14.jar;
C:\.m2\repository\org\openjfx\javafx-controls\14\javafx-controls-14-win.jar;
C:\.m2\repository\org\openjfx\javafx-graphics\14\javafx-graphics-14.jar;
C:\.m2\repository\org\openjfx\javafx-graphics\14\javafx-graphics-14-win.jar;
C:\.m2\repository\org\openjfx\javafx-base\14\javafx-base-14.jar;
C:\.m2\repository\org\openjfx\javafx-base\14\javafx-base-14-win.jar 
org.pkg.pkg.App

如果我是对的，并且理解

If I'm right and understand Packages and Modules spec correctly

在类路径中定义的
• 模块JAR被视为未命名模块
• 未命名的模块会导出所有包，即所有可见的包

但是我得到一个错误

Error: JavaFX runtime components are missing, and are required to run this application

请问一下关于Java模块的工作原理，我在这里错了吗?

Could someoune please explain me where I'm wrong here, about how Java modules work?

提前谢谢！

推荐答案

警告:尽管下面显示了所需的功能，但将JavaFX模块放在类路径上是不支持.这意味着即使您自己的代码不是模块化的，也应该将JavaFX放在模块路径上.

Warning: Although the below shows what you want is possible, placing the JavaFX modules on the class-path is not supported. This means you should place JavaFX on the module-path, even when your own code is non-modular.

您可以将JavaFX放在类路径上，并完全忽略模块 ¹ .但是，一个警告是，您的主类不能再分配给 javafx.application.Application ² .解决方法是创建一个单独的主类，该主类仅启动JavaFX应用程序.例如:

You can put JavaFX on the class-path and completely ignore modules¹. However, the one caveat is that your main class can no longer be assignable to javafx.application.Application². The workaround is to create a separate main class that simply launches the JavaFX application. For example:

import javafx.application.Application;

public class Launcher {

  public static void main(String[] args) {
    // where YourApp.class is replaced with your Application class
    Application.launch(YourApp.class, args);
  }
}

---

^{1.您不能真的完全忽略模块.类路径上的所有代码都以未命名的模块结尾，并且运行时映像中的所有模块(即JDK/JRE)仍充当命名模块.}

---

^{1. Your can't really ignore modules completely. All code on the class-path ends up in the unnamed module and all the modules in the run-time image (i.e. the JDK/JRE) still function as named modules.}

^{2.这是由于实施细节.Java包含的代码允许您在没有主方法的情况下启动JavaFX应用程序，只要该主类可分配给 Application .但是，当检测到主类可分配给 Application 时，它将在引导 ModuleLayer 中检查 javafx.graphics ，这意味着它必须位于模块路径-如果不存在，则认为缺少JavaFX.}

^{2. This is due to an implementation detail. Java contains code which allows you to launch JavaFX applications without a main method, so long as the main class is assignable to Application. But when it detects that the main class is assignable to Application it checks for javafx.graphics in the boot ModuleLayer—meaning it must be on the module-path—and if not there then it assumes JavaFX is missing.}

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