英文:
Maven dependencies in Eclipse subprojects not appearing the Java classpath
问题
在Eclipse Java中，我有以下情况：
项目1
+- 项目2
+- 项目3
项目1、项目2和项目3都是常规的Java项目，通过文件 > 新建Java项目创建，然后通过在项目资源管理器中右键单击 > Maven > 转换为Maven项目转换为Maven项目。项目1包含我的应用程序入口点（静态main方法）。项目1的代码调用项目2的代码，而项目2的代码又调用项目3的代码：
// 项目1
public class 项目1类 {
public static void main(String[] args)
{
项目2类.foo();
System.out.println("完成");
}
}
// 项目2
public class 项目2类 {
public static void foo()
{
项目3类.bar();
}
}
// 项目3
public class 项目3类 {
public static void bar()
{
// 在这里使用本地代码
}
}
项目3使用带有本地库文件（Windows上的DLL文件）的Maven依赖项。让我们称这个依赖为org.foo.bar/mylibrary：
<!-- 这个依赖项需要加载本地库 -->
<dependencies>
<dependency>
<groupId>org.foo.bar</groupId>
<artifactId>mylibrary</artifactId>
</dependency>
</dependencies>
我的问题是：
当运行或调试项目1时，我可以看到项目1、项目2和项目3的'target/classes'文件夹在类路径中，如预期所示，项目1和项目2的Maven依赖项也在类路径中，但是项目3的Maven依赖项却丢失了。结果是，无法加载本地库。
如果我将org.foo.bar/mylibrary依赖项的声明从项目3移到项目2，那么Maven依赖项确实会出现在类路径中。
我尝试过Eclipse 2019-09和2020-03，结果相同。
似乎Eclipse不会添加驻留在间接依赖项中的Maven依赖项。
我如何告诉它将Maven依赖项添加到类路径中，包括所有依赖项，即直接和间接依赖项？
编辑：我在项目2的pom.xml文件中添加了此显式声明：
<dependencies>
<dependency>
<groupId>项目3</groupId>
<artifactId>项目3</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
而且它有效。但这对我来说没有太多意义。考虑到其他情况，如果我在项目1和项目2之间不添加显式的Maven
英文:
In Eclipse Java, I have the following situation:
Project1
+- Project2
+- Project3
Project1, Project2 and Project3 are regular Java projects that have been created through File > New Java project, then converted to Maven projects through a right-click in Project Explorer > Maven > Convert to Maven. Project1 contains my application entrypoint (static main method). Project1 code calls Project2 code, which in turns calls Project3 code:
// Project1
public class Project1Class {
public static void main(String[] args)
{
Project2Class.foo();
System.out.println("Done");
}
}
// Project2
public class Project2Class {
public static void foo()
{
Project3Class.bar();
}
}
// Project3
public class Project3Class {
public static void bar()
{
// Use native code here
}
}
Project3 uses a Maven dependency with native library files (DLL files on Windows). Let's call this dependency org.foo.bar/mylibrary:
<!-- This dependency needs to load a native library -->
<dependencies>
<dependency>
<groupId>org.foo.bar</groupId>
<artifactId>mylibrary</artifactId>
</dependency>
</dependencies>
My problem is the following:
When running or debugging Project1, I can see that Project1, Project2 and Project3 'target/classes' folders are in the classpath, as expected, Maven dependencies for Project1 and Project2 also are in the classpath, but the Maven dependencies of Project3 are missing. As a result, native libraries cannot be loaded.
If I move the org.foo.bar/mylibrary dependency declaration from Project3 to Project2, then the Maven dependency indeed ends up in the classpath.
I tried with Eclipse 2019-09 and 2020-03, same result.
It seems Eclipse does not add Maven dependencies that reside in indirect dependencies.
How can I tell it to add Maven dependencies in the classpath for all dependencies, i.e. both direct and indirect?
EDIT: I added this explicit declaration in Project2's pom.xml file:
<dependencies>
<dependency>
<groupId>Project3</groupId>
<artifactId>Project3</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
and it works. But that makes little sense to me. Considering the other scenario, things do work if I don't add an explicit Maven <dependency> declaration between Project1 and Project2. Why? Why do I have to do it between Project2 and Project3 and not between Project1 and Project2 for it to work?
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