Maven的。传递依赖 [英] Maven. Transitive dependencies

问题描述

我的项目P取决于依赖关系A.依赖关系B.我的项目的pom.xml文件包含A作为依赖，它的jar包含在P的类路径中。但是，在P的运行时抛出一个 NoClassDefFoundError ，这是由于缺少B jar。

不应该Maven已经自动下载了这些依赖关系？

解决方案

我的项目P依赖于依赖关系A [范围]取决于依赖B [具有编译范围]。

除非B是 的maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html#Transitive_Dependenciesrel =noreferrer> P具有compile（*）范围（参见依赖范围并阅读注释），因此应该在运行时可用。

但是，抛出了一个NoClassDefFoundError在P，w的运行时间

由于您在Eclipse下运行该项目，所以类路径是为您设置的，所以我'将排除此级别的错误。这使我们有可选的依赖关系。

PS：调查这种问题的一个非常有用的工具是依赖：tree 。

My project P depends on dependency A which depends on dependency B. My project's pom.xml file includes A as a dependency, and its jar is included in P's classpath. However, there is a NoClassDefFoundError thrown at runtime of P, which stems from missing B jars.

Shouldn't Maven have downloaded these dependencies automatically?

解决方案

My project P depends on dependency A [with a compile scope] which depends on dependency B [with a compile scope].

Unless B is an optional dependency of A, B should be a dependency of P with a "compile(*)" scope (see the table of Dependency Scope and read the note) and should thus be available at runtime.

However, there is a NoClassDefFoundError thrown at runtime of P, which stems from missing B jars.

Since you're running the project under Eclipse, the class path is setup for you so I'll exclude a mistake at this level. This leaves us with the case of the optional dependency.

PS: A very useful tool to investigate this kind of problem is dependency:tree.

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