着色scala（jar）库的依赖关系 [英] Shading dependencies of scala (jar) library

问题描述

我想分发一个我创建的库的jar，其中包含所有依赖项。但是，我想避免与采用项目的依赖项版本冲突。

I would like to distribute a jar of a library I created with all my dependencies bundled inside. However I would like to avoid version conflicts of dependencies with the adopting project.

我认为maven shade可以做到这一点，但我找不到用Scala做到这一点的方法/ SBT。我发现OneJar但是我的实验似乎只适用于可执行文件。

I think maven shade can do this but I could not find a way to do this with Scala / SBT. I found OneJar however from my experiments with it seems to work only for executables.

我怎么能实现这个目标？

How could I achieve this?

谢谢！

推荐答案

您可以使用自己的类加载器执行此操作。

You can do this with your own classloader.

classLoader：

编写一个类加载器，它使用重写从不同的类加载器加载类文件。

The classLoader:
Write a class loader which loads class files from diferent classloader using a rewrite.

例如，您可以在获取资源时将库添加为类路径的前缀。

For example you could add library as a prefix to the classpath when fetching the resource.

我创建了使用此teqnuiqe的类加载器。
https：/ /github.com/espenbrekke/dependent/blob/master/src/main/java/no/dependent/hacks/PathRewritingClassLoader.java

I have created a classloader using this teqnuiqe. https://github.com/espenbrekke/dependent/blob/master/src/main/java/no/dependent/hacks/PathRewritingClassLoader.java

它用一个添加前缀的URLClassLoader替换方法findClass。

It replaces the method findClass in URLClassLoader with one adding a prefix.

protected Class<?> findClass(final String name) throws ClassNotFoundException {
    Class result;
    try {
        result = (Class)AccessController.doPrivileged(new PrivilegedExceptionAction() {
            public Class<?> run() throws ClassNotFoundException {

// This is where the prefix is added:
                String path = PathRewritingClassLoader.this.prefix + name.replace('.', '/').concat(".class");
                Resource res = PathRewritingClassLoader.this._ucp.getResource(path, false);
                if(res != null) {
                    try {
                        return PathRewritingClassLoader.this._defineClass(name, res);
                    } catch (IOException var4) {
                        throw new ClassNotFoundException(name, var4);
                    }
                } else {
                    return null;
                }
            }
        }, this._acc);
    } catch (PrivilegedActionException var4) {
        throw (ClassNotFoundException)var4.getException();
    }

    if(result == null) {
        throw new ClassNotFoundException(name);
    } else {
        return result;
    }
}

我们还必须重写资源加载

We also have to rewrite resource loading

@Override
public URL getResource(String name){
    return super.getResource(prefix+name);
}

以下是它的使用方法：

Here is how it is used:

_dependentClassLoader = new PathRewritingClassLoader("private", (URLClassLoader)DependentFactory.class.getClassLoader());
Class myImplementationClass=_dependentClassLoader.loadClass("my.hidden.Implementation");

建立你的jar：

在你的构建中您将所有库和私有类放在所选前缀下。在我的gradle构建中，我有一个简单的循环收集所有依赖项。

Building your jar:
In your build you place all the library and private classes under your selected prefix. In my gradle build I have a simple loop collecting all the dependencies.

task packageImplementation {
dependsOn cleanImplementationClasses

doLast {
    def paths = project.configurations.runtime.asPath
    paths.split(':').each { dependencyJar ->
        println "unpacking" + dependencyJar

        ant.unzip(src: dependencyJar,
                dest: "build/classes/main/private/",
                overwrite: "true")
        }
    }
}

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