在Groovy中动态加载jar

问题描述

我有一个时髦的脚本createWidget.groovy:

I have a groovy script createWidget.groovy:

 import com.example.widget

 Widget w = new Widget()

当我像这样运行它时，此脚本运行得很好:

This script runs great when I run it like this:

$ groovy -cp /path/to/widget.jar createWidget.groovy

但是，我想对脚本中的类路径进行硬编码，以便用户无需知道它在哪里，所以我按如下方式修改了createWidget.groovy(这是在groovy中修改类路径的方法之一):/p>

But, I wanted to hardcode the classpath within the script, so that users do not need to know where it is, so I modified createWidget.groovy as follows (which is one of the ways to modify classpath in groovy):

this.getClass().classLoader.rootLoader.addURL(new File("/path/to/widget.jar").toURL())

import com.example.widget

Widget w = new Widget()

但这总是失败，并在导入时出现运行时错误:无法解析类com.example.widget .

But this always fails with a runtime error on the import: unable to resolve class com.example.widget.

这看上去确实是非传统的，我认为您在导入之前不能与rootLoader发生冲突，还是其他东西?

This does look unorthodox and I am thinking you can't mess with the rootLoader prior to an import or is it something else?

推荐答案

// Use the groovy script's classLoader to add the jar file at runtime.
this.class.classLoader.rootLoader.addURL(new URL("/path/to/widget.jar"));

// Note: if widget.jar file is located in your local machine, use following:
// def localFile = new File("/path/tolocal/widget.jar");
// this.class.classLoader.rootLoader.addURL(localFile.toURI().toURL());

// Then, use Class.forName to load the class.
def cls = Class.forName("com.example.widget").newInstance();

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