英文:
Java URLClassLoader works in eclipse but not in cmd
问题
以下是翻译好的部分：
我有一个程序，试图使用URLClassLoader从文件夹中加载Java类。在Eclipse中运行时，类加载器能够成功加载这些类，但是当我尝试在命令行中运行时，它会抛出ClassNotFoundException异常。
文件结构：
-rootFolder/
-src/
-tests/
-test1/
-A.java
该程序接受两个参数：args[0] 是根文件夹的绝对路径，args[1] 是要读取的测试文件夹的名称。
String rootString = args[0] + File.separator + "tests" + File.separator + args[1] + File.separator;
File folder = new File(rootString);
String[] files = folder.list();
我能够使用这个路径获取文件名，在Eclipse和命令行中都可以。
然后是我的URLClassLoader部分。
URL[] urls = new URL[] {new File(rootString).toURI().toURL()};
URLClassLoader cl = new URLClassLoader(urls);
cl.loadClass("A"); // A是在文件中找到的名称，在默认包中
在Eclipse中，这部分可以正常运行，但在命令行中会抛出ClassNotFound异常。
在命令行中，脚本是这样的：
java -cp build/libs/project.jar project.Main rootFolder test1
我猜想问题可能出在类路径上，但我不太确定为什么URLClassLoader需要使用类路径而不是文件URL。
英文:
I have a program that tries to load java classes from a folder, using URLClassLoader. The classloader is able to load the classes while running in eclipse, but when I try to run it in cmd it throws ClassNotFoundException.
File structure:
-rootFolder/
-src/
-tests/
-test1/
-A.java
The program takes two arguments: args[0] the absolute path of the root folder and args[1] name of the test folder to read.
String rootString = args[0]+ File.separator + "tests" + File.separator + args[1] + File.separator;
File folder = new File(rootString);
String[] files = folder.list();
I am able to get the file names using this path, both in eclipse and cmd.
Then I have my URLClassLoader.
URL[] urls = new URL[] {new File(rootString).toURI().toURL()};
URLClassLoader cl = new URLClassLoader(urls);
cl.loadClass("A"); // A is the name found in files, in default package
This part runs in eclipse but throw ClassNotFound Exception in cmd.
In cmd the script is:
java -cp build/libs/project.jar project.Main rootFolder test1
My guess is that the classpath causes the issue but I am not very sure why URLClassLoader needs to use classpath instead of file urls.
答案1
得分: 0
所以我发现Eclipse会自动编译默认类路径文件夹下的所有Java类。反射仅对编译后创建的.class文件起作用，这就是为什么会抛出ClassNotFound异常。
英文:
So I figure out that Eclipse automatically compile all the java classes under the default classpath folder. Reflection only works on the .class files created after compile, and that is why a ClassNotFound exception was thrown.
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