我正在尝试使用Java编写一个脚本,它可以在指定目录中查找所有的.jar
文件,将它们添加到classpath
中,并在特定条件下调用它们的main()
方法。以下是我的Java信息:
java version "1.6.0_24"
OpenJDK Runtime Environment (IcedTea6 1.11.5) (6b24-1.11.5-0ubuntu1~12.04.1)
OpenJDK Server VM (build 20.0-b12, mixed mode)
以下是当前工作目录的ls
结果:
clojure.jar
loader.class
loader.java
我正在执行以下操作,以将clojure.jar
添加到classpath
并调用其主方法:
import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.MalformedURLException;
import java.lang.reflect.Method;
public final class loader {
public static void main (String[] args) {
try {
printClasspathString();
System.out.println ("**********");
URL[] classesRepo = { new File("clojure.jar").toURI ().toURL (),
new File(System.getProperty("user.dir")).toURI ().toURL ()};
ClassLoader currentThreadClassLoader = Thread.currentThread().getContextClassLoader();
URLClassLoader urlClassLoader = new URLClassLoader( classesRepo, currentThreadClassLoader);
Thread.currentThread().setContextClassLoader(urlClassLoader);
printClasspathString();
} catch (Exception ex) {
System.out.println(ex.getMessage ());
}
//Do I miss something here?
String mainClassName="clojure.main";
Class<?> mainClass = null;
try {
mainClass = Class.forName(mainClassName);
}
catch (Exception ex) {
throw new IllegalArgumentException("class not found in your jar file " + mainClassName);
}
Method mainMethod = null;
try {
mainMethod = mainClass.getMethod("main", String[].class);
}
catch (Exception ex) {
throw new IllegalArgumentException("class to launch (" + mainClassName + ") does not have a public static void main(String[]) method");
}
try {
mainMethod.invoke(null, (Object) args);
} catch (Exception ex) {
System.out.println(ex.getMessage ());
}
}
public static void printClasspathString() {
ClassLoader applicationClassLoader = Thread.currentThread().getContextClassLoader();
if (applicationClassLoader == null) {
applicationClassLoader = ClassLoader.getSystemClassLoader();
}
URL[] urls = ((URLClassLoader)applicationClassLoader).getURLs();
for(int i=0; i < urls.length; i++) {
System.out.println (urls[i].getFile());
}
}
}
很遗憾,加载器没有按预期工作:
$ java -cp . loader
/home/proofit404/data/downloads/clojure-loader/
**********
/home/proofit404/data/downloads/clojure-loader/clojure.jar
/home/proofit404/data/downloads/clojure-loader/
Exception in thread "main" java.lang.IllegalArgumentException: class not found in your jar file clojure.main
at loader.main(loader.java:37)
如果我使用
-cp
选项,一切都能正常工作:$ java -cp .:clojure.jar loader
/home/proofit404/data/downloads/clojure-loader/
/home/proofit404/data/downloads/clojure-loader/clojure.jar
**********
/home/proofit404/data/downloads/clojure-loader/clojure.jar
/home/proofit404/data/downloads/clojure-loader/
Clojure 1.4.0
user=> (System/exit 0)
所以,我需要在我的代码中做哪些更改才能使其按预期工作?