问题描述
*在运行时尝试使用以下方法加载外部示例 .jar 时出现以下异常: Class clazz = Class.forName(jarClass);.
异常: 来自服务模块加载器的模块“部署 .test.war”] java.lang.classNotFoundException: org.abc.xyz.def.abc.Sample 来自 [Module "deployment.test.war" from Service Module Loader]
*然后将类加载器从“this.getClass().getClassLoader()”修改为“ClassLoader.getSystemClassLoader()”但随后它开始抛出以下异常:
deployment.test.war//org.abc.pqr.tasks.JavaDataPlayTask$1.run(JavaDataPlayTask.java:450) - Java 数据播放包执行失败:org/abc/pqr/tasks/DataPlay java.lang.NoClassDefFoundError: org/abc/pqr/tasks/DataPlay
*执行动态类加载的一段代码在 Main.jar 中 * Sample.jar 中的类实现了 Main.jar 中可用的“DataPlay”接口
https://kostenko.org/blog/2019/06/runtime-class-loading.html
https://www.programmersought.com/article/99402552966/
https://coderanch.com/t/614007/java/Dynamic-loading-class-external-jar
https://www.programmersought.com/article/37026364495/
Jar hell: how to use a classloader to replace one jar library version with another at runtime
How to load classes from jar file at runtime?
Load jar dynamically at runtime?
*以下链接中提到的方法是否合适? https://access.redhat.com/documentation/en-us/jboss_enterprise_application_platform/6/html/migration_guide/find_the_jboss_module_dependency1
public class ClasspathHacker {
private static Logger log = Logger.getLogger(ClasspathHacker.class);
private static final Class[] parameters = new Class[] { URL.class };
public static void addFile(String s) throws IOException {
File f = new File(s);
addFile(f);
}// end method
public static void addFile(File f) throws IOException {
addURL(f.toURL());
}// end method
public static void addURL(URL u) throws IOException {
log.debug("Loading jar file: "+u);
try {
doClasssLoading(ClassLoader.getSystemClassLoader(),u);
} catch (Throwable t) {
log.debug("Error,Could not add URL to system classloader");
throw new IOException(
"Error,Could not add URL to system classloader");
}// end try catch
}// end method
public static void addJar(String jarPath,ClassLoader classLoader) throws IOException {
File f = new File(jarPath);
URL u = f.toURL();
log.debug("Class loader class: "+classLoader.getClass());
log.debug("Loading jar file: "+u);
log.debug("System class loader class: "+ClassLoader.getSystemClassLoader().getClass());
try {
doClasssLoading(classLoader,u);
} catch (Throwable t) {
// t.printstacktrace();
log.debug("Error,Could not add URL to system classloader");
}// end try catch
}
private static void doClasssLoading(ClassLoader classLoader,URL url) {
if (classLoader instanceof urlclassloader) {
log.info("Type of URL ClassLoader");
urlclassloader sysloader = (urlclassloader)classLoader;
Class sysclass = urlclassloader.class;
try {
Method method = sysclass.getDeclaredMethod("addURL",new Class[] { URL.class });
method.setAccessible(true);
method.invoke(sysloader,new Object[] { url });
} catch (Exception var5) {
var5.printstacktrace();
throw new IllegalStateException(var5.getMessage(),var5);
}
} else {
log.info("Not of type of URL ClassLoader");
try {
Field field = classLoader.getClass().getDeclaredField("ucp");
field.setAccessible(true);
Object ucp = field.get(classLoader);
Method method = ucp.getClass().getDeclaredMethod("addURL",new Class[] { URL.class });
method.setAccessible(true);
method.invoke(ucp,new Object[] { url });
} catch (Exception exception) {
exception.printstacktrace();
throw new IllegalStateException(exception.getMessage(),exception);
}
}
}
public static String getMainClass(String jarPath) throws IOException {
JarFile jarFile = new JarFile(new File(jarPath));
Attributes attributes = jarFile.getManifest().getMainAttributes();
String className = attributes.getValue("Main-Class");
return className;
}
}
解决方法
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