我目前正在开发一个Web应用程序,必须从本地驱动器上的目录加载jar文件。经过一些研究,URLClassLoaders
似乎是最合适的解决方案。
重点是:
public @Slf4j class ActionLoader {
private static void addFilesToClassPath(File path) {
URLClassLoader clazzLoader = null;
try {
clazzLoader = new URLClassLoader(new URL[] {path.toURI().toURL()},
ActionLoader.class.getClassLoader());
try {
Class.forName("de.befoe.xyz.ActionTest", false, clazzLoader);
} catch (ClassNotFoundException e) {
log.error("Class not found", e);
}
try {
clazzLoader.loadClass("de.befoe.xyz.ActionTest");
} catch (ClassNotFoundException e) {
log.error("Class not found", e);
}
} catch (SecurityException e) {
log.error("Access denied", e);
} catch (MalformedURLException e) {
log.error("Malformed URL", e);
} finally {
if (clazzLoader != null) {
try {
clazzLoader.close();
} catch (IOException e) {
log.error("Error closing the class loader", e);
}
}
}
}
}
首先是 ClassNotFoundException
:
java.lang.ClassNotFoundException: de.befoe.xyz.ActionTest
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at de.procrm.speedindexer.scr.ActionLoader.addFilesToClassPath(ActionLoader.java:80)
at de.procrm.speedindexer.scr.ActionLoader.loadActions(ActionLoader.java:31)
at de.procrm.speedindexer.scr.Init.contextInitialized(Init.java:39)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4842)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5303)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:940)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:467)
at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1612)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at org.apache.catalina.manager.ManagerServlet.check(ManagerServlet.java:1451)
at org.apache.catalina.manager.ManagerServlet.deploy(ManagerServlet.java:724)
at org.apache.catalina.manager.ManagerServlet.doPut(ManagerServlet.java:423)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:651)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:614)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1099)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
第二个 ClassNotFoundException
:
java.lang.ClassNotFoundException: de.befoe.xyz.ActionTest
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at de.procrm.speedindexer.scr.ActionLoader.addFilesToClassPath(ActionLoader.java:81)
at de.procrm.speedindexer.scr.ActionLoader.loadActions(ActionLoader.java:31)
at de.procrm.speedindexer.scr.Init.contextInitialized(Init.java:39)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4842)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5303)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:940)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:467)
at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1612)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at org.apache.catalina.manager.ManagerServlet.check(ManagerServlet.java:1451)
at org.apache.catalina.manager.ManagerServlet.deploy(ManagerServlet.java:724)
at org.apache.catalina.manager.ManagerServlet.doPut(ManagerServlet.java:423)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:651)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:614)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1099)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
路径变量指向包含jar文件的目录(我还尝试使用指向jar文件的URL初始化类加载器)。当我尝试从其中一个jar文件访问类时,会出现ClassNotFoundException。在调试器中检查类加载器时,我也可以看到packages和classes字段都为空,因此似乎类加载器没有加载任何内容。起初我认为这与缺少依赖项有关,所以我创建了第二个不带依赖项的jar文件,并将父类加载器添加到构造函数中,但结果没有改变。 有什么好的想法吗?经过一些研究后,似乎我的第一个想法(依赖项)是正确的。我有另一个用于Web应用程序和已加载的jar文件的库。如果我将此库添加到要添加到URLClassLoader的jar列表中,则可以成功加载jar文件。但是,这显然不是我想做的,因为从技术上讲,我的Web应用程序使用的是与我的jar文件不同的类,这会导致其他问题。现在的问题是为什么父类加载器的类没有被正确使用。经过进一步研究,似乎我使用的ActionLoader.class.getClassLoader()的父类加载器不正确。在eclipse调试器中,我看到一个名为delegate的字段设置为false。因此,我改用该类加载器的父类加载器,文件就可以正常加载了。
jar tf myJar.jar
(其中“myJar”是你想要加载的文件名)来查看JAR包内部。 - Alexander LeithnerclazzLoader.close();
的调用,因为您刚刚加载的类很可能还没有使用完。只是为了避免不可避免的后续问题... - Holger