java类加载是否会加载.class2019类似的文件?

今天遇到一个线上问题,A类调用B类的方法,出现异常:java.lang.NoSuchMethodError,经查看服务器上B类的目录,有B.class和B.class20190517两个文件,B.class20190517文件中确实没有报错的method,经与发布人员沟通,之前确实也出现过类似加载了.class2019的文件导致的问题。请
问sh是否有遇到过类似问题的小伙伴?不太了解为什么B.class20190517会被加载?

1个回答

问题已解决。问题并非备份的class文件的问题,而是服务使用的另一个优先加载的classpath下有该class导致

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com.ht.action.ExerciseContentAction.save(ExerciseContentAction.java:178) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) java.lang.reflect.Method.invoke(Method.java:498) com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:452) com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:291) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:254) com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263) org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:133) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:314) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:142) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:166) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:190) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.json.JSONInterceptor.intercept(JSONInterceptor.java:179) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248) org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:485) org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77) org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91) com.base.UEditorFilter.doFilter(UEditorFilter.java:21) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:174) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:77) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:78) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:77) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503) org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421) org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070) org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611) org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314) java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) java.lang.Thread.run(Thread.java:748) ```

springboot启动类不加载RetentionPolicy.CLASS注解吗?

最近写了一个注解,用的默认的Retention,也就是CLASS,里面import了一个bean,发现将这个注解加在springboot的启动类上的时候,import的bean无法实例化,如果是把这个注解加在普通@Configuration配置类的时候是可以实例化import的bean的。如果把这个注解的RetentionPolicy 改为 runtime ,加在启动类的时候也是可以实例化bean的!弄了一下午没搞明白原理!求助大神们! 这个是我写的注解,LogConfig为一个bean ``` @Import({LogConfig.class}) public @interface EnableCPSPLogConfig { } @Configuration @EnableConfigurationProperties @RefreshScope @ConfigurationProperties( prefix = "cpsplog" ) public class LogConfig { private List<String> include; private List<String> exclude; public LogConfig() { } } ``` 这种情况是可以正常使用的: ``` @Configuration @EnableCPSPLogConfig public class WebConfig { } ``` 这种情况下必须要把RetentionPolicy 改为 runtime也是可以使用的 ``` @SpringBootApplication @EnableCPSPLogConfig public class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } } ```

Java: main方法 是同时与class文件加载到方法区的吗

Java: main方法 是同时与class文件加载到方法区的吗

关于Java自定义ClassLoader的类加载问题,求大神指点

本人自定义了一个Classloader,用于加载特定文件夹下面的class。 前期准备写了一个interface Animal,代码如下: ``` package com.paul.service; public interface Animal { public void jiao(String name); } ``` 有一个实现类 Dog, 代码如下: package com.paul.impl; ``` import com.paul.service.Animal; //Animal的实现类Dog public class Dog implements Animal{ public void jiao(String name){ System.out.println("this is dog>>>>>>>>>>>>>"+name); } } ``` 有一个测试类 EffectiveJava,里面有一个方面testClassLoader(String testStr), 代码如下: ``` package com.foxconn.paul.tool; import com.paul.impl.Dog; import com.paul.service.Animal; public static void testClassLoader(String testStr){ Animal animal = new Dog(); animal.jiao(testStr); } ``` 自定义LoadClassFileClassLoader的核心代码: public class LoadClassFileClassLoader extends ClassLoader{ private String clsssFilePath; public LoadClassFileClassLoader(String clsssFilePath){ this.clsssFilePath = clsssFilePath; } private static String getClassFileName(String className){ StringBuilder sb = new StringBuilder(); className = className.substring(className.lastIndexOf(".")+1); sb.append(className).append(".class").toString(); return sb.toString(); } protected Class<?> findClass(String name) throws ClassNotFoundException { System.out.println(" LoadClassFileClassLoader >>>>>>> overwrite findClass (String name)"); String fileName = getClassFileName(name); File file = new File(clsssFilePath,fileName); System.out.println(" class filePath >>>>> " + clsssFilePath + " fileName >>> " +fileName); try { FileInputStream is = new FileInputStream(file); ByteArrayOutputStream bos = new ByteArrayOutputStream(); int len = 0; while ((len = is.read()) != -1) { bos.write(len); } byte[] data = bos.toByteArray(); is.close(); bos.close(); return defineClass(name,data,0,data.length); } catch (IOException e) { e.printStackTrace(); } return super.findClass(name); } } 请注意这三个类都不在同一个package下。然后把编译好的Animal.class、Dog.class放入本地目录E:\\classloader_test\\; 把EffectiveJava.class放入本地目录E:\\classloader_test\\other\\ 测试时LoadClassFileClassLoader与Animal、Dog、EffectiveJava不在同一个工程里面。开始测试: ``` //加载Animal、Dog LoadClassFileClassLoader classLoader = new LoadClassFileClassLoader("D:\\testClass\\"); Class<?> cInterfaceAnimal = classLoader.loadClass("com.paul.service.Animal"); Class<?> dog = classLoader.loadClass("com.paul.impl.Dog"); //加载EffectiveJava LoadClassFileClassLoader classLoaderOther = new LoadClassFileClassLoader("E:\\classloader_test\\other\\"); Class<?> c = classLoaderOther.loadClass("com.foxconn.paul.tool.EffectiveJava"); if(c != null){ System.out.println(c); Object obj = c.newInstance(); Method method = c.getDeclaredMethod("testClassLoader",String.class); System.out.println(method.invoke(obj, "哈哈哈")); } ``` 运行程序报错,提示"java.io.FileNotFoundException: E:\classloader_test\other\Animal.class (系統找不到指定的檔案。)“ 问题1. com.paul.service.Animal与com.paul.impl.Dog已经加载过了,为什么还要在加载com.foxconn.paul.tool.EffectiveJava时去加载Animal和Dog。这两个类为什么没在加载类的缓存里面? 问题2. 如果我要实现与加载java核心类库相同的效果。即我在前面已经加载过com.paul.service.Animal与com.paul.impl.Dog,那么我在com.foxconn.paul.tool.EffectiveJava可以直接引用已经加载的类

用wsdl文件生成java代码时报错,找不到。

java.lang.NoClassDefFoundError: org/apache/axis/wsdl/WSDL2Java Caused by: java.lang.ClassNotFoundException: org.apache.axis.wsdl.WSDL2Java at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) Exception in thread "main" 包都有的,在这个项目里就不行。我新建一个项目,在新项目里就可以,一到原来的项目有有问题。求大神带飞。

java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver已在lib下添加jar包还是报错怎么办

在网上好了很多的问题 都没有解决,针对web,大家用的都是的在tomcat下的lib里添加mysql-connector的jar包 但是还是没有解决 还是连接不上,也在url里面添加后缀了 package jdbc; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class JDBCDemo { private static final String URL="jdbc:mysql://localhost:3306/db4?useUnicode=true&characterEncoding=utf8&useSSL=false&serverTimezone=Hongkong"; private static final String USERNAME="root"; private static final String PWD="root"; public static void update() {//增删改 Connection connection=null; Statement stmt =null; try { //导入驱动,加载具体驱动类 Class.forName("com.mysql.cj.jdbc.Driver");//加载具体的驱动类 //与数据库建立连接 connection=DriverManager.getConnection(URL,USERNAME,PWD); //增删改 stmt = connection.createStatement(); String sql="insert into student values(4,'kxk','123')"; int result = stmt.executeUpdate(sql); //处理结果:显示受影响行数 System.out.println(result); }catch (ClassNotFoundException e) { e.printStackTrace(); }catch (Exception e) { e.printStackTrace(); }finally { if(stmt!=null) { try { stmt.close(); }catch (SQLException e) { e.printStackTrace(); } } if(connection!=null) { try { connection.close(); }catch (SQLException e) { e.printStackTrace(); } } } } public static void main(String[] args) { update(); } } 报错还是 java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver at java.net.URLClassLoader.findClass(URLClassLoader.java:381) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:338) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:264) 不知道哪里出现了问题,求助

java 动态加载class问题

java 动态加载class;写了A B类,都没有main方法。其中 A类中有静态方法f,其功能是动态加载类B的class文件。类B中有个函数;在idea中运行是没问题的 A.T.sum(2,7)) 可以调用。但是一旦把这个程序打成jar包后。在其他工程里引入jar包,就不能动态加载该类B。请大神指导下 package fff.BB; /** * Created by ***** on 2017/6/22. */ public class B { public int sum(int x, int y){ return x+y; } } import fff.BB.B; import java.io.File; import java.io.IOException; import java.net.URL; import java.net.URLDecoder; import java.util.Enumeration; import java.util.LinkedHashSet; import java.util.Set; /** * Created by liweidong on 2017/6/22. */ public class A { public static B T = null; static { registerReset(); } private static void registerReset(){ Set<Class<?>> classSet = loadClass(); for(Class cl : classSet){ try { T = (B) cl.newInstance(); } catch (Exception e) { e.printStackTrace(); } } } private static Set<Class<?>> loadClass(){ String packageDir = "fff.BB"; Set<Class<?>> classSet = new LinkedHashSet<Class<?>>(); try { Enumeration<URL> dirs = Thread.currentThread().getContextClassLoader().getResources(packageDir.replace('.','/')); while (dirs.hasMoreElements()){ URL url = dirs.nextElement(); String packagePath = URLDecoder.decode(url.getFile(),"UTF-8"); Class<?> loadClass = findClass(packageDir,packagePath); if(loadClass != null){ classSet.add(loadClass); } } }catch (IOException e){ } return classSet; } private static Class<?> findClass(String packageName,String packagePath){ File dir = new File(packagePath); if(!dir.exists() || !dir.isDirectory()){ return null; } File[] dirfiles = dir.listFiles(file -> (file.getName().endsWith(".class"))); for(File file : dirfiles){ String className = file.getName().substring(0, file.getName().length() - ".class".length()); Class<?> clazz = null; try { clazz = Thread.currentThread().getContextClassLoader().loadClass(packageName + "." + className); if(clazz != null){ return clazz; } } catch (ClassNotFoundException e) { e.printStackTrace(); } } return null; } }

vscode 将java文件放到一个包时就会出现“找不到或无法加载主类java.lang.NoClassDefFoundError”的错误

![图片说明](https://img-ask.csdn.net/upload/202003/31/1585653163_254475.png) 当我加上第一句时就会出现占不到或无法加载主类的错误,左边的main1.class没有变颜色,但是就是在那个文件夹下 ![图片说明](https://img-ask.csdn.net/upload/202003/31/1585653266_939556.png) 把第一句去掉后就正常了

读properties class.forname失败

Java 连接Mysql 加载 直接写Class.forName("com.mysql.jdbc.Driver"); 可以成功,但读properties Class.forName(drivers);); drivers = props.getProperty("driver“”( System.out.println(drivers)也可打印com.mysql.jdbc.Driver成功证明取到了 "); 就失败报java.lang.ClassNotFoundException: com.mysql.jdbc.Driver 读url user passw读到可打印 但就是报错都是 具体代码如下ord private void init() { try { // InputStream in = getClass().getResourceAsStream(FILE_PATH_NAME); InputStream in = DataConnection.class.getClassLoader().getResourceAsStream(FILE_PATH_NAME); Properties props = new Properties(); props.load(in); in.close(); drivers = props.getProperty("driver"); url = props.getProperty("url"); username = props.getProperty("username"); password = props.getProperty("password"); } catch (IOException e) { e.printStackTrace(); } } public Connection getConnection() { Connection conn = null; try { System.out.println(drivers); Class.forName(drivers); // System.out.println("com.mysql.jdbc.Driver"); // Class.forName("com.mysql.jdbc.Driver"); // conn = DriverManager.getConnection(url, username, password); conn = DriverManager.getConnection("jdbc:mysql://10.5.0.20/robottest","root", "1234"); } catch (SQLException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } return conn; } 报错 java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1856) at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1705) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:171) at dao.DataConnection.getConnection(DataConnection.java:53) at org.apache.jsp.connTest_jsp._jspService(connTest_jsp.java:120) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:731) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339) at javax.servlet.http.HttpServlet.service(HttpServlet.java:731) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at com.atguigu.javaweb.AuthorityFilter.doFilter(AuthorityFilter.java:29) at com.atguigu.javaweb.HttpFilter.doFilter(HttpFilter.java:59) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:662)

URLClassLoader加载class文件的疑惑

最近用到了URLClassLoader的loadClass()方法,就写了个测试例子,结果出现了问题。具体问题如下所述: [b]首先,给出测试代码,该代码贴到Main函数了直接可以运行[/b]: [code="java"]URLClassLoader loader = null; try { URL[] urls = new URL[1]; URLStreamHandler streamHandler = null; //E:\mp_workspace\HttpServer2.0\webRoot 是工程下一目录,用来存放测试的class文件 String respository = new URL("file",null,” E:\mp_workspace\HttpServer2.0\webRoot”)toString(); urls[0] = new URL(null,respository,streamHandler); loader = new URLClassLoader(urls); } catch (Exception e) { e.printStackTrace(); } Class className = null; try { className = loader.loadClass(“Myclass”); System.out.println(className.getName()); } catch (ClassNotFoundException e) { e.printStackTrace(); } Myclass myclass = null; try { myclass = (Myclass)className.newInstance(); myclass.test(); } catch (Exception e) { e.printStackTrace(); } [/code] 要测试的类Myclass.java的代码如下,注意它的[b]包名[/b]: [code="java"]package com.test; public class Myclass { public void test() { System.out.println("good byte"); } public static void main(String[] args) { System.out.println("hello word"); } }[/code] 现在问题是运行上面测试代码是:当Myclass.java在包com.test里面时,运行上面的测试代码会报错。错误信息是: [color=red]Exception in thread "main" java.lang.NoClassDefFoundError: Myclass (wrong name: com/test/Myclass) at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(Unknown Source) at java.security.SecureClassLoader.defineClass(Unknown Source)[/color] [color=blue][size=medium]但是比较奇怪的是,我把Myclass类直接移到源文件src下载,即Myclass没有包名时,运行则通过,没有一点问题。[/size][/color] 我想,这与我还不太了解URLClassLoader这个类有关吧。请大家帮我看看,在你们的IDE上调试下,这个问题我琢磨了很久,还是想不出所以然啊。 还有,我的工程名是HttpServer2.0 ,我在工程下建了一个目录webRoot,专门用来放测试的class文件。上面的例子,就是我先通过eclipse编译了Myclass.java,在bin下生成了Myclass.class文件,然后我将该文件复制到webRoot目录下进行测试的。 最奇怪的一点是:[size=medium][color=blue]src下有Myclass.java类则上面测试没问题,否则会报错[/color][/size]

关于java类加载的双亲委托机制的一点疑问

class Clazz2{ public static void main(String[] args) { ClassLoader classLoader = new ClassLoader() { @Override public Class<?> loadClass(String name) throws ClassNotFoundException { try { FileInputStream fileInputStream = new FileInputStream("C:\\Users\\zsx\\IdeaProjects\\springrest\\target\\test-classes\\Test0.class"); byte[] bytes = new byte[1024]; try { int offset = fileInputStream.read(bytes); return defineClass("Test0",bytes,0,offset); } catch (IOException e) { e.printStackTrace(); } } catch (FileNotFoundException e) { e.printStackTrace(); } throw new RuntimeException("class not found"); } // @Override // protected Class<?> findClass(String name) throws ClassNotFoundException { // try { // FileInputStream fileInputStream = new FileInputStream("C:\\Users\\zsx\\IdeaProjects\\springrest\\target\\test-classes\\Test0.class"); // byte[] bytes = new byte[1024]; // // try { // int offset = fileInputStream.read(bytes); // return defineClass("Test0",bytes,0,offset); // } catch (IOException e) { // e.printStackTrace(); // } // } catch (FileNotFoundException e) { // e.printStackTrace(); // } // throw new RuntimeException("class not found"); // } }; try { Class cl = classLoader.loadClass("Test0"); try { Object obj = cl.newInstance(); System.out.println(obj instanceof Test0); } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } } catch (ClassNotFoundException e) { e.printStackTrace(); } } } 代码如上,如果我不是重写findClass方法而是重写loadClass方法,不是就破坏了java的双亲委托机制了吗,那这时候我在loadClass里面不委托父加载器而是直接加载我本地的一些系统jar包比如rt.jar不是就不对了吗,java是如何检查这种问题的呢,在代码里我尝试着自己重写了loadClass方法,发现报Exception in thread "main" java.lang.ClassCircularityError: Test0这个错误,不知道他是怎么个过程,另外当加载器在尝试加载一个类的时候这个类的父类是如何加载处理的呢,谢谢。

java web项目如何调用.so文件?

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报错:java.lang.reflect.InvocationTargetException

type Exception report message description The server encountered an internal error () that prevented it from fulfilling this request. exception java.lang.reflect.InvocationTargetException sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) java.lang.reflect.Method.invoke(Method.java:597) com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:440) com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:279) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:163) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:249) org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:148) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:93) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:128) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:104) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:148) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:128) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:468) org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395) root cause com.sun.xml.ws.util.ServiceConfigurationError: com.sun.xml.ws.api.client.ServiceInterceptorFactory: Provider com.sun.xml.ws.policy.jaxws.client.PolicyServiceInterceptorFactory is specified in jar:file:/C:/Program Files/Genuitec/Common/plugins/com.genuitec.eclipse.ws.xfire_8.5.0.me201003052220/lib/webservices-rt.jar!/META-INF/services/com.sun.xml.ws.api.client.ServiceInterceptorFactorybut could not be instantiated: java.lang.ClassCastException com.sun.xml.ws.util.ServiceFinder.fail(ServiceFinder.java:237) com.sun.xml.ws.util.ServiceFinder.access$300(ServiceFinder.java:145) com.sun.xml.ws.util.ServiceFinder$LazyIterator.next(ServiceFinder.java:383) com.sun.xml.ws.api.client.ServiceInterceptorFactory.load(ServiceInterceptorFactory.java:84) com.sun.xml.ws.client.WSServiceDelegate.<init>(WSServiceDelegate.java:213) com.sun.xml.ws.client.WSServiceDelegate.<init>(WSServiceDelegate.java:186) com.sun.xml.ws.spi.ProviderImpl.createServiceDelegate(ProviderImpl.java:111) javax.xml.ws.Service.<init>(Service.java:56) junit.test.web.ws.TJServiceBizImplService.<init>(TJServiceBizImplService.java:42) com.aoyang.hms.action.DeptAction.queryEmployee(DeptAction.java:911) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) java.lang.reflect.Method.invoke(Method.java:597) com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:440) com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:279) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:163) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:249) org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:148) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:93) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:128) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:104) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:148) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:128) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:468) org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395) root cause java.lang.ClassCastException java.lang.Class.cast(Class.java:2990) com.sun.xml.ws.util.ServiceFinder$LazyIterator.next(ServiceFinder.java:378) com.sun.xml.ws.api.client.ServiceInterceptorFactory.load(ServiceInterceptorFactory.java:84) com.sun.xml.ws.client.WSServiceDelegate.<init>(WSServiceDelegate.java:213) com.sun.xml.ws.client.WSServiceDelegate.<init>(WSServiceDelegate.java:186) com.sun.xml.ws.spi.ProviderImpl.createServiceDelegate(ProviderImpl.java:111) javax.xml.ws.Service.<init>(Service.java:56) junit.test.web.ws.TJServiceBizImplService.<init>(TJServiceBizImplService.java:42) com.aoyang.hms.action.DeptAction.queryEmployee(DeptAction.java:911) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) java.lang.reflect.Method.invoke(Method.java:597) com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:440) com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:279) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242) com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:163) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:249) org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:148) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:93) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:235) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:128) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:104) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138) com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:148) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:128) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176) com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236) org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52) org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:468) org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395)

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