Incompatible magic value error_问答_开发者_运维开发者技术经验分享

I was following an example from the following link:

http://www.javaworld.com/javaworld/jw-10-1996/jw-10-indepth.html?page=1 and this is an output I am getting:

This program will use SimpleClassLoader.
        >>>>>> Load class : TestClass
        >>>>>> Not a system class.
        >>>>>> Fetching the implementation of TestClass
file was read successfully
Exception in thread "main" java.lang.ClassFormatError: Incompatible magic value 1768779887 in class file 
    at java.la开发者_Go百科ng.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(Unknown Source)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at aha.SimpleClassLoader.loadClass(SimpleClassLoader.java:80)
    at aha.SimpleClassLoader.loadClass(SimpleClassLoader.java:42)
    at aha.Example.main(Example.java:11)

here is an example of my method that reads a file:

 private byte getClassImplFromDataBase(String className)[] {
        System.out.println("        >>>>>> Fetching the implementation of "+className);
        byte result[];
        try {
            FileInputStream fi = new FileInputStream("C:/delete/"+className+".impl");
            result = new byte[fi.available()];
            fi.read(result);
            System.out.println("file was read succesfullyl");
            return result;
        } catch (Exception e) {

            /*
             * If we caught an exception, either the class wasnt found or it
             * was unreadable by our process.
             */
            return null;
        }
    }

I placed TestClass.impl file under C:/delete directory . My classes reside under package: aha So the file TestClass.impl is read ok, but something happens during the result = defineClass(classData, 0, classData.length); I know this method is deprecated but still ??

I don't know what file type .impl is but I suspect it not a class file which contains byte code. The magic number 1768779887 in hex is 696D706F or impo in ASCII. (The first four bytes of import I suspect)

So it would appear to me that you are trying to load uncompiled Java code whcih you cannot do (that is what the compiler is for) You are better of using the Compiler API, but I suspect you really need something like OSGi as trying to load classes your self requires you to have a very detailed understanding of how class loading work.

I've had a similar error with a regular struts2 project, solved cleaning the project.

8266 ERROR [main]: Excepción arrancando filtro struts2
java.lang.ClassFormatError: Incompatible magic value 0 in class file com/lm/action/musician/MusicianList
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1650)
    at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:856)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1305)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1187)
    at com.opensymphony.xwork2.util.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:144)
    at com.opensymphony.xwork2.ObjectFactory.getClassInstance(ObjectFactory.java:108)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyAction(XmlConfigurationProvider.java:424)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:378)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:495)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:286)
    at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:112)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:234)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:390)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:437)
    at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:225)
    at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:308)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:79)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3563)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4133)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
    at org.apache.catalina.core.StandardService.start(StandardService.java:450)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:680)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:536)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:275)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
8266 ERROR [main]: Excepción arrancando filtro struts2
java.lang.ClassFormatError: Incompatible magic value 0 in class file com/lm/action/musician/MusicianList
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1650)
    at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:856)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1305)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1187)
    at com.opensymphony.xwork2.util.ClassLoaderUtil.loadClass(ClassLoaderUtil.java:144)
    at com.opensymphony.xwork2.ObjectFactory.getClassInstance(ObjectFactory.java:108)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyAction(XmlConfigurationProvider.java:424)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:378)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:495)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:286)
    at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:112)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:234)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:390)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:437)
    at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:225)
    at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:308)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:79)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3563)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4133)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
    at org.apache.catalina.core.StandardService.start(StandardService.java:450)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:680)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:536)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:275)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
abr 19, 2013 10:32:25 AM org.apache.catalina.core.StandardContext start
SEVERE: Error filterStart
abr 19, 2013 10:32:25 AM org.apache.catalina.core.StandardContext start