Java 静态块中的getResourceAsStream有时返回null

我有一些代码在类的顶部执行此操作：

static {
    ...
    mapper.addMappingConfig(ModelRestMapper.class.getResourceAsStream("/com/mycompany/myapp/rest/dozer/mapping/mapping.xml"));
    ...
}

此代码有时会出现以下异常：

[#|2014-05-23T12:21:33.111-0700|SEVERE|glassfish3.1.2|org.dozer.loader.xml.MappingStreamReader|_ThreadID=305;_ThreadName=Thread-2;|Error while loading dozer mapping InputStream: [null]
    java.lang.IllegalArgumentException: InputStream cannot be null
    at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:117)
    at org.dozer.loader.xml.MappingStreamReader.read(MappingStreamReader.java:50)
    at org.dozer.DozerBeanMapper.addMapping(DozerBeanMapper.java:247)
    at com.mycompany.commons.objectmapping.Mapper.addMappingConfig(Mapper.java:62)
    at com.mycompany.myapp.rest.dozer.mapping.ModelRestMapper.<clinit>(ModelRestMapper.java:30) //the line I showed you
at sun.misc.Unsafe.ensureClassInitialized(Native Method)
at sun.reflect.UnsafeFieldAccessorFactory.newFieldAccessor(UnsafeFieldAccessorFactory.java:43)
at sun.reflect.ReflectionFactory.newFieldAccessor(ReflectionFactory.java:140)
at java.lang.reflect.Field.acquireFieldAccessor(Field.java:1057)
at java.lang.reflect.Field.getFieldAccessor(Field.java:1038)
at java.lang.reflect.Field.set(Field.java:741)
at org.glassfish.web.loader.WebappClassLoader.clearReferences(WebappClassLoader.java:1836)
at org.glassfish.web.loader.WebappClassLoader.stop(WebappClassLoader.java:1662)
at org.glassfish.web.loader.WebappClassLoader.preDestroy(WebappClassLoader.java:1631)
at org.glassfish.javaee.full.deployment.EarClassLoader.preDestroy(EarClassLoader.java:91)
at org.glassfish.deployment.common.DeploymentContextImpl.preDestroy(DeploymentContextImpl.java:151)
at com.sun.enterprise.v3.server.ApplicationLifecycle$1.actOn(ApplicationLifecycle.java:281)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:465)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:240)
at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:389)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$1.execute(CommandRunnerImpl.java:348)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:363)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1085)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1200(CommandRunnerImpl.java:95)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1291)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1259)
at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:461)
at com.sun.enterprise.v3.admin.AdminAdapter.service(AdminAdapter.java:212)
at com.sun.grizzly.tcp.http11.GrizzlyAdapter.service(GrizzlyAdapter.java:179)
at com.sun.enterprise.v3.server.HK2Dispatcher.dispath(HK2Dispatcher.java:117)
at com.sun.enterprise.v3.services.impl.ContainerMapper$Hk2DispatcherCallable.call(ContainerMapper.java:354)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:745)
|#]

---

我不应该在战争中使用这样的代码吗？为什么会发生这种情况以及如何防止这种情况？

根据堆栈跟踪，在销毁应用程序上下文时发生异常。问题似乎与Glassfish默认将所有加载类的任何静态和最终字段设置为

null

作为避免内存泄漏的解决方法有关

这可能会导致类的（重新）初始化，即调用静态初始化块，该块尝试加载资源，但由于某种竞争条件而失败

有一个系统属性

org.apache.catalina.loader.WebappClassLoader.ENABLE\u CLEAR\u REFERENCES

控制清除引用的过程（）。您可以尝试设置为

false

，然后查看发生了什么

---

另一个（更好的）选项是将资源的加载移到静态初始值设定项块之外

您在生产环境中使用的是哪种JRE？@LuiggiMendoza问得好。我更新了我的问题好的，我想我会使用更好的选项。我会看看这种情况是否会再次发生，如果它解决了问题，我会将你的答案标记为答案。

java version "1.7.0_55"
Java(TM) SE Runtime Environment (build 1.7.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)