Question

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"));
    ...
}

此代码有时因此异常而失败：

[#|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)
|#]

我说这种情况大概是每10个部署一次，而且下次我尝试时似乎总能工作。这是在战争中部署的类，应用服务器是GlassFish 3.1.2。这个班没什么特别的，只是一个pojo。当错误发生并且打开战争时，我看到xml文件应该是它应该在哪里。这是我的JRE：

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)

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？如何防止它？

Answer 1

根据堆栈跟踪，在销毁应用程序上下文时发生异常。这个问题似乎与Glassfish的WebappClassLoader默认设置为null的所有已加载类的任何静态和最终字段作为解决方法以避免内存泄漏有关。

这可能导致类的（重新）初始化，即调用静态初始化块，尝试加载资源并因某种竞争条件而失败。

有一个系统属性org.apache.catalina.loader.WebappClassLoader.ENABLE_CLEAR_REFERENCES可以控制清除引用（link）的过程。您可以尝试设置为false，看看发生了什么。

另一个（更好的）选项是将资源加载到静态初始化程序块之外。

静态块中的getResourceAsStream有时会返回null

1 个答案: