title: java 8 java.lang.OutOfMemoryError: Metaspace
body: <p>I'm having an OutOfMemoryError while running Java cs application. According to the error message,it seems that the error occurs while doing transferring XML String to Java object.</p>
  
  <p>The transfer code is below</p>
  
  <pre><code>public static Object convertXmlStrToObject(Class clazz, String xmlStr) {
      Object xmlObject = null;
      try {
          JAXBContext context = JAXBContext.newInstance(clazz);
          // 进行将Xml转成对象的核心接口
          Unmarshaller unmarshaller = context.createUnmarshaller();
          StringReader sr = new StringReader(xmlStr);
          xmlObject = unmarshaller.unmarshal(sr);
      } catch (JAXBException e) {
          e.printStackTrace();
      }
      return xmlObject;
  }
  </code></pre>
  
  <p>I have looked into my logs and located the String which triggered this error.
  Then I convert this String into java object using the code above for like 10K times.No error was reported.</p>
  
  <p>I have thousands of such applications running in windows xp system and I worried that this may cause a huge problem. I Googled this error and many says that the error occurs because the MaxMetaspaceSize is too small,while i didn't use the MaxMetaspaceSize in my application.</p>
  
  <pre><code>java.lang.OutOfMemoryError: Metaspace
      at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl.&lt;init&gt;(Unknown Source)
      at com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl.newSAXParser(Unknown Source)
      at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.getXMLReader(Unknown Source)
      at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(Unknown Source)
      at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(Unknown Source)
      at com.hgits.payCodeDebit.util.XMLUtil.convertXmlStrToObject(XMLUtil.java:91)
  </code></pre>
  
  <p>After checking recent logs,I found a strange problem. Besides the error above， there is another error which is below:</p>
  
  <pre><code>java.io.IOException: Map failed
  at sun.nio.ch.FileChannelImpl.map(Unknown Source)
  at sun.nio.ch.FileChannelImpl.transferFromFileChannel(Unknown Source)
  at sun.nio.ch.FileChannelImpl.transferFrom(Unknown Source)
  at org.apache.commons.io.FileUtils.doCopyFile(FileUtils.java:1147)
  at org.apache.commons.io.FileUtils.copyFile(FileUtils.java:1091)
  at org.apache.commons.io.FileUtils.copyFile(FileUtils.java:1038)
  at com.hgits.cron.CheckNonFareParamJob.checkRecvParamList(CheckNonFareParamJob.java:153)
  at com.hgits.cron.CheckNonFareParamJob.execute(CheckNonFareParamJob.java:54)
  at org.quartz.core.JobRunShell.run(JobRunShell.java:213)
  at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:557)
  Caused by: java.lang.OutOfMemoryError: Map failed
  at sun.nio.ch.FileChannelImpl.map0(Native Method)
  ... 10 more
  </code></pre>
  
  <p>After Googling,this seemed to be a memory problem.
  I looged the process memory with jna and windows api GetProcessMemoryInfo.
  When my application started, the jvm process memory is 615616K which is normal and everything is ok. After running about 36 hours , the jvm process memory reached 1796676K,and I start to have “java.lang.OutOfMemoryError: Map failed” error.
  While the jvm process memory reached 1796676K, I also logged the heap memory of jvm which is as below 810942464byte(Runtime.getRuntime().maxMemory()):810942464byte(Runtime.getRuntime().totalMemory()):239632736byte(Runtime.getRuntime().freeMemory()).
  So there is still 200M freeMemory in jvm heap.</p>
  
  <p>Because I used jna to load several dll,My guess is that there is some kind of memory leak in some of the dll.
  If my guess is right, how can I locate the cause? I have tried jjvisualvm and jmc,but I see nothing wrong.</p>