我正在尝试诊断和解决JAXBContext导致的严重内存泄漏。但是，尽管做了很多尝试，我还是没有成功。
简而言之，我的应用程序在执行的前50分钟内使用少量且一致的内存。大约50分钟后，类/内存的数量从少于4,000（类）增加到大约8,000（内存也会出现类似的增加）。这种方式一直保持到大约1小时16分钟为止，直到下一个执行15-20分钟内类的数量（如YourKit中所述）增长到大约246,000。
几乎同时增加了内存/类的使用率，我的程序开始使用eBay的Java SDK [com.ebay.sdk.pictureservice.eps]将图像上传到eBay服务器。
我分析了Object Allocation Call Tree中的YourKit，看来我的程序调用了以下方法：
public int uploadPictures(PhotoDisplayCodeType arg0, PictureInfo[] arg1) {
int arg2 = 0;
for (int arg3 = 0; arg3 < arg1.length; ++arg3) {
if (this.uploadPicture(arg0, arg1[arg3])) {
++arg2;
}
}
return arg2;
}
public boolean uploadPicture(PhotoDisplayCodeType arg0, PictureInfo arg1) {
UploadSiteHostedPicturesRequestType arg2 = new UploadSiteHostedPicturesRequestType();
if (arg0.equals(PhotoDisplayCodeType.SUPER_SIZE) || arg0.equals(PhotoDisplayCodeType.PICTURE_PACK)) {
arg2.setPictureSet(PictureSetCodeType.SUPERSIZE);
}
return this.UpLoadSiteHostedPicture(arg1, arg2);
}
public boolean UpLoadSiteHostedPicture(PictureInfo arg0, UploadSiteHostedPicturesRequestType arg1) {
ApiLogging arg2 = this.apiContext.getApiLogging();
System.out.println("Starting picture upload..");
try {
Document arg3 = this.marshal(arg1);
this.addAuthToken(arg3);
String arg4;
if (arg2 != null && arg2.isLogSOAPMessages()) {
arg4 = XmlUtil.getXmlStringFromDom(arg3);
this.logMessage("UploadSiteHostedPicturesRequest", arg4);
}
arg4 = this.xmlToString(arg3);
String arg5 = this.sendFile(arg0.getPictureFilePath(), arg4);
if (arg2 != null && arg2.isLogSOAPMessages()) {
Document arg6 = XmlUtil.createDom(arg5);
String arg7 = XmlUtil.getXmlStringFromDom(arg6);
this.logMessage("UploadSiteHostedPicturesResponse", arg7);
}
UploadSiteHostedPicturesResponseType arg9 = this.unmarshal(arg5);
arg0.setReponse(arg9);
if (arg9.getErrors() != null && arg9.getErrors().length != 0) {
if (arg9.getErrors().length > 0 && arg9.getAck() == AckCodeType.WARNING) {
arg0.setURL(arg9.getSiteHostedPictureDetails().getFullURL());
arg0.setErrorType("PICTURE SERVICE RESPONSE WARNING");
arg0.setErrorMessage(arg9.getErrors()[0].getShortMessage());
if (arg2 != null && arg2.isLogExceptions()) {
log.warn("PICTURE SERVICE RESPONSE WARNING");
log.warn(arg9.getErrors()[0].getShortMessage());
}
return true;
} else {
arg0.setErrorType("PICTURE SERVICE RESPONSE ERROR");
arg0.setErrorMessage(arg9.getErrors()[0].getShortMessage());
if (arg2 != null && arg2.isLogExceptions()) {
log.error("PICTURE SERVICE RESPONSE ERROR");
log.error(arg9.getErrors()[0].getShortMessage());
}
return false;
}
} else {
arg0.setURL(arg9.getSiteHostedPictureDetails().getFullURL());
return true;
}
} catch (Exception arg8) {
arg0.setErrorType("PICTURE SERVICE UPLOAD ERROR");
arg0.setErrorMessage(arg8.getMessage());
if (arg2 != null && arg2.isLogExceptions()) {
log.error("fail to upload picture to eBay picture server!");
log.error(arg8.getMessage());
}
return false;
}
}
private Document marshal(UploadSiteHostedPicturesRequestType arg0)
throws JAXBException, ParserConfigurationException {
**// Is this line causing memory leak?**
JAXBContext arg1 = JAXBContext.newInstance(new Class[] { UploadSiteHostedPicturesRequestType.class });
Marshaller arg2 = arg1.createMarshaller();
if (arg0 == null) {
arg0 = new UploadSiteHostedPicturesRequestType();
}
JAXBElement arg3 = (new ObjectFactory()).createUploadSiteHostedPicturesRequest(arg0);
DocumentBuilderFactory arg4 = DocumentBuilderFactory.newInstance();
arg4.setNamespaceAware(true);
DocumentBuilder arg5 = arg4.newDocumentBuilder();
Document arg6 = arg5.newDocument();
arg2.marshal(arg3, arg6);
return arg6;
}
我的程序连续调用uploadPictures()几百次。在我看来，大约在程序调用此函数时内存就开始急剧增加。
我的诊断正确吗？我该如何解决？
更新：
我找到了这个related thread on SO。如果我的诊断正确，那似乎是JAXBContext使用的EBay SDK版本的错误。
更新：
我尝试通过将JAXBContext类更改为单例来解决此问题，但不幸的是，它没有解决问题：
public class JAXBContextFactory {
private static JAXBContextFactory instance = new JAXBContextFactory();
private static final Map< String, JAXBContext > INSTANCES = new ConcurrentHashMap<String, JAXBContext>();
private JAXBContextFactory() {
}
/**
* Returns an existing JAXBContext if one for the particular namespace exists,
* else it creates an instance adds it to a internal map.
* @param contextPath the context path
* @throws JAXBException exception in creating context
* @return a created JAXBContext
*/
public JAXBContext getJaxBContext(final String contextPath) throws JAXBException {
JAXBContext context = INSTANCES.get(contextPath);
if (context == null) {
context = JAXBContext.newInstance(contextPath);
INSTANCES.put(contextPath, context);
}
return context;
}
/**
* Returns an existing JAXBContext if one for the particular namespace exists,
* else it creates an instance adds it to a internal map.
* @param contextPath the context path
* @throws JAXBException exception in creating context
* @return a created JAXBContext
*/
public JAXBContext getJaxBContext(final Class contextPath) throws JAXBException {
JAXBContext context = INSTANCES.get(contextPath.getName());
if (context == null) {
context = JAXBContext.newInstance(contextPath);
INSTANCES.put(contextPath.getName(), context);
}
return context;
}
/**
* Get instance.
* @return Instance of this factory
*/
public static JAXBContextFactory getInstance() {
return instance;
}
}
当我查看Inspections下YourKit中"Other memory oddities"的{{1}}时，发现的唯一问题是243,959 "Classes with same name"。当我检查类时，我看到它们都包含术语'JAXB'。基于这些观察，我有几个问题：
1）为什么Singleton模式解决的问题不能创建许多JAXBContext？
2），即使没有Singleton，为什么在我的应用程序清楚地使用完它们/上载图像后，为什么所有相关类也没有被垃圾回收？上传完成后，我没有引用JAXBContext类。
谢谢！
答案 0 :(得分：1)
在您的marshal(UploadSiteHostedPicturesRequestType arg0)方法中，有一行
// Is this line causing memory leak?
JAXBContext arg1 = JAXBContext.newInstance(new Class[] { UploadSiteHostedPicturesRequestType.class });
尽管此行严格来说不是内存泄漏，
它占用大量内存，并占用大量CPU时间，
因为它每次都会创建一个新的重JAXBContext对象。
从此方法返回后
不再引用局部变量JAXBContext arg1，
但它将一直保留在内存中，直到被垃圾回收为止
（而且很长一段时间可能不会发生）。
您应该将这一行替换为
JAXBContext arg1 = JAXBContextFactory.getInstance().getJaxBContext(UploadSiteHostedPicturesRequestType.class);
这应该可以大大改善内存使用率和CPU时间。