Threads getting blocked JAXB

问题

even after creating new object of unmarshaller every time, threads are getting blocked Please help

"http-80-3" daemon prio=10 tid=0x000000004fabe800 nid=0x7147 waiting for monitor entry [0x0000000042401000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at java.util.zip.ZipFile$ZipFileInputStream.read(ZipFile.java:457)
    - waiting to lock <0x00000000c02cce20> (a sun.net.www.protocol.jar.URLJarFile)
    at java.util.zip.ZipFile$ZipFileInputStream.read(ZipFile.java:475)
    at java.io.FilterInputStream.read(FilterInputStream.java:66)
    at java.io.DataInputStream.readInt(DataInputStream.java:371)
    at com.sun.xml.internal.bind.v2.bytecode.ClassTailor.tailor(ClassTailor.java:165)
    at com.sun.xml.internal.bind.v2.runtime.reflect.opt.AccessorInjector.tailor(AccessorInjector.java:108)
    at com.sun.xml.internal.bind.v2.runtime.reflect.opt.AccessorInjector.prepare(AccessorInjector.java:68)
    at com.sun.xml.internal.bind.v2.runtime.reflect.opt.OptimizedAccessorFactory.get(OptimizedAccessorFactory.java:156)
    at com.sun.xml.internal.bind.v2.runtime.reflect.Accessor$FieldReflection.optimize(Accessor.java:245)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.<init>(SingleElementNodeProperty.java:79)
    at sun.reflect.GeneratedConstructorAccessor21.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:113)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:145)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:479)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:305)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1100)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:143)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:110)
    at sun.reflect.GeneratedMethodAccessor47.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:202)
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:376)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:574)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:522)

回答1:

(Moving my comment to an answer)

Are you creating a JAXBContext every time? JAXBContext is thread safe and should be created once and reused. An Unmarshaller is not thread safe an a new one should be created per thread.

Now I am maintaining a map (ConcurrentHashMap contexts ) wrapped by thread safe code to store all JAXBContexts(one per type) as of now it is working nicely. Any other better suggestion ??

It depends on your application. You can also create one JAXBContext on many classes:

JAXBContext jc = JAXBContext.newInstance(A.class, B.class, C.class, D.class);

or

JAXBContext jc = JAXBContext.newInstance("com.foo:org.bar");

回答2:

a good solution to performance troublesooting reliable to JAXB Context when developping multithreaded web apps can be creation of singleton which provide JAXBContext like this :

class JAXBContextServletHelper  extends HttpServlet {
    static final JAXBContext context = initContext();
    private static JAXBContext initContext() {
        return JAXBContext.newInstance(MyClasse1.class,MyClasse2.class);
    }
}

and call it using ;

JAXBContext context =   JAXBContextServletHelper. initContext();
Unmarshaller u = context.createUnmarshaller();
        u.unmarshal(...);

for more details on this question please visit the jaxb tutorial on java.net here

来源：https://stackoverflow.com/questions/7203893/threads-getting-blocked-jaxb