如何从osgi中的字节反序列化对象

Question

在我的osgi应用程序中,我有三个包travel.api,table.api和utils.travel.api取决于table.api哪个取决于utils.注意,travel.api不直接依赖utils.我使用aQute Bnd来生成清单,我相信它工作正常.清单如下所示.

有一个叫做类PageData的字段TableData,它有一个类型的字段,而这个字段又有一个类型的字段TestObject.PageData坐落于travel.api,TableData位于table.api以及TestObject位于utils.加载包时,这一切都正常.当我收到表示PageData对象的字节数组时,问题出现了.我必须在travel.api捆绑中反序列化它.这应该不是问题,因为它是定义的地方.我使用org.jboss.netty.handler.codec.serialization.ObjectDecoderInputStream并从travel.apibundle中传入类加载器.抛出以下异常,但基本上它说:

Caused by: java.lang.ClassNotFoundException: com.openaf.utils.TestObject not 
    found by travel.api [9].

现在,这是有道理的,因为如果你看Import-Package的travel.api,你会看到com.openaf.utils(其中TestObject位于)未列出.如果我添加此包,则正确反序列化.但是,这似乎不是一个好的通用解决方案,因为我必须遍历每个PageData使用的字段并确保它们都在此模块中导入,并递归地在这些字段包含的每个字段等.

我在这里做错了吗？

使用OSGi时反对对象反序列化的最佳方法是什么？

如果我正确地做了并且我必须指定所有"深度"导入,有没有办法让Bnd进行"深度"生成？

任何帮助将不胜感激!

我正在使用felix v4作为我的osgi库.

Manifest-Version: 1
Bnd-LastModified: 1355404320862
Bundle-ManifestVersion: 2
Bundle-Name: travel.api
Bundle-SymbolicName: travel.api
Bundle-Version: 0
Created-By: 1.7.0_07 (Oracle Corporation)
Export-Package: com.openaf.travel.api;uses:="scala.runtime,scala,scala.c
 ollection,com.openaf.pagemanager.api,scala.reflect,com.openaf.table.api
 ";version="0.0.0"
Import-Package: com.openaf.pagemanager.api,com.openaf.table.api,scala,sc
 ala.collection,scala.reflect,scala.runtime
Tool: Bnd-1.44.0

Manifest-Version: 1
Bnd-LastModified: 1355404158858
Bundle-ManifestVersion: 2
Bundle-Name: table.api
Bundle-SymbolicName: table.api
Bundle-Version: 0
Created-By: 1.7.0_07 (Oracle Corporation)
Export-Package: com.openaf.table.api;uses:="scala.runtime,scala,scala.co
 llection,scala.reflect,scala.collection.immutable,scala.collection.gene
 ric,com.openaf.utils";version="0.0.0"
Import-Package: com.openaf.utils,scala,scala.collection,scala.collection
 .generic,scala.collection.immutable,scala.reflect,scala.runtime
Tool: Bnd-1.44.0

Manifest-Version: 1
Bnd-LastModified: 1355404158801
Bundle-ManifestVersion: 2
Bundle-Name: utils
Bundle-SymbolicName: utils
Bundle-Version: 0
Created-By: 1.7.0_07 (Oracle Corporation)
Export-Package: com.openaf.utils;uses:="scala.runtime,scala,scala.collec
 tion,scala.reflect";version="0.0.0"
Import-Package: scala,scala.collection,scala.reflect,scala.runtime
Tool: Bnd-1.44.0

java.io.InvalidClassException: failed to read class descriptor
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1585)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1514)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1750)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1347)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1964)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1888)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1771)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1347)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1964)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1888)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1771)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1347)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369)
at org.jboss.netty.handler.codec.serialization.ObjectDecoderInputStream.readObject(ObjectDecoderInputStream.java:115)
at com.openaf.rmi.common.DefaultObjectEncoder$.decode(RMICommon.scala:33)
at com.openaf.rmi.client.ClientHandler.messageReceived(ClientPipelineFactory.scala:43)
at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:296)
at org.jboss.netty.handler.codec.frame.FrameDecoder.unfoldAndFireMessageReceived(FrameDecoder.java:363)
at org.jboss.netty.handler.codec.frame.FrameDecoder.callDecode(FrameDecoder.java:345)
at org.jboss.netty.handler.codec.frame.FrameDecoder.messageReceived(FrameDecoder.java:211)
at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:268)
at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:255)
at org.jboss.netty.channel.socket.nio.NioWorker.read(NioWorker.java:94)
at org.jboss.netty.channel.socket.nio.AbstractNioWorker.processSelectedKeys(AbstractNioWorker.java:372)
at org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:246)
at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:38)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.ClassNotFoundException: com.openaf.utils.TestObject not found by travel.api [9]
at org.apache.felix.framework.BundleWiringImpl.findClassOrResourceByDelegation(BundleWiringImpl.java:1460)
at org.apache.felix.framework.BundleWiringImpl.access$400(BundleWiringImpl.java:72)
at org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.loadClass(BundleWiringImpl.java:1843)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at org.jboss.netty.handler.codec.serialization.ClassLoaderClassResolver.resolve(ClassLoaderClassResolver.java:30)
at org.jboss.netty.handler.codec.serialization.CachingClassResolver.resolve(CachingClassResolver.java:39)
at org.jboss.netty.handler.codec.serialization.CompactObjectInputStream.readClassDescriptor(CompactObjectInputStream.java:55)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
... 28 more

谢谢,尼克.

Answer 1

这实际上听起来像反序列化的严重缺点？一个不错的反序列化器应该使用导致负载的类的类加载器.给定的类加载器应该只用于顶级对象,因为还没有父对象.

因此,在这种情况下,给定的类加载器用于加载PageData.PageData的加载器用于加载TableData,而TableData的加载器必须用于加载TestObject.除非您使用的解串器确实是脑损坏,否则没有合理的理由,因为这是VM用于加载类的模型.我很惊讶Java解串器这样做,我认为这种行为是一个严重的错误,因为它使用的规则不同于VM.

序列化是OSGi中的一个问题,因为模块化是关于隐藏实现类; 反序列化倾向于想要访问这些私有类,这是模块化的对立面.但是,有很好的解决方案(不包括Dynamic-ImportPackage,它以比使用普通Java更复杂和更昂贵的方式恢复到JAR地狱).基本技巧是从公共API获得一个root对象,该对象可以访问私有/瞬时需要的类.嗯,这听起来不像是服务吗？

解

看看负面人士是如何做到这一点的,一个小例子如何解决Java Serialization(即ObjectInputStream和ObjectOutputStream)的问题.在你的问题中,你提到了ObjectDecoderInputStream,这是一个我不熟悉的类.

设置是:

Bundle A:    class a.A { B b; }   (import b)
Bundle B:    class b.B { C c; }   (import c)
Bundle C:    class c.C { }

所以让我们首先序列化一个对象:

ByteArrayOutputStream bous = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bous);

oos.writeObject(this);
oos.close();

现在困难的部分.我们覆盖resolveObject方法,这使我们有机会实际进行适当的类加载...

ObjectInputStream in = new ObjectInputStream(new ByteArrayInputStream(bous.toByteArray())) {
    Set<ClassLoader>    lhs = new LinkedHashSet<ClassLoader>();
    {
        // Keep a set if discovered class loaders
        lhs.add(getClass().getClassLoader());
    }

    @Override
    protected Class< ? > resolveClass(ObjectStreamClass desc) 
         throws ClassNotFoundException, IOException {

         for (ClassLoader cl : lhs) try {
             Class< ? > c = cl.loadClass(name);

             // we found the class, so we can use its class loader,
             // it is in the proper class space  if the uses constraints 
             // are set properly (and you're using bnd so you should be ok)

             lhs.add(c.getClassLoader());

             // The paranoid among us would check
             // the serial uuid here ...
             // long uuid = desc.getSerialVersionUID();
             // Field field = c.getField("serialVersionUID");
             // assert uuid == field.get(null)

             return c;
         } catch (Exception e) {
           // Ignore
         }

         // Fallback (for void and primitives)
         return super.resolveClass(desc);
     }
 };

 // And now we've successfully read the object ...

 A clone = (A) in.readObject();

请注意,只有正确导出瞬态图表,这才有效.即如果你能做到new TableData这一点,这也应该有效.一个不起作用的例子是你从一个接口获得一个实现.接口类未连接到impl.类.即如果你有一个扩展TableData的TableDataImpl,你就会被搞砸.在这些情况下,您需要一些服务来查找实现的"域".

祝好运.