java - Google App Engine 上的 GSON 抛出安全异常

Question

我正在尝试使用 Google App Engine 上的 GSON 库将对象转换为 JSON。出于某种原因，它抛出了这个异常，我不知道如何解决这个问题。有什么建议吗？

java.lang.SecurityException: java.lang.IllegalAccessException: Reflection is not allowed on private static final int java.util.BitSet.ADDRESS_BITS_PER_WORD
    at com.google.appengine.runtime.Request.process-8d5b435d6736643f(Request.java)
    at java.lang.reflect.AccessibleObject.setAccessible(AccessibleObject.java:29)
    at com.google.gson.ObjectNavigator.navigateClassFields(ObjectNavigator.java:141)
    at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:123)
    at com.google.gson.JsonSerializationVisitor.getJsonElementForChild(JsonSerializationVisitor.java:148)
    at com.google.gson.JsonSerializationVisitor.addAsArrayElement(JsonSerializationVisitor.java:139)
    at com.google.gson.JsonSerializationVisitor.visitArray(JsonSerializationVisitor.java:83)
    at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:109)
    at com.google.gson.JsonSerializationVisitor.getJsonElementForChild(JsonSerializationVisitor.java:148)
    at com.google.gson.JsonSerializationVisitor.addAsChildOfObject(JsonSerializationVisitor.java:126)
    at com.google.gson.JsonSerializationVisitor.visitArrayField(JsonSerializationVisitor.java:95)
    at com.google.gson.ObjectNavigator.navigateClassFields(ObjectNavigator.java:154)
    at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:123)
    at com.google.gson.JsonSerializationContextDefault.serialize(JsonSerializationContextDefault.java:56)
    at com.google.gson.Gson.toJsonTree(Gson.java:230)
    at com.google.gson.Gson.toJson(Gson.java:315)
    at com.google.gson.Gson.toJson(Gson.java:270)
    at com.google.gson.Gson.toJson(Gson.java:250)
    at companionmodel.Sample_Model_PopulateServlet.printOutput(Sample_Model_PopulateServlet.java:59)
    at companionmodel.Sample_Model_PopulateServlet.doGet(Sample_Model_PopulateServlet.java:28)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:693)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:97)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:238)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:250)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5838)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:5836)
    at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:398)
    at com.google.net.rpc.impl.Server$2.run(Server.java:852)
    at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56)
    at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:576)
    at com.google.net.rpc.impl.Server.startRpc(Server.java:807)
    at com.google.net.rpc.impl.Server.processRequest(Server.java:369)
    at com.google.net.rpc.impl.ServerConnection.messageReceived(ServerConnection.java:442)
    at com.google.net.rpc.impl.RpcConnection.parseMessages(RpcConnection.java:319)
    at com.google.net.rpc.impl.RpcConnection.dataReceived(RpcConnection.java:290)
    at com.google.net.async.Connection.handleReadEvent(Connection.java:474)
    at com.google.net.async.EventDispatcher.processNetworkEvents(EventDispatcher.java:831)
    at com.google.net.async.EventDispatcher.internalLoop(EventDispatcher.java:207)
    at com.google.net.async.EventDispatcher.loop(EventDispatcher.java:103)
    at com.google.net.rpc.RpcService.runUntilServerShutdown(RpcService.java:251)
    at com.google.apphosting.runtime.JavaRuntime$RpcRunnable.run(JavaRuntime.java:413)
    at java.lang.Thread.run(Unknown Source)

我正在使用的代码:

Gson gson = new Gson();
String json = gson.toJson(modelObject);

Answer 1

应用引擎确实支持反射 - 但是您正试图反射 JRE 类的私有(private)字段:

Reflection

An application is allowed full, unrestricted, reflective access to its own classes. It may query any private members, use java.lang.reflect.AccessibleObject.setAccessible(), and read/set private members.

An application can also also reflect on JRE and API classes, such as java.lang.String and javax.servlet.http.HttpServletRequest. However, it can only access public members of these classes, not protected or private.

An application cannot reflect against any other classes not belonging to itself, and it can not use the setAccessible() method to circumvent these restrictions.

...来自http://code.google.com/appengine/docs/java/runtime.html#The_Sandbox :

我会考虑为 Bitset 编写自定义序列化程序。

参见:http://sites.google.com/site/gson/gson-user-guide#TOC-Custom-Serialization-and-Deserializ

还有:http://groups.google.com/group/google-gson/browse_thread/thread/535892ffcf691aa/897f27e37e03ce58?lnk=gst&q=bitset#897f27e37e03ce58

http://groups.google.com/group/google-gson/browse_thread/thread/535892ffcf691aa