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[英]Gson.toJson()"Exception java.lang.IllegalArgumentException: class java.text.DecimalFormat declares multiple JSON fields named maximumIntegerDigits"
[英]java.lang.IllegalArgumentException: class java.text.DecimalFormat declares multiple JSON fields named maximumIntegerDigits
我正在對servlet進行ajax調用。 我希望數據從servlet返回到jsp:
PrintWriter out = response.getWriter();
String isbn = (String) request.getParameter("isbn");
BookDetail bd = new BookDetail();
if(bd.ISBNFound(isbn)){
ArrayList<KitapData> Books = bd.LoadBooksByISBN(isbn);
Gson gson = new Gson();
String json = gson.toJson(Books);
response.setContentType("application/json");
System.out.print(json);
out.print(json);
}
我在類路徑中添加了GSon.jar。 但我得到一些錯誤:完整列表如下:我在這里缺少什么?
WARNING: StandardWrapperValve[Book_CheckISBN]: Servlet.service() for servlet Book_CheckISBN threw exception
java.lang.IllegalArgumentException: class java.text.DecimalFormat declares multiple JSON fields named maximumIntegerDigits
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:122)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:72)
at com.google.gson.Gson.getAdapter(Gson.java:356)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.<init>(ReflectiveTypeAdapterFactory.java:82)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.createBoundField(ReflectiveTypeAdapterFactory.java:81)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:118)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:72)
at com.google.gson.Gson.getAdapter(Gson.java:356)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:55)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:96)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:60)
at com.google.gson.Gson.toJson(Gson.java:593)
at com.google.gson.Gson.toJson(Gson.java:572)
at com.google.gson.Gson.toJson(Gson.java:527)
at com.google.gson.Gson.toJson(Gson.java:507)
at book.ctrl.Book_CheckISBN.doPost(Book_CheckISBN.java:41)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:722)
我的情況是DO中的SimpleDateFormat
字段導致錯誤,
在添加transient
之后,問題就解決了
您實際上不太可能想要將DecimalFormat
類型的字段序列化為JSON。 如果您可以修改KitapData
類,您可以考慮刪除該字段,或將其設置為transient
,這將告訴Gson(和其他序列化程序)忽略該字段。
private transient DecimalFormat whateverTheFieldIsCalled;
如果您無法修改KitapData
類,還有其他方法可以告訴Gson從序列化中排除該字段 - 例如,請參閱Gson:如何從序列化中排除特定字段而不注釋
您的類KitapData
具有DecimalFormat
屬性。 Gson正在貶低它,因為它不是標准的Java類型,它具有內置支持,如String
, Number
, Boolean
, Date
, List
等。
您需要刪除該DecimalFormat
屬性。 不僅因為Gson無法在沒有注冊類型適配器的情況下自動消化它,而且因為它不可能代表“bean屬性”而且它本質上是緊耦合的。 而且, NumberFormat
就像DateFormat
所有的朋友都不是線程安全的 。 將它作為bean屬性表明它可以在多個線程之間共享。 這可能會導致格式化或甚至異常。
也許您只想存儲格式模式或其他相關屬性。 在這種情況下,將它們存儲為String
, Integer
等,並確保代碼始終在方法本地范圍內基於這些“松散”屬性創建全新的DecimalFormat
實例。
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