使用JPA的Google App Engine [英] Google App Engine using JPA

问题描述

我正在使用Google App Engine使用JPA（java持久性API）创建应用程序。但是，当我试图获取存储的记录时，我得到空指针异常。

请帮帮我。





java.lang.NullPointerException

com.google.appengine.datanucleus.query.QueryEntityPKFetchFieldManager.fetchIntField（QueryEntityPKFetchFieldManager.java:70）

at org。 adanucleus.identity.IdentityUtils.getApplicationIdentityForResultSetRow（IdentityUtils.java:93）

com.google.appengine.datanucleus.EntityUtils.entityToPojo（EntityUtils.java:1009）

at com.google.appengine.datanucleus.query.DatastoreQuery $ 2.apply（DatastoreQuery.java:228）

com.google.appengine.datanucleus.query.DatastoreQuery $ 2.apply（DatastoreQuery.java:225 ）com /google.appengine中的
。com.google.appengine.datanucleus.query.LazyResult上的
com.google.appengine.datanucleus.query.LazyResult.resolveNext（LazyResult.java:96）

.resolveAll（LazyResult.java:121）

com.google.appengine.datanucleus.query.LazyResult .size（LazyResult.java:115）

com.google.appengine.datanucleus.query.StreamingQueryResult.size（StreamingQueryResult.java:151）

at org.apache .jsp.AdminEvent_jsp._jspService（AdminEvent_jsp.java:68）

at org.apache.jasper.runtime.HttpJspBase.service（HttpJspBase.java:97）

at javax .servlet.http.HttpServlet.service（HttpServlet.java:717）

org.mortbay.jetty.servlet.ServletHolder.handle（ServletHolder.java:511）

在org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1166）

com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter（ParseBlobUploadFilter.java:125）

at org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1157）

com.google.apphosting.runtime.jetty.SaveSessionFilter。 doFilter（SaveSessionFilter.java:35）

at org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1157)

com.google.apphosting.utils.servlet.JdbcMySqlConnectionCleanupFilter.doFilter（JdbcMySqlConnectionCleanupFilter.java:57）

at org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1157 ）

com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter（TransactionCleanupFilter.java:43）

at org.mortbay.jetty.servlet.ServletHandler $ CachedChain .doFilter（ServletHandler.java:1157）

org.mortbay.jetty.servlet.ServletHandler.handle（ServletHandler.java:388）

at org.mortbay.jetty .security.SecurityHandler.handle（SecurityHandler.java:216）

org.mortbay.jetty.servlet.SessionHandler.handle（SessionHandler.java:182）

at org .mortbay.jetty.handler.ContextHandler.handle（ContextHandler.java:765）

org.mortbay.jetty.webapp.WebAppContext.handle（WebAppContext.java:418）

at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle（AppVersionHandlerMap.java:266）

org.mortbay.jetty.handler.HandlerWrapper.handle（HandlerWrapper.java:152）

at org.mortbay.jetty.Server.handle（Server.java： 326）

org.mortbay.jetty.HttpConnection.handleRequest（HttpConnection.java:542）

at org.mortbay.jetty.HttpConnection $ RequestHandler.headerComplete（HttpConnection。 java：923）

com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable（RpcRequestParser.java:76）

org.mortbay.jetty.HttpConnection。处理（HttpConnection.java:404）

com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest（JettyServletEngineAdapter.java:146）
com.google上的
。 apphosting.runtime.JavaRuntime $ RequestRunnable.run（JavaRuntime.java:438）

com.google.tracing.TraceContext $ TraceContextRunnable.runInContext（TraceContext.java:480)

com.google.tracing.TraceContext $ TraceContextRunnable $ 1.run（TraceContext.java:487）

com.google.tracing.TraceC ontext.runInContext（TraceContext.java:774）

com.google.tracing.TraceContext $ DoInTraceContext.runInContext（TraceContext.java:751）

com.google。 tracing.TraceContext $ AbstractTraceContextCallback.runInInheritedContextNoUnref（TraceContext.java:342）

com.google.tracing.TraceContext $ AbstractTraceContextCallback.runInInheritedContext（TraceContext.java:334）

at com.google.tracing.TraceContext $ TraceContextRunnable.run（TraceContext.java:484）

com.google.apphosting.runtime.ThreadGroupPool $ PoolEntry.run（ThreadGroupPool.java:251)< br / >
在java.lang.Thread.run（Thread.java:679）

I am creating an application using JPA(java persistence API) using Google App Engine. But when i am trying to fetch record which are stored i am getting null pointer exception.
Please help me out.


java.lang.NullPointerException
at com.google.appengine.datanucleus.query.QueryEntityPKFetchFieldManager.fetchIntField(QueryEntityPKFetchFieldManager.java:70)
at org.datanucleus.identity.IdentityUtils.getApplicationIdentityForResultSetRow(IdentityUtils.java:93)
at com.google.appengine.datanucleus.EntityUtils.entityToPojo(EntityUtils.java:1009)
at com.google.appengine.datanucleus.query.DatastoreQuery$2.apply(DatastoreQuery.java:228)
at com.google.appengine.datanucleus.query.DatastoreQuery$2.apply(DatastoreQuery.java:225)
at com.google.appengine.datanucleus.query.LazyResult.resolveNext(LazyResult.java:96)
at com.google.appengine.datanucleus.query.LazyResult.resolveAll(LazyResult.java:121)
at com.google.appengine.datanucleus.query.LazyResult.size(LazyResult.java:115)
at com.google.appengine.datanucleus.query.StreamingQueryResult.size(StreamingQueryResult.java:151)
at org.apache.jsp.AdminEvent_jsp._jspService(AdminEvent_jsp.java:68)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:125)
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.JdbcMySqlConnectionCleanupFilter.doFilter(JdbcMySqlConnectionCleanupFilter.java:57)
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:266)
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$RequestHandler.headerComplete(HttpConnection.java:923)
at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:146)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:438)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:480)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:487)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:774)
at com.google.tracing.TraceContext$DoInTraceContext.runInContext(TraceContext.java:751)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:342)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:334)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:484)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:679)

推荐答案

2.apply（DatastoreQuery.java:228）
com.google.appengine.datanucleus.query.DatastoreQuery

2.apply(DatastoreQuery.java:228)
at com.google.appengine.datanucleus.query.DatastoreQuery

2.apply（DatastoreQuery.java:225）

com.google .appengine.datanucleus.query.LazyResult.resolveNext（LazyResult.java:96）
com.google.appengine.datanucleus上的
.query.LazyResult.resolveAll（LazyResult.java:121）

com.google.appengine.datanucleus.query.LazyResult.size（LazyResult.java:115)

在com.google.appengine.datanucleus.query.StreamingQueryResult.size（StreamingQueryResult.java:151）

at org.apache.jsp.AdminEvent_jsp._jspService（AdminEvent_jsp.java:68）

at org.apache.jasper.runtime.HttpJspBase.service(httpJspBase.java:97）

at javax.servlet.http.HttpServlet.service（HttpServlet.java:717)br />
at org.mortbay.jetty.servlet.ServletHolder.handle（ServletHolder.java:511）

at org.mortbay.jetty.servlet.ServletHandler

2.apply(DatastoreQuery.java:225)
at com.google.appengine.datanucleus.query.LazyResult.resolveNext(LazyResult.java:96)
at com.google.appengine.datanucleus.query.LazyResult.resolveAll(LazyResult.java:121)
at com.google.appengine.datanucleus.query.LazyResult.size(LazyResult.java:115)
at com.google.appengine.datanucleus.query.StreamingQueryResult.size(StreamingQueryResult.java:151)
at org.apache.jsp.AdminEvent_jsp._jspService(AdminEvent_jsp.java:68)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler

CachedChain.doFilter（ServletHandler.java:1166）

com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter（ParseBlobUploadFilter.java:125）

org.mortbay.jetty.servlet.ServletHandler

CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler

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