java - java.lang.String 中的 NullPointerException

Question

堆栈跟踪:

[#|2013-02-19T16:05:25.596-0500|WARNING|glassfish3.1.2|org.eclipse.persistence.session.file:/opt/glassfish3/glassfish/domains/domain1/applications/PulseEngine/PulseEngine-ejb_jar/_PulsePU|    _ThreadID=103;_Th
readName=Thread-2;|java.lang.NullPointerException
at java.lang.String.checkBounds(String.java:374)
at java.lang.String.<init>(String.java:415)
at com.mysql.jdbc.SingleByteCharsetConverter.<init>(SingleByteCharsetConverter.java:153)
at com.mysql.jdbc.SingleByteCharsetConverter.initCharset(SingleByteCharsetConverter.java:108)
at com.mysql.jdbc.SingleByteCharsetConverter.getInstance(SingleByteCharsetConverter.java:86)
at com.mysql.jdbc.Connection.getCharsetConverter(Connection.java:3505)
at com.mysql.jdbc.ResultSet.getStringInternal(ResultSet.java:5667)
at com.mysql.jdbc.ResultSet.getString(ResultSet.java:5544)
at com.mysql.jdbc.ResultSet.getFloat(ResultSet.java:2523)
at com.sun.gjc.spi.base.ResultSetWrapper.getFloat(ResultSetWrapper.java:239)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.getObjectThroughOptimizedDataConversion(DatabaseAccessor.java:1267)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.getObject(DatabaseAccessor.java:1170)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.fetchRow(DatabaseAccessor.java:999)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.processResultSet(DatabaseAccessor.java:723)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:621)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:535)
at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:1717)
at org.eclipse.persistence.sessions.server.ClientSession.executeCall(ClientSession.java:253)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:207)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:193)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeSelectCall(DatasourceCallQueryMechanism.java:264)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.selectAllRows(DatasourceCallQueryMechanism.java:646)
at org.eclipse.persistence.internal.queries.ExpressionQueryMechanism.selectAllRowsFromTable(ExpressionQueryMechanism.java:2611)
at org.eclipse.persistence.internal.queries.ExpressionQueryMechanism.selectAllRows(ExpressionQueryMechanism.java:2570)
at org.eclipse.persistence.queries.ReadAllQuery.executeObjectLevelReadQuery(ReadAllQuery.java:420)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery(ObjectLevelReadQuery.java:1081)
at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:844)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:1040)
at org.eclipse.persistence.queries.ReadAllQuery.execute(ReadAllQuery.java:392)
at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork(ObjectLevelReadQuery.java:1128)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2871)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1516)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1498)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1463)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.executeReadQuery(EJBQueryImpl.java:485)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getSingleResult(EJBQueryImpl.java:773)
at enkia.pulse.indexing.SentimentAnalysisIndexer.insertSentiment(SentimentAnalysisIndexer.java:376)
at enkia.pulse.indexing.SentimentAnalysisIndexer.insertSentiments(SentimentAnalysisIndexer.java:355)
at enkia.pulse.indexing.SentimentAnalysisIndexer.clusterCategorySentiments(SentimentAnalysisIndexer.java:530)
at enkia.pulse.indexing.beans.SAIBean.ejbTimeout(SAIBean.java:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052)
at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124)
at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5388)
at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundTimeout(SystemInterceptorProxy.java:149)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:370)
at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5360)
at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5348)
at com.sun.ejb.containers.BaseContainer.callEJBTimeout(BaseContainer.java:4058)
at com.sun.ejb.containers.EJBTimerService.deliverTimeout(EJBTimerService.java:1832)
at com.sun.ejb.containers.EJBTimerService.access$100(EJBTimerService.java:108)
at com.sun.ejb.containers.EJBTimerService$TaskExpiredWork.run(EJBTimerService.java:2646)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)

我完全迷失了。我尝试在 OpenJDK 和 Oracle JDK 之间来回切换。我使用的是 Ubuntu 12.10。该项目使用 mysql-connector-java-5.1.13 作为 jdbc 驱动程序。

感谢任何线索。

Answer 1

如果你查看 String 的源代码:

private static void checkBounds(byte[] bytes, int offset, int length) {
    if (length < 0)
        throw new StringIndexOutOfBoundsException(length);
    if (offset < 0)
        throw new StringIndexOutOfBoundsException(offset);
    if (offset > bytes.length - length)
        throw new StringIndexOutOfBoundsException(offset + length);
}

这似乎表明您可能正在传递一个为空的字节数组。第三个 if 语句是抛出 NPE 的地方。

也许您的结果集有一个空值 (byte[])，您正尝试将其转换为字符串。