java - 德比 Apache 随机 NullPointerException

Question

我们在使用嵌入式 Apache Derby 时遇到问题。无明显原因发生空指针异常。该代码使用 EmbeddedSimpleDataSource 类来访问 DB 和 Statement 来执行查询。

该应用程序在带有嵌入式 Derby 版本的 java Foundation profile/CDC 1.1（使用 cvm 而不是 jvm）上运行

奇怪的是这个问题是完全随机的（至少对我们来说，我们无法重现它）。正如您从下面的日志中看到的那样，异常发生在一个非常简单的选择查询上。

有时我们会出现 3 次或多次异常，然后一切恢复正常。（很少对数据库的所有后续调用都失败，重新获得访问权限的唯一方法是重新启动应用程序（有时我们甚至必须删除数据库文件夹并重新创建它））

这是 derby 日志文件的摘录：

   Tue Oct 01 22:51:51 CEST 2013:
Booting Derby version The Apache Software Foundation - Apache Derby - 10.10.1.1 - (1458268): instance c013800d-0141-75ca-8140-000000068414 
on database directory /mnt/nand/lu/smarthubdb with class loader sun.misc.Launcher$AppClassLoader[ucp=sun.misc.URLClassPath[path=file:/mnt/nand/lu/SmartHub.jar],parent=sun.misc.Launcher$ExtClassLoader[ucp=sun.misc.URLClassPath[path=file:/usr/lib/ext/API_3.05.jar,file:/usr/lib/ext/sunjce_provider.jar],parent=null]] 
Loaded from file:/mnt/nand/lu/lib/derby.jar
java.vendor=Sun Microsystems Inc.
user.dir=/mnt/nand/lu
os.name=Linux
os.arch=sh3
os.version=2.6.25.9-svn298-dirty2
derby.system.home=null
Database Class Loader started - derby.database.classpath=''
Wed Oct 02 05:53:23 CEST 2013 Thread[main,5,main] (XID = 33536), (SESSIONID = 3), (DATABASE = smarthubdb), (DRDAID = null), Cleanup action starting
Wed Oct 02 05:53:23 CEST 2013 Thread[main,5,main] (XID = 33536), (SESSIONID = 3), (DATABASE = smarthubdb), (DRDAID = null), Failed Statement is: SELECT device.serial_number, tariff,reference_power_active, overload_power_limit_active, breaker_state,logical_device_type.name FROM device, logical_device_type WHERE device.id_logical_device_type = logical_device_type.id AND serial_number='041068350153'
java.lang.NullPointerException
    at org.apache.derby.exe.ac601a400fx0141x75cax8140x00000006841480.createResultSet(Compiled Method)(Unknown Source)
    at org.apache.derby.impl.sql.execute.CursorActivation.decorateResultSet(Unknown Source)
    at org.apache.derby.impl.sql.execute.BaseActivation.execute(Unknown Source)
    at org.apache.derby.impl.sql.GenericActivationHolder.execute(Unknown Source)
    at org.apache.derby.impl.sql.GenericPreparedStatement.executeStmt(Compiled Method)(Unknown Source)
    at org.apache.derby.impl.sql.GenericPreparedStatement.execute(Compiled Method)(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedStatement.execute(Compiled Method)(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedStatement.executeQuery(Unknown Source)
    at com.s.g.a.c(Unknown Source)
    at com.s.g.a.a(Unknown Source)
    at com.s.g.b.a(Unknown Source)
    at com.s.statemachine.b.e.b(Unknown Source)
    at com.s.statemachine.b.i.c(Compiled Method)(Unknown Source)
    at com.s.statemachine.SmartHub.A(Compiled Method)(Unknown Source)
    at com.s.statemachine.SmartHub.a(Unknown Source)
    at com.s.statemachine.SmartHub.main(Unknown Source)
    at sun.misc.CVM.runMain(Unknown Source)
Cleanup action completed
Wed Oct 02 06:15:26 CEST 2013 Thread[main,5,main] (XID = 34359), (SESSIONID = 7), (DATABASE = smarthubdb), (DRDAID = null), Cleanup action starting
Wed Oct 02 06:15:26 CEST 2013 Thread[main,5,main] (XID = 34359), (SESSIONID = 7), (DATABASE = smarthubdb), (DRDAID = null), Failed Statement is: SELECT device.serial_number, tariff,reference_power_active, overload_power_limit_active, breaker_state,logical_device_type.name FROM device, logical_device_type WHERE device.id_logical_device_type = logical_device_type.id AND serial_number='041067350131'
java.lang.NullPointerException
    at org.apache.derby.exe.ac601a400fx0141x75cax8140x00000006841485.createResultSet(Compiled Method)(Unknown Source)
    at org.apache.derby.impl.sql.execute.CursorActivation.decorateResultSet(Unknown Source)
    at org.apache.derby.impl.sql.execute.BaseActivation.execute(Unknown Source)
    at org.apache.derby.impl.sql.GenericActivationHolder.execute(Unknown Source)
    at org.apache.derby.impl.sql.GenericPreparedStatement.executeStmt(Compiled Method)(Unknown Source)
    at org.apache.derby.impl.sql.GenericPreparedStatement.execute(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedStatement.execute(Compiled Method)(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedStatement.executeQuery(Unknown Source)
    at com.s.g.a.c(Unknown Source)
    at com.s.g.a.a(Unknown Source)
    at com.s.g.b.a(Unknown Source)
    at com.s.statemachine.b.e.b(Unknown Source)
    at com.s.statemachine.b.i.c(Compiled Method)(Unknown Source)
    at com.s.statemachine.SmartHub.A(Compiled Method)(Unknown Source)
    at com.s.statemachine.SmartHub.a(Unknown Source)
    at com.s.statemachine.SmartHub.main(Unknown Source)
    at sun.misc.CVM.runMain(Unknown Source)
Cleanup action completed

这是表的结构：

private final static String               MCS_TABLE      = "metering_campaign_strategy";
private final static String[]             MCS_COLS       = { "serial_number",
            "measure_kind", "frequencyUnit", "frequency", "begin_date", "end_date", "last_retrieve_date" };
private final static String[]             MCS_COLS_TYPES = { "varchar(40) NOT NULL",
            "varchar(15) NOT NULL", "varchar(10) NOT NULL", "integer", "timestamp NOT NULL", "timestamp", "timestamp" }

;

如您所见，出现问题的表是以编程方式创建的。

我添加了 DumpClassFile 选项，一旦我得到结果就会更新这篇文章

根据要求，这是数据库的架构；

Wed Oct 02 18:53:14 CEST 2013 Thread[main,5,main] (XID = 165), (SESSIONID = 0), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:14 CEST 2013 Thread[main,5,main] (XID = 165), (SESSIONID = 0), (DATABASE = smarthubdb), (DRDAID = null), Rolling back
Wed Oct 02 18:53:14 CEST 2013 Thread[main,5,main] (XID = 166), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:15 CEST 2013 Thread[main,5,main] (XID = 167), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE device (serial_number varchar(40), id_logical_device_type integer, tariff varchar(16), reference_power_active integer, overload_power_limit_active integer, breaker_state integer) :End prepared statement
Wed Oct 02 18:53:21 CEST 2013 Thread[main,5,main] (XID = 167), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE device (serial_number varchar(40), id_logical_device_type integer, tariff varchar(16), reference_power_active integer, overload_power_limit_active integer, breaker_state integer) :End prepared statement
Wed Oct 02 18:53:22 CEST 2013 Thread[main,5,main] (XID = 167), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE device (serial_number varchar(40), id_logical_device_type integer, tariff varchar(16), reference_power_active integer, overload_power_limit_active integer, breaker_state integer) :End prepared statement
Wed Oct 02 18:53:23 CEST 2013 Thread[main,5,main] (XID = 167), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:24 CEST 2013 Thread[main,5,main] (XID = 171), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE measure (id_device varchar(40) NOT NULL, date timestamp NOT NULL, value decimal(12,2), type integer, sent boolean) :End prepared statement
Wed Oct 02 18:53:24 CEST 2013 Thread[main,5,main] (XID = 171), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE measure (id_device varchar(40) NOT NULL, date timestamp NOT NULL, value decimal(12,2), type integer, sent boolean) :End prepared statement
Wed Oct 02 18:53:24 CEST 2013 Thread[main,5,main] (XID = 171), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE measure (id_device varchar(40) NOT NULL, date timestamp NOT NULL, value decimal(12,2), type integer, sent boolean) :End prepared statement
Wed Oct 02 18:53:26 CEST 2013 Thread[main,5,main] (XID = 171), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:27 CEST 2013 Thread[main,5,main] (XID = 184), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE message (id_device varchar(40) NOT NULL, date integer, message varchar(100)) :End prepared statement
Wed Oct 02 18:53:27 CEST 2013 Thread[main,5,main] (XID = 184), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE message (id_device varchar(40) NOT NULL, date integer, message varchar(100)) :End prepared statement
Wed Oct 02 18:53:27 CEST 2013 Thread[main,5,main] (XID = 184), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE message (id_device varchar(40) NOT NULL, date integer, message varchar(100)) :End prepared statement
Wed Oct 02 18:53:27 CEST 2013 Thread[main,5,main] (XID = 184), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:28 CEST 2013 Thread[main,5,main] (XID = 187), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE logical_device_type (id integer, name varchar(100)) :End prepared statement
Wed Oct 02 18:53:28 CEST 2013 Thread[main,5,main] (XID = 187), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE logical_device_type (id integer, name varchar(100)) :End prepared statement
Wed Oct 02 18:53:28 CEST 2013 Thread[main,5,main] (XID = 187), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE logical_device_type (id integer, name varchar(100)) :End prepared statement
Wed Oct 02 18:53:28 CEST 2013 Thread[main,5,main] (XID = 187), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:29 CEST 2013 Thread[main,5,main] (XID = 193), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE load_curve (id_device varchar(40) NOT NULL, date timestamp NOT NULL, value integer, error integer, sent boolean) :End prepared statement
Wed Oct 02 18:53:29 CEST 2013 Thread[main,5,main] (XID = 193), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE load_curve (id_device varchar(40) NOT NULL, date timestamp NOT NULL, value integer, error integer, sent boolean) :End prepared statement
Wed Oct 02 18:53:29 CEST 2013 Thread[main,5,main] (XID = 193), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE load_curve (id_device varchar(40) NOT NULL, date timestamp NOT NULL, value integer, error integer, sent boolean) :End prepared statement
Wed Oct 02 18:53:29 CEST 2013 Thread[main,5,main] (XID = 193), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:29 CEST 2013 Thread[main,5,main] (XID = 196), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE load_curve_last_collect (id_device varchar(40) NOT NULL, date timestamp NOT NULL) :End prepared statement
Wed Oct 02 18:53:30 CEST 2013 Thread[main,5,main] (XID = 196), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE load_curve_last_collect (id_device varchar(40) NOT NULL, date timestamp NOT NULL) :End prepared statement
Wed Oct 02 18:53:30 CEST 2013 Thread[main,5,main] (XID = 196), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE load_curve_last_collect (id_device varchar(40) NOT NULL, date timestamp NOT NULL) :End prepared statement
Wed Oct 02 18:53:30 CEST 2013 Thread[main,5,main] (XID = 196), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:30 CEST 2013 Thread[main,5,main] (XID = 199), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE tariff (type integer, name varchar(100)) :End prepared statement
Wed Oct 02 18:53:30 CEST 2013 Thread[main,5,main] (XID = 199), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE tariff (type integer, name varchar(100)) :End prepared statement
Wed Oct 02 18:53:30 CEST 2013 Thread[main,5,main] (XID = 199), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE tariff (type integer, name varchar(100)) :End prepared statement
Wed Oct 02 18:53:31 CEST 2013 Thread[main,5,main] (XID = 199), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:31 CEST 2013 Thread[main,5,main] (XID = 202), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE state_configuration (state_name varchar(50), last_execution timestamp) :End prepared statement
Wed Oct 02 18:53:31 CEST 2013 Thread[main,5,main] (XID = 202), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE state_configuration (state_name varchar(50), last_execution timestamp) :End prepared statement
Wed Oct 02 18:53:31 CEST 2013 Thread[main,5,main] (XID = 202), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE state_configuration (state_name varchar(50), last_execution timestamp) :End prepared statement
Wed Oct 02 18:53:31 CEST 2013 Thread[main,5,main] (XID = 202), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing
Wed Oct 02 18:53:32 CEST 2013 Thread[main,5,main] (XID = 205), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Begin compiling prepared statement: CREATE TABLE metering_campaign_strategy (serial_number varchar(40) NOT NULL, measure_kind varchar(15) NOT NULL, frequencyUnit varchar(10) NOT NULL, frequency integer, begin_date timestamp NOT NULL, end_date timestamp, last_retrieve_date timestamp) :End prepared statement
Wed Oct 02 18:53:32 CEST 2013 Thread[main,5,main] (XID = 205), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), End compiling prepared statement: CREATE TABLE metering_campaign_strategy (serial_number varchar(40) NOT NULL, measure_kind varchar(15) NOT NULL, frequencyUnit varchar(10) NOT NULL, frequency integer, begin_date timestamp NOT NULL, end_date timestamp, last_retrieve_date timestamp) :End prepared statement
Wed Oct 02 18:53:32 CEST 2013 Thread[main,5,main] (XID = 205), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Executing prepared statement: CREATE TABLE metering_campaign_strategy (serial_number varchar(40) NOT NULL, measure_kind varchar(15) NOT NULL, frequencyUnit varchar(10) NOT NULL, frequency integer, begin_date timestamp NOT NULL, end_date timestamp, last_retrieve_date timestamp) :End prepared statement
Wed Oct 02 18:53:33 CEST 2013 Thread[main,5,main] (XID = 205), (SESSIONID = 1), (DATABASE = smarthubdb), (DRDAID = null), Committing

谢谢

score 0 · Accepted Answer

问题只是你有一些数据，由于某种原因，你在某些时间和其他时间NULL没有识别出来。NOT NULL

如果此数据来自数据库，则制作所有列NOT NULLABLE将公开NULL插入数据的位置。

如果数据来自您的模型代码，那么您可以使用Google的 JSR 305 库在您的所有方法签名中对所有内容进行注释@Nonnull，您将找到NULL传递引用的位置。

从长远来看，这两件事都会提高代码的可维护性和质量。

score 0 · Accepted Answer

这是调试的一个挑战，因为在执行查询时发生在生成的代码内部。

对于您的查询，生成的代码可能正在评估限制谓词（WHERE serial_number = '041169700007' AND measure_kind='INDEX'）

首先，这里有一些关于如何更多地了解生成代码内部的信息：http ://wiki.apache.org/db-derby/DumpClassFile

问题似乎是间歇性发生的这一事实使其更加困难，因为如果没有可重现的案例，您将难以追踪和解决错误。

您的应用程序是单线程的吗？还是有多个线程在运行？

你检查过资源不足的问题吗？JVM内存不足、磁盘空间不足等？

可能值得考虑的一件事是 Derby 语句缓存是否正在发挥作用。禁用缓存会影响问题吗？http://wiki.apache.org/db-derby/StatementCache

您提到数据库模式（表、索引等）是动态创建的。您可以更新您的问题以包含确切的架构信息吗？一种方法是在运行应用程序后对数据库运行“dblook”。或者使用“-Dderby.language.logStatementText=true”运行您的应用程序，所有执行的 SQL 语句都应回显到日志中。

如果您自己没有走得太远，您可以尝试联系 Apache 邮件列表上的 Derby 社区，因为他们会有更多建议供您尝试。

java - 德比 Apache 随机 NullPointerException

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