【发布时间】：2013-01-21 04:06:32
【问题描述】：
我正在尝试插入具有两列的 Oracle 数据库-
ID Primary Key varchar2 (4000)
ACCOUNT varchar2 (4000)
我为此编写了一个多线程程序。每个线程每次都使用unique id 插入ID column，因为ID 是主键。
我在某些时候面临的唯一问题是 - 下面的代码在运行几秒钟后抛出以下异常。
1) Null Pointer Exception
2) java.sql.SQLException: Listener refused the connection with the following error:ORA-12519, TNS:no appropriate service handler found
我无法在我的代码中找到此问题的任何根本原因，因为对我来说一切都很好。当我正确关闭每个连接时。那么这个 NPE 是如何被抛出的以及其他异常呢？
ExecutorService service = Executors.newFixedThreadPool(10);
try {
// queue some tasks
for (int i = 0; i < 100 * 10; i++) {
service.submit(new ThreadTask());
}
service.shutdown();
service.awaitTermination(Long.MAX_VALUE, TimeUnit.SECONDS);
while (!service.isTerminated()) {
}
} catch (InterruptedException e) {
LOG.warn("Threw a Interrupted Exception in" + XMPLoadTest.class.getSimpleName()
+ ".XMPLoadTest: boss told me to stop...Not my fault!!");
}
下面是ThreadTask类-
class ThreadTask implements Runnable {
private static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
private static final String CONNECTION = "jdbc:oracle:thin:@localhost:1521:ORCL";
private static final String USER = "scott";
private static final String PASSWORD = "tiger";
private static Connection dbConnection = null;
private static PreparedStatement preparedStatement = null;
private static final AtomicInteger id = new AtomicInteger(1);
private final static Logger LOG = Logger.getLogger(ThreadTask.class.getName());
public ThreadTask() {
}
@Override
public void run() {
try {
dbConnection = getDBConnection();
preparedStatement = dbConnection.prepareStatement(Constants.INSERT_ORACLE_SQL);
preparedStatement.setString(1, String.valueOf(id.getAndIncrement()));
preparedStatement.setString(2, Constants.A_ACCOUNT);
preparedStatement.executeUpdate();
} catch (Exception e) {
// NPE getting thrown here/And second exception as well
LOG.error("Threw a SQLException in " + getClass().getSimpleName(), e);
} finally {
if (preparedStatement != null) {
try {
preparedStatement.close();
preparedStatement = null;
} catch (SQLException e) {
//Oouch...
LOG.error("Threw a SQLException in finally block of prepared statement " + getClass().getSimpleName(), e);
}
}
if (dbConnection != null) {
try {
dbConnection.close();
dbConnection = null;
} catch (SQLException e) {
//Better go and look for SQL.
LOG.error("Threw a SQLException in finally block of dbConnection " + getClass().getSimpleName(), e);
}
}
}
}
/**
* Attempts to establish a connection to the given database URL
*
* @return the db connection
*/
private Connection getDBConnection() {
Connection dbConnection = null;
try {
Class.forName(XMP_DRIVER);
dbConnection = DriverManager.getConnection(CONNECTION, USER, PASSWORD);
} catch (ClassNotFoundException e) {
LOG.error("Threw a ClassNotFoundException in " + getClass().getSimpleName(), e);
} catch (SQLException e) {
//DAMN! I'm not....
LOG.error("Threw a SQLException in " + getClass().getSimpleName(), e);
} catch (Exception e) {
LOG.error("Threw a Exception in " + getClass().getSimpleName(), e);
}
return dbConnection;
}
}
我的代码有任何潜在问题吗？我更担心这个 NPE。
堆栈跟踪：
19:14:28,372 ERROR ThreadTask:187 - Threw a SQLException in ThreadTask
java.sql.SQLException: Listener refused the connection with the following error:
ORA-12519, TNS:no appropriate service handler found
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:458)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:236)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)
at java.sql.DriverManager.getConnection(DriverManager.java:322)
at java.sql.DriverManager.getConnection(DriverManager.java:358)
at com.ebay.xmp.lnp.ThreadTask.getDBConnection(XMPLoadTest.java:179)
at com.ebay.xmp.lnp.ThreadTask.run(XMPLoadTest.java:137)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:452)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:314)
at java.util.concurrent.FutureTask.run(FutureTask.java:149)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:897)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:919)
at java.lang.Thread.run(Thread.java:736)
Caused by: oracle.net.ns.NetException: Listener refused the connection with the following error:
ORA-12519, TNS:no appropriate service handler found
at oracle.net.ns.NSProtocol.connect(NSProtocol.java:395)
at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1102)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:320)
... 14 more
19:14:28,376 ERROR ThreadTask:139 - Threw a SQLException in ThreadTask
java.lang.NullPointerException
at com.ebay.xmp.lnp.ThreadTask.run(XMPLoadTest.java:137)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:452)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:314)
at java.util.concurrent.FutureTask.run(FutureTask.java:149)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:897)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:919)
at java.lang.Thread.run(Thread.java:736)
【问题讨论】：
-
您使用的是哪个版本的 oracle？这个java代码看起来不错。似乎您的 oracle 设置有问题。您是否尝试只为 1 个线程运行该程序（没有太多线程）？这个链接可能对你也有用dadbm.com/2011/11/…
-
感谢 Prateek 的帮助。我忘记了 Oracle 版本，但我认为它是
11g or 10g关于我的第一个异常Null Pointer Exception有什么想法吗？什么阶段会出现？与此同时，我会看看你提供给我的文章。 -
您没有给出发生此错误的确切位置，但很可能是由于从 getDBConnection 方法返回的空 dbConnection。
-
请使用空指针异常的堆栈跟踪更新您的答案。我可以假设的一件事是变量
dbConnection在竞争条件下被设置为 null，而另一个线程试图在其上运行preparedStatement.executeUpdate()。 -
我也用 Stacktrace 更新了我的问题。我也相信它只是因为
dbConnection null而发生的，我很困惑 dbConnection 是如何为空的？这可能是一个竞争条件。我确实进行了调试，并发现 dbConnection 返回 null。但这怎么可能？我们如何解决这个问题？
标签： java multithreading oracle executorservice ora-12519