在Java中对ResultSet调用next时发生超时异常

Question

我正在处理数据库，我正在从中选择一些东西，就像我做了一千次一样。但这一次，程序只是在调用resultSet.next()时冻结，过了一段时间就会抛出超时异常。有什么想法吗，我哪里会出错？这是我的代码：

 try {
        connection = dataSource.getConnection();
        connection.setAutoCommit(false);
        query = connection.prepareStatement(
                "SELECT * FROM INGREDIENTS WHERE RECIPEID = ?");
        query.setLong(1, recipe.getId());
        ResultSet resultsDB = query.executeQuery();
        SortedSet<Ingredient> result = new TreeSet<Ingredient>();
        while (resultsDB.next()) {
            Ingredient output = rowToIngredient(resultsDB);
            validate(output);
            result.add(output);
        }
        connection.commit();
        return result;
     }

当程序被调用为while循环中的条件时，它正好冻结在resultsDB.next()。当这部分代码第一次执行时，它就工作了，当程序用另一个数据第二次到达那里时，.next()方法冻结程序。程序从未进入循环，我使用了断点，它在评估条件的那一行失败了。感谢的建议

这整个代码都在循环中，可以吗？就我使用的数据源而言，它应该是

错误：

java.sql.SQLTransactionRollbackException: A lock could not be obtained within the time requested
    at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown Source)
    at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedResultSet.closeOnTransactionError(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedResultSet.next(Unknown Source)
    at org.apache.commons.dbcp.DelegatingResultSet.next(DelegatingResultSet.java:207)
    at org.apache.commons.dbcp.DelegatingResultSet.next(DelegatingResultSet.java:207)
    at fi.muni.pv168.RecipebookImpl.getIngredientsOfRecipe(RecipebookImpl.java:53)
    at fi.muni.pv168.RecipebookImpl.isIngredientInRecipe(RecipebookImpl.java:324)
    at fi.muni.pv168.RecipebookImpl.addIngredientsToRecipe(RecipebookImpl.java:92)
    at fi.muni.pv168.RecipebookImplTest.testFindRecipesByIngredients(RecipebookImplTest.java:390)
    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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.apache.maven.surefire.junit4.JUnit4TestSet.execute(JUnit4TestSet.java:53)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:123)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:104)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:164)
    at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:110)
    at org.apache.maven.surefire.booter.SurefireStarter.invokeProvider(SurefireStarter.java:175)
    at org.apache.maven.surefire.booter.SurefireStarter.runSuitesInProcessWhenForked(SurefireStarter.java:107)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:68)
Caused by: java.sql.SQLException: A lock could not be obtained within the time requested
    at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown Source)
... 46 more

并且很少有更多的

Answer 1

您必须有另一个并发的未提交事务，该事务正在更新您试图读取的行。这将导致行被锁定，并且您的事务将等待此锁定释放。

如果您正在使用一个工具对数据库执行请求，请确保在此工具中提交或回滚当前事务。如果您有另一个应用程序，或者使用同一数据库的同一应用程序中的另一个线程，请检查它是否没有长时间运行的事务。