我有一个配置了 hadoop 2.7.2 和 hive 2.1.0 的 hadoop 集群。
我正在使用 beeline 通过以下命令连接到配置单元:
beeline
beeline> !connect jdbc:hive2://localhost:10000
Enter username for jdbc:hive2://localhost:10000:
首先，键入任意用户名都可以成功连接到hive。但是，配置以下设置后，出现错误。
//within hive-site.xml and hiveserver2-site.xml
<property>
<name>hive.server2.enable.doAs</name>
<value>true</value>
<description>
Setting this property to true will have HiveServer2 execute
Hive operations as the user making the calls to it.
</description>
</property>
//within core-site.xml
<property>
<name>hadoop.proxyuser.hive.hosts</name>
<value>*</value>
</property>
<property>
<name>hadoop.proxyuser.hive.groups</name>
<value>*</value>
</property>
我已经重启了hadoop集群，但是仍然出现如下信息:
Error: Failed to open new session: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive (state=,code=0)
hiveserver2 的调试输出如下:
16/11/15 11:28:46 [IPC Client (241742811) connection to /10.104.90.40:8020 from hive]: DEBUG ipc.Client: IPC Client (241742811) connection to /10.104.90.40:8020 from hive: starting, having connections 1
16/11/15 11:28:46 [IPC Client (241742811) connection to /10.104.90.40:8020 from hive]: DEBUG ipc.Client: IPC Client (241742811) connection to /10.104.90.40:8020 from hive got value #-3
16/11/15 11:28:46 [IPC Client (241742811) connection to /10.104.90.40:8020 from hive]: DEBUG ipc.Client: closing ipc connection to /10.104.90.40:8020: User: hive is not allowed to impersonate hive
org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hadoop.ipc.Client.call(Client.java:1475)
at org.apache.hadoop.ipc.Client.call(Client.java:1412)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
at com.sun.proxy.$Proxy27.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getFileInfo(ClientNamenodeProtocolTranslatorPB.java:771)
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:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:191)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
at com.sun.proxy.$Proxy28.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.getFileInfo(DFSClient.java:2108)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1305)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1301)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1301)
at org.apache.hadoop.fs.FileSystem.exists(FileSystem.java:1424)
at org.apache.hadoop.hive.ql.session.SessionState.createRootHDFSDir(SessionState.java:674)
at org.apache.hadoop.hive.ql.session.SessionState.createSessionDirs(SessionState.java:622)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:550)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:513)
at org.apache.hive.service.cli.session.HiveSessionImpl.open(HiveSessionImpl.java:165)
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:606)
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:78)
at org.apache.hive.service.cli.session.HiveSessionProxy.access$000(HiveSessionProxy.java:36)
at org.apache.hive.service.cli.session.HiveSessionProxy$1.run(HiveSessionProxy.java:63)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:59)
at com.sun.proxy.$Proxy45.open(Unknown Source)
at org.apache.hive.service.cli.session.SessionManager.createSession(SessionManager.java:327)
at org.apache.hive.service.cli.session.SessionManager.openSession(SessionManager.java:279)
at org.apache.hive.service.cli.CLIService.openSessionWithImpersonation(CLIService.java:189)
at org.apache.hive.service.cli.thrift.ThriftCLIService.getSessionHandle(ThriftCLIService.java:414)
at org.apache.hive.service.cli.thrift.ThriftCLIService.OpenSession(ThriftCLIService.java:310)
at org.apache.hive.service.rpc.thrift.TCLIService$Processor$OpenSession.getResult(TCLIService.java:1377)
at org.apache.hive.service.rpc.thrift.TCLIService$Processor$OpenSession.getResult(TCLIService.java:1362)
at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:39)
at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:39)
at org.apache.hive.service.auth.TSetIpAddressProcessor.process(TSetIpAddressProcessor.java:56)
at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:286)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
16/11/15 11:28:46 [IPC Client (241742811) connection to /10.104.90.40:8020 from hive]: DEBUG ipc.Client: IPC Client (241742811) connection to /10.104.90.40:8020 from hive: closed
16/11/15 11:28:46 [IPC Client (241742811) connection to /10.104.90.40:8020 from hive]: DEBUG ipc.Client: IPC Client (241742811) connection to /10.104.90.40:8020 from hive: stopped, remaining connections 0
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: WARN service.CompositeService: Failed to open session
java.lang.RuntimeException: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:89)
at org.apache.hive.service.cli.session.HiveSessionProxy.access$000(HiveSessionProxy.java:36)
at org.apache.hive.service.cli.session.HiveSessionProxy$1.run(HiveSessionProxy.java:63)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:59)
at com.sun.proxy.$Proxy45.open(Unknown Source)
at org.apache.hive.service.cli.session.SessionManager.createSession(SessionManager.java:327)
at org.apache.hive.service.cli.session.SessionManager.openSession(SessionManager.java:279)
at org.apache.hive.service.cli.CLIService.openSessionWithImpersonation(CLIService.java:189)
at org.apache.hive.service.cli.thrift.ThriftCLIService.getSessionHandle(ThriftCLIService.java:414)
at org.apache.hive.service.cli.thrift.ThriftCLIService.OpenSession(ThriftCLIService.java:310)
at org.apache.hive.service.rpc.thrift.TCLIService$Processor$OpenSession.getResult(TCLIService.java:1377)
at org.apache.hive.service.rpc.thrift.TCLIService$Processor$OpenSession.getResult(TCLIService.java:1362)
at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:39)
at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:39)
at org.apache.hive.service.auth.TSetIpAddressProcessor.process(TSetIpAddressProcessor.java:56)
at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:286)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:578)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:513)
at org.apache.hive.service.cli.session.HiveSessionImpl.open(HiveSessionImpl.java:165)
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:606)
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:78)
... 21 more
Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hadoop.ipc.Client.call(Client.java:1475)
at org.apache.hadoop.ipc.Client.call(Client.java:1412)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
at com.sun.proxy.$Proxy27.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getFileInfo(ClientNamenodeProtocolTranslatorPB.java:771)
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:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:191)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
at com.sun.proxy.$Proxy28.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.getFileInfo(DFSClient.java:2108)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1305)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1301)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1301)
at org.apache.hadoop.fs.FileSystem.exists(FileSystem.java:1424)
at org.apache.hadoop.hive.ql.session.SessionState.createRootHDFSDir(SessionState.java:674)
at org.apache.hadoop.hive.ql.session.SessionState.createSessionDirs(SessionState.java:622)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:550)
... 28 more
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: DEBUG security.UserGroupInformation: PrivilegedAction as:hive (auth:PROXY) via hive (auth:SIMPLE) from:org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:59)
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: INFO session.SessionState: Updating thread name to 74dcfeae-04c1-494d-b491-df53f0d20039 HiveServer2-Handler-Pool: Thread-38
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: INFO session.SessionState: Resetting thread name to HiveServer2-Handler-Pool: Thread-38
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: DEBUG session.SessionState: Removing resource dir /tmp/hive_resources
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: INFO hive.metastore: Trying to connect to metastore with URI thrift://10.104.90.40:9083
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: INFO hive.metastore: Opened a connection to metastore, current connections: 3
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: INFO hive.metastore: Connected to metastore.
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: DEBUG metadata.Hive: Closing current thread's connection to Hive Metastore.
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: INFO hive.metastore: Closed a connection to metastore, current connections: 2
16/11/15 11:28:46 [HiveServer2-Handler-Pool: Thread-38]: DEBUG ipc.Client: stopping client from cache: org.apache.hadoop.ipc.Client@78fd9232
16/11/15 11:28:47 [HiveServer2-Handler-Pool: Thread-38]: WARN thrift.ThriftCLIService: Error opening session:
org.apache.hive.service.cli.HiveSQLException: Failed to open new session: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hive.service.cli.session.SessionManager.createSession(SessionManager.java:336)
at org.apache.hive.service.cli.session.SessionManager.openSession(SessionManager.java:279)
at org.apache.hive.service.cli.CLIService.openSessionWithImpersonation(CLIService.java:189)
at org.apache.hive.service.cli.thrift.ThriftCLIService.getSessionHandle(ThriftCLIService.java:414)
at org.apache.hive.service.cli.thrift.ThriftCLIService.OpenSession(ThriftCLIService.java:310)
at org.apache.hive.service.rpc.thrift.TCLIService$Processor$OpenSession.getResult(TCLIService.java:1377)
at org.apache.hive.service.rpc.thrift.TCLIService$Processor$OpenSession.getResult(TCLIService.java:1362)
at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:39)
at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:39)
at org.apache.hive.service.auth.TSetIpAddressProcessor.process(TSetIpAddressProcessor.java:56)
at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:286)
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:745)
Caused by: java.lang.RuntimeException: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:89)
at org.apache.hive.service.cli.session.HiveSessionProxy.access$000(HiveSessionProxy.java:36)
at org.apache.hive.service.cli.session.HiveSessionProxy$1.run(HiveSessionProxy.java:63)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:59)
at com.sun.proxy.$Proxy45.open(Unknown Source)
at org.apache.hive.service.cli.session.SessionManager.createSession(SessionManager.java:327)
... 13 more
Caused by: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:578)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:513)
at org.apache.hive.service.cli.session.HiveSessionImpl.open(HiveSessionImpl.java:165)
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:606)
at org.apache.hive.service.cli.session.HiveSessionProxy.invoke(HiveSessionProxy.java:78)
... 21 more
Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User: hive is not allowed to impersonate hive
at org.apache.hadoop.ipc.Client.call(Client.java:1475)
at org.apache.hadoop.ipc.Client.call(Client.java:1412)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
at com.sun.proxy.$Proxy27.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getFileInfo(ClientNamenodeProtocolTranslatorPB.java:771)
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:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:191)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
at com.sun.proxy.$Proxy28.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.getFileInfo(DFSClient.java:2108)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1305)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1301)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1301)
at org.apache.hadoop.fs.FileSystem.exists(FileSystem.java:1424)
at org.apache.hadoop.hive.ql.session.SessionState.createRootHDFSDir(SessionState.java:674)
at org.apache.hadoop.hive.ql.session.SessionState.createSessionDirs(SessionState.java:622)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:550)
... 28 more
我在网上搜索并发现大多数与此错误相关的解决方案实际上是我配置的导致问题的设置。
有谁知道如何解决这个问题？
更新:
经过一番尝试，我发现这个错误与使用哪个用户启动hive服务有关。
在我让用户 hive 启动 hive metastore 和 hiveserver2 之前，这会导致出现错误消息。
但是使用启动 hadoop namenode 的用户 hadoop 来启动 hiveserver2 可以消除错误消息。
我没有弄清楚为什么使用不同的用户是一种临时解决方法。
最佳答案
遇到同样的问题时偶然发现了这个线程。我尝试更改 hive-site.xml 中的模拟属性以使其正常工作。希望这对其他人有帮助。
<property>
<name>hive.server2.enable.doAs</name>
<value>false</value>
</property>
关于hadoop - hive 不允许冒充 hive ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40603714/
我正在处理旧代码的一部分。beforedoallow_any_instance_of(SportRateManager).toreceive(:create).and_return(true)endRubocop错误如下:Avoidstubbingusing'allow_any_instance_of'我读到了RuboCop::RSpec:AnyInstance我试着像下面那样改变它。由此beforedoallow_any_instance_of(SportRateManager).toreceive(:create).and_return(true)end对此:let(:sport_
1.1.1 YARN的介绍 为克服Hadoop1.0中HDFS和MapReduce存在的各种问题⽽提出的，针对Hadoop1.0中的MapReduce在扩展性和多框架⽀持⽅⾯的不⾜，提出了全新的资源管理框架YARN. ApacheYARN（YetanotherResourceNegotiator的缩写）是Hadoop集群的资源管理系统，负责为计算程序提供服务器计算资源，相当于⼀个分布式的操作系统平台，⽽MapReduce等计算程序则相当于运⾏于操作系统之上的应⽤程序。 YARN被引⼊Hadoop2,最初是为了改善MapReduce的实现，但是因为具有⾜够的通⽤性，同样可以⽀持其他的分布式计算模
目录第1题连续问题分析：解法：第2题分组问题分析：解法：第3题间隔连续问题分析：解法：第4题打折日期交叉问题分析：解法：第5题同时在线问题分析：解法：第1题连续问题如下数据为蚂蚁森林中用户领取的减少碳排放量iddtlowcarbon10012021-12-1212310022021-12-124510012021-12-134310012021-12-134510012021-12-132310022021-12-144510012021-12-1423010022021-12-154510012021-12-1523.......找出连续3天及以上减少碳排放量在100以上的用户分析：遇到这类
我正在使用DMOZ的listofurltopics，其中包含一些具有包含下划线的主机名的url。例如:608609TheOuterHeaven610InformationandimagegalleryofMcFarlane'sactionfiguresforTrigun,Akira,TenchiMuyoandotherJapaneseSci-Fianimations.611Top/Arts/Animation/Anime/Collectibles/Models_and_Figures/Action_Figures612虽然此url可以在网络浏览器中使用(或者至少在我的浏览器中可以使用:
我读过这个:Let’sstartwithasimpleRubyprogram.We’llwriteamethodthatreturnsacheery,personalizedgreeting.defsay_goodnight(name)result="Goodnight,"+namereturnresultend我的理解是，方法是定义在类中的函数或子程序，可以关联到类(类方法)或对象(实例方法)。那么，如果它不是在类中定义的，怎么可能是方法呢？ 最佳答案 当你在Ruby中以这种方式在全局范围内定义一个函数时，它在技术上变成了Obje
在DavidFlanagan的TheRubyProgrammingLanguage中；松本幸弘theystatethatthevariableprefixes($,@,@@)areonepricewepayforbeingabletoomitparenthesesaroundmethodinvocations.谁可以给我解释一下这个？ 最佳答案 这是我不成熟的意见。如果我错了，请纠正我。假设实例变量没有@前缀，那么我们如何声明一个实例变量？classMyClassdefinitialize#Herefooisaninstanceva
我已经设法制作了一个仅用于注册和登录的应用程序。目前，我允许用户通过邮件帐户激活(按照本教程:https://www.railstutorial.org/book/account_activation_password_reset和“railsgeneratecontrollerAccountActivations--no-test-framework')但我希望管理员能够激活或停用用户。在我的用户模型中，我设法定义了两种方法:defactivate_account!update_attribute:is_active,trueenddefdeactivate_account!upda
我正在制作一个应用程序，我需要用户使用所见即所得的编辑器输入描述。我不能信任用户输入，所以我只需要允许a、em、ul、li标签。我如何轻松剥离其他的？ 最佳答案 https://github.com/rgrove/sanitize/ 关于ruby-on-rails-允许用户只输入特定的标签，我们在StackOverflow上找到一个类似的问题： https://stackoverflow.com/questions/7390075/
目录：一、简介二、HQL的执行流程三、索引四、索引案例五、Hive常用DDL操作六、Hive常用DML操作七、查询结果插入到表八、更新和删除操作九、查询结果写出到文件系统十、HiveCLI和Beeline命令行的基本使用十一、Hive配置一、简介Hive是一个构建在Hadoop之上的数据仓库，它可以将结构化的数据文件映射成表，并提供类SQL查询功能，用于查询的SQL语句会被转化为MapReduce作业，然后提交到Hadoop上运行。特点：简单、容易上手(提供了类似sql的查询语言hql)，使得精通sql但是不了解Java编程的人也能很好地进行大数据分析；灵活性高，可以自定义用户函数(UDF)和
如何在我的模型中验证:title以便只接受字母a-z、A-z和0-9？validates:title,:format=>{with:REGULAREXPRESSION,:message=>'nospecialcharacters,onlylettersandnumbers'}正则表达式应该是什么？ 最佳答案 正则表达式为/^[a-zA-Z0-9]*$/您基本上定义了三个允许的符号范围，首先是a-z，然后是A-Z，最后是0-9。最后的星号定义需要匹配零个或多个前面所述的字符，这意味着允许使用空标题。如果您需要至少一个字符，请使用+而不