记录初学者学习Hive时踩过的坑
- 1. 缺少MySQL驱动包
- 1.1 问题描述
Caused by: org.datanucleus.store.rdbms.connectionpool.DatastoreDriverNotFoundException: The specified datastore driver ("com.mysql.jdbc.Driver") was not found in the CLASSPATH. Please check your CLASSPATH specification, and the name of the driver.
at org.datanucleus.store.rdbms.connectionpool.AbstractConnectionPoolFactory.loadDriver(AbstractConnectionPoolFactory.java:58)
at org.datanucleus.store.rdbms.connectionpool.BoneCPConnectionPoolFactory.createConnectionPool(BoneCPConnectionPoolFactory.java:54)
at org.datanucleus.store.rdbms.ConnectionFactoryImpl.generateDataSources(ConnectionFactoryImpl.java:213)
- 1.2. 解决方案
上述问题很可能是缺少mysql的jar包,下载mysql-connector-java-5.1.32.tar.gz,复制到hive的lib目录下:
- 2. 元数据库mysql初始化
- 2.1 问题描述
运行./hive脚本时,无法进入,报错: Exception in thread "main" java.lang.RuntimeException: Hive metastore database is not initialized. Please use schematool (e.g. ./schematool -initSchema -dbType ...) to create the schema. If needed, don't forget to include the option to auto-create the underlying database in your JDBC connection string (e.g. ?createDatabaseIfNotExist=true for mysql)
- 2.2 解决方案
在scripts目录下运行 schematool -initSchema -dbType mysql命令进行Hive元数据库的初始化:
xiaosi@yoona:~/opt/hive-2.1.0/scripts$ schematool -initSchema -dbType mysql
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/xiaosi/opt/hive-2.1.0/lib/log4j-slf4j-impl-2.4.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/xiaosi/opt/hadoop-2.7.3/share/hadoop/common/lib/slf4j-log4j12-1.7.10.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
Metastore connection URL: jdbc:mysql://localhost:3306/hive_meta?createDatabaseIfNotExist=true
Metastore Connection Driver : com.mysql.jdbc.Driver
Metastore connection User: root
Starting metastore schema initialization to 2.1.0
Initialization script hive-schema-2.1.0.mysql.sql
Initialization script completed
schemaTool completed
- 3. Relative path in absolute URI
- 3.1 问题描述
Exception in thread "main" java.lang.IllegalArgumentException: java.net.URISyntaxException: Relative path in absolute URI: ${system:java.io.tmpdir%7D/$%7Bsystem:user.name%7D
...
Caused by: java.net.URISyntaxException: Relative path in absolute URI: ${system:java.io.tmpdir%7D/$%7Bsystem:user.name%7D
at java.net.URI.checkPath(URI.java:1823)
at java.net.URI.<init>(URI.java:745)
at org.apache.hadoop.fs.Path.initialize(Path.java:202)
... 12 more
- 3.2 解决方案
产生上述问题的原因是使用了没有配置的变量,解决此问题只需在配置文件hive-site.xml中配置system:user.name和system:java.io.tmpdir两个变量,配置文件中就可以使用这两个变量:
<property>
<name>system:user.name</name>
<value>xiaosi</value>
</property>
<property>
<name>system:java.io.tmpdir</name>
<value>/home/${system:user.name}/tmp/hive/</value>
</property>
- 4. 拒绝连接
- 4.1 问题描述
on exception: java.net.ConnectException: 拒绝连接; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
...
Caused by: java.net.ConnectException: Call From Qunar/127.0.0.1 to localhost:9000 failed on connection exception: java.net.ConnectException: 拒绝连接; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
...
Caused by: java.net.ConnectException: 拒绝连接
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531)
at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:495)
at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:614)
at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:712)
at org.apache.hadoop.ipc.Client$Connection.access$2900(Client.java:375)
at org.apache.hadoop.ipc.Client.getConnection(Client.java:1528)
at org.apache.hadoop.ipc.Client.call(Client.java:1451)
... 29 more
- 4.2 解决方案
有可能是Hadoop没有启动,使用jps查看一下当前进程发现:
xiaosi@yoona:~/opt/hive-2.1.0$ jps
7317 Jps
可以看见,我们确实没有启动Hadoop。开启Hadoop的NameNode和DataNode守护进程 xiaosi@yoona:~/opt/hadoop-2.7.3$ ./sbin/start-dfs.sh
Starting namenodes on [localhost]
localhost: starting namenode, logging to /home/xiaosi/opt/hadoop-2.7.3/logs/hadoop-xiaosi-namenode-yoona.out
localhost: starting datanode, logging to /home/xiaosi/opt/hadoop-2.7.3/logs/hadoop-xiaosi-datanode-yoona.out
Starting secondary namenodes [0.0.0.0]
0.0.0.0: starting secondarynamenode, logging to /home/xiaosi/opt/hadoop-2.7.3/logs/hadoop-xiaosi-secondarynamenode-yoona.out
xiaosi@yoona:~/opt/hadoop-2.7.3$ jps
8055 Jps
7561 NameNode
7929 SecondaryNameNode
7724 DataNode
- 5. 创建Hive表失败
- 5.1 问题描述
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask. MetaException(message:For direct MetaStore DB connections, we don't support retries at the client level.)
- 5.2 解决方案
查看Hive日志,看到这样的错误日志: NestedThrowablesStackTrace:
Could not create "increment"/"table" value-generation container `SEQUENCE_TABLE` since autoCreate flags do not allow it.
org.datanucleus.exceptions.NucleusUserException: Could not create "increment"/"table" value-generation container `SEQUENCE_TABLE` since autoCreate flags do not allow it.
出现上述问题主要因为mysql的bin-log format默认为statement ,在mysql中通过 show variables like 'binlog_format'; 语句查看bin-log format的配置值 mysql> show variables like 'binlog_format';
+---------------+-----------+
| Variable_name | Value |
+---------------+-----------+
| binlog_format | STATEMENT |
+---------------+-----------+
1 row in set (0.00 sec)
修改bin-log format的默认值,在mysql的配置文件/etc/mysql/mysql.conf.d/mysqld.cnf中添加 binlog_format="MIXED" ,重启mysql,再启动 hive即可。 mysql> show variables like 'binlog_format';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| binlog_format | MIXED |
+---------------+-------+
1 row in set (0.00 sec)
再次执行创表语句: hive> create table if not exists employees(
> name string comment '姓名',
> salary float comment '工资',
> subordinates array<string> comment '下属',
> deductions map<string,float> comment '扣除金额',
> address struct<city:string,province:string> comment '家庭住址'
> )
> comment '员工信息表'
> ROW FORMAT DELIMITED
> FIELDS TERMINATED BY '\t'
> LINES TERMINATED BY '\n'
> STORED AS TEXTFILE;
OK
Time taken: 0.664 seconds
- 6. 加载数据失败
- 6.1 问题描述
hive> load data local inpath '/home/xiaosi/hive/input/result.txt' overwrite into table recent_attention;
Loading data to table test_db.recent_attention
Failed with exception Unable to move source file:/home/xiaosi/hive/input/result.txt to destination hdfs://localhost:9000/user/hive/warehouse/test_db.db/recent_attention/result.txt
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.MoveTask
查看Hive日志,看到这样的错误日志: Caused by: org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /home/xiaosi/hive/warehouse/recent_attention/result.txt could only be replicated to 0 nodes instead of minReplication (=1). There are 0 datanode(s) running and no node(s) are excluded in this operation.
看到 0 datanodes running 我们猜想可能datanode挂掉了,jps验证一下,果然我们的datanode没有启动起来。
- 6.2 问题解决
这个问题是由于datanode没有启动导致的,至于datanode为什么没有启动起来,去看另一篇博文:那些年踩过的Hadoop坑(http://blog.csdn.net/sunnyyoona/article/details/51659080)
- 7. Java连接Hive 驱动失败
- 7.1 问题描述
java.lang.ClassNotFoundException: org.apache.hadoop.hive.jdbc.HiveDriver
at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_91]
at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_91]
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[na:1.8.0_91]
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_91]
at java.lang.Class.forName0(Native Method) ~[na:1.8.0_91]
at java.lang.Class.forName(Class.java:264) ~[na:1.8.0_91]
at com.sjf.open.hive.HiveClient.getConn(HiveClient.java:29) [classes/:na]
at com.sjf.open.hive.HiveClient.run(HiveClient.java:53) [classes/:na]
at com.sjf.open.hive.HiveClient.main(HiveClient.java:77) [classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_91]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_91]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_91]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_91]
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) [idea_rt.jar:na]
- 7.2 解决方案
private static String driverName = "org.apache.hadoop.hive.jdbc.HiveDriver";
取代 private static String driverName = "org.apache.hive.jdbc.HiveDriver"
- 8. create table问题
- 8.1 问题描述
create table if not exists employee(
name string comment 'employee name',
salary float comment 'employee salary',
subordinates array<string> comment 'names of subordinates',
deductions map<string,float> comment 'keys are deductions values are percentages',
address struct<street:string, city:string, state:string, zip:int> comment 'home address'
)
comment 'description of the table'
tblproperties ('creator'='yoona','date'='20160719')
location '/user/hive/warehouse/test.db/employee';
错误信息: FAILED: ParseException line 10:0 missing EOF at 'location' near ')'
- 8.2 解决方案
Location放在TBPROPERTIES之前: create table if not exists employee(
name string comment 'employee name',
salary float comment 'employee salary',
subordinates array<string> comment 'names of subordinates',
deductions map<string,float> comment 'keys are deductions values are percentages',
address struct<street:string, city:string, state:string, zip:int> comment 'home address'
)
comment 'description of the table'
location '/user/hive/warehouse/test.db/employee'
tblproperties ('creator'='yoona','date'='20160719');
create table命令:https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-CreateTable
- 9. JDBC Hive 拒绝连接
- 9.1 问题描述
15:00:50.815 [main] INFO org.apache.hive.jdbc.Utils - Supplied authorities: localhost:10000
15:00:50.832 [main] INFO org.apache.hive.jdbc.Utils - Resolved authority: localhost:10000
15:00:51.010 [main] DEBUG o.a.thrift.transport.TSaslTransport - opening transport org.apache.thrift.transport.TSaslClientTransport@3ffc5af1
15:00:51.019 [main] WARN org.apache.hive.jdbc.HiveConnection - Failed to connect to localhost:10000
15:00:51.027 [main] ERROR com.sjf.open.hive.HiveClient - Connection error!
java.sql.SQLException: Could not open client transport with JDBC Uri: jdbc:hive2://localhost:10000/default: java.net.ConnectException: 拒绝连接
at org.apache.hive.jdbc.HiveConnection.openTransport(HiveConnection.java:219) ~[hive-jdbc-2.1.0.jar:2.1.0]
at org.apache.hive.jdbc.HiveConnection.<init>(HiveConnection.java:157) ~[hive-jdbc-2.1.0.jar:2.1.0]
at org.apache.hive.jdbc.HiveDriver.connect(HiveDriver.java:107) ~[hive-jdbc-2.1.0.jar:2.1.0]
at java.sql.DriverManager.getConnection(DriverManager.java:664) ~[na:1.8.0_91]
at java.sql.DriverManager.getConnection(DriverManager.java:247) ~[na:1.8.0_91]
at com.sjf.open.hive.HiveClient.getConn(HiveClient.java:29) [classes/:na]
at com.sjf.open.hive.HiveClient.run(HiveClient.java:52) [classes/:na]
at com.sjf.open.hive.HiveClient.main(HiveClient.java:76) [classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_91]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_91]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_91]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_91]
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) [idea_rt.jar:na]
Caused by: org.apache.thrift.transport.TTransportException: java.net.ConnectException: 拒绝连接
at org.apache.thrift.transport.TSocket.open(TSocket.java:226) ~[libthrift-0.9.3.jar:0.9.3]
at org.apache.thrift.transport.TSaslTransport.open(TSaslTransport.java:266) ~[libthrift-0.9.3.jar:0.9.3]
at org.apache.thrift.transport.TSaslClientTransport.open(TSaslClientTransport.java:37) ~[libthrift-0.9.3.jar:0.9.3]
at org.apache.hive.jdbc.HiveConnection.openTransport(HiveConnection.java:195) ~[hive-jdbc-2.1.0.jar:2.1.0]
... 12 common frames omitted
Caused by: java.net.ConnectException: 拒绝连接
at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_91]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_91]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_91]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_91]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_91]
at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_91]
at org.apache.thrift.transport.TSocket.open(TSocket.java:221) ~[libthrift-0.9.3.jar:0.9.3]
... 15 common frames omitted
- 9.2 解决方案
(1) 检查hive server2是否启动:
xiaosi@Qunar:/opt/apache-hive-2.0.0-bin/bin$ sudo netstat -anp | grep 10000
如果没有启动hive server2,首先启动服务: xiaosi@Qunar:/opt/apache-hive-2.0.0-bin/conf$ hive --service hiveserver2 >/dev/null 2>/dev/null &
[1] 11978
(2) 检查配置:
<property>
<name>hive.server2.thrift.port</name>
<value>10000</value>
<description>Port number of HiveServer2 Thrift interface when hive.server2.transport.mode is 'binary'.</description>
</property>
- 10. User root is not allowed to impersonate anonymous
- 10.1 问题描述
Failed to open new session: java.lang.RuntimeException: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.authorize.AuthorizationException): User:xiaosiis not allowed to impersonate anonymous
- 10.2 解决方案
修改hadoop 配置文件 etc/hadoop/core-site.xml,加入如下配置项
<property>
<name>hadoop.proxyuser.root.hosts</name>
<value>*</value>
</property>
<property>
<name>hadoop.proxyuser.root.groups</name>
<value>*</value>
</property>
备注 hadoop.proxyuser.XXX.hosts 与 hadoop.proxyuser.XXX.groups 中XXX为异常信息中User:* 中的用户名部分 <property>
<name>hadoop.proxyuser.xiaosi.hosts</name>
<value>*</value>
<description>The superuser can connect only from host1 and host2 to impersonate a user</description>
</property>
<property>
<name>hadoop.proxyuser.xiaosi.groups</name>
<value>*</value>
<description>Allow the superuser oozie to impersonate any members of the group group1 and group2</description>
</property>
- 11. 安全模式
- 11.1 问题描述
Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.server.namenode.SafeModeException): Cannot create directory /tmp/hive/xiaosi/c2f6130d-3207-4360-8734-dba0462bd76c. Name node is in safe mode.
The reported blocks 22 has reached the threshold 0.9990 of total blocks 22. The number of live datanodes 1 has reached the minimum number 0. In safe mode extension. Safe mode will be turned off automatically in 5 seconds.
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkNameNodeSafeMode(FSNamesystem.java:1327)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:3893)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:983)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.mkdirs(ClientNamenodeProtocolServerSideTranslatorPB.java:622)
at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:969)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2049)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2045)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2043)
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$Invoker.invoke(ProtobufRpcEngine.java:229)
at com.sun.proxy.$Proxy32.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.mkdirs(ClientNamenodeProtocolTranslatorPB.java:558)
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.$Proxy33.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.primitiveMkdir(DFSClient.java:3000)
at org.apache.hadoop.hdfs.DFSClient.mkdirs(DFSClient.java:2970)
at org.apache.hadoop.hdfs.DistributedFileSystem$21.doCall(DistributedFileSystem.java:1047)
at org.apache.hadoop.hdfs.DistributedFileSystem$21.doCall(DistributedFileSystem.java:1043)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirsInternal(DistributedFileSystem.java:1043)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirs(DistributedFileSystem.java:1036)
at org.apache.hadoop.hive.ql.session.SessionState.createPath(SessionState.java:682)
at org.apache.hadoop.hive.ql.session.SessionState.createSessionDirs(SessionState.java:617)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:526)
... 9 more
- 11.2 问题分析
hdfs在启动开始时会进入安全模式,这时文件系统中的内容不允许修改也不允许删除,直到安全模式结束。安全模式主要是为了系统启动的时候检查各个DataNode上数据块的有效性,同时根据策略必要的复制或者删除部分数据块。运行期通过命令也可以进入安全模式。在实践过程中,系统启动的时候去修改和删除文件也会有安全模式不允许修改的出错提示,只需要等待一会儿即可。
- 11.3 问题解决
可以等待其自动退出安全模式,也可以使用手动命令来离开安全模式:
xiaosi@yoona:~$ hdfs dfsadmin -safemode leave
Safe mode is OFF
转载出处:https://blog.csdn.net/sunnyyoona/article/details/51648871
记录初学者学习Hive时踩过的坑的更多相关文章
- 记录使用git submodule时踩的坑
在使用git子模块的时候踩了一个坑 在使用git submodule updata --init --recursive命令,即递归更新子模块并初始化时碰到了一个问题: 经过一段不短时间的排查,发现问 ...
- [问题解决]RedHat7更换CentOS7的yum源时踩过的坑
更换yum源的流程 查看当前yum程序 $ rpm -qa|grep yum 这里推荐将其结果截屏或拷贝出来,以免后面报错修复. 删除原有yum源 $ rpm -aq | grep yum|xargs ...
- 使用Ajax中get请求发送Token时踩的那些坑
在使用惯了各种牛X的插件以后,在使用原生组件写一些小东西的时候总是有踩不完的坑! 今天就来说一说我使用原生ajax请求时踩得坑: 下面是我的代码: var xmlhttp; if (window.XM ...
- UWP:记录一下这几天踩到的坑
最近在玩微软的Desktop Bridge项目,遇到了如下几个坑: 1.文档中给的是js项目魔改的方法,其实C#项目也可以魔改加入UWP部分的,区别在于: 不用在项目文件里写<AppxGener ...
- 记录一下学习Android时遇到一些问题
实在是不擅长Android开发,但在努力的学习当中.这篇文章就记录一下学习过程中,自己犯下的一些错误,同时也让自己记住别再犯同样的错误了.各位看官勿见笑! 一个关于空指针的错误 错误类型一: 未对对象 ...
- 记录在vue中使用jsx时踩过的坑
使用方法及细节就不一一说了. 1.给input或者textarea绑定value时,出现失效的问题.解决方法:https://github.com/vuejs/babel-plugin-transfo ...
- 那些年我用awk时踩过的坑——awk使用注意事项
由于项目经历原因,经常使用awk处理一些文本数据.甚至,我特意下载了一个windows上的awk:gawk.exe,这样在windows上也能享受awk处理数据的方便性,. 俗话说,"常在河 ...
- 前端开发工具Brackets介绍,安装及安装Emme插件时踩过的坑
对于前端开发的园友来说有可能IDE工具有很多,层次不穷,还有每个人的喜好及习惯也不一样,因为我是一名后端开发的.Net程序员,但是大家都知道,现在都提倡什么全栈工程师,所以也得会点前端开发,所以我对于 ...
- python与C,在写程序时踩过的坑!
1. python与C有很多相似之处, 其一就是指针的大量应用, 因此在使用临时变量保存数据, 并将临时变量传递给其他变量时需要创建内存; 例如,在C中, char *temp 每次获取到不同的字 ...
随机推荐
- Confluence 6 自定义主面板
主面板(dashboard)是你 Confluence 站点的默认载入页面.这个页面能够给用户能够找到其他页面的所有必须的工具,重新进入未完成的工作或者快速导航到喜欢的空间和页面 站点的欢迎信息将会在 ...
- WEB漏洞 XSS(一)
1.xss的形成原理 xss 中文名是“跨站脚本攻击”,英文名“Cross Site Scripting”.xss也是一种注入攻击,当web应用对用户输入过滤不严格,攻击者写入恶意的脚本代码(HTML ...
- poj2417 bsgs算法非逆元模板,用于求解A^x=B(mod C)的方程
参考博客 https://blog.csdn.net/clover_hxy/article/details/50683832关于欧拉定理推论的证明 https://www.cnblogs.com/as ...
- cf14d 树的直径,枚举删边
#include<bits/stdc++.h> using namespace std; #define maxn 300 ]; int n,head[maxn],tot,a,b,dis[ ...
- new/new[]和delete/delete[]是如何分配空间以及释放空间的
C++中程序存储空间除栈空间和静态区外,每个程序还拥有一个内存池,这部分内存被称为或堆(heap).程序可以用堆来存储动态分配的对象,即那些在程序运行时创建的对象.动态对象的生存期由程序来控制 ,当动 ...
- 如何使用Scrapy框架实现网络爬虫
现在用下面这个案例来演示如果爬取安居客上面深圳的租房信息,我们采取这样策略,首先爬取所有租房信息的链接地址,然后再根据爬取的地址获取我们所需要的页面信息.访问次数多了,会被重定向到输入验证码页面,这个 ...
- 华硕X75VB安装ubuntu12.10网卡不可用等相关问题总结
笔记本相关信息: 电脑型号:华硕X75VB 笔记本电脑 处理器:i5-3230M 2.60GHz 双核 主板:华硕X75VB (英特尔 Ivy Bridge - HM76 Express芯片组) 内存 ...
- WebService服务介绍与调用
一: WebService简介 WebService是一个平台独立的,低耦合的,自包含的.基于可编程的web的应用程序,可使用开放的XML(标准通用标记语言的下的一个子集)标准来描述.发布.发现.协调 ...
- gradle构建时跳过指定tests
https://blog.csdn.net/u012672646/article/details/58598532
- jquery轻量级数字动画插件jquery.countup.js
插件描述: jquery.countup.js 是一款轻量级jquery数字动画插件.该数字动画插件可以在页面滚动时,将指定的数字从0开始计数增加动画. 插件说明 jquery.countup.js ...