- html - 出于某种原因,IE8 对我的 Sass 文件中继承的 html5 CSS 不友好?
- JMeter 在响应断言中使用 span 标签的问题
- html - 在 :hover and :active? 上具有不同效果的 CSS 动画
- html - 相对于居中的 html 内容固定的 CSS 重复背景?
我的软件中存在管道损坏的问题。我正在使用 Hibernate 4.3.7 和 JPA 2.1 Final 以及 C3P0,我已经尝试了所有方法,但当 MySQL 时间到期时仍然给出损坏的管道。
来自 tomcat 的日志:
ERROR: The last packet successfully received from the server was 57,069,477 milliseconds ago. The last packet sent successfully to the server was 57,069,477 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.
Nov 06, 2014 8:27:23 AM com.sun.faces.lifecycle.InvokeApplicationPhase execute
WARNING: #{controleLogin.efetuarLogin()}: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
javax.faces.FacesException: #{controleLogin.efetuarLogin()}: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:72)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:200)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
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:744)
Caused by: javax.faces.el.EvaluationException: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
... 26 more
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1763)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
at org.hibernate.jpa.internal.QueryImpl.getResultList(QueryImpl.java:458)
at br.com.clikyapp1.modelo.UsuarioDAO.login(UsuarioDAO.java:26)
at br.com.clikyapp1.controle.ControleLogin.efetuarLogin(ControleLogin.java:29)
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.el.parser.AstValue.invoke(AstValue.java:278)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
... 27 more
Caused by: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:132)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:91)
at org.hibernate.loader.Loader.getResultSet(Loader.java:2066)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1863)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1839)
at org.hibernate.loader.Loader.doQuery(Loader.java:910)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:355)
at org.hibernate.loader.Loader.doList(Loader.java:2554)
at org.hibernate.loader.Loader.doList(Loader.java:2540)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2370)
at org.hibernate.loader.Loader.list(Loader.java:2365)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:497)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:387)
at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:236)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1264)
at org.hibernate.internal.QueryImpl.list(QueryImpl.java:103)
at org.hibernate.jpa.internal.QueryImpl.list(QueryImpl.java:573)
at org.hibernate.jpa.internal.QueryImpl.getResultList(QueryImpl.java:449)
... 37 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 57,069,477 milliseconds ago. The last packet sent successfully to the server was 57,069,477 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1137)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3983)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2596)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2776)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2840)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2082)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2212)
at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:116)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:82)
... 53 more
Caused by: java.net.SocketException: Broken pipe
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:113)
at java.net.SocketOutputStream.write(SocketOutputStream.java:159)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3964)
... 60 more
Nov 06, 2014 8:27:23 AM com.sun.faces.context.AjaxExceptionHandlerImpl handlePartialResponseError
SEVERE: javax.faces.el.EvaluationException: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:72)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:200)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1763)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
at org.hibernate.jpa.internal.QueryImpl.getResultList(QueryImpl.java:458)
at br.com.clikyapp1.modelo.UsuarioDAO.login(UsuarioDAO.java:26)
at br.com.clikyapp1.controle.ControleLogin.efetuarLogin(ControleLogin.java:29)
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.el.parser.AstValue.invoke(AstValue.java:278)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
... 27 more
Caused by: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:132)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:91)
at org.hibernate.loader.Loader.getResultSet(Loader.java:2066)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1863)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1839)
at org.hibernate.loader.Loader.doQuery(Loader.java:910)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:355)
at org.hibernate.loader.Loader.doList(Loader.java:2554)
at org.hibernate.loader.Loader.doList(Loader.java:2540)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2370)
at org.hibernate.loader.Loader.list(Loader.java:2365)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:497)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:387)
at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:236)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1264)
at org.hibernate.internal.QueryImpl.list(QueryImpl.java:103)
at org.hibernate.jpa.internal.QueryImpl.list(QueryImpl.java:573)
at org.hibernate.jpa.internal.QueryImpl.getResultList(QueryImpl.java:449)
... 37 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 57,069,477 milliseconds ago. The last packet sent successfully to the server was 57,069,477 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1137)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3983)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2596)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2776)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2840)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2082)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2212)
at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:116)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:82)
... 53 more
Caused by: java.net.SocketException: Broken pipe
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:113)
at java.net.SocketOutputStream.write(SocketOutputStream.java:159)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3964)
... 60 more
这是我的 persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="clikyapp1">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<class>br.com.clikyapp1.bean.Cultura</class>
<class>br.com.clikyapp1.bean.Cidade</class>
<class>br.com.clikyapp1.bean.Estado</class>
<class>br.com.clikyapp1.bean.TipoDespesa</class>
<class>br.com.clikyapp1.bean.Safra</class>
<class>br.com.clikyapp1.bean.TipoContrato</class>
<class>br.com.clikyapp1.bean.Area</class>
<class>br.com.clikyapp1.bean.Armazem</class>
<class>br.com.clikyapp1.bean.Conta</class>
<class>br.com.clikyapp1.bean.Parceiro</class>
<class>br.com.clikyapp1.bean.Usuario</class>
<class>br.com.clikyapp1.bean.Contrato</class>
<properties>
<property name="javax.persistence.jdbc.user" value="root" />
<property name="javax.persistence.jdbc.password" value="senha" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/clikyapp1" />
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="hibernate.cache.provider_class" value="org.hibernate.cache.NoCacheProvider" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
<property name="hibernate.connection.autocommit" value="false" />
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.connection.provider_class"
value="org.hibernate.connection.C3P0ConnectionProvider" />
<property name="hibernate.c3p0.acquire_increment" value="1" />
<property name="hibernate.c3p0.idle_test_period" value="100" />
<property name="hibernate.c3p0.timeout" value="1800" />
<property name="hibernate.c3p0.max_size" value="5" />
<property name="hibernate.c3p0.min_size" value="3" />
<property name="hibernate.c3p0.max_statement" value="50" />
<property name="hibernate.c3p0.preferredTestQuery" value="select 1;" />
<property name="hibernate.c3p0.interactive_timeout" value="10" />
<property name="hibernate.c3p0.connect_timeout" value="20" />
</properties>
</persistence-unit>
有什么想法吗?
最佳答案
1) 您的 c3p0 配置中有一个拼写错误。
<property name="hibernate.c3p0.max_statement" value="50" />
应该是
<property name="hibernate.c3p0.max_statements" value="50" />
2) 在
<property name="hibernate.c3p0.preferredTestQuery" value="select 1;" />
...去掉分号。也就是说,只是...
<property name="hibernate.c3p0.preferredTestQuery" value="select 1" />
3) 这两个属性不是有效的 c3p0 配置:
<property name="hibernate.c3p0.interactive_timeout" value="10" />
<property name="hibernate.c3p0.connect_timeout" value="20" />
您似乎正在尝试设置 mysql 服务器属性。 interactive_timout
是无关紧要的;它是 mysql 命令行工具的配置参数。 connect_timout
(和 wait_timeout
)是 system variables你可以set on the server side
4) 验证您想要的配置是否是 c3p0 实际看到的配置。 c3p0 在池初始化时将其配置转储到 INFO 中。看看那个。
5) 假设您想要的配置已经通过,您还没有完全配置可靠的测试机制。您经常测试空闲连接,但理论上繁忙的池可能永远不会让连接空闲足够长的时间来进行测试。鉴于 MySQL 提示的是未使用的而不是繁忙的连接,这不太可能是您的问题。但仍然最好 impose a better testing regime ,例如设置 testConnectionOnCheckin
至true
.
6) 一旦配置正确,如果仍然看到错误,可能的原因是您的应用程序长时间保留连接(例如作为成员变量),而不是根据需要检查它们,并且立即 close() 它们。这是个坏主意。如果您的应用程序让连接保持 checkout 状态,c3p0 无法帮助您保持连接新鲜,而连接池的目的是消除即时连接 checkout 的性能成本。所以,解决这个问题。
如果您不确定或认为您的应用程序没有长时间保持任何连接打开状态,则可以使用两个设置 unreturnedConnectionTimeout
和debugUnreturnedConnectionStackTraces
。第一个将导致客户端应用程序保持打开状态的时间超过配置为强制返回池的秒数。第二个将导致检查坏连接的代码的堆栈跟踪被转储到日志中。请参阅here .
关于java - jpa 2.1、Hibernate 4.3.7 和 C3P0 的管道损坏,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/26783755/
关于strcat函数。 while (*p) p++; 和 while (*++p) ; 两者都有效,但是 while (*p++) ; 不起作用。我认为 first 和 th
" in HTML?(HTML中的““是什么
?)
下面例子中的第一行代码是什么。我看到一个YouTuber在写下面的代码,它显示了一个设计在csswar Challenges中。我也尝试了一下,它很管用。但我以前从未在任何HTML教程上看到过它,我在
vs.
是不间断空格,表示没有换行的空白处。 如果我用 我在两个段落之间有一个空格(更大的间隔)。如果我使用 我在两个段落之间只有一个新行(没有中断)。为什么? 最佳答案 在 HTML 中
这个问题已经有答案了: Why are these constructs using pre and post-increment undefined behavior? (14 个回答) 已关闭 9
我对编程还很陌生,只是想知道为什么这段代码: for ( ; *p; ++p) *p = tolower(*p); 当 p 指向一个字符串时,可以降低 c 中字符串的大小写吗? 最佳答案 一般来说,这
代码 int n = 25; int *p = &n; printf("%x\n %d\n %x\n", p, p[0], p[1]); 返回: \ 当然我永远不会这样做,但在 K&R 中声明
所以,我想创建一个简单的程序,返回有关连续素数的计算结果。首先,我创建一个包含所有这些素数的列表,然后尝试计算结果,但这给了我一个超出范围的索引。有人可以帮助我吗?我的程序: primes = []
这个问题在这里已经有了答案: With arrays, why is it the case that a[5] == 5[a]? (20 个答案) 关闭 9 年前。 我想知道 C/C++ 中以下四
我仍在努力理解 *p、&p 和 p 之间的区别。根据我的理解,* 可以被认为是“指向的值”,而 & 可以被认为是“地址”。换句话说,* 保存值,而 & 保存地址。如果这是真的,那么 *p 和 p 之间
你是吗? [xxxrecipientFirstNamexxx]
和你是吗? {recipientFirstName}
需要更换 你是吗? [xxxrecipientFirstNamexxx] 和 你是吗? {recipientFirstName} 。我尝试使用边界匹配器。但结果并不符合预期。我尝试使用下面的代码 "A
我想按 IsTop 属性升序排序对象,然后按 JobId 属性降序排序: query = query.OrderBy(p => p.IsTop).ThenOrderByDescending(p =
在我尝试使用 Apache POI 进行转换的 Excel 文件中,我有一个单元格的数值为 -3.97819466831428,自定义格式为“0.0 p.p.;(0.0 p.p.)”。因此,在 Exc
我想创建一个扩展方法,允许我调用 ToSerializableDictionary(p => p.ID)而不是 .ToDictionary(p => p.ID)在以下 LINQ 上下文中。虽然我不确定
在下面的 HTML 代码上运行此 jQuery 代码会返回不同的结果,我认为它们应该返回相同的值。 jQuery 代码: var counter = 0; $("p").each(function()
在下面的代码片段中,符号 *p 等同于 p[0],*(p + 1) 等同于p[1],依此类推。 int* p = new int[3] { 1, 2, 3}; cout << *p << ' ' <<
这个问题在这里已经有了答案: What will happen when I call a member function on a NULL object pointer? [duplicate]
这个问题在这里已经有了答案: 关闭 10 年前。 Possible Duplicate: Undefined Behavior and Sequence Points 按照标准中的定义,E1 +=
" in HTML?(在HTML中“
以下示例中的第一行代码是什么。我看到一个youtube用户写下面的代码,它显示在cssbattle挑战的设计。我也试过,它的作品。但我从来没有见过它在任何HTML教程之前,我在谷歌上搜索它,但它只显示
每当我收到来自 MS outlook 的电子邮件时,我都会收到此标记 & nbsp ; (没有空格)哪个显示为?在 <>. 当我将其更改为 ISO-8859-1 时,浏览器页面字符集编码为 UTF-8
p1
TESTp2
代码: from bs4 import BeautifulSoup soup = BeautifulSoup('p1TESTp2') print soup.div() 结果: [p1, p2] 为什么
我是一名优秀的程序员,十分优秀!