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25
4
我正在处理一个 Spring、MySQL 和 Hibernate 项目，如果该项目在 8 小时内未被使用，我会收到以下错误。有人可以告诉我为什么。看起来如果我重新启动服务器一切正常直到晚上或者如果没有人在中午使用系统几个小时。有人能帮帮我吗我刚刚在我的几个项目中发现了这个问题所以我一定在很多项目中犯了同样的错误..请帮忙
这是我的 java 代码示例，我是否遗漏了什么:
public void saveVisit(VisitModel visit) throws Exception {
LOGGER.debug("[" + visit.toString() + "]");
sessionFactory.getCurrentSession().saveOrUpdate(visit);
}
@SuppressWarnings("unchecked")
public School_lookupModel getSchoolInformation(String schoolCode)
{
return (School_lookupModel) sessionFactory.getCurrentSession()
.createCriteria(School_lookupModel.class)
.add( Restrictions.like("school", schoolCode))
.uniqueResult();
}
这是错误的控制台输出:
2012-09-06 08:00:07,088 [http-8080-2] WARN org.hibernate.util.JDBCExceptionReporter - SQL Error: 0, SQLState: 08S01
2012-09-06 08:00:07,088 [http-8080-2] ERROR org.hibernate.util.JDBCExceptionReporter - Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.io.EOFException
STACKTRACE:
java.io.EOFException
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1963)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2375)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2874)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3249)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1403)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:93)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1849)
at org.hibernate.loader.Loader.doQuery(Loader.java:718)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270)
at org.hibernate.loader.Loader.doList(Loader.java:2294)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2172)
at org.hibernate.loader.Loader.list(Loader.java:2167)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1706)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
at org.uftwf.schoolvisit.dao.SchoolVisitDAOImpl.getSelectableReporters(SchoolVisitDAOImpl.java:56)
at org.uftwf.schoolvisit.service.SchoolVisitServiceImpl.getSelectableReporters(SchoolVisitServiceImpl.java:130)
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:616)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
at $Proxy36.getSelectableReporters(Unknown Source)
at org.uftwf.schoolvisit.controller.swf.FlowActions.initializeSelectableReports(FlowActions.java:57)
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:616)
at org.springframework.expression.spel.support.ReflectiveMethodExecutor.execute(ReflectiveMethodExecutor.java:69)
at org.springframework.expression.spel.ast.MethodReference.getValueInternal(MethodReference.java:84)
at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:57)
at org.springframework.expression.spel.ast.SpelNodeImpl.getTypedValue(SpelNodeImpl.java:102)
at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:97)
at org.springframework.binding.expression.spel.SpringELExpression.getValue(SpringELExpression.java:84)
at org.springframework.webflow.action.EvaluateAction.doExecute(EvaluateAction.java:75)
at org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:188)
at org.springframework.webflow.execution.AnnotatedAction.execute(AnnotatedAction.java:145)
at org.springframework.webflow.execution.ActionExecutor.execute(ActionExecutor.java:51)
at org.springframework.webflow.engine.ActionList.execute(ActionList.java:155)
at org.springframework.webflow.engine.Flow.start(Flow.java:534)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:366)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:222)
at org.springframework.webflow.executor.FlowExecutorImpl.launchExecution(FlowExecutorImpl.java:140)
at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:193)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:679)
** END NESTED EXCEPTION **
Last packet sent to the server was 13 ms ago.
2012-09-06 08:00:07,089 [http-8080-2] WARN org.hibernate.util.JDBCExceptionReporter - SQL Error: 0, SQLState: null
2012-09-06 08:00:07,089 [http-8080-2] ERROR org.hibernate.util.JDBCExceptionReporter - Already closed.
2012-09-06 08:00:07,089 [http-8080-2] WARN org.hibernate.util.JDBCExceptionReporter - SQL Error: 0, SQLState: null
2012-09-06 08:00:07,089 [http-8080-2] ERROR org.hibernate.util.JDBCExceptionReporter - Already closed.
Sep 6, 2012 8:00:07 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet spring threw exception
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.io.EOFException
STACKTRACE:
java.io.EOFException
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1963)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2375)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2874)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3249)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1403)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:93)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1849)
at org.hibernate.loader.Loader.doQuery(Loader.java:718)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270)
at org.hibernate.loader.Loader.doList(Loader.java:2294)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2172)
at org.hibernate.loader.Loader.list(Loader.java:2167)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1706)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
at org.uftwf.schoolvisit.dao.SchoolVisitDAOImpl.getSelectableReporters(SchoolVisitDAOImpl.java:56)
at org.uftwf.schoolvisit.service.SchoolVisitServiceImpl.getSelectableReporters(SchoolVisitServiceImpl.java:130)
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:616)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
at $Proxy36.getSelectableReporters(Unknown Source)
at org.uftwf.schoolvisit.controller.swf.FlowActions.initializeSelectableReports(FlowActions.java:57)
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:616)
at org.springframework.expression.spel.support.ReflectiveMethodExecutor.execute(ReflectiveMethodExecutor.java:69)
at org.springframework.expression.spel.ast.MethodReference.getValueInternal(MethodReference.java:84)
at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:57)
at org.springframework.expression.spel.ast.SpelNodeImpl.getTypedValue(SpelNodeImpl.java:102)
at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:97)
at org.springframework.binding.expression.spel.SpringELExpression.getValue(SpringELExpression.java:84)
at org.springframework.webflow.action.EvaluateAction.doExecute(EvaluateAction.java:75)
at org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:188)
at org.springframework.webflow.execution.AnnotatedAction.execute(AnnotatedAction.java:145)
at org.springframework.webflow.execution.ActionExecutor.execute(ActionExecutor.java:51)
at org.springframework.webflow.engine.ActionList.execute(ActionList.java:155)
at org.springframework.webflow.engine.Flow.start(Flow.java:534)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:366)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:222)
at org.springframework.webflow.executor.FlowExecutorImpl.launchExecution(FlowExecutorImpl.java:140)
at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:193)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:679)
** END NESTED EXCEPTION **
Last packet sent to the server was 13 ms ago.
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2586)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2874)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3249)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1403)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:93)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1849)
at org.hibernate.loader.Loader.doQuery(Loader.java:718)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270)
at org.hibernate.loader.Loader.doList(Loader.java:2294)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2172)
at org.hibernate.loader.Loader.list(Loader.java:2167)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1706)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
at org.uftwf.schoolvisit.dao.SchoolVisitDAOImpl.getSelectableReporters(SchoolVisitDAOImpl.java:56)
at org.uftwf.schoolvisit.service.SchoolVisitServiceImpl.getSelectableReporters(SchoolVisitServiceImpl.java:130)
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:616)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
at $Proxy36.getSelectableReporters(Unknown Source)
at org.uftwf.schoolvisit.controller.swf.FlowActions.initializeSelectableReports(FlowActions.java:57)
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:616)
at org.springframework.expression.spel.support.ReflectiveMethodExecutor.execute(ReflectiveMethodExecutor.java:69)
at org.springframework.expression.spel.ast.MethodReference.getValueInternal(MethodReference.java:84)
at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:57)
at org.springframework.expression.spel.ast.SpelNodeImpl.getTypedValue(SpelNodeImpl.java:102)
at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:97)
at org.springframework.binding.expression.spel.SpringELExpression.getValue(SpringELExpression.java:84)
at org.springframework.webflow.action.EvaluateAction.doExecute(EvaluateAction.java:75)
at org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:188)
at org.springframework.webflow.execution.AnnotatedAction.execute(AnnotatedAction.java:145)
at org.springframework.webflow.execution.ActionExecutor.execute(ActionExecutor.java:51)
at org.springframework.webflow.engine.ActionList.execute(ActionList.java:155)
at org.springframework.webflow.engine.Flow.start(Flow.java:534)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:366)
at org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:222)
at org.springframework.webflow.executor.FlowExecutorImpl.launchExecution(FlowExecutorImpl.java:140)
at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:193)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:679)
最佳答案
使用c3p0对于池，它已准备好用于生产
使用这个参数(你可以修改优化)，这将保持你的连接活跃
<property name="hibernate.c3p0.timeout">1800</property>
<property name="hibernate.c3p0.idle_test_period">100</property>
编辑您还可以通过以下参数增加 8 小时限制
http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html#sysvar_wait_timeout
关于java - Spring、MySQL 和 Hibernate : Database error if the system is not used within 8 hours，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12299751/
25
4
0
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我们使用 Azure 弹性池，生成多个客户端数据库和一个引用客户端数据库的主数据库。 我们已经拥有多个数据库，并且正在开发新版本的代码。我们使用 EF6 代码优先。当我们对模型进行更改(添加属性)时，
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我们正在使用MySQL数据库在Go中创建一个Web应用程序。我们的用户一次只能拥有一个活跃的客户端。就像Spotify一样，您一次只能在一台设备上听音乐。为此，我制作了一个映射，将用户ID和作为其值的
我已经尝试在 PostgreSQL 中创建数据库好几天了，遇到了几个问题，但似乎卡住了。 我在 PostgreSQL 中手动创建了一个名为 postgres_development 的数据库，因为 b
我正在创建一个 iMessage 应用程序，它需要连接到与我的常规应用程序相同的数据库。 我调用 FirebaseApp.configure() 并对用户进行身份验证，但出于某种原因，在所有 Data
就像std::unordered_map但所有数据都应存储在磁盘上而不是内存中。 按照我的理解，应该做两部分:索引和存储。我已经学习了一些关于索引的数据结构，比如 Linear-Hash 或 B-Tr
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