那些遇到过的问题

apache commons dbcp connection pool error: Timeout waiting for idle object in a Spring + Hibernate app using Spring Transactions

Dhw*_*nit 5 java mysql hibernate spring-transactions apache-commons-dbcp

I have read through various Stackover flow Questions and contents on the web on similar problem. However, I couldnt find useful hints that would allow me to narrow down on my problem. Here is my usecase which results in this error.

2 entities Campus and Programs --> One-to-many relation from Campus to Program and One-to-one from Program to Campus.

i am trying to create multiple programs associated with campuses. Each insert will create a new program with same details and attach it to a different(unique) campus. eg. Java 101 Course offered at New York, San Francisco, Dallas, Chicago will create a new program for each campus.

持续单个程序没有问题.对于最多46个校园来说,没有任何问题,但这个错误出现在第47个校园.

这是我的应用程序的配置:

属性文件:

datasource.classname=com.mysql.jdbc.Driver
datasource.url=jdbc:mysql://localhost:3306/edu
datasource.username=xxx
datasource.password=xxx123
datasource.initialsize=15
datasource.maxactive=50
datasource.maxidle=15
datasource.minidle=5
datasource.maxwait=10000
datasource.dialect=org.hibernate.dialect.MySQLDialect
datasource.validationquery =select 1
datasource.minEvictableIdleTimeMillis = 180000
datasource.timeBetweenEvictionRunsMillis = 180000

hibernate.batchsize=30
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这是我的spring-hibernate配置的样子

<context:property-placeholder location="classpath:database.properties" order="1" ignore-unresolvable="true" />
<context:property-placeholder location="classpath:app.properties" order="2" ignore-unresolvable="true" />

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
    <property name="driverClassName" value="${datasource.classname}" />
    <property name="url" value="${datasource.url}" />
    <property name="username" value="${datasource.username}" />
    <property name="password" value="${datasource.password}" />
    <property name="initialSize" value="${datasource.initialsize}" />
    <property name="maxActive" value="${datasource.maxactive}" />
    <property name="maxIdle" value="${datasource.maxidle}" />
    <property name="minIdle" value="${datasource.minidle}" />
    <property name="maxWait" value="${datasource.maxwait}" />
    <property name="minEvictableIdleTimeMillis" value="${datasource.minEvictableIdleTimeMillis}" />
    <property name="timeBetweenEvictionRunsMillis" value="${datasource.timeBetweenEvictionRunsMillis}" />
    <property name="validationQuery" value="${datasource.validationquery}" />
    <property name="testOnBorrow" value="true" />
    <property name="removeAbandoned" value="true"/>
    <property name="removeAbandonedTimeout" value="60"/>
    <property name="logAbandoned" value="true"/>
</bean>

<bean id="sessionFactory"
    class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">${datasource.dialect}</prop>
            <prop key="hibernate.show_sql">false</prop>
            <prop key="hibernate.format_sql">true</prop>
            <prop key="hibernate.batch_size">${hibernate.batchsize}</prop>
            <prop key="hibernate.current_session_context_class">org.springframework.orm.hibernate3.SpringSessionContext</prop>

            <prop key="hibernate.cache.use_second_level_cache">true</prop>
            <prop key="hibernate.cache.use_query_cache">true</prop>
            <prop key="hibernate.cache.provider_configuration_file_resource_path">/WEB-INF/ehcache-entity.xml</prop>
            <prop key="hibernate.cache.region.factory_class">net.sf.ehcache.hibernate.EhCacheRegionFactory</prop>
            <prop key="hibernate.generate_statistics">false</prop>
            <!-- <prop key="hibernate.connection.release_mode">auto</prop> -->
        </props>
    </property>

    <property name="packagesToScan">
        <list>
            <value>com.edapp.core</value>
            <value>com.edapp.data.engine</value>
            <value>com.edapp.service.engine</value>
        </list>
    </property>
</bean>

<bean id="transactionManager"
    class="org.springframework.orm.hibernate3.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory" />
</bean>

<aop:config proxy-target-class="true"/> <!-- necessary to call methods on classes than proxies -->

<context:annotation-config /> 
<context:component-scan base-package="com.edapp" />

<!-- transaction settings -->

<tx:annotation-driven transaction-manager="transactionManager" />
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这是我的应用程序流程的样子

ProgramController - > ProgramService - > ProgramDAO

服务类注释为: @Transactional(propagation=Propagation.REQUIRED, isolation=Isolation.READ_COMMITTED)

DAO类注释为: @Transactional(propagation=Propagation.MANDATORY, isolation=Isolation.READ_COMMITTED)

这是Controller的作品

List<String> campuses = Arrays.asList(gson.fromJson(campusesJSArray, String[].class));      
        if(campuses.size() > 0){
            List<Program> programList = new ArrayList<Program>();
            AreaOfStudy aos = this.areaOfStudyService.getById(areaOfStudyId);
            Concentration con = this.concentrationService.getById(concentrationId);
            for(String c : campuses){
                Long campusid = Long.parseLong(c);
                Program p = new Program();
                Campus campus = this.campusService.getById(campusid);
                if(campus != null){
                    System.out.println(campus.toString());
                    p.setName(name);
                    p.setCampus(campus);
                    p.setCode(code);
                    p.setLevel(level);
                    p.getCampus().getPrograms().add(p);
                    p.setAreaOfStudy(aos);
                    p.setConcentration(con);
                    p.setActive(true);
                }               
                programList.add(p);
            }
            ((ProgramServiceImpl)programService).saveOrUpdate(programList);
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这是Service的一个片段

    if(programList == null){
        log.error("ProgramList cannot be null");
        return null;
    }

    Map<Integer, String> errors = new HashMap<Integer, String>();
    log.info("Saving program list of size:"+programList.size());

    for(int i=0; i<programList.size();i++){
        try{
            this.saveOrUpdate(programList.get(i));
        }catch(HibernateException e){
            errors.put(i, "error");
        }
    }
    return errors;
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这是DAO的一个片段:

@Transactional(isolation=Isolation.REPEATABLE_READ)
    public void create(final T entity) {
        if(entity == null){
            IllegalArgumentException e = new IllegalArgumentException();
            throw(e);
        }
        Session session = this.sessionFactory.getCurrentSession();
        try{
            session.persist(entity);
            session.flush();
        }catch(ConstraintViolationException cve){
            log.error("School with same code already exists "+ this.clazz.getName(),cve);
            throw cve;
        }catch(HibernateException e){
            log.error("Error persisting entity of type "+ this.clazz.getName(),e);
            throw new HibernateException(e);
        }finally{
            session.clear();
        }
    }
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Batchsize = 30

@Transactional(isolation=Isolation.REPEATABLE_READ)
    public void create(List<T> entityList){
        if(entityList == null){
            IllegalArgumentException e = new IllegalArgumentException();
            throw(e);
        }
        Session session = this.sessionFactory.getCurrentSession();
          try{
            for(int i=0;i<entityList.size();i++){
                T entity = entityList.get(i);

                if(entity == null){
                    log.error("List "+ this.clazz.getName() + " of cannot contain null");
                    throw new NullPointerException("List "+ this.clazz.getName() + " of cannot contain null");
                }
                session.persist(entity);
                if(i% this.batchSize == 0){
                    session.flush();
                    session.clear();
                }
            }
        }catch(HibernateException e){
            log.error("Error persisting entity of type "+ this.clazz.getName(),e);
            throw new HibernateException(e);
        }finally{
            session.flush();
            session.clear();
        }
    }
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尝试使用这两种方法来坚持但结果相同.

这是完整的堆栈跟踪

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.transaction.CannotCreateTransactionException: Could not open Hibernate Session for transaction; nested exception is org.hibernate.exception.GenericJDBCException: Cannot open connection
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:932)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:233)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

root cause

org.springframework.transaction.CannotCreateTransactionException: Could not open Hibernate Session for transaction; nested exception is org.hibernate.exception.GenericJDBCException: Cannot open connection
    org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:597)
    org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:372)
    org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:329)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
    com.tr.leadgen.service.engine.CampusServiceImpl$$EnhancerByCGLIB$$68d579ad.getById(<generated>)
    com.tr.leadgen.web.edu.controllers.ProgramController.add(ProgramController.java:74)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:233)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

root cause

org.hibernate.exception.GenericJDBCException: Cannot open connection
    org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:140)
    org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:128)
    org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52)
    org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449)
    org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
    org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:160)
    org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:81)
    org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1473)
    org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:556)
    org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:372)
    org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:329)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
    com.tr.leadgen.service.engine.CampusServiceImpl$$EnhancerByCGLIB$$68d579ad.getById(<generated>)
    com.tr.leadgen.web.edu.controllers.ProgramController.add(ProgramController.java:74)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:233)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

root cause

org.apache.commons.dbcp.SQLNestedException: Cannot get a connection, pool error Timeout waiting for idle object
    org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:114)
    org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
    org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:83)
    org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
    org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
    org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:160)
    org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:81)
    org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1473)
    org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:556)
    org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:372)
    org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:329)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
    com.tr.leadgen.service.engine.CampusServiceImpl$$EnhancerByCGLIB$$68d579ad.getById(<generated>)
    com.tr.leadgen.web.edu.controllers.ProgramController.add(ProgramController.java:74)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:233)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

root cause

java.util.NoSuchElementException: Timeout waiting for idle object
    org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1174)
    org.apache.commons.dbcp.AbandonedObjectPool.borrowObject(AbandonedObjectPool.java:79)
    org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:106)
    org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
    org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:83)
    org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
    org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
    org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:160)
    org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:81)
    org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1473)
    org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:556)
    org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:372)
    org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:329)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
    com.tr.leadgen.service.engine.CampusServiceImpl$$EnhancerByCGLIB$$68d579ad.getById(<generated>)
    com.tr.leadgen.web.edu.controllers.ProgramController.add(ProgramController.java:74)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:233)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
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这是我从hibernate获取会话的唯一方法:

@Transactional(propagation=Propagation.NOT_SUPPORTED)
    protected Session getCurrentSession(){
        if(this.sessionFactory == null){
            log.error("SessionFactory is null");
        }
        return this.sessionFactory.getCurrentSession();
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}

Also per my app logs, code execution does not make it to service layer. It throws an error while looping in the controller to populate the list of program entites (refer controller snippet)

I would be thankful if anyone can point me in the right direction.

ger*_*tan 2

我看到您有一个池设置，用于验证借用连接，并且从堆栈跟踪中我可以看到此验证失败（似乎超时）。我能想到的可能原因有两个：

  1. 您的应用程序和数据库服务器之间的网络连接已损坏。这可能是由于连接丢失、防火墙设置更改、陈旧的 DNS 条目、数据库服务器突然死机，甚至路由器有一个设置来杀死可疑的 tcp 套接字（我们曾经发生过一次）

  2. 池中的可用连接已耗尽。这是不太可能的，因为我假设堆栈跟踪会给出更多提示，但值得监视您的池并在问题发生时检查可用 conn 的数量

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