Question

I’m using spring 2.5 SimpleJdbcTemplate to access MySQL db. When I try to access the DB too often(using Quartz to access it every minute) i get this stack trace:

org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.)
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:82)
    at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:382)
    at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:458)
    at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:466)
    at org.springframework.jdbc.core.JdbcTemplate.queryForList(JdbcTemplate.java:497)
    at org.springframework.jdbc.core.simple.SimpleJdbcTemplate.queryForList(SimpleJdbcTemplate.java:223)
    at com.db.timexis.dao.UserDaoJdbc.getListOfAllUsers(UserDaoJdbc.java:137)
    at com.db.timexis.service.AuthServiceImpl.getListOfAllUsers(AuthServiceImpl.java:77)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
    at $Proxy0.getListOfAllUsers(Unknown Source)
    at com.mail.timexis.ReminderBean.execute(ReminderBean.java:25)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:276)
    at org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean$MethodInvokingJob.executeInternal(MethodInvokingJobDetailFactoryBean.java:260)
    at org.springframework.scheduling.quartz.QuartzJobBean.execute(QuartzJobBean.java:86)
    at org.quartz.core.JobRunShell.run(JobRunShell.java:216)
    at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:549)
Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.)
    at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1225)
    at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:113)
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:79)
    ... 30 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2260)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:787)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:49)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:357)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
    at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
    at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:294)
    at org.apache.commons.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1247)
    at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1221)
    ... 33 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The driver was unable to create a connection due to an inability to establish the client portion of a socket.

This is usually caused by a limit on the number of sockets imposed by the operating system. This limit is usually configurable. 

For Unix-based platforms, see the manual page for the 'ulimit' command. Kernel or system reconfiguration may also be required.

For Windows-based platforms, see Microsoft Knowledge Base Article 196271 (Q196271).
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181)
    ... 46 more
Caused by: java.net.BindException: Address already in use: connect
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
    at java.net.Socket.connect(Socket.java:519)
    at java.net.Socket.connect(Socket.java:469)
    at java.net.Socket.<init>(Socket.java:366)
    at java.net.Socket.<init>(Socket.java:209)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:293)
    ... 47 more

The code executed every minute:

public void execute() {
        List<User> regularUsers = null;
        try {
            // get all regular users
            ApplicationContext ctx = new ClassPathXmlApplicationContext(
                    "applicationContext.xml");
            AuthService authService = (AuthService) ctx.getBean("authService");

            regularUsers = authService.getListOfAllUsers();
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            if (regularUsers != null) {
                for (User u : regularUsers) {
                    if (u.getEmail().matches("^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9-]+)*(\\.[_A-Za-z0-9-]+)")) {
                        mailSender.sendMailReminder(u.getEmail(),
                                u.getFirstName());
                        // log mail sending
                        Date date = Calendar.getInstance().getTime();
                        SimpleDateFormat sdf = new SimpleDateFormat(
                                "yyyy/MM/dd HH:mm:ss");
                        String strDate = sdf.format(date);
                        System.out.println(strDate + "Reminder mail send...");
                        // log mail sending
                    }else{
                        System.out.println("invalid mail address");
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

It’s executed every minute for testing purposes. It will be executed once a week in the future.

My DBCP propertyes:

jdbc.maxActive=15
jdbc.maxIdle=10
jdbc.minIdle=5
jdbc.maxWait=5000
jdbc.validationQuery=select 1
jdbc.timeBetweenEvictionRunsMillis=1000
jdbc.numTestsPerEvictionRun=10
jdbc.minEvictableIdleTimeMillis=1200000

The data base is accessable trough the command line.

Answer 1

Note that you create a new instance of application context each time your method is invoked, and don’t close it. It means that resources allocated by beans decalred in this context (for example, connections created by connection pool) are not released.

Typically you need to create application context only once during startup of your application and close it upon shutdown, so I suggest you to implement it this way.

If you actullay need to create a new application context each time you call that method, don’t forget to close() it at the end of the method (in finally block for reliability).

Also note that you should declare an appropriate destroy-method for your connection pool bean in order to release resources when context is being closed.