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H2 DB is empty and no tables are shown

I'm trying to connect perform an integration test and for that I need the H2 db to recreate some views.
I am using these properties:
<bean id="internalXaDataSource" class="org.h2.jdbcx.JdbcDataSource">
<property name="URL" value="jdbc:h2:./target/testing/h2db/#{randomUUID1.toString()}/:testdb;MODE=MSSQLServer"/>
<property name="description" value="#{randomUUID1.toString()}jdbcXa"/>
<property name="user" value="sa"/>
<property name="password" value=""/>
</bean>
<bean id="h2Server" class="org.h2.tools.Server" factory-method="createTcpServer" init-method="start" destroy-method="stop">
<constructor-arg>
<array>
<value>-tcp</value>
<value>-tcpAllowOthers</value>
<value>-tcpPort</value>
<value>8043</value>
</array>
</constructor-arg>
</bean>
I've tried connecting in several different ways:
Using the debugger to get the generated URL
then connecting to it with a jdbc connection URL like:
jdbc:h2:./target/testing/h2db/#3434-sdfjsd9o3849-df34/:testdb;MODE=MSSQLServer
I have a successful connection but the DB is empty, no tables are shown. However, using the information schema to get the list of schemata in the database shows that the testdb database is there.
Via the tcp server
I've tried several different URLs, but none connect. e.g.
jdbc:h2:tcp://localhost:8043/testdb:public;LOCK_MODE=0
jdbc:h2:tcp://localhost:8043/:testdb;LOCK_MODE=0
This is worse - not able to connect - just hangs.
Changing the underlying datasource to run on a port
<bean id="internalXaDataSource" class="org.h2.jdbcx.JdbcDataSource" depends-on="h2Server">
<property name="URL" value="jdbc:h2:tcp://localhost:8043/mem:public;MODE=MSSQLServer"/>
<property name="description" value="#{randomUUID1.toString()}jdbcXa"/>
<property name="user" value="sa"/>
< property name="password" value=""/>
</bean>
This also just hangs when trying to connect.
Can you explain what am I doing wrong?
Thanks

Figured this out. Had paused the running integration test with the IntelliJ debugger so I could connect to H2. However the breakpoint setting was set to stop the entire JVM. Fixed by editing the breakdown setting in IntelliJ to only pause the thread. Then was able to connect via the third method above.

Heap full of com.mysql.jdbc.JDBC4Connection

I'm analyzing a heap dump where I have 50% live set in the heap. This is caused by a large amount of heap reserved just to hold all the JDBC4Connection and it's internal properties hashmap. This is a heapdump of an application running for a couple of days.
It looks like it's holding thousands of JDBC connection objects and it's configuration.
I found a question which asked a similar question, but got dismissed suggesting that the user was not closing connections: Too many instances of "com.mysql.jdbc.JDBC4Connection"
However, I'm using the org.springframework.data.jpa.repository.JpaSpecificationExecutor.findAll, without querying the database directly. Code:
Specification<AccountProfile> spec = getUserInfoListSurfacing(userInfo);
JPAImpl.findAll(spec, new PageRequest(0, 1, Sort.Direction.DESC, "reportedDate")).getContent()
Here is the bean definition for this connection pool
<bean id="db" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="dataSourceName" value="users"/>
<property name="driverClass" value="${userdb.driver}"/>
<property name="forceUseNamedDriverClass" value="true"/>
<property name="jdbcUrl" value="${userdb.url}"/>
<property name="user" value="${userdb.username}"/>
<property name="password" value="${userdb.password}"/>
<property name="initialPoolSize" value="${userdb.hibernate.c3p0.initialPoolSize}"/>
<property name="maxPoolSize" value="${userdb.hibernate.c3p0.max_size}"/>
<property name="minPoolSize" value="${userdb.hibernate.c3p0.min_size}"/>
<property name="idleConnectionTestPeriod" value="${userdb.hibernate.c3p0.idle_test_period}"/>
<property name="maxStatements" value="${userdb.hibernate.c3p0.max_statements}"/>
<property name="maxIdleTime" value="${userdb.hibernate.c3p0.idle_test_period}"/>
<property name="preferredTestQuery" value="${userdb.hibernate.c3p0.validationQuery}"/>
<property name="testConnectionOnCheckout" value="${userdb.hibernate.c3p0.testOnBorrow}"/>
<property name="acquireIncrement" value="${userdb.hibernate.c3p0.acquireincrement}"/>
<property name="unreturnedConnectionTimeout"
value="${userdb.hibernate.c3p0.unreturnedConnectionTimeout}"/>
<property name="debugUnreturnedConnectionStackTraces" value="${userdb.hibernate.c3p0.debugUnreturnedConnectionStackTraces}"/>
<property name="maxConnectionAge" value="${userdb.hibernate.c3p0.maxconnectionage}"/>
<property name="numHelperThreads" value="${userdb.hibernate.c3p0.numHelperThreads}"/>
<property name="connectionCustomizerClassName" value="${userdb.hibernate.c3p0.connectionCustomizerClassName}"/>
</bean>
I have not been able to find confirmed reports of memory leaks in the Hibernate versions that I'm using.
I'm using spring-data-jpa version 2.0.6.Final
hibernate-core version 4.3.5.Final
hibernate-jpa-2.1-api version 1.0.2.Final

You show 224 instances of the object "managed". There is one instance of "managed" per Connection pool, so you have 224 Connection pools holding references to Connections, not just one. You have to understand why you are instantiating so many pools when a typical application just wants one.
The usual error that could cause this is to create a new Connection pool every time you mean to establish a new Connection. The less common cause is using the same DataSource to establish Connections under multiple authentications using dataSource.getConnection( user, password ). A new Connection pool is established for each distinct authentication.
Since you are not directly instantiating your Connection pool but using Spring to do it, it's not so easy to debug how why you are instantiating so any pools. One thing you should definitely add is a destroy-method attribute to your bean XML tag. That is...
<bean id="db" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
...
</bean>
You could be generating all these pools just by hot redeploying your app a lot, and failing to cleanup the old pools because Spring doesn't know it has to clean up your beans. See Spring's Destruction Callbacks.

Spring connection pooling configurations

I've been searching around the web for some time now and i've yet to fix this issue:
I have the following datasource configuration:
<bean id="cpms.prod.ds" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName"><value>com.mysql.jdbc.Driver</value></property>
<property name="url"><value>jdbc:mysql://localhost/mysql</value></property>
<property name="username"><value>test</value></property>
<property name="password"><value>test</value></property>
<property name="initialSize" value="1" />
<property name="maxActive" value="2" />
<property name="maxIdle" value="1"></property>
</bean>
This should be enough to make sure there are only 2 active connections at one point and those are the ones used for the pool.
In my java code i'm using SimpleJdbcTemplate to do three queries, and as I understand it this object should be returning the connections to the pool after each query ends, should also be blocking the third query while one of the others end.
When looking at my database administration console I see 3 connections appear, and then change to sleep state. If I run the queries again I see another 3 connections popup and the other 3 stay there.
The only way i've found for the connections to be closed is by setting:
<property name="removeAbandoned" value="true"/>
<property name="removeAbandonedTimeout" value="1"/>
<property name="minIdle" value="0"></property>
<property name="timeBetweenEvictionRunsMillis" value="1000"></property>
<property name="minEvictableIdleTimeMillis" value="1000"></property>
which forces the abandoned connections procedure to run and clean the old connections.
I shouldn't have to meddle with these parameters, and especially not be setting them so low as it might have performance issues.
I've also tried the solution shown here to the same effect until i change the timeBetweenEvictionRunsMillis and minEvictableIdleTimeMillis to the lower values. And it still doesn't limit the connections to 2.

All connections in the JdbcTemplate are via DataSourceUtils.doGetConnection. What you are seeing might be due to the 'intelligence' in BasicDataSource
From the API:
Abandonded connections are identified and removed when getConnection() is invoked and the following conditions hold:
getRemoveAbandoned() = true
getNumActive() > getMaxActive() - 3
getNumIdle() < 2
The data source seems to allow 3 more active connections than the specified max-active.

Hibernate and too many connections

I am working on web-project with Hibernate ans Spring MVC.
My hibernate configuration is:
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost/xxx</property>
<property name="connection.username">xxx</property>
<property name="connection.password">xxx</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">20</property>
<property name="hibernate.c3p0.timeout">1800</property>\<property name="hibernate.c3p0.max_statements">50</property>
<property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
<property name="connection.useUnicode">true</property>
<property name="connection.characterEncoding">UTF-8</property>
<property name="current_session_context_class">thread</property>
<property name="show_sql">true</property>
The hibernate sessions are closing in service-classes destructors (these service-classes have DAO objects). But after publishing at production server I've got too many connections exception from mysql.Every server call, the mysql connection was opened. When the connections amount become 101 - db failed. I think that destructors had not time enought for executes so the connections were opened all the time.
Then, I rebuilded the structure. Now, the Spring controllers call the service-class function, that releases the session mannualy. But it doesn't help: the connections are still opened and now I can not use LAZY-collections in views because the session already closed.
How can I solve that problem? What is the usual approach here?
Thank you.

How to avoid stale MySQL/Hibernate connections (MySQLNonTransientConnectionException)

I have a Java webapp using Hibernate and MySQL. If the site isn't used for a few days, the MySQL connection goes stale, and I am met with the following exception:
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Connection.close() has already been called. Invalid operation in this state.
From experience using raw JDBC it is possible to configure the connection to attempt to recover from errors or stale connections, but I don't know how to do this using Hibernate. I am not explicitly calling close() anywhere (but I am betting Hibernate does somewhere deep down in its guts).
Does anybody know what I should do?

What connection pool are you using?
The Hibernate suggestion is not to use the built-in pooling, but use the application server datasource or something like Commons DBCP or C3PO.

I had that problem. Using connection pooling (c3p0) made it go away. It is also a good idea in general to use some connection pooling.

Thanks for the advice. For posterity's sake, I changed the hibernate.cfg.xml from the following:
<property name="connection.url">jdbc:mysql://localhost/FooDB</property>
<property name="connection.username">root</property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="connection.password">secret</property>
<property name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
... to the following:
<property name="connection.datasource">java:/comp/env/jdbc/FooDB</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
This also required adding a standard 'context' entry in my web app's context.xml:
<Resource name="jdbc/FooDB"
auth="Container"
type="javax.sql.DataSource"
maxActive="100"
maxIdle="30"
maxWait="10000"
username="root"
password="secret"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/ss?autoReconnect=true" />

We had a similar problem of hibernate mysql connection getting timed out.
So we tried C3P0, with the following configuration:
<property name=c3p0.acquire_increment>1</property>
<property name=c3p0.idle_test_period>3600</property>
<property name=c3p0.max_statements>0</property>
<property name=c3p0.min_size>1</property>
<property name=c3p0.timeout>3605</property>
<property name=hibernate.c3p0.preferredTestQuery>select 1;</property>
Hibernate connection_pool size was set to 1.
This made the timeout problem go away. But we started facing another problem. Long waits.
We have a service (servlet running on jboss), which receives something like 5-6 requests per second. Every request needs to connect to mysql through hibernate. Most of our requests do selects, with an insert/update every 5th-6th request. Normally the request serve time for us is 2-3ms for select and 40-50ms for insert/update. But, after using the above C3P0 configuration, we saw that every request completing after an update was taking almost 4-5 minutes! From our logs, it seemed that randomly a select request will get stuck and will be able to complete only after an update request was received and served.
Above problem goes away if we remove the C3P0 config. Can somebody suggest what we could be doing wrong?
Here is the complete hibernate config for reference:
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://xxx.xxx.xxx</property>
<property name="connection.username">xxx</property>
<property name="connection.password">xxx</property>
<property name="connection.pool_size">1</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="current_session_context_class">thread</property>
<property name="hibernate.cache.use_query_cache">false</property>
<property name="hibernate.cache.use_second_level_cache">false</property>
<property name="show_sql">true</property>
<!-- Transaction isolation 2 = READ_COMMITTED -->
<property name="connection.isolation">2</property>
<property name="connection.autocommit">true</property>
<!-- configuration pool via c3p0-->
<property name="c3p0.acquire_increment">1</property>
<property name="c3p0.idle_test_period">3600</property> <!-- seconds -->
<property name="c3p0.max_size">1</property>
<property name="c3p0.max_statements">0</property>
<property name="c3p0.min_size">1</property>
<property name="c3p0.timeout">3605</property> <!-- seconds -->
<property name="hibernate.c3p0.preferredTestQuery">select 1;</property>
</session-factory>
</hibernate-configuration>

<property name="c3p0.acquire_increment">1</property>
<property name="c3p0.idle_test_period">120</property> <!-- seconds -->
<property name="c3p0.max_size">100</property>
<property name="c3p0.max_statements">0</property>
<property name="c3p0.min_size">10</property>
<property name="c3p0.timeout">180</property> <!-- seconds -->
override these settings on your config file. It ll helps to you.