EclipseLink-4021 - Unable to acquire a connection from driver - mysql

Question

I often get an exception EclipseLink-4021 "Unable to acquire a connection from driver [null], user [null] and URL [null]" when my application start.
This mean that Eclipselink doesn't find persistence.xml defined to connect to MySQL.
My persistence.xml is in folder /WEB-INF/classes, I think this is the standard place.
When I start tomcat again and again it finally work.
When anything run well, I get this log.
[EL Info]: 2016-07-01 11:22:55.268--ServerSession(975412652)--EclipseLink, version: Eclipse Persistence Services - 2.6.3.v20160428-59c81c5
[EL Info]: connection: 2016-07-01 11:22:56.794--ServerSession(975412652)--/file:/D:/Workspace_Eclipse/xxxWebapp/target/classes/_db1 login successful
I think this could come from my WebApp's architecture but I don't understand what is going wrong.
My WebApp is develop with Java 8, ZK 8, EclipseLink 2.6.3, MySQL 5.7.10
At the init a HttpServlet (GlobalEnvProperties.java) is called to prepare things like connections to other database and quartz scheduler.
web.xml complete content :
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:web="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_4.xsd"
version="2.4">
<description>app</description>
<display-name>Webapp</display-name>
<servlet>
<description>ZK loader for ZUML pages</description>
<servlet-name>zkLoader</servlet-name>
<servlet-class>org.zkoss.zk.ui.http.DHtmlLayoutServlet</servlet-class>
<init-param>
<param-name>update-uri</param-name>
<param-value>/zkau</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>zkLoader</servlet-name>
<url-pattern>*.zul</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>zkLoader</servlet-name>
<url-pattern>*.zhtml</url-pattern>
</servlet-mapping>
<servlet>
<description>The asynchronous update engine for ZK</description>
<servlet-name>auEngine</servlet-name>
<servlet-class>org.zkoss.zk.au.http.DHtmlUpdateServlet</servlet-class>
<load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>auEngine</servlet-name>
<url-pattern>/zkau/*</url-pattern>
</servlet-mapping>
<listener>
<description>ZK listener for session cleanup</description>
<listener-class>org.zkoss.zk.ui.http.HttpSessionListener</listener-class>
</listener>
<session-config>
<session-timeout>14400</session-timeout>
</session-config>
<servlet>
<description>Gestion des environnements</description>
<servlet-name>GlobalEnvProperties</servlet-name>
<servlet-class>com.company.app.webapp.common.GlobalEnvProperties</servlet-class>
<load-on-startup>3</load-on-startup>
</servlet>
<mime-mapping>
<extension>doc</extension>
<mime-type>application/vnd.ms-word</mime-type>
</mime-mapping>
<mime-mapping>
<extension>gif</extension>
<mime-type>image/gif</mime-type>
</mime-mapping>
<mime-mapping>
<extension>htm</extension>
<mime-type>text/html</mime-type>
</mime-mapping>
<mime-mapping>
<extension>html</extension>
<mime-type>text/html</mime-type>
</mime-mapping>
<mime-mapping>
<extension>jpeg</extension>
<mime-type>image/jpeg</mime-type>
</mime-mapping>
<mime-mapping>
<extension>jpg</extension>
<mime-type>image/jpeg</mime-type>
</mime-mapping>
<mime-mapping>
<extension>js</extension>
<mime-type>text/javascript</mime-type>
</mime-mapping>
<mime-mapping>
<extension>pdf</extension>
<mime-type>application/pdf</mime-type>
</mime-mapping>
<mime-mapping>
<extension>png</extension>
<mime-type>image/png</mime-type>
</mime-mapping>
<mime-mapping>
<extension>txt</extension>
<mime-type>text/plain</mime-type>
</mime-mapping>
<mime-mapping>
<extension>xls</extension>
<mime-type>application/vnd.ms-excel</mime-type>
</mime-mapping>
<mime-mapping>
<extension>xml</extension>
<mime-type>text/xml</mime-type>
</mime-mapping>
<mime-mapping>
<extension>zhtml</extension>
<mime-type>text/html</mime-type>
</mime-mapping>
<mime-mapping>
<extension>zul</extension>
<mime-type>text/html</mime-type>
</mime-mapping>
<welcome-file-list>
<welcome-file>auth.zul</welcome-file>
</welcome-file-list>
</web-app>
In the init void of the servlet GlobalEnvProperties, I get EntityManager with Persistence.createEntityManagerFactory("db1")
public void init() throws ServletException {
bddFactories = new HashMap<String, EntityManagerFactory>();
entityManagers = new HashMap<String, EntityManager>();
//global properties
configProp = new Properties();
InputStream ficProperties = Thread.currentThread().getContextClassLoader().getResourceAsStream("META-INF/app.properties");
try {
configProp.load(new InputStreamReader(ficProperties, "UTF-8"));
} catch (IOException e) {
CustomLogger.info("Unable to open properties file");
CustomLogger.tracerErreurFatale(e);
}
/*
* BDD connection
*/
// Base db1
try {
final int sleepChargementPersitence = 10000;
Thread.sleep(sleepChargementPersitence);
bddFactories.put("db1", Persistence.createEntityManagerFactory("db1"));
} catch (javax.persistence.PersistenceException | DatabaseException e) {
CustomLogger.info("Unable to connect db1");
CustomLogger.tracerErreurFatale(e);
} catch (InterruptedException e) {
CustomLogger.info("Sleep failed");
}
OtherConnectionsLoad();
//scheduler
try {
CustomLogger.debug("Scheduler start");
DailyTreatmentScheduler.main(null);
} catch (Exception ex) {
ex.printStackTrace();
}
}
My persistence.xml content :
?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="db1">
<class>com.company.app.model.Action</class>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<shared-cache-mode>NONE</shared-cache-mode>
<properties>
<property name="javax.persistence.jdbc.user" value="root" />
<property name="javax.persistence.jdbc.password" value="*******" />
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url"
value="jdbc:mysql://server:3306/db1?useSSL=false" />
<property name="eclipselink.deploy-on-startup" value="true" />
<property name="javax.persistence.jdbc.initialSize" value="2" />
<property name="javax.persistence.jdbc.maxActive" value="10" />
<property name="javax.persistence.logging.level" value="INFO" />
<property name="eclipselink.query-results-cache" value="false" />
<property name="javax.persistence.refresh" value="true" />
</properties>
</persistence-unit>
</persistence>
I hope someone could explain where I'm wrong.
Thanks for those who will try to understand my problem.