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POHibernate Entity manager auto flush before query and commit changes to DB in transaction
 

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    <p>I am using Hibernate 3.6.0 with JPA 2 on Jboss AS 6.0.0 final. In an EJB of mine, there's a method which updated entity values and do some query on it. The whole method is running in a BMT transaction. If anything fails, all changes should be rollback and not committed to DB.</p> <p>The Database is mySql.</p> <p>Before running JPA query, JPA will auto flush the changed states to DB to prevent any stale data from returning. However, within my method, the auto-flush directly update and commits the changes to DB and even something went wrong afterwards, the changes are not rollback. So I would like to ask if there's wrong configuration in my set up or this is a bug or something.</p> <p>EJB</p> <pre><code>@Stateless(mappedName = "MyManagementBean") @Local @TransactionManagement(TransactionManagementType.BEAN) public class MyManagement implements MyManagementLocal,MyManagementRemote { @PersistenceUnit(unitName="MyEjb") EntityManagerFactory emf; @Resource UserTransaction utx; @Resource SessionContext ctx; /** * Default constructor. */ public MyManagement () { // TODO Auto-generated constructor stub } public void dosomething(String id) throws Exception { try { utx.begin(); em = emf.createEntityManager(); Myline line = em.find(Myline.class, id); line.setStatus("R"); Stromg q += " from Myline as line "; //auto flush apply here and directly committed to DB... Iterator iter = em.createQuery(q).getResultList().iterator(); em.flush(); utx.commit();// changes should only commit after this } catch (Exception e) { e.printStackTrace(); if (utx != null) utx.rollback(); throw e; // or display error message } finally { em.close(); } } } </code></pre> <p>persistence.xml</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"&gt; &lt;persistence-unit name="MyEjb" transaction-type="JTA"&gt; &lt;provider&gt;org.hibernate.ejb.HibernatePersistence&lt;/provider&gt; &lt;jta-data-source&gt;java:MyDS&lt;/jta-data-source&gt; &lt;class&gt;com.quincy.entity.MyLine&lt;/class&gt; &lt;properties&gt; &lt;property name="hibernate.connection.defaultNChar" value="true"/&gt; &lt;property name="hibernate.dialect" value="org.hibernate.dialect.MySQLMyISAMDialect"/&gt; &lt;property name="hibernate.ejb.cfgfile" value="META-INF/hibernate.cfg.xml"/&gt; &lt;/properties&gt; &lt;/persistence-unit&gt; &lt;/persistence&gt; </code></pre> <p>hibernate.cfg.xml</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"&gt; &lt;hibernate-configuration&gt; &lt;session-factory&gt; &lt;property name="transaction.manager_lookup_class"&gt;org.hibernate.transaction.JBossTransactionManagerLookup&lt;/property&gt; &lt;!-- Echo all executed SQL to stdout --&gt; &lt;property name="show_sql"&gt;true&lt;/property&gt; &lt;property name="hibernate.max_fetch_depth"&gt;3&lt;/property&gt; &lt;/session-factory&gt; &lt;/hibernate-configuration&gt; </code></pre> <p>mysql-ds.xml</p> <pre><code>&lt;datasources&gt; &lt;local-tx-datasource&gt; &lt;jndi-name&gt;MyDS&lt;/jndi-name&gt; &lt;connection-url&gt;jdbc:mysql://10.10.150.57:3306/myds&lt;/connection-url&gt; &lt;driver-class&gt;com.mysql.jdbc.Driver&lt;/driver-class&gt; &lt;user-name&gt;user&lt;/user-name&gt; &lt;password&gt;pwd&lt;/password&gt; &lt;exception-sorter-class-name&gt;org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter&lt;/exception-sorter-class-name&gt; &lt;metadata&gt; &lt;type-mapping&gt;mySQL&lt;/type-mapping&gt; &lt;/metadata&gt; &lt;/local-tx-datasource&gt; &lt;/datasources&gt; </code></pre> <p>Upon further investigating, I found out that when ever there's a flush, the dirty changes are written and committed to DB directly. If I remove the flush(), everything works fine. However, there are system triggered flush before query and I think it's necessary.</p> <p>It seems to me that the db is auto-commited. I have tried to set the property <code>hibernate.connection.autocommit</code> to <code>false</code> but the problem just persist and a EJB warning of violating spec is prompted.</p> <p><strong>UPDATE:</strong> The cause should come from mysql. As if I switch to mssql server, the problem goes away.I also tried mysql with <code>xa-datasource</code> , still no luck...</p>
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    1. COSince you are using JTA, what's the datasource configuration for the mySQL database? In particular, you need to use the XA driver for mySQL for transaction enlistment to work.
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    2. CO@Clement P: Thanks for the reply. I have updated to include the jdbc setting as well. Mysql version is 5.0 and I am using mysql-connector-java-5.1.13
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