Hibernate Entity manager auto flush before query and commit changes to DB in transaction
Solution 1
Problem resolved.
The cause is that tables in the mysql is using MyISAM
engine by default and tables using this engine do not support transaction.
Switching tables to innoDB
make thing works.
Hope this would be useful for anyone, so they will not waste as much time as I did. :(
Solution 2
What is set as the entityManager FlushModeType
void setFlushMode(FlushModeType flushMode)
Set the flush mode that applies to all objects contained in the persistence context.
The method takes a enum defined here.
Enum Constant Summary
AUTO
(Default) Flushing to occur at query execution.
COMMIT
Flushing to occur at transaction commit.
Also try checking the following
@PersistenceContext(unitName="MyEJB") private EntityManager em
after you declare the Entity manager factory.
Quincy
Updated on June 04, 2022Comments
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Quincy almost 2 years
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.
The Database is mySql.
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.
EJB
@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(); } } }
persistence.xml
<?xml version="1.0" encoding="UTF-8"?> <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"> <persistence-unit name="MyEjb" transaction-type="JTA"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jta-data-source>java:MyDS</jta-data-source> <class>com.quincy.entity.MyLine</class> <properties> <property name="hibernate.connection.defaultNChar" value="true"/> <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLMyISAMDialect"/> <property name="hibernate.ejb.cfgfile" value="META-INF/hibernate.cfg.xml"/> </properties> </persistence-unit> </persistence>
hibernate.cfg.xml
<?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="transaction.manager_lookup_class">org.hibernate.transaction.JBossTransactionManagerLookup</property> <!-- Echo all executed SQL to stdout --> <property name="show_sql">true</property> <property name="hibernate.max_fetch_depth">3</property> </session-factory> </hibernate-configuration>
mysql-ds.xml
<datasources> <local-tx-datasource> <jndi-name>MyDS</jndi-name> <connection-url>jdbc:mysql://10.10.150.57:3306/myds</connection-url> <driver-class>com.mysql.jdbc.Driver</driver-class> <user-name>user</user-name> <password>pwd</password> <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name> <metadata> <type-mapping>mySQL</type-mapping> </metadata> </local-tx-datasource> </datasources>
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.
It seems to me that the db is auto-commited. I have tried to set the property
hibernate.connection.autocommit
tofalse
but the problem just persist and a EJB warning of violating spec is prompted.UPDATE: The cause should come from mysql. As if I switch to mssql server, the problem goes away.I also tried mysql with
xa-datasource
, still no luck... -
Luke almost 13 years
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Quincy almost 13 yearsIf I set the flush mode to COMMIT, the flush wouldn't happen. However, the query returns stale data. The problem right now is the flush is committing changes to DB directly. It is supposed to only flush the changes to DB but not commit.
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Luke almost 13 yearsCan't you execute the query (with data in sync) first, then make your change to the particular line and then commit?
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Quincy almost 13 yearsNo. During the query process, there's some kind of checking and may result in failure. I want the changes to rollback in this case. In my understanding, even flush mode is set to AUTO, the changes would only be flushed to be visible to other queries but not directly committed to the DB. So I was wondering if I had done anything wrong with my config. (This is my first time to use JPA API, I was using native hibernate before)
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Quincy almost 13 yearsUpon further investigating, I found out that when ever there's a flush, the dirty changes are written and committed to DB directly. It seems that the em is not really binding to a transaction. However, I still cannot work it out. :/
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Luke almost 13 yearsI'm not 100 % sure what you're trying to acheive so can't really suggest a code solution.
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Quincy almost 13 yearsTo simply the problem, is that doing flush() in my case will directly commit changes to db, which is kind of breaking the transaction. And I believe this is not the expected behaviour and look for a solution.
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mmey over 10 yearsWorked for me as well. To see current engine, use show table status;. To change the engine for a table, use alter table table_name engine=InnoDB;