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6.0

On simultaneous request "object references an unsaved transient instance" error problem

Asked by TheFACTORY_Max in Java Programming Language, Spring, J2EE Frameworks

Tags: hibernate, spring, struts, session, transient, unsaved

Hello experts,

I have yet another hibernate question, I have an application that works with hibernate + spring MVC + struts. The problem I am having is with, I think, the sessions and detached objects.

When I test the application with one user it works flawlessly, however I have now started some stress testing using JMeter which can simulate as many simultaneous visits as you want, while trying this with 10 simultaneous visits at the time it gives an hibernate error every now and then.
The error given on the page is the following:

javax.servlet.ServletException: org.springframework.dao.InvalidDataAccessApiUsageException: object references an unsaved transient instance - save the transient instance before flushing: com.GolfOnline.Beans.Course; nested exception is org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.GolfOnline.Beans.Course

The stack gives this as error:
object references an unsaved transient instance - save the transient instance before flushing: com.GolfOnline.Beans.Course

and refers to a very simple query in the GolferTypeDAO which goes wrong:
ArrayList results = (ArrayList)getHibernateTemplate().find("from GolferType where course = ? and title='Guest'", course);
(where course is a reference to a 'Course' object retrieved earlier in the same request)

As you can see I use the getHibernateTemplate helper class http://static.springframework.org/spring/docs/2.0.x/api/org/springframework/orm/hibernate/HibernateTemplate.html
The spring application context holds the SessionFactory and gives this to the available DAO's, where the getHibernateTemplate handles the sessions from.

I've searched the error and found many stories telling about the sessionfactory, sessions, transactions and different patterns (such as the session-per-request, session-per-request-with-detached-objects, session-per-conversation , open-session-in-view-pattern)

Firstly I am not exactly sure why it gives me this error, I think it is because in one request I retrieve a 'Course' object and in this same request I use this to retrieve a 'GolferType' object using an association to a 'Course' object. With many simultaneous requests at the same time the first retrieved 'Course' object becomes detached for some reason and can't be used again in a query then?
This is easily solved by using the ID's in the query but It does not feel good as this is more of a workaround instead of actually solving the problem (which probably will come back somewhere else)

Could you advise me on which way to go in order to solve the problem?
All relevant code is below and I will give any addition information if needed.

Thanks in advance,
Max

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             ------------------------------------------------------- applicationContext.xml
 
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
    
    <!-- Hibernate (persistence) -->
    
    <bean id="golfOnlineDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
         --censored--
</bean>
 
    <bean id="golfOnlineSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
        <property name="dataSource" ref="golfOnlineDataSource"/>
        <property name="mappingResources">
            <list>
                <value>com/GolfOnline/Hibernate/Course.hbm.xml</value>
                <value>com/GolfOnline/Hibernate/GolferType.hbm.xml</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.current_session_context_class">thread</prop>
                <prop key="hibernate.connection.pool_size">0</prop>
                <prop key="hibernate.dbcp.maxActive">15</prop>
                <prop key="hibernate.dbcp.maxIdle">5</prop>
                <prop key="hibernate.dbcp.maxWait">120000</prop>
                <prop key="hibernate.dbcp.whenExhaustedAction">1</prop>
                <prop key="hibernate.dbcp.testOnBorrow">true</prop>
                <prop key="hibernate.dbcp.testOnReturn">true</prop>
                <prop key="hibernate.dbcp.validationQuery">--censored--</prop>
                <prop key="hibernate.dbcp.ps.maxActive">0</prop>
                <prop key="hibernate.dbcp.ps.maxIdle">0</prop>
                <prop key="hibernate.dbcp.ps.maxWait">-1</prop>
                <prop key="hibernate.dbcp.ps.whenExhaustedAction">2</prop>
            </props>
        </property>
    </bean>
    
    <bean id="golfOnlineTransactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="sessionFactory">
            <ref local="golfOnlineSessionFactory"/>
        </property>
    </bean>
    
    <!-- Service objects -->
    <bean id="courseService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">	
        <property name="transactionManager"><ref local="golfOnlineTransactionManager"/></property>
        <property name="target"><ref local="courseServiceTarget"/></property>
        <property name="transactionAttributes">
            <props>
                <prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
                <prop key="search*">PROPAGATION_REQUIRED,readOnly</prop>
                <prop key="check*">PROPAGATION_REQUIRED,readOnly</prop>
                <prop key="add*">PROPAGATION_REQUIRED</prop>
                <prop key="update*">PROPAGATION_REQUIRED</prop>
                <prop key="delete*">PROPAGATION_REQUIRED</prop>
            </props>
        </property>
    </bean>
    
    <!-- Service target objects -->
    <bean id="courseServiceTarget" class="com.GolfOnline.Services.CourseServiceImpl">
        <property name="courseDAO"><ref local="courseDAO"/></property>
        <property name="golferTypeDAO"><ref local="golferTypeDAO"/></property>
    </bean>
    
    <!-- DAO objects -->
    <bean id="courseDAO" class="com.GolfOnline.DAOs.CourseDAOImpl">
        <property name="sessionFactory" ref="golfOnlineSessionFactory"/>
    </bean>
    <bean id="golferTypeDAO" class="com.GolfOnline.DAOs.GolferTypeDAOImpl">
        <property name="sessionFactory" ref="golfOnlineSessionFactory"/>
    </bean>
    
</beans>
 
------------------------------------------------------- course.hbm
 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
  <class name="com.GolfOnline.Beans.Course" table="tbl_Course">
    <id column="cr_ID" name="id" type="short">
      <generator class="native"/>
    </id>
    <property column="cr_Name" name="name"/>
  </class>
</hibernate-mapping>
 
------------------------------------------------------- golfertype.hbm
 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
  <class name="com.GolfOnline.Beans.GolferType" table="tbl_GolferType">
    <id column="gt_ID" name="id" type="short">
      <generator class="native"/>
    </id>
    <many-to-one class="com.GolfOnline.Beans.Course" column="gt_Course_cr_ID" name="course"/>
    <property column="gt_Title" name="title"/>
  </class>
</hibernate-mapping>

           
         

20091021-EE-VQP-81 - Hierarchy / EE_QW_3_20080625

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On simultaneous request "object references an unsaved transient instance" error problem

Asked by TheFACTORY_Max in Java Programming Language, Spring, J2EE Frameworks

Tags: hibernate, spring, struts, session, transient, unsaved

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