org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session

Exception: 

com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Access denied for user ''@'localhost' to database 'school' at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2985) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:885) at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:3421) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1247) at com.mysql.jdbc.Connection.createNewIO(Connection.java:2775) at com.mysql.jdbc.Connection.(Connection.java:1555) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) at java.sql.DriverManager.getConnection(DriverManager.java:582) at java.sql.DriverManager.getConnection(DriverManager.java:154)...

Reason  : 

1. you are passing transient object instead of persistent object for delete

Possible solution : 

1. Pass persistent object instead of transient object.

For example :

you would be trying something like this.Here studentToDelete is transient.

    public void deleteStudent(Student studentToDelete)
    {
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();
        // Here studentToDelete is transient object
        session.delete(studentToDelete);
        session.getTransaction().commit();
        session.flush();
    }

We will remove persisted object and pass to delete function like below one.

    public void deleteStudentA(Student studentToDelete)
    {
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();
        // Getting persisted object of Student.
        Student persistentStudent = (Student) session.get(Student.class, studentToDelete.getId());
        session.delete(persistentStudent);
        session.getTransaction().commit();
        session.flush();
    }

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javax.servlet.jsp.JspException: Cannot find message resources under key org.apache.struts.action.MESSAGE

Exception: 

javax.servlet.jsp.JspException: Cannot find message resources under key org.apache.struts.action.MESSAGE at org.apache.struts.taglib.TagUtils.retrieveMessageResources(TagUtils.java:1189) at org.apache.struts.taglib.TagUtils.message(TagUtils.java:1038) at org.apache.struts.taglib.TagUtils.message(TagUtils.java:1013) at org.apache.struts.taglib.bean.WriteTag.retrieveFormatString(WriteTag.java:254) at org.apache.struts.taglib.bean.WriteTag.formatValue(WriteTag.java:317) at org.apache.struts.taglib.bean.WriteTag.doStartTag(WriteTag.java:232)...

Reason  : 

1. you have not included properties file in  resource stuts config file.

Possible solution : 

1. Define a property file and add in resources of struts-config.xml.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts-config PUBLIC 
"-//Apache Software Foundation//DTD Struts Configuration 1.3//EN" 
"http://jakarta.apache.org/struts/dtds/struts-config_1_3.dtd">
 
<struts-config>
 
    <message-resources
        parameter="com.test.common.properties.person" />
 
</struts-config>

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com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Access denied for user ''@'localhost' to database 'school'

Exception: 

java.lang.ClassNotFoundException: javax.transaction.Synchronization at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233) at org.hibernate.impl.SessionImpl.(SessionImpl.java:248) at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:627) at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:651) at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:659)...

Reason  : 

you have not included jta.jar 

Possible solution : 

1. Download jta.jar from http://mvnrepository.com/artifact/javax.transaction/jta
   and include it in library.

    2. For maven user, Include  jta in pom.xml

        

<dependency>
    <groupId>javax.transaction</groupId>
    <artifactId>jta</artifactId>
    <version>1.1</version>
</dependency>

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java.lang.ClassNotFoundException: javax.transaction.Synchronization

Exception: 

com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Access denied for user ''@'localhost' to database 'school' at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2985) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:885) at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:3421) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1247) at com.mysql.jdbc.Connection.createNewIO(Connection.java:2775) at com.mysql.jdbc.Connection.(Connection.java:1555) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) at java.sql.DriverManager.getConnection(DriverManager.java:582) at java.sql.DriverManager.getConnection(DriverManager.java:154)...

Reason  : 

1. your username and password are incorrect
2. your username does not have enough privilege on database
3. you might be trying to access wrong database.

Possible solution : 

1. Check your username and password
2. Check privilege assigned to your username or role from which you are trying to access database.you might not be granted permission to access the database
3. Check the database you are trying to access.you might be trying to access wrong database.

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java.lang.ClassNotFoundException: javassist.util.proxy.MethodFilter

Exception: 

java.lang.ClassNotFoundException: javassist.util.proxy.MethodFilter at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233) at org.hibernate.bytecode.javassist.BytecodeProviderImpl.getProxyFactoryFactory(BytecodeProviderImpl.java:49) at org.hibernate.tuple.entity.PojoEntityTuplizer.buildProxyFactoryInternal(PojoEntityTuplizer.java:207) at org.hibernate.tuple.entity.PojoEntityTuplizer.buildProxyFactory(PojoEntityTuplizer.java:185)...

Reason  : 

you have not included javassist.jar 

Possible solution : 

1. Download javassist.jar from http://www.csg.is.titech.ac.jp/~chiba/javassist and include it in library.

    2 . For maven user, Include javassist in pom.xml

        

<dependency>
    <groupId>javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>3.12.1.GA</version>
</dependency>

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