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Is there anyways to control insert, update of the fields of persist objects at runtime??

Yes, there are attributes arround property tag in the HBM configuration file
those can be used appropriately for controlling various functionalities
arround the way insert/update of fields/properties of persistent objects.

Suppose there is a field such as EmployeeId from a Employee class file, can it is
desirable to have this id immutable, or should not added or inserted from the 
business logic, instead this ID will be updated by some SQL script that is 
being executed by some other legacy application. In this situation we will have to
inform Hibernate not to consider those fields marked with certain attribute
such as insert="false". Like wise we can instruct Hibernate not to update
certain fields/properties by putting update="false" attribute in the 
respective HBM configuration XML file.


Similarly there are ways to instruct Hibernate about whether to include fields
for those are modified or un-modified to be or not to be included as candidate
for insert/update operations associated with the respective object.

In HBM configuration file under class tag, we can have attributes like 
dynamic-insert="true" or dynamic-insert="false"
and dynamic-update="true" or dynamic-update="false".

I think these attributes are self-explainatory, for example dynamic-insert with
value as true will make Hibernate to include all un-modified properties also
in the insert SQL statement that is generated by Hibernate.

Like-wise dynamic-update="false" means Hibernate will not include un-modified
properties/fields during update SQL statement executed in database.

In order to try out these setting I have created following example :

SampleBean..java
package com.techienjoy.hibernate.example;

public class SampleBean {

    long id;
    String empId;
    String name;
    int age;
    String addrLine1;
    String addrLine2;
    String phone;
    
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getEmpId() {
        return empId;
    }
    public void setEmpId(String empId) {
        this.empId = empId;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getAddrLine1() {
        return addrLine1;
    }
    public void setAddrLine1(String addrLine1) {
        this.addrLine1 = addrLine1;
    }
    public String getAddrLine2() {
        return addrLine2;
    }
    public void setAddrLine2(String addrLine2) {
        this.addrLine2 = addrLine2;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
}


with corresponding HBM XML file as follows:
Example.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
   "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.techienjoy.hibernate.example">
   <class name="SampleBean" table="SAMPLE_BEAN">
    <id name="id" type="long" column="ID"/>
    <property name="empId" type="string" column="EMPID" insert="false"/>
    <property name="name" type="string" column="NAME"/>
    <property name="age" type="int" column="AGE"/>
    <property name="addrLine1" type="string" column="ADDRLINE1"/>
    <property name="addrLine2" type="string" column="ADDRLINE2"/> 
    <property name="phone" type="string" column="PHONE"/>               
   </class>

</hibernate-mapping>


And the Test harness code as follows:
Test.java
package com.techienjoy.hibernate.example;

/**
 * This code is provided on "AS IS" basis, without warranty
 * or guaranty of any kind.
 * Author : TechiEnjoy
 * Date: 28-November-2010
 */
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class Test {

    private static SessionFactory sessionFactory;

    /**
     * @param args
     */
    public static void main(String[] args) {

        try {
            sessionFactory = new Configuration().configure()
                    .buildSessionFactory();
            SampleBean a = new SampleBean();
            a.setId(1001);
            a.setEmpId("E001");
            a.setName("Johney Rieder");
            a.setAddrLine1("Address Line 2");
            a.setAddrLine2("Address Line 2");
            a.setAge(45);
            a.setPhone("333-333-3333");
            
            Session session = sessionFactory.openSession();
            Transaction tx = session.beginTransaction();
            tx.begin();
            session.saveOrUpdate(a);
            session.flush();
            tx.commit();
            session.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }

    }

}


SQL found on Eclipse console :
Hibernate: select samplebean_.ID, samplebean_.empId as empId0_, samplebean_.NAME 
as NAME0_, samplebean_.AGE as AGE0_, samplebean_.ADDRLINE1 as ADDRLINE5_0_, 
samplebean_.ADDRLINE2 as ADDRLINE6_0_, samplebean_.PHONE as PHONE0_ from SAMPLE_BEAN 
samplebean_ where samplebean_.ID=?
Hibernate: insert into SAMPLE_BEAN (NAME, AGE, ADDRLINE1, ADDRLINE2, PHONE, ID) 
values (?, ?, ?, ?, ?, ?)


As you might noticed in the above Example.hbm.xml file, property empId is configured
with a attribute as insert="false", this makes the final insert statement generated
and executed by Hibernate, not included EMPID column in it. So even after setting
a value for empId field in the test harness code, we can see null value for the corresponding
column EMPID in database table.

Like wise one can try puting dynamic-update="false" for a class tag and see the result
to know and understand how this configuration setting works.

SQL on console for the dynamic-update="false":
Hibernate: update SAMPLE_BEAN set EMPID=?, NAME=?, AGE=?, ADDRLINE1=?, ADDRLINE2=?, PHONE=? where ID=?

and SQL on console for the dynamic-update="true":
Hibernate: update SAMPLE_BEAN set ADDRLINE1=? where ID=?

Changed code for this to work as follows:
Example.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
   "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.techienjoy.hibernate.example">
   <class name="SampleBean" table="SAMPLE_BEAN" dynamic-update="true">
    <id name="id" type="long" column="ID"/>
    <property name="empId" type="string" column="EMPID" insert="false"/>
    <property name="name" type="string" column="NAME"/>
    <property name="age" type="int" column="AGE"/>
    <property name="addrLine1" type="string" column="ADDRLINE1"/>
    <property name="addrLine2" type="string" column="ADDRLINE2"/> 
    <property name="phone" type="string" column="PHONE"/>               
   </class>

</hibernate-mapping>


And 

Test.java
package com.techienjoy.hibernate.example;

/**
 * This code is provided on "AS IS" basis, without warranty
 * or guaranty of any kind.
 * Author : TechiEnjoy
 * Date: 28-November-2010
 */
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class Test {

    private static SessionFactory sessionFactory;

    /**
     * @param args
     */
    public static void main(String[] args) {

        try {
            sessionFactory = new Configuration().configure()
                    .buildSessionFactory();
            SampleBean a = new SampleBean();
            a.setId(1001);
            a.setEmpId("E001");
            a.setName("Johney Rieder");
            a.setAddrLine1("Address Line 2");
            a.setAddrLine2("Address Line 2");
            a.setAge(45);
            a.setPhone("333-333-3333");
            
            Session session = sessionFactory.openSession();
            Transaction tx = session.beginTransaction();
            tx.begin();
            session.saveOrUpdate(a);
            a.setAddrLine1("ADD1");
            session.saveOrUpdate(a);
            session.flush();
            tx.commit();
            session.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }

    }
}


Hope this helps.


If anything missed out , please let me know at
techienjoy at yahoo . com

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