Mapping Classes with Relational Databases

Java/J2EE Programming Training
Mapping Classes With Relational Databases

Classification: Restricted
Agenda
• Mapping Properties
• Entity Type Vs ValueTypes
• Mapping Collections
• Relationship in hibernate
• One-To-One
• One-To-One Mapping
• One-To-Many
• Many-to-Many

Mapping Properties
Employee
int employee_id;
String first_name
String last_name
Employee
employee_id integer primary key
first_name varchar2( 200 )
last_name varchar2( 200)
EMPLOYEES
employee_id first_name last_name
100 John Mike
101 Fay Lorentz

Hibernate Types
apping type Java type ANSI SQL Type
integer int or java.lang.Integer INTEGER
long long or java.lang.Long BIGINT
short short or java.lang.Short SMALLINT
float float or java.lang.Float FLOAT
double double or java.lang.Double DOUBLE
big_decimal java.math.BigDecimal NUMERIC
character java.lang.String CHAR(1)
string java.lang.String VARCHAR
byte byte or java.lang.Byte TINYINT
boolean boolean or java.lang.Boolean BIT
yes/no boolean or java.lang.Boolean CHAR(1) ('Y' or 'N')
true/false boolean or java.lang.Boolean CHAR(1) ('T' or 'F')

Entity Type Vs ValueTypes
• Entity Type
• is an independent entity and has its own identity.
• has primary key
• can be referenced by other entity
• Value type
• does not have its entity depends on another object for its existence
Employee
int employee_id
String first_name
String last_name
Address
String street;
String city;

<class table=“EMPLOYEE”>
<id name=“employee_id” type=“integer”>
<column name=“employee_id”/>
<generator class=“assigned”/>
</id>
<property name=“first_name”/>
<property name=“last_name”/>
<component name=“address” class=“Address”>
<property name=“street”/>
<property name=“city”/>
</componenet>Employee
int employee_id
String first_name
String last_name
Address address
Address
String street;
String city;

Mapping Collections
• <Set>
• <List>
• <bag>
• <map>

LIST
Employee
int employee_id
String first_name
String last_name
List<Skills> skillSet
Skills
int skill_id
String skill_name
String level_name1
*

Employee
int employee_id
String first_name
String last_name
Skills
int skill_id
String skill_name
String level_name1
*
<class table=“Employee”>
<id name=“employee_id”>
<key column=“employee_id”/>
</id>
<set name=“skills cascade=“all”>
<key column=“skill_id”/>
<one-to-many class=“Skills”/>
<class name=“Skills” table=“SKILLS”>
<id name=“skill_id”>
<column name=“skill_id”/>
</id>
<property name=“skill_name”/>
<property name=“level_name”/>
</class>
</class>
SET

Employee
int employee_id
String first_name
String last_name
Skills
int skill_id
String skill_name
String level_name1
*
</id>
<list name=“skills cascade=“all”>
<list-index column=“index_position”/>
</id>
</class>
</class>
LIST

employee_id skill_id last_name

Relationship in hibernate
• One-to-one
• one-to-many
• many-to-many

One-To-One
package model;
public class Employee {
private int employee_id;
private String first_name;
private String last_name;
Department department;
//setters and getters
}
public class Department {
private int department_id;
private String department_name;
private int location_id;
private Employee employee;
}

One-To-One Mapping
<id name="employee_id" type="integer">
<column name="EMPLOYEE_ID"/>
<generator class="native"/>
</id>
<property name="first_name" type="string">
<column name="FIRST_NAME" not-null="true"/>
</property>
<property name="last_name" type="string">
<column name="LAST_NAME" not-null="false"/>
</property>
<one-to-one name="department" cascade="all"
class="model.Department"/>
• emp.hbm.xml
• department.hbm.xml
<id name="department_id" type="integer">
<column name="DEPARTMENT_ID"/>
<generator class="foreign">
<param name="property">employee</param>
</generator>
</id>
<one-to-one name="employee"
class="model.Employee" constrained="true"/>
<property name="department_name"
type="string">
<column name="DEPARTMENT_NAME"/>
</property>

One-To-Many
package model;
public class Employee {
private int employee_id;
private String first_name;
private String last_name;
Set <Skills> skills;
}
package model;
public class Skills{
private int skill_id
private String skill_name;
private String level_name
}

One-To-Many
100 John Mike
employee_id skill_id skill_name level_name
100 1 Java Expert
100 2 C# Intermediate
100 3 WCD Expert

One-To-Many
</id>
<list name=“skills cascade=“all”>
<list-index column=“index_position”/>
</id>
</class>
</class>
Employee
int employee_id
String first_name
String last_name
Skills
int skill_id
String skill_name
String level_name

Many-to-Many
Student
Student_id int
primary key
first_name
varchar2( 20 )
Course
course_id int primary key
cours_name varchar2( 20 )
duration int
Student_COURSE
student_id int
course_id int

Many-To-Many
Student_id Student_name
100 John
course_id course_name
C1 Java
c2 C#
c3 HTML
student_id course_id
100 c1
100 c2
100 c3

<id name="student_id" type="integer">
<column name="STUDENT_ID"/>
</id>
<property name="first_name" type="string">
<column name="FIRST_NAME"/>
</property>
<set name="courses" cascade="all"
table="STUDENT_COURSE">
<key column="STUDENT_ID"/>
<many-to-many class="model.Courses"
column="course_id"/>
</set>
• student.hbm.xml • courses.hbm.xml
<id name="course_id" type="integer">
<column name="COURSE_ID" />
</id>
<property name="courseName"
type="string">
<column name="COURSE_NAME"/>
</property>
<property name="duration" type="integer">
<column name="DURATION"/>
</property>

Employees
int employee_id
String first_name
String last_name
Address
String city
String street
Employmet_History
int employee_id
Date start_date
Date end_Date
String jobRole

Thank You

Mapping Classes with Relational Databases

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