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JavaInterviewPoint

Java Development Tutorials

Hibernate Component Mapping using XML

April 11, 2017 by javainterviewpoint Leave a Comment

Previously we have learned about Component Mapping in Hibernate using Annotations. In this example, we will learn about Hibernate Component Mapping using XML. In our example, we have two classes Employee and EmployeeAddress. The Employee can have an Address but Address cannot exist separately without Employee. Since the Employee and Address entities are strongly related, it is better to store them in a single table using component mapping(<component> tag).

Creating table

Create EMPLOYEE Table, simply Copy and Paste the following SQL query in the query editor to get the table created.

CREATE TABLE "EMPLOYEE" 
 (
    "EMP_ID" NUMBER(10,0) NOT NULL ENABLE, 
    "EMP_NAME" VARCHAR2(255 CHAR), 
    "DEPARTMENT" VARCHAR2(255 CHAR), 
    "STREET" VARCHAR2(255 CHAR), 
    "CITY" VARCHAR2(255 CHAR), 
    "STATE" VARCHAR2(255 CHAR), 
    PRIMARY KEY(EMP_ID)
 );

Folder Structure:

Hibernate Component Mapping using XML

  1. Create a simple Maven Project “HibernateTutorial” and create a package for our source files “com.javainterviewpoint” under  src/main/java 
  2. Now add the following dependency in the POM.xml
     <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0	http://maven.apache.org/xsd/maven-4.0.0.xsd">
       <modelVersion>4.0.0</modelVersion>
       <groupId>HibernateTutorial</groupId>
       <artifactId>HibernateTutorial</artifactId>
       <version>0.0.1-SNAPSHOT</version>
       <properties>
          <hibernate.version>4.3.11.Final</hibernate.version>
          <oracle.connector.version>11.2.0</oracle.connector.version>
       </properties>
    
       <dependencies>
         <!-- Hibernate -->
         <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>${hibernate.version}</version>
         </dependency>
    
         <!-- Oracle -->
         <dependency>
            <groupId>com.oracle</groupId>
            <artifactId>ojdbc14</artifactId>
            <version>${oracle.connector.version}</version>
         </dependency>
       </dependencies>
       <build>
         <sourceDirectory>src</sourceDirectory>
         <plugins>
           <plugin>
             <artifactId>maven-compiler-plugin</artifactId>
             <version>3.3</version>
             <configuration>
             <source>1.7</source>
             <target>1.7</target>
             </configuration>
           </plugin>
         </plugins>
       </build>
     </project>
  3. Create the Java classes Employee.java, EmployeeAddress.java and ComponentMapping.java under  com.javainterviewpoint folder.
  4. Place the hibernate.cfg.xml and employee.hbm.xml under the src/main/resources  directory

Other interesting articles which you may like …

  • Hibernate Hello World Example in Eclipse (XML Mapping)
  • Hibernate Hello World Example in Eclipse (Annotation)
  • Hibernate One To One Bidirectional Mapping XML Example with Primary Key
  • Hibernate One To One Mapping XML Example with Foreign Key
  • Hibernate One To Many Mapping XML Example
  • Hibernate Many To Many Mapping Example – XML Mapping
  • Hibernate One To One Bidirectional Mapping – Primary Key(Annotation)
  • Hibernate One To One Bidirectional Mapping Example – Foreign Key(Annotation)
  • Hibernate One To Many Mapping Example Using Annotation
  • Hibernate Many To Many Mapping Example – Annotation
  • Hibernate CRUD Example in Eclipse (XML Mapping) with Maven + Oracle
  • Hibernate Inheritance – Table Per Class Hierarchy (XML Mapping & Annotation)
  • Hibernate Inheritance – Table Per Subclass Hierarchy (XML Mapping & Annotation)
  • Hibernate Inheritance – Table Per Concrete Class Hierarchy Example(XML Mapping & Annotation)
  • Hibernate Composite Primary Key Tutorial – Using composite-id tag & Annotations
  • Hibernate Embeddable Composite Primary Key | @Embeddable, @EmbeddedId
  • Difference between session.get() and session.load() in Hibernate

Hibernate Component Mapping using XML

EmployeeAddress.java

package com.javainterviewpoint;

import java.io.Serializable;

public class EmployeeAddress implements Serializable
{
    private static final long serialVersionUID = 1L;
    
    private String street;
    private String city;
    private String state;
    
    public EmployeeAddress()
    {
        super();
    }
    
    public EmployeeAddress(String street, String city, String state)
    {
        super();
        this.street = street;
        this.city = city;
        this.state = state;
    }

    public String getStreet()
    {
        return street;
    }
    public void setStreet(String street)
    {
        this.street = street;
    }
    public String getCity()
    {
        return city;
    }
    public void setCity(String city)
    {
        this.city = city;
    }
    public String getState()
    {
        return state;
    }
    public void setState(String state)
    {
        this.state = state;
    }

    @Override
    public String toString()
    {
        return "Employee_Address [street=" + street + ", city=" + city + ", state=" + state + "]";
    }
}

Our EmployeeAddress class is a simple POJO class consisting of the getters and setters for the EmployeeAddress class properties (street, city, state).

Employee.java

package com.javainterviewpoint;

import java.io.Serializable;

public class Employee implements Serializable
{
    private static final long serialVersionUID = 1L;
    
    private int id;
    private String name;
    
    private EmployeeAddress employeeAddress;

    public Employee()
    {
        super();
    }
    public Employee(int id, String name, EmployeeAddress employeeAddress)
    {
        super();
        this.id = id;
        this.name = name;
        this.employeeAddress = employeeAddress;
    }

    public int getId()
    {
        return id;
    }
    public void setId(int id)
    {
        this.id = id;
    }
    public String getName()
    {
        return name;
    }
    public void setName(String name)
    {
        this.name = name;
    }
    public EmployeeAddress getEmployeeAddress()
    {
        return employeeAddress;
    }
    public void setEmployeeAddress(EmployeeAddress employeeAddress)
    {
        this.employeeAddress = employeeAddress;
    }

    @Override
    public String toString()
    {
        return "Employee [id=" + id + ", name=" + name + ", employeeAddress=" + employeeAddress + "]";
    }
}

Our Employee class is a simple POJO class consisting of the getters and setters for the Employee class properties (id, name, employeeAddress).

employee.hbm.xml

<?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 package="com.javainterviewpoint">
   <class name="Employee" table="EMPLOYEE">
      <id name="id" type="int" column="EMP_ID">
        <generator class="native" />
      </id>
      <property name="name" column="EMP_NAME" />
      <component name="EmployeeAddress" class="com.javainterviewpoint.EmployeeAddress">
         <property name="street" column="STREET" />
         <property name="city" column="CITY" />
         <property name="state" column="STATE" />
      </component>
    </class>
</hibernate-mapping>
  • The “employee.hbm.xml” tells hibernate to map “Employee” and “EmployeeAddress” class with the “EMPLOYEE” table in the database.
  • We have a new tag <component> tag added which lets us add a component mapping in hibernate.
  • <property> tag maps the property of both Employee and EmployeeAddress to the corresponding column in EMPOYEE table.

hibernate.cfg.xml

Place the hibernate.cfg.xml file also under the src/main/resources folder

 <?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
 "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

 <session-factory>

 <!-- Database connection settings -->
 <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
 <property name="hibernate.connection.username">root</property>
 <property name="hibernate.connection.password">root</property>
 <property name="hibernate.connection.url">jdbc:oracle:thin:@mydb:40051:dev</property>

 <!-- JDBC connection pool (use the built-in) -->
 <property name="connection.pool_size">1</property>

 <!-- SQL dialect -->
 <property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>

 <!-- Echo all executed SQL to stdout -->
 <property name="show_sql">true</property>

 <!-- Drop and re-create the database schema on startup -->
 <property name="hibernate.hbm2ddl.auto">update</property>

 <!-- Mapping Resource-->
 <mapping resource="employee.hbm.xml"/>
</session-factory> 
</hibernate-configuration>
  • First and foremost property is for specifying the JDBC Driver class, in my case it OracleDriver
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
  • Give the connection URL for connecting the database and provide username and password for connecting the above database
<property name="hibernate.connection.url">jdbc:oracle:thin:@mydb:40051:dev</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">root</property>
  • Specify the connection pool size, this property limits the number of connections in the Hibernate connection pool.
<property name="connection.pool_size">1</property>
  • Dialect Property makes the Hibernate generate the SQL for the corresponding database which is being used. In this example we are using Oracle database hence Oracle query will be generated. If you are using MySQL database then you need to change the dialect accordingly.
<property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>
  • The show_sql property will print the executed sql in the console when set to true.
<property name="show_sql">true</property>
  • If the property “hibernate.hbm2ddl.auto” is set to “create”  This will drop and recreate the database schema on every execution. If it is set to “update” then the database schema will be updated every time rather than dropping and recreating.
<property name="hibernate.hbm2ddl.auto">update</property>
  • Under the Mapping resource tag, we need to specify all the mapping resources for which we need the table to be created or updated.
<mapping resource="employee.hbm.xml"/>

ComponentMapping.java

package com.javainterviewpoint;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class ComponentMapping
{
    public static void main(String args[])
    {
        //Reading the hibernate configuration file
        Configuration configuration = new Configuration().configure("hibernate.cfg.xml");
        StandardServiceRegistryBuilder regBuilber = new StandardServiceRegistryBuilder();
        regBuilber.applySettings(configuration.getProperties());
        ServiceRegistry serviceRegistry = regBuilber.build();
        
        //Create SessionFacctory
        SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        
        //Create Session from SessionFactory
        Session session = sessionFactory.openSession();
        
        //Begin the transaction
        session.beginTransaction();
        
        //Create a new EmployeeAddress object
        EmployeeAddress address = new EmployeeAddress();
        address.setStreet("Tharamani");
        address.setCity("Chennai");
        address.setState("TamilNadu");
        
        //Create a new Employee object
        Employee employee = new Employee();
        //employee.setId(1);
        employee.setName("JavaInterviewPoint");
        employee.setAddress(address);
        
        session.save(employee);
        
        //Commit the changes
        session.getTransaction().commit();
        //Close the session
        session.close();
    }
}
  • Create the Configuration object and read the configuration file using the configure() method.
Configuration configuration = new Configuration().configure("hibernate.cfg.xml");
  • Get the SessionFactory object through the buildSessionFactory() method of the configuration object.
SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
  • openSession() method opens up the new session and begin a new transaction
Session session = sessionFactory.openSession();
session.beginTransaction();
  • Create EmployeeAddress and Employee object and set values to its properties
//Create a new EmployeeAddress object
 EmployeeAddress address = new EmployeeAddress();
 address.setStreet("Tharamani");
 address.setCity("Chennai");
 address.setState("TamilNadu");
 
 //Create a new Employee object
 Employee employee = new Employee();
 //employee.setId(1);
 employee.setName("JavaInterviewPoint");
 employee.setAddress(address);
  • save() method of the session object will persist the Employee object
session.save(employee);
  • Finally get the transaction and commit the changes and close the session.
session.getTransaction().commit();
session.close();

Console

INFO: HHH000261: Table found: EMPLOYEE
Apr 05, 2017 5:48:54 PM org.hibernate.tool.hbm2ddl.TableMetadata <init>
INFO: HHH000037: Columns: [emp_name, street, emp_id, state, city]
Apr 05, 2017 5:48:54 PM org.hibernate.tool.hbm2ddl.TableMetadata <init>
INFO: HHH000108: Foreign keys: []
Apr 05, 2017 5:48:54 PM org.hibernate.tool.hbm2ddl.TableMetadata <init>
INFO: HHH000126: Indexes: [sys_c0015424]
Apr 05, 2017 5:48:54 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000232: Schema update complete
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: insert into EMPLOYEE (EMP_NAME, STREET, CITY, STATE, EMP_ID) values (?, ?, ?, ?, ?)

Table

Hibernate Component Mapping using XML1

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