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:
- Create a simple Maven Project “HibernateTutorial” and create a package for our source files “com.javainterviewpoint” under src/main/java
- 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> - Create the Java classes Employee.java, EmployeeAddress.java and ComponentMapping.java under com.javainterviewpoint folder.
- Place the hibernate.cfg.xml and employee.hbm.xml under the src/main/resources directory
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
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