Month: June 2010

How to configure Hibernate in Spring.


The objective of the tutorial is to understand how the DB can be configured in Spring using Hibernate.
To start with download:
1) spring jars
2) hibernate jars
3) mysql driver

Following is the list of jars I used.

1) create a Db in mysql with name “reco_engine”;
2) Create a table User and add some columns to it.
3) Insert some records into the table using mysql..

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">

<bean id="hibernateDao" class="HibernateAccessDao">
<property name="hibernateTemplate">
<ref bean="hibernateTemplate"/>
</property>
</bean>
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/reco_engine"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</bean>

<bean id="mySessionFactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="mappingResources">
<list>
<value>Users.hbm.xml</value>
</list>
</property>
<property name="hibernateProperties">
<value>hibernate.dialect=org.hibernate.dialect.HSQLDialect</value>
</property>
</bean>


<bean id="hibernateTemplate"
class="org.springframework.orm.hibernate3.HibernateTemplate">
<property name="sessionFactory">
<ref bean="mySessionFactory"/>
</property>
</bean>
</beans>

The bean “datasource” is used to configure the properties of the DB.
The bean “mySessionFactory” is used to maintain the session of hibernate. This is taken care by the spring container now.
The property “mappingResources” takes the list of hbm files which will be mapped to this session. Also the datasource property is set in this bean.

The bean hibernateTemplate is the one used to interact with the DB. The Spring application context will manage its lifecycle, initializing and shutting down the factory as part of the application. LocalSessionFactoryBean is the preferred way of obtaining a reference to a specific Hibernate SessionFactory, at least in a non-EJB environment.

The bean “hibernateDao” is the java class and the hibernateTemplate property is set.

The Users table has to be mapped in Hibernate. To map it , Users.java and Users.hbm.xml need to be created . I have used the Hibernate plugin for eclipse provided by JBoss to generate the files automatically. http://jboss.org/tools

The files will be as follows:


public class Users  implements java.io.Serializable {


    // Fields    

     private int id;
     private String firstname;
     private String lastname;
    
    // Constructors

    /** default constructor */
    public Users() {
    }

	/** minimal constructor */
    public Users(int id) {
        this.id = id;
    }
    
  
    // Property accessors

    public int getId() {
        return this.id;
    }
    
    public void setId(int id) {
        this.id = id;
    }

      public String getFirstname() {
        return this.firstname;
    }
    
    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    public String getLastname() {
        return this.lastname;
    }
    
    public void setLastname(String lastname) {
        this.lastname = lastname;
    }
}

The Users.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">
<!-- Generated Jun 3, 2010 9:15:59 PM by Hibernate Tools 3.1.0.beta4 -->
<hibernate-mapping>
    <class name="Users" table="users" catalog="reco_engine">
        <id name="id" type="int">
            <column name="id" />
            <generator class="assigned" />
        </id>
        <property name="firstname" type="string">
            <column name="firstname" length="45" />
        </property>
        <property name="lastname" type="string">
            <column name="lastname" length="45" />
        </property>
        <property name="designation" type="string">
            <column name="designation" length="45" />
        </property>
        <property name="department" type="string">
            <column name="department" length="45" />
        </property>
    </class>
</hibernate-mapping>

The Dao class to interact with the database:


public class HibernateAccessDao {

	HibernateTemplate hibernateTemplate;

	public void setHibernateTemplate(HibernateTemplate hibernateTemplate) {
		this.hibernateTemplate = hibernateTemplate;
	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		ApplicationContext context =   new ClassPathXmlApplicationContext("spring.xml");
		HibernateAccessDao dao =(HibernateAccessDao) context.getBean("hibernateDao");
		dao.getRecords();
	}
	
// This method retrieves the record with id =1
	private void getRecords(){
		
		Session session = hibernateTemplate.getSessionFactory().openSession();
		Users user = (Users) session.load(Users.class, 1);
		System.out.println(user.getFirstname());
	}

}

The session.load(User.class,1) will load the record of the user with id =1

Connecting database using Spring JdbcTemplate


Another salient feature of Spring is to connect and work with database at great ease which is what I am going to demonstrate.
This article is the basic to load and configure beans to interact with DB and aims to help people who are trying to user the spring ‘JdbcTemplate’ for the first time.

Configurations:
1) Download Spring 3.0.zip from http://www.springframework.org and extract it.
2) Create a normal Java project using ecplise.
3) Database I am using in MySQL so download Mysql driver class

There are several ways in which DB can be access.
• JdbcTemplate is the classic Spring JDBC approach and the most popular. This “lowest level” approach and all others use a JdbcTemplate under the covers, and all are updated with Java 5 support such as generics and varargs.
• NamedParameterJdbcTemplate wraps a JdbcTemplate to provide named parameters instead of the traditional JDBC “?” placeholders. This approach provides better documentation and ease of use when you have multiple parameters for an SQL statement.
• SimpleJdbcTemplate combines the most frequently used operations of JdbcTemplate and NamedParameterJdbcTemplate.
• SimpleJdbcInsert and SimpleJdbcCall optimize database metadata to limit the amount of necessary configuration. This approach simplifies coding so that you only need to provide the name of the table or procedure and provide a map of parameters matching the column names. This only works if the database provides adequate metadata. If the database doesn’t provide this metadata, you will have to provide explicit configuration of the parameters.
• RDBMS Objects including MappingSqlQuery, SqlUpdate and StoredProcedure requires you to create reusable and thread-safe objects during initialization of your data access layer. This approach is modeled after JDO Query wherein you define your query string, declare parameters, and compile the query. Once you do that, execute methods can be called multiple times with various parameter values passed in.

Extracted from Spring jdbc docs

The demo is done using JdbcTemplate.

1) Configure the Datasource in the “spring.xml”. One needs to configure the connection properties in the spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">
    
    <bean id="jdbcDao" class="JDBC_Acess">
        <property name="dataSource" ref="dataSource"/>
    </bean>
    
    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/reco_engine"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    </bean>

    

</beans>

2) Create a Dao class and configure the bean in the “spring.xml”. Here the class is “JDBCDao.java”. The datasource property created in step 1 is configured for the Dao class.
3) In JDBCDao class the object of JdbcTemplate is created with the constructor argument as Datasource configured in step 1.

public class JDBCDao {

	 private JdbcTemplate jdbcTemplate;

	    private void getUser(){
	    	String sql = "select * from users";
	    	try{
	    	List list = jdbcTemplate.query(sql, new UserMapper());
	    	System.out.println("Total Records "+ list.size());
	    	}catch(DataAccessException e){
	    		e.printStackTrace();
	    	}
	    }
	    private void insertUser(){
	    	String sql = "insert into users values ('21','spring,java,perl,oracle','golf,cooking,music,cricket','3','embedded','7','victor','mathews','team lead','NULL')";
	    	try{
	    	 jdbcTemplate.update(sql);
	    	 System.out.println("record inserted succesffuly");
	    	}catch(DataAccessException e){
	    		e.printStackTrace();
	    	}
	    }
	public static void main(String[] args) {
		
		ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
		JDBCDao dao = (JDBCDao)context.getBean("jdbcDao");
		dao.getUser();
		dao.insertUser();
	}
	
	
	public void setDataSource(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

}
class UserMapper implements RowMapper{

	@Override
	public User mapRow(ResultSet rs, int arg1) throws SQLException {

		User user = new User();
		user.setFirstName(rs.getString("firstName"));
		user.setLastName(rs.getString("lastName"));
		return user;
	}
	
}