Spring Context - Writing Application Context
In this section we will wire up the components by defining the Application context definition file (applicationContext-hibernate.xml). This file is used by context loader servlet to initialize the Spring application context.
About Application ApplicationContext
An ApplicationContext is the central interface to provide configuration for an
application.
An ApplicationContext provides the following functionalities:
- Bean factory methods, inherited from ListableBeanFactory. This avoids the need for applications to use singletons.
- The ability to resolve messages, supporting internationalization. Inherited from the MessageSource interface.
- The ability to load file resources in a generic fashion. Inherited from the ResourceLoader interface.
- The ability to publish events. Implementations must provide a means of registering event listeners.
- Inheritance from a parent context. Definitions in a descendant context will always take priority. This means, for example, that a single parent context can be used by an entire web application, while each servlet has its own child context that is independent of that of any other servlet.
Here is the code of our applicationContext-hibernate.xml file:
| <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd"> <!-- - Application context definition for RoseIndia Login Application on Hibernate. --> <beans> <!-- ========================= RESOURCE DEFINITIONS ========================= --> <!-- Configurer that replaces ${...} placeholders with values from a properties file --> <!-- (in this case, JDBC-related settings for the dataSource definition below) --> <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location"><value>/WEB-INF/jdbc.properties</value></property> </bean> <!-- Local DataSource that works in any environment --> <!-- Note that DriverManagerDataSource does not pool; it is not intended for production --> <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName"><value>${jdbc.driverClassName}</value></property> <property name="url"><value>${jdbc.url}</value></property> <property name="username"><value>${jdbc.username}</value></property> <property name="password"><value>${jdbc.password}</value></property> </bean> <!-- JNDI DataSource for J2EE environments --> <!-- Hibernate SessionFactory --> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource"><ref local="dataSource"/></property> <property name="mappingResources"> <list> <value>roseindia/dao/hibernate/Login.hbm.xml</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">${hibernate.dialect}</prop> <prop key="hibernate.show_sql">true</prop> </props> </property> </bean> <!-- Transaction manager for a single Hibernate SessionFactory (alternative to JTA) --> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory"><ref local="sessionFactory"/></property> </bean> <!-- ========================= BUSINESS OBJECT DEFINITIONS ========================= --> <!-- Data access object: Hibernate implementation. --> <bean id="HibernateSpringDaoTarget" class="roseindia.dao.SpringHibernateDAOImpl"> <property name="sessionFactory"><ref local="sessionFactory"/></property> </bean> <!-- - Transactional proxy for Login Application central data access object. - - Defines specific transaction attributes with "readOnly" markers, - which is an optimization that is particularly valuable with Hibernate - (to suppress unnecessary flush attempts for read-only operations). - - Note that in a real-life app with multiple transaction proxies, - you will probably want to use parent and child bean definitions - as described in the manual, to reduce duplication. --> <bean id="SpringHibernateDao" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean"> <property name="transactionManager"><ref local="transactionManager"/></property> <property name="target"><ref local="HibernateSpringDaoTarget"/></property> <property name="transactionAttributes"> <props> <prop key="get*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="find*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="load*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="store*">PROPAGATION_REQUIRED</prop> </props> </property> </bean> <!-- Email Service--> <bean id="mailbean" class="roseindia.web.common.SendMail"> <property name="strSmtp"><value>192.168.10.14</value></property> </bean> </beans> |
Understanding the applicationContext-hibernate.xml configuration file
Data source configuration:
The following line of the configuration file configures the data source for the application.
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName"><value>${jdbc.driverClassName}</value></property>
<property name="url"><value>${jdbc.url}</value></property>
<property name="username"><value>${jdbc.username}</value></property>
<property name="password"><value>${jdbc.password}</value></property>
</bean>
The values for ${jdbc.driverClassName}, ${jdbc.url}, ${jdbc.username} and ${jdbc.password} are defined in the jdbc.properties file which is present in the /WEB-INF/ directory of the web application.
Hibernate Session Factory:
Following line of the configuration file configures the Hibernate Session Factory.
<!-- Hibernate SessionFactory -->
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource"><ref local="dataSource"/></property>
<property name="mappingResources">
<list>
<value>roseindia/dao/hibernate/Login.hbm.xml</value>
</list>
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">${hibernate.dialect}</prop>
<prop key="hibernate.show_sql">true</prop>
</props>
</property>
</bean>
Configuring the Transaction Proxy for the DAO
Following line of the configures the Transaction Proxy for the DAO bean.
<bean id="SpringHibernateDao" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="transactionManager"><ref local="transactionManager"/></property>
<property name="target"><ref local="HibernateSpringDaoTarget"/></property>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="find*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="load*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="store*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>
Mailer Bean
In our application we are sending the emails when new account is created or user asks for the forgotten password. Following code configures the mailer bean.
<bean id="mailbean" class="roseindia.web.common.SendMail">
<property name="strSmtp"><value>192.168.10.14</value></property>
</bean>
In this section we have developed the configuration file that is used for configuring the Spring Context. In the next section we will learn how to add the required configuration in the web.xml file to load the Spring context though Spring's context loader servlet.