一 Spring DAO philosophy
?1 Understanding Spring's DataAccesssException
?Spring's DAO frameworks donot throw teechnology-specific exceptions such as SQLException
or HibernateeExcepiton.Instead ,all exceptions thrown are subclasses of DataAccessException
?2 You are not forced to handle DataAccessExceptions
?DataAccessException is a RuntimeException,so it si an unchecked exception.Since these are quite often unrecoverable,you are not forced to handle these exception.
? Instead ,you can catch the exception if recovery is possible.since DataAccessException is not only a RuntimeException,but it subclasses Spring's NestedRuntimeException. This menas that the root Exception is alwarys via NestedRuntimeException's getCause() method.
?3 Work with DataSources
? a getting a Datasource from JNDI
?? <bean id="dataSource"
????? class="org.springframework.jndi.JndiObjectFactoryBean">
?? <property name="jndiName">
??? <value>java:comp/env/jdbc/myDatasource</value>
?? </property>
?? </bean>
? b Creating a Datasource connection pool
?? <bean id="dataSource"
????? class="org.apache.commons.dbcp.BasicDataSource">
? <property name="driver">
??? <value>${db.driver}</value>
? </property>
? <property name="url">
??? <value>${db.url}</value>
? </property>
? <property name="username">
??? <value>${db.username}</value>
? </property>
? <property name="password">
??? <value>${db.password}</value>
? </property>
</bean>
?c Using a DataSource while testing
? DriverManagerDataSource dataSource = new DriverManagerDataSource();
? dataSource.setDriverClassName(driver);
? dataSource.setUrl(url);
? dataSource.setUsername(username);
? dataSource.setPassword(password);
?4 Consistent DAO support
? Spring template class handle the invariant part of data access-controling the trancsaction
manage resource,handling exception .Implementation of callback interface define what is specific to your application--creating statement,binding parameter and marshalling result set.
?Spring separates the fixed an vaiant parts of data access process into tow distince classes:
template and callbacks.Template manage the fixed parts of the process while callback are where you fill in the implement details;
?one the top of template-callback desing ,spring framework provide a support class which your own data access subclass it. And the support class already have a property for holding a template.
?二 Integerating Hibernate with Spring
? 1 Managing Hibernate resources
?? you will keep a single instance of SessionFactory throughtout your application
?? <bean id="sessionFactory"class="org.springframework.
?????????? orm.hibernate.LocalSessionFactoryBean">
???? <bean id="sessionFactory" class="org.springframework.
?????? orm.hibernate.LocalSessionFactoryBean">
???? <property name="dataSource">
?????? <ref bean="dataSource"/>
???? </property>
? </bean>
? you also want to manager how hibernate is configured
? <bean id="sessionFactory" class="org.springframework.
?????? orm.hibernate.LocalSessionFactoryBean">
? <property name="hibernateProperties">
??? <props>
????? <prop key="hibernate.dialect">net.sf.hibernate.
?????????? dialect.MySQLDialect</prop>
??? </props>
? </property>
? …
?</bean>
?and the last thing is whick map files is read
? <bean id="sessionFactory" class="org.springframework.
?????? orm.hibernate.LocalSessionFactoryBean">
? <property name="mappingResources">
???? <list>
???? <value>Student.hbm.xml</value>
???? <value>Course.hbm.xml</value>
???? …
?? </list>
? </property>
???? …
? </bean>
?Now? you have fully configured your sessionfactory ,so we need do create an object which we
will access hibernate. As we know, we will use a template class
? <bean id="hibernateTemplate"
????? class="org.springframework.orm.hibernate.HibernateTemplate">
? <property name="sessionFactory">
??? <ref bean="sessionFactory"/>
? </property>
?</bean>
? <bean id="courseDao" class="com.springinaction.
?????? training.dao.hibernate.CourseDaoHibernate">
? <property name="hibernateTemplate">
??? <ref bean="hibernateTemplate"/>
? </property>
?</bean>
?2 Accessing Hibernate through HibernatTemplate
? The template-callback mechanism in Hibernatee is pretty simple.There is the HibernatTmpplate and one callback interface
? public Student getStudent(final Integer id) {
? return (Student) hibernateTemplate.execute(
??? new HibernateCallback() {
????? public Object doInHibernate(Session session)
????????? throws HibernateException {
??????? return session.load(Student.class, id);
????? }
??? });
?
? The HibernateTemplate class provides some convience methods that implicit create a HibernateCallback instance:
? (Student) hibernateTemplate.load(Student.class, id);
?? hibernateTemplate.update(student);
? hibernateTemplate.find("from Student student " +
??????????????????????????????? "where student.lastName = ?",
??????????????????????????????? lastName, Hibernate.STRING);
? 3 Subclassing HibernateDaoSupport
? public class StudentDaoHibernate extends HibernateDaoSupport
??? implements StudentDao {
? …
? }
? getHibernateTemplate()
? getSession()