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What kind of exceptions those spring DAO classes throw?
The spring’s DAO class does not throw any technology related exceptions such
as SQLException. They throw exceptions which are subclasses of
DataAccessException.
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What is DataAccessException?
DataAccessException is a RuntimeException. This is an Unchecked Exception. The
user is not forced to handle these kinds of exceptions.
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How can you configure a bean to get DataSource from JNDI?
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<bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
<property
name="jndiName">
<value>java:comp/env/jdbc/myDatasource</value>
</property>
</bean>
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How can you create a DataSource connection pool?
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<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>
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How JDBC can be used more efficiently in spring framework?
JDBC can be used more efficiently with the help of a template class provided
by spring framework called as JdbcTemplate.
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How JdbcTemplate can be used?
With use of Spring JDBC framework the burden of resource management and error
handling is reduced a lot. So it leaves developers to write the statements and
queries to get the data to and from the database.
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JdbcTemplate
template = new JdbcTemplate(myDataSource);
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A simple DAO class looks like this.
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public class StudentDaoJdbc implements StudentDao {
private JdbcTemplate jdbcTemplate;
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
more..
}
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The configuration is shown below.
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<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource">
<ref bean="dataSource"/>
</property>
</bean>
<bean id="studentDao" class="StudentDaoJdbc">
<property name="jdbcTemplate">
<ref bean="jdbcTemplate"/>
</property>
</bean>
<bean id="courseDao" class="CourseDaoJdbc">
<property name="jdbcTemplate">
<ref bean="jdbcTemplate"/>
</property>
</bean>
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How do you write data to backend in spring using JdbcTemplate?
The JdbcTemplate uses several of these callbacks when writing data to the
database. The usefulness you will find in each of these interfaces will vary.
There are two simple interfaces. One is PreparedStatementCreator and
the other interface is BatchPreparedStatementSetter.
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Explain about PreparedStatementCreator?
PreparedStatementCreator is one of the most common used interfaces for writing
data to database. The interface has one method createPreparedStatement().
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PreparedStatement createPreparedStatement(Connection conn)
throws SQLException;
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When this interface is implemented, we should create and return a
PreparedStatement from the Connection argument, and the exception handling is
automatically taken care off. When this interface is implemented, another
interface SqlProvider is also implemented which has a method called
getSql() which is used to provide sql strings to JdbcTemplate.
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Explain about BatchPreparedStatementSetter?
If the user what to update more than one row at a shot then he can go for
BatchPreparedStatementSetter. This interface provides two methods
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setValues(PreparedStatement ps, int i) throws SQLException;
int getBatchSize();
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The getBatchSize() tells the JdbcTemplate class how many statements to create.
And this also determines how many times setValues() will be called.
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Explain about RowCallbackHandler and why it is used?
In order to navigate through the records we generally go for ResultSet. But
spring provides an interface that handles this entire burden and leaves the
user to decide what to do with each row. The interface provided by spring is
RowCallbackHandler. There is a method processRow() which needs to be
implemented so that it is applicable for each and everyrow.
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void
processRow(java.sql.ResultSet
rs);
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