Spring db-access mod03

Database Access Using the
Spring Framework

What this presentation will be

 Brief overview of wiring applications using
Spring
 Using Spring’s JDBC framework
 Spring’s transaction support

What this presentation will not cover

 In-depth coverage of Spring
 Creating web applications using Spring

Overview of wiring with Spring

 Discuss…

Concerns when accessing database

 Managing transactions
 Managing resources
 Connection pooling
 Cleaning up resources

Some typical JDBC code

Code Example

The problem with traditional JDBC code

 It’s redundant
 It repeats itself quite a bit
 The exact same code appears in lots of
places
 You find yourself doing the same things over
and over again
 It’s redundant

The problem with redundant code

 Violates the DRY principle
 Maintenance nightmare since JDBC code is
inherently messy
 JDBC code is critical, so it is important to get
it right, once

Spring’s solution – The Template Pattern

 Template Pattern – “Define the skeleton of an
algorithm in an operation, deferring some
steps to subclasses. Template Method lets
subclasses redefine certain steps of an
algorithm without changing the algorithm's
structure.”
 Uses “callbacks” for implementation specific
tasks

So what do this mean in a JDBC context?

DAO Template Your code

1. Prepare Resources 3. Execute Statement
2. Start Transaction

5. Commit/Rollback 4. Execute Statement
6. Clean up resource
7. Handle exceptions

But before we get too far ahead…
…let’s see how we
 Obtain/create a DataSource
 Wire a DataSource to our XxxDao classes

Working with DataSources
Getting a DataSource from JNDI
<bean id=“dataSource”
class=“org.springframework.jndi.JndiObjectFactoryBean”>
<property name=“jndiName”
value=“java:comp/env/jdbc/MyDataSourceName”/>
</bean>


Creating a connection pool
<bean id=“dataSource” class=“org.apache.commons.dbcp.BasicDataSource”>
<property name="url“ value=“jdbc:mysql://localhost/demo”/>>
<property name="driverClassName“ value=“com.mysql.jdbc.Driver”/>
<property name="username” value=“test”/>
<property name=“password” value=“password”/>
</bean>


Code Example

Overview of Spring JDBC features

 As mentioned, provides framework so that
Spring manages:
 Resources
 Transactions
 Exceptions
 Consistent exception hierarchy
 Subclass RuntimeException
 Specific and meaningful (no vendor error codes!)
 Extensable

Some Spring JDBC callback interfaces

 PreparedStatementCreator
 Has one method –
createPreparedStatement(Connection)
 Responsible for creating a PreparedStatement
 Does not need to handle SQLExceptions


 SQLProvider
 Has one method – getSql()
 Typically implemented by
PreparedStatementCreator implementers
 Useful for debugging


 RowCallbackHandler
 Has one method – processRow(ResultSet)
 Called for each row in ResultSet
 Typically stateful


 RowMapper
 Has one method – mapRow(ResultSet rs,
int rowNum)
 Maps a single row to an Object

Using JdbcTemplate

 Central class for Spring JDBC framework
 Uses callbacks “under the covers”
 All you will need for most JDBC operations

Using JdbcTemplate

Code Example

Spring Incrementers

 Used to increment primary key value for
newly persisted object
 Implements
DataFieldMaxValueIncrementer
 Supports
 Oracle sequences
 DB2 sequences
 PostgreSQL sequences
 MySQL for non-auto-increment columns

Hibernate intro

 Open source ORM tool
 Very mature (version 3.2 on horizon)
 Feature-complete
 Caching
 Eager-fetching
 Lazy-loading
 Proxying

Using Hibernate

 Configure classes to be mapped through
 Manually created configuration files
 XDoclet generated configuration files
 Annotations (JPA and Hibernate)
 Configure global properties through
hibernate.properties file
 Hibernate class analogies
 DataSource : SessionFactory
 Connection : Session

Using Spring with Hibernate

 Use Spring to configure Hibernate
 Configure Hibernate mappings
 Configure Hibernate properties

 Wire dependant object to SessionFactory

 Use HibernateTemplate as abstraction to
Hibernate API
 Manages obtaining Session from
SessionFactory
 Handles/converts exceptions
 Manages transactions

Spring Transaction Management

 Supports programmatic (yuck!) and declarative
(yeah!) transactions
 Declarative transaction management achieved via
Spring’s AOP
 Declarative transactions can be defined in Spring
configuration file or in annotations
 Supports many transaction properties
 Propagation
 Isolation level
 Rollback conditions

Spring Proxy Overview

depends on
SomeClient DaoInterface

is wired delegates
ProxyBean DaoImpl

Coming in Spring 2.0

 Support for AspectJ pointcut language
 JPA support?
 SimpleJdbcTemplate
 Support generics
 Support variable argument methods

Spring db-access mod03

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