Database Access Using the Spring Framework

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Database Access Using the Spring Framework

• Ryan Breidenbach
• Countrywide Financial Corporation

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What this presentation will be

• Brief overview of wiring applications using
  Spring
• Using Springs JDBC framework
• Integrating Spring with Hibernate
• Springs transaction support

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What this presentation will not cover

• In-depth coverage of Spring
• Creating web applications using Spring
• How to use Hibernate

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Who am I

• Currently a Software Technical Specialist for
  Countrywide
• Developing Java applications for nearly seven
  years, mostly at Michaels Stores
• Co-author of Spring in Action with Craig Walls

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Overview of wiring with Spring

• Discuss

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Concerns when accessing database

• Managing transactions
• Managing resources
• Connection pooling
• Cleaning up resources

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Some typical JDBC code

• Code Example

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The problem with traditional JDBC code

• Its 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
• Its redundant

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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

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Springs 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

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So what do this mean in a JDBC context?
Your code
DAO Template

• Prepare Resources
• Start Transaction

• Execute Statement

• Commit/Rollback
• Clean up resource
• Handle exceptions

• Execute Statement

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But before we get too far aheadlets see how we

• Obtain/create a DataSource
• Wire a DataSource to our XxxDao classes

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Working with DataSources

• Getting a DataSource from JNDI
• ltbean iddataSource
• classorg.springframework.jndi.JndiObjectFa
  ctoryBeangt
• ltproperty namejndiName
• valuejavacomp/env/jdbc/MyDataSource
  Name/gt
• lt/beangt

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Working with DataSources

• Creating a connection pool
• ltbean iddataSource classorg.apache.commons.db
  cp.BasicDataSourcegt
• ltproperty name"url valuejdbcmysql//localho
  st/demo/gtgt
• ltproperty name"driverClassName
  valuecom.mysql.jdbc.Driver/gt
• ltproperty name"username valuetest/gt
• ltproperty namepassword valuepassword/gt
• lt/beangt

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Working with DataSources

• Code Example

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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

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Some Spring JDBC callback interfaces

• PreparedStatementCreator
• Has one method createPreparedStatement(Connectio
  n)
• Responsible for creating a PreparedStatement
• Does not need to handle SQLExceptions

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Some Spring JDBC callback interfaces

• SQLProvider
• Has one method getSql()
• Typically implemented by PreparedStatementCreator
  implementers
• Useful for debugging

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Some Spring JDBC callback interfaces

• RowCallbackHandler
• Has one method processRow(ResultSet)
• Called for each row in ResultSet
• Typically stateful

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Some Spring JDBC callback interfaces

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

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Using JdbcTemplate

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

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Using JdbcTemplate

• Code Example

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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

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Using JdbcTemplate

• Code Example

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Hibernate intro

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

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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

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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

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Using JdbcTemplate

• Code Example

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Spring Transaction Management

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

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Spring Proxy Overview
depends on
is wired
delegates
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Using JdbcTemplate

• Code Example

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Coming in Spring 2.0

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

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Questions Answers

• ryan_breidenbach_at_yahoo.com