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>

Working with DataSources 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>

Working with DataSources 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

Some Spring JDBC callback interfaces  SQLProvider  Has one method – getSql()  Typically implemented by PreparedStatementCreator implementers  Useful for debugging

Some Spring JDBC callback interfaces  RowCallbackHandler  Has one method – processRow(ResultSet)  Called for each row in ResultSet  Typically stateful

Some Spring JDBC callback interfaces  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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