Spring 2.5

The Spring Framework
Paul Bakker

Goals

An introduction

Not pointing a winner

Outline
• History and overview
• Dependency Injection
• AOP
• Module deep dive
• Testing

History

Founded by Rod Johnson

First introduced in his book
“J2EE Design &
Development”

Why Dependency Injection?

public double calculateTotalPrice() {
    ProductService productService = new ProductService();
    List products = productService.getProducts();

//iterate products and sum prices

return total;
}

How would you test this method?

productService.getProducts()

Database

Throws
public void testCalculateTotalPrice() {
Calculator calc = new Calculator();
Exception...
assertEquals(150, calc.calculateTotalPrice());
}

    ProductService productService = new ProductService();


return total;
}

public Calculator(ProductService productService) {
this.productService = productService;
}



return total;
}

public void testCalculateTotalPrice() {
Calculator calc = 
  new Calculator(new ProductServiceMock());

assertEquals(150, calc.calculateTotalPrice());
}

Program to interfaces

not to
implementations

Inversion of Control
A container manages dependencies

IoC Container

ProductService Calculator

Conﬁguring a container

ProductService pService = new ProductServiceImpl();
Calculater calc = new Calculator(pService);

//init other instances

This will be a lot of work however...

Conﬁguration using
XML
<bean id=quot;productServicequot;   
   class=quot;services.ProductServiceImplquot;/>

<bean id=quot;calculatorquot; class=quot;calc.Calculatorquot;>
   <constructor‐arg index=quot;0quot; ref=quot;productServicequot;/>       
 
</bean>

Spring version 1 way

Conﬁguration using
annotations
@Stateless(name = quot;ProductEJBquot;)
public class ProductBean {
    public ProductBean() {
    }
}

@EJB ShoppingBasketBean shoppingBasket; 

JEE 5 way

Spring annotations

• Spring can now be conﬁgured using
annotations
• Use annotations for component
declarations
• Use XML for container wide conﬁguration

Annotation example

@Service
public class SimpleMovieLister {
   private MovieFinder movieFinder;
   
   @Autowired
   public SimpleMovieLister(MovieFinder movieFinder) {
      this.movieFinder = movieFinder;
   }
}

AutoWiring

• Don’t explicitly wire dependencies
• Just declare beans

Autowiring qualiﬁers
<bean class=quot;example.SimpleMovieCatalogquot;>
   <qualifier value=quot;mainquot;/>
</bean>

<bean class=quot;example.SimpleMovieCatalogquot;>
   <qualifier value=quot;actionquot;/>
</bean>

@Autowired
@Qualifier(quot;mainquot;)
private MovieCatalog movieCatalog;

Aspect Oriented
Programming

• Used internally by Spring;
• e.g. Transaction Management
• AspectJ integration for easy AOP on your
Spring beans

2 minute AOP intro
Class A

public void trace(..) {
//log something
Before }

public void myMethod(..) {
//do something
}

JdbcTemplate

int countOfActorsNamedJoe = this.jdbcTemplate.queryForInt(
quot;select count(0) from t_actors where first_name = ?quot;, 
 new Object[]{quot;Joequot;});

JdbcTemplate

this.jdbcTemplate.update(
 quot;delete from actor where id = ?quot;,
  new Object[] {new Long.valueOf(actorId)});

SimpleJdbcTemplate

String sql = quot;select id, first_name, last_name from T_ACTOR where id = ?quot;;

ParameterizedRowMapper<Actor> mapper = new ParameterizedRowMapper<Actor>() 
{
  public Actor mapRow(ResultSet rs, int rowNum) throws SQLException {
     Actor actor = new Actor();
     actor.setId(rs.getLong(quot;idquot;));
     actor.setFirstName(rs.getString(quot;first_namequot;));
     actor.setLastName(rs.getString(quot;last_namequot;));
     return actor;
  }
};

return this.simpleJdbcTemplate.queryForObject(sql, mapper, id);

Exceptions
• Spring wraps every jdbc exception
• Same structure for ORM exceptions
• Handle speciﬁc database exceptions in a
uniform way
• Translate checked exception to unchecked
exceptions

ORM Integration

• Hibernate
• iBATIS
• JDO
• TopLink
• JPA

Session Factory
Conﬁguration
<bean id=quot;mySessionFactoryquot;  
  class=quot;org.springframework.orm.hibernate3.LocalSessionFactoryBeanquot;>
   <property name=quot;dataSourcequot; ref=quot;myDataSourcequot;/>
   <property name=quot;mappingResourcesquot;>
      <list>
         <value>product.hbm.xml</value>
      </list>
   </property>
   <property name=quot;hibernatePropertiesquot;>
      <value>
         hibernate.dialect=org.hibernate.dialect.HSQLDialect
      </value>
   </property>
</bean>

Hibernate Template
Conﬁguration

<bean id=quot;myProductDaoquot; class=quot;product.ProductDaoImplquot;>
<property name=quot;sessionFactoryquot; ref=quot;mySessionFactoryquot;/>
</bean>

Hibernate Template
public class HibernateProductDao extends HibernateDaoSupport {

   public Collection loadProductsByCategory(String category) throws      
         DataAccessException, MyException {

      return this.hibernateTemplate.find(
     quot;from test.Product product where product.category=?quot;, category);
}
}

Transactions

It’s just more conﬁguration

<bean id=quot;myTxManagerquot;      
  class=quot;org.springframework.orm.hibernate3.HibernateTransactionManagerquot;>
   <property name=quot;sessionFactoryquot; ref=quot;mySessionFactoryquot;/>
</bean>

<aop:config>
   <aop:pointcut id=quot;productServiceMethodsquot; expression=quot;execution(*    
     product.ProductService.*(..))quot;/>
   <aop:advisor advice‐ref=quot;txAdvicequot; pointcut‐  
     ref=quot;productServiceMethodsquot;/>
</aop:config>

<tx:advice id=quot;txAdvicequot; transaction‐manager=quot;myTxManagerquot;>
   <tx:attributes>
      <tx:method name=quot;increasePrice*quot; propagation=quot;REQUIREDquot;/>
      <tx:method name=quot;someOtherBusinessMethodquot; 
        propagation=quot;REQUIRES_NEWquot;/>
      <tx:method name=quot;*quot; propagation=quot;SUPPORTSquot; read‐only=quot;truequot;/>
   </tx:attributes>
</tx:advice>

</bean>

<aop:config>
</aop:config>

</tx:advice>

Transaction manager

</bean>

<aop:config>
</aop:config>

</tx:advice>

Pointcut and Advisor

</bean>

<aop:config>
</aop:config>

</tx:advice>

Advice - Propagation properties

Web MVC
Components

• Controllers
• View Handlers
• Validation

Controller Hierarchy
AbstractController MultiactionController

CommandController

FormController

WizzardController

Compared to other
web frameworks
• Web MVC is very simple
• It’s ‘action’ based
• Close to the request/response model
• It doesn’t have conversational state

Spring Portlets

• Web MVC for JSR-168
• Exactly the same programming model for
Portlets and Servlets
• Doesn’t hide the Portlet speciﬁc ﬂow

Testing
• Spring Mock
• Integration Testing

Spring Mocks

• Mock often used objects
• Request, Response, Session, JNDI etc.

Spring integration
testing

• Test Wiring
• Test DAOs

Test DAOs

• Wire beans
• Manage transactions
• Rollback transaction after each test
• Mix Hibernate and plain JDBC in one
transaction

DAO test example

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={quot;daos.xmlquot;})
public final class HibernateTitleDaoTests {
   @Autowired
   private HibernateTitleDao titleDao;
   
   public void testLoadTitle() throws Exception {
      Title title = this.titleDao.loadTitle(new Long(10));
      assertNotNull(title);
   }
}

The verdict

• Spring is very complete
• It’s “environment friendly”
• It helps loose coupling
• It’s much better than J2EE

Do we still need it?

• JEE 5 has a similar programming model
• Seam is a much better web framework

Where to start

• http://springframework.org
• Reference documentation
• Spring Pet store

Spring related

• Spring Webﬂow
• Spring security (acegi)
• Spring webservices
• Spring integration

Spring 2.5

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