Chapter 3. Extensions
Prev   Next

Chapter 3. Extensions

This chapter documents a set of Hades extensions that enable Hades usage in a variety of contexts. Currently most of the integration is targeted towards Spring MVC.

3.1. Domain class web binding for Spring MVC

Given you are developing a Spring MVC web applications you typically have to resolve domain class ids from URLs. By default it's your task to transform that request parameter or URL part into the domain class to hand it layers below then or execute business logic on the entities directly. This should look something like this:

@Controller
@RequestMapping("/users")
public class UserController {

  private final UserDao userDao;

  public UserController(UserDao userDao) {
    this.userDao = userDao;
  }

  @RequestMapping("/{id}")
  public String showUserForm(@PathVariable("id") Long id, Model model) {
    
    // Do null check for id
    User user = userDao.readByPrimaryKey(id);
    // Do null check for user
    // Populate model
    return "user";
  }
}

First you pretty much have to declare a repository dependency for each controller to lookup the entity managed by the controller or DAO respectively. Beyond that looking up the entity is boilerplate as well as it's always a readByPrimaryKey(…) call. Fortunately Spring provides means to register custom converting components that allow conversion between a String value to an arbitrary type.

PropertyEditors

For versions up to Spring 3.0 simple Java PropertyEditors had to be used. Thus, Hades offers a GenericDaoPropertyEditorRegistrar, that will look up all Hades repositories registered in the ApplicationContext and register a custom PropertyEditor for the managed domain class

<bean class="….web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
  <property name="webBindingInitializer">
    <bean class="….web.bind.support.ConfigurableWebBindingInitializer">
      <property name="propertyEditorRegistrars">
        <bean class="org.synyx.hades.extensions.beans.GenericDaoPropertyEditorRegistrar" />
      </property>
    </bean>
  </property>
</bean>

If you have configured Spring MVC like this you can turn your controller into the following that reduces a lot of the clutter and boilerplate.

@Controller
@RequestMapping("/users")
public class UserController {

  @RequestMapping("/{id}")
  public String showUserForm(@PathVariable("id") User user, Model model) {

    // Do null check for user
    // Populate model
    return "userForm";
  }
}

ConversionService

As of Spring 3.0 the PropertyEditor support is superseeded by a new conversion infrstructure that leaves all the drawbacks of PropertyEditors behind and uses a stateless X to Y conversion approach. Hades extensions now ship with a GenericDaoConverter that pretty much mimics the behaviour of GenericDaoPropertyEditorRegistrar. To register the converter you have to declare ConversionServiceFactoryBean, register the converter and tell the Spring MVC namespace to use the configured conversion service:

<mvc:annotation-driven conversion-service="conversionService" />

<bean id="conversionService" class="….context.support.ConversionServiceFactoryBean">
  <property name="converters">
    <list>
      <bean class="org.synyx.hades.extensions.conversion.GenericDaoConverter">
        <constructor-arg ref="conversionService" />
      </bean>
    </list>
  </property>
</bean>
Prev   Next
2.10. Custom implementations Home 3.2. Web pagination