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Data Validation with the Spring Framework
by
Jacob Briscoe
What is the first thing that comes to mind when you hear the word “validation”? Input
length?Input type? Required/not-required? How about JavaScript or wait commons-validator? Probably,
it's not the Spring Framework.
Did you know the Spring Framework offers excellent support for validation?
Most applications require data validation in some form or another. In this article, you’ll build a
validation framework, to be implemented by a sample task list service application. This service
provides a good example of the real-world validation you may have encountered in your own
applications. The task list service is quite simple, consisting of only one method, the full
implementation of which is left to your discretion. Because implementing the task list service is
out of the scope of this article, we’ll focus solely on the data being passed to it. Follow along
by downloading the source code, all of which is written and targeted to work with Java 1.5 (using
jdk1.5.0_06) but could be easily ported to Java 1.4 or lower. You will notice the source code
contains a pom.xml file—this is because this project uses using Maven 2 (if you
haven't tried Maven 2 yet, it is a great upgrade from Maven 1). If you're not comfortable using
Maven, Ant works too. All of the dependencies for this application are listed in the pom.xml
file.
The Sample Task List Service
The sample application enables users to create new tasks—sort of like a “to-do” list you might
see on stationary. For now, the task service will focus on creating tasks for any number of
employees. When creating a new task, the service will not be able to recreate a task that has
already been completed. The new task must have priority assignment, such as low, normal, or high.
The due date for the new task is included and can’t be set before today. All tasks must always be
assigned to at least one employee, along with the employees’ information, such as name, employee
identification number, and home address. A new task must have an estimate of time-to-completion in
hours, at a minimum of .01 hours. While creating a new task, the estimate of time-to-completion in
hours must not exceed the due date. And finally, the new task must include a detailed description.
The domain model in
Figure 1 shows the service's requirements.
Figure 1. The Task Service:
This image shows the service's requirements.
The task service requires a single method to create a new task.The following code shows the
interface and implementation:
<Task Service Interface>
package jbriscoe.article.spring.validation.service;
import jbriscoe.article.spring.validation.entity.Task;
import jbriscoe.article.spring.validation.exception.ValidationException;
public interface TaskService {
public Boolean createTask(final Task task);
}
<Task Service Impl.>
package jbriscoe.article.spring.validation.service.impl;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import jbriscoe.article.spring.validation.entity.Task;
import jbriscoe.article.spring.validation.service.TaskService;
public class TaskServiceImpl implements TaskService {
private Log log = LogFactory.getLog(getClass());
public Boolean createTask(final Task task) {
log.info("createTask is executing...");
log.info(task.toString());
return Boolean.TRUE;
}
}
As you can see, the task service implementation is lacking the real code to create a task. To
activate the code, wire a task data access object that uses a database, file system, Web service, or
any other storage medium. Next, you need to tell Spring about the task service. The tasklist-core.xml
file shown below contains a couple of bean definitions:
<bean id="taskService"
class="jbriscoe.article.spring.validation.service.impl.TaskServiceImpl" />
<bean id="customEditorConfigurer"
class="org.springframework.beans.factory.config.CustomEditorConfigurer">
<property name="customEditors">
<map>
<entry key="java.util.Date">
<bean
class="jbriscoe.article.spring.validation.SimpleDateEditor">
<constructor-arg index="0">
<bean class="java.text.SimpleDateFormat">
<constructor-arg index="0" value="M/d/yy" />
</bean>
</constructor-arg>
<constructor-arg index="1" value="true" />
</bean>
</entry>
</map>
</property>
</bean>
You may not be familiar with the customEditorConfigurer bean listed in tasklist-core.xml.
This bean comes in handy when you want to inject an instance of the java.util.Date type
from Spring’s XML configuration. Specifying a java.util.Date instance might at first
glance seem trivial but, because a date's format is locale sensitive, conversion is necessary.
Conversion from the java.lang.String to the java.util.Date is done using
the standard Java bean’s property editor, shown in
Listing 1.
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