After exploring Java Enterprise, Servlets & JSPs I felt ready to return to Spring and dive deeper into what Spring MVC is all about.
This project goes against the principle of:
Make JAR, not WAR!
-- Josh Long
However, we will learn a lot about the inner workings of Spring. Also, there might be older projects we need to work on depending on this monolithic type of packaging. (Or projects that for some reason need to save on web space, or depend on some other advantages of .war.)
We don't start this project with the Spring initializr though, but use the Maven 'archetype-web-app' option under Maven projects.
We could also just make a maven project and enable web application support. In IntelliJ we navigate to:
'File -> Project Structure -> Modules'. There, select your web facet and click the plus button.)
From what I understand, Spring hides some older project structure from the user, but to start off this project we will need access to the web.xml
in the "webapp > WEB-INF" - file structure. It is where we can set up and configure our connections to the 'invisible' dispatcher servlet,
the front-controller that has been doing all the hard work in our Spring projects without taking any credit.
Be sure to check the POM to see common dependencies we will want to add to our project.
When using the Spring Initializr, it includes some of these dependencies already.
As its name suggests, it is a central dispatcher for HTTP request handlers/controllers, e.g. for web UI controllers or HTTP-based remote service exporters.
The dispatcher servlet dispatches requests and responses to registered handlers for processing, providing convenient mapping and exception handling facilities.
We started off with a full XML-based configuration of the web application and the dispatcher servlet. Then we discarded the 'web.xml'
and switched to using the annotated class 'MyWebInitializer'. After that we also changed out the -servlet.xml for the 'MyConfig' class.
Here
we can find more information on how to set up either an XML-based configuration, a code-based one or even a hybrid.
Because all requests go through our dispatcher servlet we can also add a prefix and suffix to our views here.
If we ever change the view layer we would just need to change the suffix in one location.
Java Config:
@Bean
public InternalResourceViewResolver viewResolver(){
InternalResourceViewResolver vr = new InternalResourceViewResolver();
vr.setPrefix("/WEB-INF/");
vr.setSuffix(".jsp");
return vr;
}
Xml:
<bean id="viewResolver"
class="org.springframework.web.servlet.view.UrlBasedViewResolver">
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/>
</bean>
It is also possible to mix or chain, more on this here.
Because we are not using spring boot, but are rather augmenting a Java web application with Spring features we would actually need web.xml in this case. There is no Java Config equivalent for:
<error-page>
<location>/error</location>
</error-page>
In this example we can see how to fetch the error message along with the status code and exception type.
We will continue exploring The Spring Servlet Stack in two separate repositories to avoid confusion.
These repositories can be found here: