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During this video, I'll give you an overview of what each part of the Spring Framework offers to us for developing web apps.
JavaBeans vs. Spring Beans
Spring beans typically adhere to the requirements of the JavaBean specification. Independent of Spring, a JavaBean is any object that meets the following requirements:
- has a public, default constructor,
- has fields that are accessed through public getters & setters, which follow the standard naming convention of getFieldName (or isFieldName for boolean fields) and setFieldName, and
- implements
java.io.Serializable.
In general, Spring beans follow this convention, except that Spring beans do not need to implement java.io.Serializable.
In general, Spring beans are any object constructed and managed by the Spring Framework. Spring beans are the objects eligible for injection with the @Autowired annotation, as you'll see later in the course.
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[MUSIC]
0:00
Writing a Java application that can run
on a web server is tricky business.
0:04
This is where the Spring frame
works swoops in to save the day.
0:08
In the last stage, I mentioned that
crafting a response to a browser request
0:12
to the web server would be
the job of our application, and
0:16
it is this very application that
we'll be talking about and creating.
0:20
That is, we'll be using the Spring
Framework to write the Java code necessary
0:24
to respond to requests
that come to GIFLIB.
0:28
The entire Spring Framework consists
of many different components,
0:32
some of which we won't
be using in this course.
0:35
And what is a component exactly?
0:38
A component is simply a set of
related functionality that,
0:41
in the case of Spring,
resides in a JAR file of its own.
0:45
With that said, let's take a look at
the components that we'll be using, and
0:48
see how they'll help us accomplish
the task of writing a Web application.
0:52
The core component contains lots of
the gears that turn the spring engine.
0:56
Most of the classes you
won't directly use,
1:00
even though it's all being used by
other pieces of the spring framework.
1:03
The beans component is the part of
the spring framework that allows
1:07
any Java object to be created and used
in what's called the Servlet Container,
1:10
which is the container of your entire
running application on the web server.
1:15
You want to use all that object-oriented
business you've learned in previous
1:20
Treehouse courses, right?
1:23
Well, the beans component will load your
objects in a way that makes them usable,
1:25
and even reusable, while your application
is up and running on the web server.
1:30
Those objects are called beans.
1:34
All right, cool beans.
1:37
[SOUND] In addition to
other functionality,
1:38
the Context Component gives us a bunch
of annotations that will leverage in
1:40
configuring our application including,
the Configuration Annotation
1:45
which will apply to classes that
application configuration code,
1:49
the Controller Annotation which will be
applied to a class that we write to handle
1:53
requests to specific URIs, and the
ComponentScan annotation, which will tell
1:58
the spring framework to scan our Java
classes for things like controllers.
2:03
SpEL stands for Spring Expression
Language, and is a language that we'll
2:07
put to use in our HTML templates
that will allow us to iterate over,
2:12
perform operations with, and
format Java data for display.
2:17
AOP stands for Aspect-Oriented
Programming, this component allows us to
2:22
cleanly apply functionality to many,
or all parts of our web application.
2:27
Such as adding a security check to verify
that a user is logged-in before performing
2:31
certain tasks like uploading new GIFs, or
marking or unmarking GIFs as favorites.
2:36
Now on to the web container starting
with the servlet component.
2:42
If you remember in the first stage we used
cradle to download the spring web mvc
2:47
library, in fact what spring web mvc
refers to is the servlet component, it is
2:51
this component that contains a key player
in the functioning of our web application.
2:58
What is this key player?
3:03
It's called a Dispatcher Servlet.
3:05
Think of the Dispatcher Servlet
as our application's usher,
3:08
who is there to receive requests
from the web server, and usher or
3:12
dispatch them according to
our configuration and code.
3:15
When our code is done
processing the request,
3:19
the dispatcher servlet ushers
the response to the door,
3:22
handing it back to the web server
to send it back to the client.
3:25
[SOUND] Finally, there's the web
component, from which we'll get
3:28
the ability to capture a request
to a specific resource and
3:33
take action accordingly.
3:37
For example, in our GIFLib application,
a visitor might click on a navigation link
3:39
for categories, the URI for
which we could capture,
3:43
then respond with the page that
shows them all the categories.
3:47
Or from the homepage, they could
click on a specific GIF, the URI for
3:51
which we could capture and
then respond with the page that shows
3:55
all the details for that GIF, including
the date uploaded, and a sharable URL.
3:59
[SOUND] That's a lot of information.
4:05
I realize at this point that
discussing the organization of this
4:08
powerful framework might seem
a bit abstract and confusing now.
4:11
Don't worry, we'll continue to revisit
these components as we use each of them.
4:16
And, kind of like your
favorite coding books, or
4:20
bookmarked websites, feel free to
come back to this video and rewatch.
4:23
Next, we'll look at how exactly
we're going to use Java code
4:28
to incorporate the components of
the spring framework into our application.
4:32
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