JSP Tutorial #15 – JSP Built-In Server Objects

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JSP Tutorial Transcript

Hey, in this video I’m going to show you how to make use of JSP Built-In Server Objects. What Built-In Server Objects, these are given to you for free so there’s no need to create them, you can simply use them directly in your JSP page. We’ve actually played around with some of these earlier, and I’ll show you this on the next slide. Here is the list of the commonly used JSP Server Objects. Starting here at the top with request, it contains information about the HTTP request headers and also form data, we’re going to use this a lot in some of the following videos for reading form data. There’s also the response object for sending back HTTP specific information and we will use this also in the following video on making use of cookies. This one Server object you use already, the out Object, and we use that for our out dot print line in one of the previous videos. Again, a Built-In Server Object given to you for free.

There’s two others here, session, it’s a unique session for each user. You can think of the Session Object as like the shopping cart, each user has their own unique shopping cart, we will use this on the following video. Finally there’s the Application Object, this is shared for all users of a given web app and I’ll discuss various use cases on how to use the Application Object. Just for disclaimer, this is not an exhaustive list, there’re other server objects out there but these are the ones that are commonly used for JSP web apps. Here’s the idea, you have the browser communicating with the JSP, behind the scenes the HTTP protocol, they actually send our request object, this request object contains header information and body information. JSP can perform some work on that information and then send back a response, so we have the whole request response protocol going. In the demo I’ll show you how to make use of the request object.

Let’s go ahead and move into Eclipse, what I wanted to do is continue to use the existing project JSP demo and I would like to move down to the folder your web content because we’re going to create a new file. I just say right click, I say new file. The name I’ll give here, I’ll call it builtin-test.jsp because we’re of course testing some of the built-in objects. Once you’re happy with the name we’ll go ahead and click finish. Let’s expand the window here for a second and I will bring file and start writing some code. Again, I start off with my HTML and my body information. I’ll just set up a header three just to give us a little name here for the page. Now what I want to do is, I want to read some information about the request so I want to find out what type of browser the user is using to access my JSP page. You can access this information using the request object.

So I can say, request.getHeader and then you get the header name of user-Agent. This will tell you the actual browser that the client is using, also it will tell you the operating system that they’re running on. Let me go ahead and add some line breaks here. I want to find out what language the client is making use of in their browser so if they’re using english, Spanish, German, French. Here I say request.getLocale and this will get me the actual locale that the user has set up on their system. We can use this to customize the type of pages we send the user based on their actual locale, like English or German or Spanish. That’s basically it for this very basic demo here. Go ahead and save your file and let’s go ahead and run this program. I move to the file builtin-test.jsp, I’ll do a right click and I’ll say run as and then run on server so the application runs.

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