Master The Art Of Java: Key Differences Between Servlet and JSP

Being one of the oldest and most popular languages in the software industry, Java shelters a treasure trove of tools and technologies. This fact proves to be both a blessing and a challenge for developers who are still in the process of familiarizing themselves with the nuances of Java.

When it comes to complex technicalities, developers often face the dilemma of Servlet vs. JSP. To help untangle this complexity, we will explore the key differences between Servlet and JSP in this blog.

Primary Differences Between Servlet and JSP

Java servlets and JSPs (Java server pages) are essentially programs (specific to Java) that run on a Java application server. They are primarily designed to extend the capabilities of the web server.

To better understand the difference between these two technologies we have to first study them individually.

What Are Java Servlets?

Java servlets play an important role when it comes to creating web applications. A servlet in Java is a class used to enhance the functionality of servers that host applications accessed by a request-response model.

Popularly called as Java classes, the Java servlets are adept at responding to HTTP requests in the context of a web application. The servlet containers are that aspect of web servers that can be run in a separate process.

In this process, there are three types of servlet container states – standalone, in-process, and out-of-process.

Servlet Life Cycle

The Servlet life cycle consists of five steps. Let’s take a quick look at what the process looks like:

1. Load Servlet Class:

This step is executed only once at the time of the first request. To begin with, the web container loads the servlet once the first request is received.

2. Create Servlet instance:

Once the servlet class is loaded, the web container then creates the servlet instance. There is only one dedicated instance for each servlet. After that, all the other concurrent requests are executed on that same servlet instance.

3. Call init() method:

Then, the servlet instance web container evokes the servlet’s init() method. This method focuses on initializing the servlet before processing the first request. It is called only once by the web container.

4. Call service() method:

After the initialization, the web container proceeds to call the service method. The service() method has to be called for every request. Developers have to create a dedicated thread for every request servlet.

5. Call destroy() method:

Here, the destroy method is called by the web container before removing the servlet instance. It is called only once by the web container after all threads of the servlet have been removed. This is also where the servlet releases all the resources associated with it.

What Are Java Server Pages (JSPs)?

Much like Servlets, Java server pages in advanced Java are used to build intuitive web applications. In its simplest sense, a JSP is a text document. It comprises two types of text – static data and dynamic data.

The static data can be expressed in any text-based format (like HTML, XML, SVG, and WML). JSP elements are leveraged to express the dynamic data.

The Java server pages architecture has three key pillars – client, web server, and database. The client is the web browser or application on the user side. To process JSP, the web server uses a JSP Engine.

This engine builds Java Servlet, compiles and executes Java code, and returns the HTML page to the client. The web server is linked to the Database which is also connected to the JSP engine.

JSP Life Cycle

Converting JSP Page Into Servlets:
The JSP life cycle begins with translating JSP pages into Java codes. This step is where the Syntactic correctness of JSP is analyzed. Here test.jsp file is translated to test.java.

1. Compiling The JSP Pages:

In the second step, the generated Java servlet file (test.java) is compiled into a class file (test.class).

2. Classloading:

After the compilation, the Servlet class which has been loaded from the JSP source is then loaded into the container.

3. Instantiation:

The fourth step is where an instance of the class is generated. The container takes care of one or more instances by providing responses to requests.

4. Initialization:

Shortly after the generation of the Servlet instance from JSP, the jspInit() method is called. This is done only once during the entire JSP life cycle.

5. Request Processing:

Then, the _jspService() method is used to serve the raised requests by JSP. In this method, the request and response objects are considered as parameters. This step cannot be overridden.

6. JSP Clean-up:

In the final stage, the jspDestroy() method is used to erase the JSP by the container or to destroy the method for servlets. Ideally, this method is called only once.

However, if there are instances where performing any clean-up task like closing open files, or releasing database connections is a must, then the jspDestroy() method can be overridden.

Servlet vs JSP – Key Differences

Now that we have studied the purpose of these tools individually along with their life cycles, let’s take a look at some of the more particular distinctions between the two.

Servlet JSP
   
Servlets are essentially Java codes. Whereas JSP is an HTML-based code.
   
When it comes to projects with tight schedules, Servlets are considered to perform faster than JSPs are their processing cycle is much shorter and simpler. JSP is slower in comparison as the pages have to first be translated into Java codes and then compiled for further use.
   
Servlets are hosted and executed on Web Servers. JSP is compiled in Java Servlets before their execution.
   
In MVC architectures, Servlets play the role of controllers. On the other hand, JSPs act as a view to present the output to the users in MVC architectures.
   
The task of writing codes for servlets is much more complex than JSP. This is because it is HTML in Java. Contrarily, it is quite easy to code JSPs because it is Java in HTML.
   
Servlets are capable of accepting all protocol requests. JSPs can only accept HTTP requests.
   
With Servlets, developers do not have the option of running JavaScript on the client side. Developers can use client-side validation when running JavaScript on the client side in JSP.
   
Writing custom tags is not possible when working with Servlets. JSPs enable developers to build the JSP tags easily, which can directly call JavaBeans.
   
The default session management is not enabled in Servlets. Developers have to enable it separately. Developers can skip this step with JSPs as session management is automatically enabled here.
   
Servlets do not feature any in-built implicit objects. In-built implicit objects are already present in JSPs.
   
Developers have to implement everything like business logic and presentation logic in just one Servlet file. With JSP, business logic is separated from presentation logic by using JavaBeansclient-side.
   
The necessary packages have to be imported on top of Servlets. Packages can be easily imported into the JSP program via the bottom, middle client-side, or top.
   
Making modifications in Servlet can be a tedious task. It involves reloading, recompiling, JavaBeans, and restarting the server. With JSP, making modifications is a cakewalk comparatively. Developers are simply required to click the refresh button.
   
The service() function can be overridden in Servlets. The service() function cannot be overridden in JSPs.
   
Extensive data processing is an easier step in Servlets. JSPs fall a little short when handling an influx of data.

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