Java Servlet

Java Servlet

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A Java Servlet is a Java software component that extends the capabilities of a server. These are used to extend the functionality of web servers that host applications accessed via a request-response model. Most commonly, Java Servlets are used to implement web applications.

The Servlet API, which you can use in your applications to interact with the web server, includes interfaces and classes for writing Servlets. The most important class is javax.servlet.Servlet, an interface that must be implemented by any class that acts as a Servlet.

A Servlet’s lifecycle can be defined by the following three methods:

  1. init(): This method is called by the Servlet container to initialize the Servlet. It is called only once during the lifecycle of a Servlet, similar to the constructor in Java classes.
  2. service(): This method is responsible for handling requests coming from clients. It is called for each request, and it dispatches the request to one of the doXXX() methods (doGet(), doPost(), etc.) depending on the type of the client’s request.
  3. destroy(): This method is called by the Servlet container before removing the Servlet instance from service. It is only called once, and it is the last method that is called in a Servlet’s lifecycle.

Servlets have several advantages over CGI and other APIs:

  • Performance: Because a new thread is created for each client request (instead of a new process, as with CGI), Servlets are more efficient.
  • Persistence: Servlets persist between client requests, allowing them to store information from previous requests, making them useful for things like session management and caching.
  • Portability: Servlets are written in Java, so they can be used on any operating system that supports the Java Virtual Machine (JVM).
  • Power: Servlets have all the abilities of Java, including networking and database connectivity.

Servlets are a fundamental technology underlying Java EE web applications and many web frameworks such as Spring MVC and JSF. They are typically used in conjunction with JSP (JavaServer Pages) to create dynamic web content.

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