The architecture of a servlet involves several components that interact with each other to process client requests and generate responses. Here's a detailed explanation of the architecture:
1. Client/Browser
The client, typically a web browser, initiates the process by sending an HTTP request to the web server. This request could be triggered by the user entering a URL or interacting with a web page that sends a request to the server[1].
2. Web Server
The web server receives the HTTP request from the client and forwards it to the servlet container. The web server's primary role is to manage incoming network connections and facilitate the communication between the client and the servlets[1][3].
3. Servlet Container (Web Container)
The servlet container, also known as a web container, is a crucial component of the servlet architecture. It is responsible for managing the lifecycle of servlets, mapping requests to specific servlets, and ensuring that the servlets have the necessary resources to process requests. Examples of servlet containers include Apache Tomcat, Jetty, and JBoss[1][2][3][4][8].
Lifecycle Management
The servlet container controls the lifecycle of a servlet through several stages:
Loading: The servlet class is loaded into memory when it is first requested or when the server starts, depending on the container's configuration[1][6].
Instantiation: The servlet container creates an instance of the servlet[6].
Initialization: The init() method is called once when the servlet is first loaded. This method is used for resource-intensive setup tasks that need to be performed only once[1][6].
Request Handling: For each client request, the service() method is called. Depending on the type of request (GET, POST, etc.), this method may call doGet(), doPost(), or another similar method[1][6].
Destruction: When the servlet is no longer needed, or when the server is shutting down, the destroy() method is called. This method is used for cleanup activities such as releasing resources[1][6].
Request and Response Objects
The servlet container creates ServletRequest and ServletResponse objects for each request. These objects provide methods to read data from the client (request) and send data back to the client (response)[1][3][19].
