Updated February 14, 2023
Introduction to Servlet Life Cycle Methods
A servlet’s life cycle is the duration from its production until its eventual termination. The servlet life cycle uses the init(), service(), and destroy() methods. The servlet life cycle method includes constructing an instance of the servlet, initialization information, sending requests to the servlet instance, and deleting the instance. The servlet life cycle works with the object and its operation using the servlet method. The servlet life cycle starts, destroys, and sends a request to the other objects using the method.
Overview of Servlet Life Cycle
The servlet container that employs javax. Servlet manages the life cycle of a Servlet. The servlet interface comprehends and controls the servlet object. To establish a servlet object, let’s understand the servlet object’s life cycle, which means the servlet container handles the servlet object. The servlet life cycle uses mainly three methods to initialize the object, send a request to another servlet and destroy the object after operation completion. It must load the servlet page before starting the servlet life cycle method. The servlet life cycle loads the servlet page and then uses the init, service, and destroy methods. After executing destroy() method, the servlet request goes to garbage collection.
Different Servlet Life Cycle Methods
There are three methods used by a servlet life cycle:
- init() method: The servlet page initializes the object using the init method in the life cycle operation.
- service() method: The servlet page calls client requests or provides services using the service method in the life cycle operation.
- destroy() method: The servlet page destroys objects using destroy method in the life cycle operation.
The below information gives servlet life cycle methods information with the syntax:
1. init() method
The servlet init() method calls single time. It is only invoked at the creation of the servlet object. Ordinarily, the servlet is produced when a user creates a URL matching the servlet. When the server is launched, you can alternatively request that the servlet be loaded. When a user creates a servlet, a single instance or object of each servlet is produced with each user request. The init() method only generates or loads data that will be utilized throughout the lifetime of the servlet.
Syntax:
The following syntax shows how to use the init() method:
public void init() throws ServletException { // Initialization servlet object and servlet }2. service() method
The service() method is the primary method used to complete the life cycle operation. The servlet web server runs the service method to process requests from browsers. The browser returns a structured response after the process of the method. Every time the server page receives a servlet request, it creates a new thread and invokes the service. The service () method examines the HTTP request type and calls the necessary methods accordingly.
Syntax:
The following syntax shows how to use the service() method.
public void service(ServletRequest svltrequest, ServletResponse svltresponse) throws ServletException { }3. destroy() method
The destroy() method calls only once after a servlet’s life cycle operation. This method provides the opportunity for your servlet to end database connections. In addition, it works to clean up tasks and use garbage collection.
Syntax:
The following syntax shows how to use destroy() method.
public void destroy() throws ServletException { // Finalize servlet object and servlet }Servlet Life Cycle
The web container maintains a servlet instance’s life cycle.
- The loaded servlet class: The servlet class has to be loaded by the classloader. When the web container receives the initial request for the servlet, the servlet class is loaded.
- A new servlet instance is made: After loading the servlet class, the web container generates the servlet instance. In the servlet life cycle, the servlet instance is produced only a single time.
- The init method is used: After generating the servlet instance, the web container only makes one call to the init function. It belongs to the javax. Servlet package of the life cycle function. The servlet is initialized using the init function.
- It calls the service method: The service () method is the most crucial procedure to establish a connection between the client and server is the service() method. The “doGet()”, “doPost()”, and other methods use as a service method for the servlet life cycle.
Two parameters are accepted by the service method, such as request and response. The connection between the client and server is contained within the ServletRequest with the object. The connection from the server back to the client is contained in the ServletResponse with the object. - It calls the destroy method: Before completing and disabling the servlet instance from the service, the web container uses the destroy() method. It provides a chance for the servlet to clean up servlet resources.
Servlet Life Cycle Web Container
The essential part of the servlet life cycle is a web container. It interacts with the servlet page using the web container.
A servlet life cycle’s web container has two primary duties:
- Servlet lifecycle management
- Mapped URLs
The web container is a server-side component that manages and processes all requests from the servlet page.
Servlet deployment takes occurs in a container. The server delivers the request to the container and then the servlet directly when a client sends a request to a web server that hosts a servlet. After determining the requested servlet, the container loads the servlet’s doGet() or doPost() methods. These methods pass the servlet the HTTP request and response ().
Architecture
The following figure shows you the basic architecture of the servlet life cycle and its methods.
It shows the servlet life cycle operation with each method and servlet container.
- First, HTTP requests arriving at the server are routed to the servlet container.
- The init method comes from a web container to initialize each object.
- The servlet container loads the servlet before running the service() method.
- The servlet container handles numerous requests by generating many threads. It executes the service() method of a single object of the life cycle of the servlet.
- The destroy() method closes the connections and cleans up the instance of the servlet.
Conclusion
The servlet life cycle is an essential function for servlet web development applications. It helps create different web, online, and desktop applications.
Recommended Articles
This is a guide to Servlet Life Cycle Methods. Here we discuss the introduction, different servlet life cycle methods, web containers, and architecture. You may also have a look at the following articles to learn more –
