The javax.servlet package is a part of the Java Servlet API. It contains a number of classes and interfaces that are used to create servlets and to interact with web servers.

Some of the important Interface in the javax.servlet package include:

• Servlet: This is the main interface that must be implemented by a servlet. A servlet is a Java class that runs on a web server and is used to handle client requests.
• ServletRequest and ServletResponse: These interfaces represent the request and response objects that are passed between the servlet and the web server.
• ServletConfig: This interface represents the configuration for a servlet, including initialization parameters and the servlet's context (the servlet's environment).
• ServletContext: This interface represents the context in which a servlet is running, including information about the web application and the container in which the servlet is running.
• SingleThreatModel: This is an interface that is used to make a servlet accessible to only one thread at a time. The main advantage of this approach is that the servlet object can be accessible to only one tread and the object is now a threat safe. But by this approach waiting time of threads increase, which can reduce the performance.
• RequestDispatcher: This interface is used to displace request from one servlet to another servlet.

Some of the important classes in the javax.servlet package includes:

• GenericServlet: This class implements the servlet interface and acts as a base class to develop protocol independent servlet.
• ServletInputStream: This class is use to read binary data sent by end user.
• ServletOutputStream: This class is use to write binary data to the response.
• ServletException: This is the exception that is thrown when a servlet encounters an error.

There are many other interface and class inside the javax.servlet package, But these are the important interface and class inside javax.servlet package.

Web container and its type

A web container (also known as a servlet container) is a component of a web server that is responsible for running servlets. A servlet is a Java class that runs on a web server and is used to handle client requests. The web container is responsible for managing the lifecycle of servlets, mapping requests to servlets, and ensuring that servlets are properly initialized and destroyed.

There are several different types of web containers, including:

• Apache Tomcat: This is an open-source web container that is widely used in Java-based web applications.
• Jetty: This is another open-source web container that is used in a variety of applications.
• GlassFish: This is an open-source web container that is part of the Oracle Corporation's Java EE platform.
• WebLogic: This is a web container developed by Oracle Corporation and is part of the Oracle WebLogic Server application server.
• WebSphere: This is a web container developed by IBM what is web container and its type

All the web container are categories in three types.

1. Standalone web containers:

In This web container the web server and the web container are available as a single integrated component.

2. In process web containers:

In this web containers the web b container is not a part of a web server but it is connected to the web server as plug-in and both web server and web container are running in the same address space (same machine).

3. Out process web containers:

In this web containers the web server and the web containers are running on the separate machine.