Implementing Servlets in Java Web Applications
Tech
1
Servlet Introduction
----------
By default, Java classes cannot be accessed through a browser. In JavaWeb, there's a special type of class that can be accessed via browser URLs, known as dynamic resources. These are called Servlets.
JavaWeb consists of three layers:
service: Business layer
server: Server, server-side
servlet: JavaWeb dynamic resources
Implementation Steps
### 1. Implement the javax.servlet.Servlet Interface
First, you need to implement the Servlet interface, which is located in the Servlet-api.jar file. Then, override its methods as shown in the following code example.
### 2. Override Servlet Methods
* Initialization method, a lifecycle method that doesn't require manual invocation.
* It's called by the Tomcat server after the Servlet object is created.
@Override
public void init(ServletConfig servletConfig) throws ServletException {
System.out.println("BServlet has been initialized...");
* Get the ServletConfig object, which contains configuration information for the Servlet
* This is not a lifecycle method
@Override
public ServletConfig getServletConfig() {
return null;
}
* Service method, a lifecycle method called once for each user request to this Servlet
@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
System.out.println("Hello, I'm BServlet, glad to assist you...");
}
* Non-lifecycle method to get Servlet description information
@Override
public String getServletInfo() {
return "BServlet is an efficient Servlet";
}
* Lifecycle method called before the Servlet object is destroyed
* Used for resource cleanup
@Override
public void destroy() {
System.out.println("BServlet is being destroyed....");
}
### 3. Configure the Servlet
Configure the Servlet by binding it to a URL (the path clients will use to access the Servlet). This configuration is done in the WEB-INF/web.xml file.
BServlet
com.example.servlet.BServlet
BServlet
/BServlet
### 4. Deployment with Tomcat
Launch the application using Tomcat to make the Servlet accessible through the configured URL.
