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This article mainly explains "introduction and working principle of servlet". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "introduction and working principle of servlet".

Introduction to Servlet

Like the JavaBean learned before, Servlet is essentially a Java class, writing Servlet needs to follow the basic syntax of java, but unlike general Java classes, Servlet is a Java class that can only run on the server side, and must follow special specifications and have its own life cycle in the process of running. These features are unique to Servlet. In addition, Servlet and HTTP protocols are closely related, so using Servlet can deal with almost all aspects of HTTP protocol, which is the biggest reason why Servlet is favored by developers.

How Servlet works

A simple login example for jsp+servlet

JSP page code

Name:

LoginServlet code

Package com.bjpowernode.test; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet {@ Override public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String username=request.getParameter ("username"); System.out.println ("username=" + username); response.setContentType ("text/html;charset=UTF-8") Response.getWriter () .println (username+ "login success"); @ Override public void doPost (HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet (req, resp);}}

Profile code

Index.jsp MyServlet com.bjpowernode.test.LoginServlet MyServlet / loginServlet

Detailed explanation of process

1. Submit the form to Tomcat in the jsp page, and the requested url is http://127.0.0.1:8080/JavaWebExercise/loginServlet.

2. When the request reaches the Tomcat, the server intercepts the url to obtain the project name requested by the client (in this case, JavaWebExercise).

3. Find the project, and then intercept the corresponding servlet access name according to url. Here is loginServlet.

4. Find Servlet-name according to loginServlet. Here is MyServlet.

5. Find the corresponding class file according to Servlet-name. Here is the LoginServlet class under the com.bjpowernode.test package.

6. Use reflection to instantiate the found servlet class.

7. According to the category of the request, call the service method in the servlet parent class to distribute

8. Call the corresponding doGet/doPost according to the distribution of the service (here we call the get method).

9. Get the passed parameter value.

10. Call other javaBean to complete the business logic.

11. Complete the business logic and return to Servlet.

12. Output html string

13. Return html to the Tomcat server

14. Render the page through the resulting html.

Thank you for your reading, the above is the content of "introduction and working principle of servlet". After the study of this article, I believe you have a deeper understanding of the introduction and working principle of servlet, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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