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What is the reason why Spring MVC can respond to HTTP requests? I believe many inexperienced people don't know what to do about it. Therefore, this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

Many Java interviewers like to ask this question:

In a Spring MVC project file, developers do not develop their own Servlet, but only define that the method home can respond to requests sent to / mvc/test1 by annotating @ RequestMapping.

Using the url http://localhost:9098/MavenSandbox/mvc/test1 test, you can observe the string returned by the home method. What is the working principle behind this?

We answer through our own research. Set a breakpoint on line 53 above. Visit url http://localhost:9098/MavenSandbox/mvc/test1 again and the breakpoint is triggered. We observe the call stack and find that there is a stack frame DispatcherServlet.doService (HttpServletRequest, HttpServletResponse). This Servlet will be responsible for adding the return string in our @ RequestMapping annotated method to the HttpServletResponse, which is why we can see the return string in the browser.

Let's see if the HttpServletResponse in DispatcherServlet.doService contains the desired output string. Expand the response variable in the debugger:

Response- > outputBuffer- > bb- > buff, you can see this string array buffer in buff:

104is the ASCII code of H, 101is the ASCII code of e, 108is the ASCII code of l, so it is proved that response does contain the string returned by the developer in the home method: hello this is a most simple example.

Finally, where did DispatcherServlet come from?

Found in the Eclipse debugger, it is the standard Servlet of the Spring framework:

Org.springframework.web.servlet.DispatcherServlet

This Servlet is our Servlet in the web.xml file in the WEB-INF folder.

So the answer to the interviewer is: the Spring MVC framework still requires Servlet, but this Servlet is provided by the Spring framework and does not require repeated implementation by application developers.

After reading the above, have you mastered the reason why Spring MVC can respond to HTTP requests? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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