How does @PostMapping work?

[greg mic]

Hi all!

I know it's a very basic and broad question but how does postmapping work?

For a school project, I have to build a spring application, that has both a @getmapping and a @postmapping method (?), and I think I nailed the @getmapping part, but I have no idea how to do the other one.


For the getmapping part, my task was to write "Hello user" to localhost if localhost has no parameters, and write "Hello *name*" if localhost does have a name parameter.

For the postmapping, I should write a code that posts the following text backwards to localhost if it has no text parameter: " Have a nice day" and if it does have a text parameter, then the text written in the text parameter should be posted backwards.

I hope it's not too confusing and sorry for the cr@ppy english but I barely understand the task in my native language.

I'll post what I have so far:


I have a "Greeting.java" class:

public class Greeting {

    private final String content;

    public Greeting(String content) {

        this.content = content;
    }

    public String getContent() {
        return content;
    }
}

And I have a "GreetingController.java" class:

import java.util.concurrent.atomic.AtomicLong;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GreetingController {


        private static final String template = "Hello, %s!";
        private final AtomicLong counter = new AtomicLong();

        @PostMapping

       .............

        }

        @GetMapping("/greeting")

        public Greeting greeting(@RequestParam(value = "name", defaultValue = "User") String name) {
            return new Greeting(String.format(template, name));
        }
    public String getMessage(@RequestParam String name) {
        return String.format("hello %s", name);
        }
    }

Thank you for your help in advance and sorry for the long question.

[Campbell Ritchie]

greg mic wrote:. . . it's a very basic . . . question  . .

No, it isn't. Let's move you to the Spring forum, where we usually discuss that sort of question.

[greg mic]

Campbell Ritchie wrote:

greg mic wrote:. . . it's a very basic . . . question  . .

No, it isn't. Let's move you to the Spring forum, where we usually discuss that sort of question.

Sorry for posting in the wrong forum

[Campbell Ritchie]

Think nothing of it.

[Himai Minh]

Hi, Greg,
Back to your question , how does @PostMapping work?
You may want to search for tutorials about Restful web services. There are four operations, CRUD. C stands for "create", which is what post mapping do.
If you have a database, post is to create new data.
One of the references:
https://stackabuse.com/get-http-post-body-in-spring/

[Stephan van Hulst]

greg mic wrote:write "Hello user" to localhost

First off, it's important to get the vocabulary right. You don't "write to localhost". You "write a response" or you "write to a page hosted at localhost". When we talk about localhost, we mean the machine the software is currently running on.

if localhost has no parameters, and write "Hello *name*" if localhost does have a name parameter.

Again, localhost is a machine. It doesn't have parameters. You mean "if the URL contains a name argument".

Sorry for being nitpicky, but if you don't use the correct terminology it's going to be hard for people to help you.

Anyway, yes you nailed the GET mapping. Now let's take a look at the POST mapping.

For the postmapping, I should write a code that posts the following text backwards to localhost if it has no text parameter: " Have a nice day" and if it does have a text parameter, then the text written in the text parameter should be posted backwards.

It's extremely unfortunate that the assignment immediately teaches you wrong things.

POST messages are used when you want to make a change to an application, such as saving data to a database. When the action doesn't make any changes to the application, but only transforms your input and then spits it out again, you would use a GET message.

This is not your fault. Just keep in mind that POST is not normally used for the kinds of tasks like the one in your assignment.

What have you tried? What are you stuck on? Do you know how to trigger a POST request?