I am getting a 404 Error on API Call in Spring Boot

Question

I am working on a Spring Boot Application. I am getting a 404 error on hitting the URL-path which I have configured. Where am I going wrong?

HomeController.java

package com.example.homes;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController("/add")
public class HomeController {

    @GetMapping("/hello")
    public String add() {
        return "Hello";
    }

}

HomeApplication.java

package com.example.homes;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
public class HomeApplication {

    public static void main(String[] args) {
        SpringApplication.run(HomeApplication.class, args);
        System.out.println("Inside main");
    }

}

Answer 1

You are missing RequestMapping for /add. You kept as @RestController property. It should be @RequestMapping("/add"). In your current code hello is mapped to root.

try localhost:8080/hello and it will work.

If you wantlocalhost:8080/add/hello

Then it should be like below:

@RestController
@RequestMapping("/add")
public class HomeController {

    @GetMapping(value = "/hello") 
    public String add() {
        return "Hello";
    }
}

Answer 2

Instead of doing @RestController("/add"), Do this,

@RestController
@RequestMapping("/add")

Then you should be able to call localhost:8080/<ApplicationContext>/add/hello

Answer 3

@RestController is a specialized version of @Controller which adds @Controller and @ResponseBody annotation automatically. so we do not have to add @ResponseBody to our mapping methods.

@RequestMapping maps HTTP requests to handler methods of MVC and REST controllers.

Here possible suspect is @RestController("/add") which should be @RequestMapping("/add")

@RequestMapping at Class Level

@RestController
@RequestMapping("/add")
public class HomeController {

    //localhost:8080/add/hello (No Context Path in application.properties)
    @GetMapping("/hello")
    public String add() {
        return "Hello";
    }

}

@RequestMapping at Method Level

@RestController
public class HomeController {

    //localhost:8080/hello (No Context Path in application.properties)
    @GetMapping("/hello")
    public String add() {
        return "Hello";
    }

}

If you don't have any context path defined in application.properties then calling
localhost:8080/add/hello will give the desired output

In case you have a context path as app then call localhost:8080/app/add/hello