Java controller always return a 404 no matter what I do

I was following an example from the spring boot documentation and the java controller always returns a 404 for some reason

This is what I tried

package com.example.accessingdatamysql;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller // This means that this class is a Controller
@RequestMapping(path="/demo") // This means URL's start with /demo (after Application path)
public class MainController {
  @Autowired // This means to get the bean called userRepository
         // Which is auto-generated by Spring, we will use it to handle the data
  private UserRepository userRepository;

  @PostMapping(path="/add") // Map ONLY POST Requests
  public @ResponseBody String addNewUser (@RequestParam String name
      , @RequestParam String email) {
    // @ResponseBody means the returned String is the response, not a view name
    // @RequestParam means it is a parameter from the GET or POST request

    User n = new User();
    n.setName(name);
    n.setEmail(email);
    userRepository.save(n);
    return "Saved";
  }

  @GetMapping(path="/all")
  public @ResponseBody Iterable<User> getAllUsers() {
    // This returns a JSON or XML with the users
    return userRepository.findAll();
  }
}

which is the example given by spring boot here https://spring.io/guides/gs/accessing-data-mysql/

Then I also tried

@RestController
@RequestMapping("/demo")
public class GreetingClass {

	@GetMapping("/greeting")
	public String getGreeting() {
		return "hello";
	}
}

.pom file:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.2.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.braintobytes</groupId>
	<artifactId>Finance_microservice</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>Finance_microservice</name>
	<description>Finance service</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-rest</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-mail</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-webflux</artifactId>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>
		<!-- https://mvnrepository.com/artifact/javax.persistence/javax.persistence-api -->
		<dependency>
			<groupId>javax.persistence</groupId>
			<artifactId>javax.persistence-api</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
		<dependency>
			<groupId>io.projectreactor</groupId>
			<artifactId>reactor-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

I know this is weird, I set up everything as instructed on the page but apparently nothing works, and I also checked other questions similar to this none of them answer my question.

It does seem that the tomcat server is hit, because it says when I make a call

o.s.web.servlet.DispatcherServlet        : Completed initialization in 9 ms

but then I get with this call curl 'http://localhost:8080/demo/greeting' and with 'http://localhost:8080/demo/all'

curl : The remote server returned an error: (404) Not Found.

Logs (the file path is removed on the first line):

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.2.RELEASE)

2020-08-31 08:19:16.508  INFO 20708 --- [           main] c.b.f.FinanceMicroserviceApplication     : Starting FinanceMicroserviceApplication on DESKTOP-A65224I with PID 20708 ()
2020-08-31 08:19:16.510  INFO 20708 --- [           main] c.b.f.FinanceMicroserviceApplication     : No active profile set, falling back to default profiles: default
2020-08-31 08:19:17.096  INFO 20708 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-08-31 08:19:17.101  INFO 20708 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-08-31 08:19:17.101  INFO 20708 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.37]
2020-08-31 08:19:17.150  INFO 20708 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-08-31 08:19:17.150  INFO 20708 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 618 ms
2020-08-31 08:19:17.465  INFO 20708 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-08-31 08:19:17.675  INFO 20708 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-08-31 08:19:17.681  INFO 20708 --- [           main] c.b.f.FinanceMicroserviceApplication     : Started FinanceMicroserviceApplication in 1.328 seconds (JVM running for 1.835)
2020-08-31 08:20:21.893  INFO 20708 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2020-08-31 08:20:21.893  INFO 20708 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2020-08-31 08:20:21.905  INFO 20708 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 12 ms

Response:

{
    "timestamp": "2020-08-31T13:20:21.930+00:00",
    "status": 404,
    "error": "Not Found",
    "message": "",
    "path": "/demo/greeting"
}

This works if I do this:

https://github.com/BraintoByte/Test_App_Stack/tree/master/demo

Different example:

I have attached a different example with hirarchy exactly the same but business logic omitted:

Code in controller:

package com.braintobytes.controllers;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import com.braintobytes.data.Currency;
import com.braintobytes.data.repository.CurrencyRepository;

@RestController
@RequestMapping("/demo")
public class CurrencyController {
	@Autowired
	private CurrencyRepository currencyRepository;
	
	@GetMapping("/currency")
	public String getCurrency() {
		return "currency";
	}
}

Project hierarchy:

Same exact pom and in application.properties:

spring.jpa.hibernate.ddl-auto=update
spring.datasource.url=jdbc:mydatabase
spring.datasource.username=myusername
spring.datasource.password=mypassword

Your controller is in package - com.example.accessingdatamysql

Spring boot startup log shows your main application class c.b.f.FinanceMicroserviceApplication is in another non related package hierarchy.

Spring boot recommends to locate main application class in a root package above other classes so that the component scan works out of box.

If you keep package com.example as root package and move your main application class FinanceMicroserviceApplication to it then everything should work as expected.

If you don't follow Spring boot recommendation for package hierarchy then you need to explicitly specify packages to scan with @SpringBootApplication annotation.

Alright so none of the suggestions above worked, we were on the right path though.

Changing the structure as so worked:

There was also a pathing problem in the application.properties and thus I changed as so:

spring.datasource.url=jdbc:mysql://${MYSQL_HOST:localhost}

To:

jdbc:mysql://localhost

And finally:

package com.braintobytes.finance.data.repository;

import org.springframework.data.repository.CrudRepository;

import com.braintobytes.finance.data.Currency;

public interface CurrencyRepository extends CrudRepository<Currency, Integer> {

}

Woah!

For anyone whom facing this wired issue, just move the main class of spring boot to become in the main package of the application, something like that, my main class named, Demo2Application