Controller Class 从未在 Springboot 中使用 Maven

Question

I have created a very basic Spring Boot rest api Application. But somehow the application is not able to read the controller class, I am Using IntelliJ Idea Community Version.

If I hover the mouse to the controller class name it says - the class is never used. The application starts with no error, Tomcat server is up and running.

But while accessing the http://localhost:8080/details url I am getting 404 not found.

I have tried scanbasepackages too. The Controller class is in subpackage.

Below is my 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>2.3.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>11</java.version>
    </properties>
    <dependencies>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <version>2.5.0</version>
</dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.3.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.plugin</groupId>
            <artifactId>spring-plugin-core</artifactId>
            <version>2.0.0.RELEASE</version>
        </dependency>
    </dependencies>

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

</project>

Controller class:

package com.example.demo.controllers;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class APIController {
    @GetMapping("/details")
    public String foo() {
        return "success";
    }
}

Application class:

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication(scanBasePackages={"com.example.demo"})
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

If anyone can help please, Thanks in advance.

Answer 1

Add this dependency to your pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Answer 2

You can use start.spring.io and add missing dependencies. In your case you need spring-boot-starter-web

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

You can click on button explore and you will see a pom.xml file and simply add missing dependency to your project.

After that you can reload pom.xml file to resolve new maven dependencies.

You can use this approach whenever you need to add a new dependency to your spring boot project.