SpringBoot doesn't recognize RestController from another module in multi module Java application

Question

I've spent quite some time but I can't get past this (configuration) issue.

Technology stack : Java (1.8), Springboot (starter-parent, starter-web), Maven, IntelliJ IDEA

Description: Trying to create a multi module Java application composed (at first) of 2 modules :

1. core module : main module (main business logic, every other module should see and interact through this one). This module contains the main application class.
2. webgateway module : Simple Rest Controller that will map a request and make calls to the core module

Issue: Springboot doesn't load/scan the RestController from the webgateway module => 404 error when sending the http request

Github repo : https://github.com/Sorin-J/Greeter

Project configuration :

Greeter 
   |
   + pom.xml (parent pom)
   |
   + -- core                                            
   |     |
   |     + ...
   |     |
   |     + pom.xml
   |
   + -- webgateway 
         |
         + ...
         |
         + pom.xml (depends on core pom.xml)

Parent pom.xml :

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.bet.jbs</groupId>
    <artifactId>Greeter</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>

    <modules>
        <module>core</module>
        <module>webgateway</module>
    </modules>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.3.RELEASE</version>
    </parent>

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

core module pom.xml :

<?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   http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <parent>
        <artifactId>Greeter</artifactId>
        <groupId>com.bet.jbs</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <modelVersion>4.0.0</modelVersion>

    <artifactId>core</artifactId>

</project>

webgateway module pom.xml :

<?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  http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <parent>
        <artifactId>Greeter</artifactId>
        <groupId>com.bet.jbs</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <modelVersion>4.0.0</modelVersion>

    <artifactId>webgateway</artifactId>

    <dependencies>
        <dependency>
            <groupId>com.bet.jbs</groupId>
            <artifactId>core</artifactId>
            <version>1.0-SNAPSHOT</version>
        </dependency>
    </dependencies>
</project>

MainApplication class from core module :

package com.bet.jbs.core;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan(basePackages = {"com.bet.jbs.core", "com.bet.jbs.webgateway"})
@EnableAutoConfiguration
public class MainApplication {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(MainApplication.class, args);
    }
}

GreetingController class from webgateway module :

package com.bet.jbs.webgateway.controller;

import com.bet.jbs.core.util.GreetingGenerator;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GreetingController {

    @RequestMapping(value = "/webgreeting", method = RequestMethod.GET)
    public String getGreeting() {
        return "WEBGATEWAY module says " + GreetingGenerator.getRandomGreeting();
    }
}

Just to test that an identical REST controller would work fine if it is located in the core module, I've created a similar GreetingController class also in core module (and this one works fine) :

package com.bet.jbs.core.controller;

import com.bet.jbs.core.util.GreetingGenerator;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
/*
 * This REST controller should not be in the CORE component.
 * It is just for proving that this controller is recognized and the other one from WEBGATEWAY component is not.
 *
 */
@RestController
public class GreetingController {

    @RequestMapping(value = "/coregreeting", method = RequestMethod.GET)
    public String getGreeting() {
        return "CORE module says " + GreetingGenerator.getRandomGreeting();
    }
}

Answer 1

The Spring Boot main application is in the core module, which does not have a dependency on the webgateway module. Therefore the class with the controller will not be present at runtime and can not be discovered by spring.

Fix: Add dependency to the webgateway to the core or move the launcher/main class to the webgateway module.

You can also use a third module that does the launching and has the dependencies to core and webgateway.

Answer 2

I was stuck in this problems since last one day... The solution below will save you a lot of time for sure!

Here is how I solved it:

1. Create a separate module for main Application class.

   x-service

   • pom.xml (parent)
   • child1-module
     • pom.xml
   • child2-module
     • pom.xml
   • app-module
     • pom.xml (contains dependency for both child1 and child2)
     • src/main/java/Application.java

2. Add all the modules as dependencies in the pom of the module having application class.

    <?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 
                      http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>x-service</artifactId>
        <groupId>com.a.b.c</groupId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
   
    <artifactId>app-module</artifactId>
   
    <dependencies>
        <dependency>
            <groupId>com.a.b.cs</groupId>
            <artifactId>child1-module</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>com.a.b.cs</groupId>
            <artifactId>child1-module</artifactId>
            <version>0.0.1-SNAPSHOT</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
   
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>true</filtering>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <executable>true</executable>
                </configuration>
            </plugin>
        </plugins>
    </build>
   

3. Keep the main pom as parent pom.

    <?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 
      http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <packaging>pom</packaging>
    <modules>
        <module>child1-module</module>
        <module>child2-module</module>
        <module>app-module</module>
    </modules>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.2.RELEASE</version>
        <relativePath/>
    </parent>
   
    <groupId>com.a.b.c</groupId>
    <artifactId>x-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
   
    <properties>
        <java.version>1.8</java.version>
    </properties>
   
    <dependencies>
   
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
   
   
    </dependencies>
   
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-checkstyle-plugin</artifactId>
                <version>3.0.0</version>
            </plugin>
        </plugins>
    </build>
   

4. Add the parent pom artifect as parent in all child poms.

    <?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 
         http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>dxg-service</artifactId>
        <groupId>com.a.b.c</groupId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
   
    <groupId>com.a.b.c</groupId>
    <artifactId>child1-module</artifactId>
    <version>0.0.1-SNAPSHOT</version>
   
    <dependencies>
        <dependency>
            <groupId>com.a.b.c</groupId>
            <artifactId>child2-modulde</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>
   

More details here: https://medium.com/macoclock/how-create-multi-module-project-in-intellij-on-macos-50f07e52b7f9

Answer 3

I had added the correct dependency and Spring Boot still did not find my new Controller. Seems like IntelliJ IDEA (2020.3.2) or Maven (3.3.6) don't update properly when a module gets added. This solved it for me:

1. Maven: clean + install on the parent project

2. In IntelliJ from the file menu Invalidate Caches / Restart..

Answer 4

as mentioned you should have parent pom with setup spring web starter in that and other modules must get that parent pom as their parent. be carful to add your root pom project to maven. to do this open maven in IDE and add pom.