Spring Boot multi module project with Gradle doesn't build

Question

I'm working on a Spring Boot app with multiple modules and we're using Gradle to build it. Unfortunately I can't get the Gradle configuration right.

The project structure is this:

parent
  |
  + build.gradle
  |
  + settings.gradle
  |
  + core
  |   |
  |   + build.gradle
  | 
  + apis
  |   |
  |   + build.gradle
  |
  + services
  |   |
  |   + build.gradle
  | 
  + data
  |   |
  |   + build.gradle

When I try to build the project, I get compilation errors like error: cannot find symbol saying, that the classes from data used in services aren't imported. And I assume this is true between all the modules.

My parent build.gradle looks like this:

buildscript {
    ext {
        springBootVersion = '2.0.0.BUILD-SNAPSHOT'
    }
    repositories {
        mavenCentral()
        maven { url "https://repo.spring.io/snapshot" }
        maven { url "https://repo.spring.io/milestone" }
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'eclipse'
apply plugin: 'idea'

allprojects {
    apply plugin: 'java'
    apply plugin: 'org.springframework.boot'
    apply plugin: 'io.spring.dependency-management'

    group = 'com.example'
    version = '0.0.1-SNAPSHOT'
    sourceCompatibility = 1.8
    targetCompatibility = 1.8

    repositories {
        mavenCentral()
        maven { url "https://repo.spring.io/snapshot" }
        maven { url "https://repo.spring.io/milestone" }
    }

    dependencies {
        testCompile('org.springframework.boot:spring-boot-starter-test')
    }
}

dependencies {
    compile project(':data')
    compile project(':services')
    compile project(':apis')
    compile project(':core')
}

jar {
    baseName = 'my-jar'
    version = '0.0.1-SNAPSHOT'
}

settings.gradle:

rootProject.name = 'my-app'
include ':apis'
include ':core'
include ':data'
include ':services'

one of children (core) has this in it's build.gradle:

dependencies {
    compile('org.springframework.boot:spring-boot-starter-actuator')
    compile('org.springframework.boot:spring-boot-starter-quartz')
    compile('org.springframework.boot:spring-boot-starter-tomcat')
    runtime('com.h2database:h2')

    compile project(':data')
    compile project(':services')
    compile project(':apis')
}

services build.gradle looks like this:

dependencies {
    compile('org.springframework.boot:spring-boot-starter-quartz')
    compile('org.springframework.boot:spring-boot-starter-data-jpa')
    runtime('com.h2database:h2')

    compile project(':data')
}

The other ones also declare only dependencies.

The dependency structure looks like this:

core - apis, services, data

apis - services, data

services - data

data -

Example of the compilation errors:

/my-app/services/src/main/java/com/example/my-app/business/IssuedTokenService.java:3: error: package com.examples.data.dao does not exist import com.examples.data.dao.IssuedToken;

/my-app/services/src/main/java/com/example/my-app/business/IssuedTokenService.java:4: error: package com.examples.data.repository does not exist import com.examples.data.repository.IssuedTokenRepository;

/my-app/services/src/main/java/com/example/my-app/business/IssuedTokenService.java:12: error: cannot find symbol 
    private IssuedTokenRepository issuedTokenRepository;

    symbol:   class IssuedTokenRepository
   location: class IssuedTokenService

/my-app/services/src/main/java/com/example/my-app/business/IssuedTokenService.java:15: error: cannot find symbol
   public void saveToken(IssuedToken issuedToken) {
                                  ^
   symbol:   class IssuedToken
   location: class IssuedTokenService

So core depends on data, services and apis, right? do you have one of them depending on core as well? What's your actual error, and your dependency tree? usually you would have something like services->data->apis->core as a dependency chain. — Kylar
– Kylar, Commented Dec 1, 2017 at 17:53
Based on your description, services can't find data classes. So what matters is the configuration of the services module, that you didn't post. Post the relevant code, and the exact and complete message. — JB Nizet
– JB Nizet, Commented Dec 1, 2017 at 17:54
@JBNizet I have added both error messages and dependencies. As far as the compilation error goes, it is quite simple. Every symbol from data module used in code in services module is unknown to the compiler. — bajermi2
– bajermi2, Commented Dec 1, 2017 at 18:12
My guess is that it's because you're applying the boot plugin to all projects. They're not boot projects. They're just regular Java projects. Only the top-level one (the bizarrely named core I guess, which depends on everything else and is thus the shell rather than the core), should be a boot project. — JB Nizet
– JB Nizet, Commented Dec 1, 2017 at 18:18
@JBNizet I have already tried to do that, but when the boot plugin isn't there, Gradle doesn't recognize any of the org.springframework.boot:spring-boot-starter- dependencies. — bajermi2
– bajermi2, Commented Dec 1, 2017 at 18:22

Juan Rada · Accepted Answer · 2020-07-02 19:11:59Z

85

In your utility (data) projects put:

bootJar {
    enabled = false
}

jar {
    enabled = true
}

If kotlin dsl

tasks.getByName<BootJar>("bootJar") {
    enabled = false
}

tasks.getByName<Jar>("jar") {
    enabled = true
}

edited Jul 2, 2020 at 19:11

Juan Rada

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answered Dec 6, 2017 at 11:21

Prime

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6 Comments

Yore Over a year ago

My friend thanks very much! I've tried to solve my dependency problem for 2 days

Max Over a year ago

Can you pls explain why do we need to add these lines?

agilob Over a year ago

@Max because spring boot builds jars with JarLauncher which has different structure than normal jar, it's meant to be executable and your classes become dependencies inside the spring-boot-jar. The code above changes build structure and disabled bootJar and JarLauncher, compiles module to standard jar without BOOT-INF directory in it. which is a normal not executable library.

andy Over a year ago

I put the above code in subprojects { ... }. According to @agilob's explanation the boot stuff should be sufficient on the root project.

Deividi Cavarzan Over a year ago

Thanks much! This answer should be marked as correct.

|

jihor · Accepted Answer · 2018-02-13 16:51:18Z

18

The answer is similar to this one.

Gradle documentation on multi-project builds states:

A “lib” dependency is a special form of an execution dependency. It causes the other project to be built first and adds the jar with the classes of the other project to the classpath.

A repackaged jar, thus, poses a problem.

If, say, project B depends on project A, and the project A has a org.springframework.boot plugin applied to it, a simple compile project(':A') dependency will not work because the project jar is repackaged during the bootRepackage or bootJar task. The resulting fat jar has different structure, preventing Gradle from loading its classes.

In this case, the dependencies should be written the following way:

dependencies {
  compile project(':A').sourceSets.main.output
}

Using output of a source set directly is equivalent to using the "normal" resulting jar of project A before it is repackaged.

edited Feb 13, 2018 at 16:51

answered Feb 13, 2018 at 15:18

jihor

2,61916 silver badges29 bronze badges

3 Comments

r590 Over a year ago

Hmmm... sourceSets does not seem to be a valid property for me anymore.

jihor Over a year ago

@r590 They're still there as of gradle 4.6: docs.gradle.org/current/dsl/org.gradle.api.Project.html#N14D97

bajermi2 Over a year ago

Lot seems to be changing between versions of gradle and also versions of spring plugins for gradle

dariovmartine · Accepted Answer · 2018-01-05 19:59:46Z

5

bootJar {
    enabled = false
}

jar {
    enabled = true
}

This works for my. In my case use spring boot with spring cloud with multi project and gradle fail to build. With this solution works!

answered Jan 5, 2018 at 19:59

dariovmartine

694 bronze badges

1 Comment

Milos Over a year ago

Even though It's late response, I have faced that issue now, and you helped me.. so I had to honor that :D

M. Deinum · Accepted Answer · 2019-01-10 10:35:20Z

5

You should exclude org.springframework.boot from all submodules (root build.gradle file, allProjects block), that are stands as dependencies for your core module, which will be build to fat-jar.

Include dependencyManagement configuration into all of your spring-boot managed submodules:

dependencyManagement {
    imports {
        mavenBom "org.springframework.boot:spring-boot-starter-parent:${springBootVersion}"
    }
}

The reason of your problem is the absence of submodules compiled jar files inside your core module fat-jar.

edited Jan 10, 2019 at 10:35

M. Deinum

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answered Jan 10, 2019 at 10:13

Alexandr Solo

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