How are some gradle dependencies working with no version supplied

Question

As far as I know gradle requires a version number when setting dependencies, but partial wildcards are allowed. For example if I want Guava, I cannot do this as it fails:

compile('com.google.guava:guava')

It has to be (as an example):

compile('com.google.guava:guava:21.0')

However, I'm learning Spring, which has the following:

compile("org.springframework.boot:spring-boot-starter")
compile("org.springframework:spring-web")
compile("com.fasterxml.jackson.core:jackson-databind")

How are these dependencies working with no version supplied?

Is it because of the following, but I thought these lines were required only for my plugin 'org.springframework.boot':

buildscript {
 repositories {
    mavenCentral()
 }
 dependencies {
    classpath("org.springframework.boot:spring-boot-gradle-plugin:1.4.3.RELEASE")
 }
}

score 39 · Accepted Answer · edited Jun 09 '22 at 14:04

39

It is worth mentioning that the trick is called BOM (bill of materials) and the actual versions can be checked in the related POM file (in this example, it is for the version 2.7.0) inside spring-boot-dependencies package. This is mentioned in the Spring Boot official documentation here: Build Systems.

Another way that Spring provides this (for non Boot projects) is through Spring Platform BOM where it actually provides version for the following dependencies.

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'io.spring.gradle:dependency-management-plugin:0.6.0.RELEASE'
    }
}

apply plugin: 'io.spring.dependency-management'

dependencyManagement {
    imports {
        mavenBom 'io.spring.platform:platform-bom:Athens-SR2'
    }
}

edited Jun 09 '22 at 14:04

informatik01

16,038
10
74
104

answered Jan 16 '17 at 13:40

hakamairi

4,464
4
30
53

thanks. I'm actually just starting reading through the boot reference guide to teach myself and never noticed this bit, I think I just skipped it given I have it working :) – Neil Walker Jan 16 '17 at 16:24
1

You can find all the dependency versions it uses [here](https://docs.spring.io/spring-boot/docs/current/reference/html/appendix-dependency-versions.html) – forresthopkinsa May 02 '18 at 17:46

score 15 · Answer 2 · answered Jan 16 '17 at 13:09

15

TL;DR - spring boot uses custom dependencies resolver.

A spring boot plugin that is applied with the following piece of code:

apply plugin: 'spring-boot'

handles the dependencies that are listed without version. This logic is implemented in this class which delegates it to here. DependencyManagementPluginFeatures are applied here.

answered Jan 16 '17 at 13:09

Opal

81,889
28
189
210

The links in this post no longer work. fyi – user3126529 Feb 11 '22 at 05:19

score 8 · Answer 3 · answered Aug 10 '17 at 11:35

The spring boot gradle plugin documentation states the following:

The version of the spring-boot gradle plugin that you declare determines the version of the spring-boot-starter-parent bom that is imported (this ensures that builds are always repeatable). You should always set the version of the spring-boot gradle plugin to the actual Spring Boot version that you wish to use.

score 5 · Answer 4 · answered Feb 27 '20 at 19:26

Spring Boot Dependency Management Plugin is not necessary.
You may use build-in Gradle BOM support instead of Spring Boot Dependency Management Plugin

For example:

    plugins {
        id 'java'
        id 'org.springframework.boot' version '2.1.0.RELEASE'
    }
    repositories {
        jcenter()
    }
    dependencies {
        implementation platform('org.springframework.boot:spring-boot-dependencies:2.1.0.RELEASE')

    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-security'
    }

and for multi-module project: in root build.gradle :

plugins {
    id 'java-library'
    id 'org.springframework.boot' version '2.1.0.RELEASE'
}


allprojects {
    apply plugin: 'java-library'

    repositories {
        jcenter()
    }
}

dependencies {
    implementation project(':core')
    implementation 'org.springframework.boot:spring-boot-starter-web'
}

and in core/build.gradle

 dependencies {
    api platform('org.springframework.boot:spring-boot-dependencies:2.1.0.RELEASE')
    implementation 'org.springframework.boot:spring-boot-starter-web'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

How are some gradle dependencies working with no version supplied

4 Answers4

Linked