# How to Upgrade Transitive Dependencies in Gradle

version 9.2.0

This guide explains how to manage and upgrade versions of transitive dependencies in Gradle using dependency constraints.

## Why Upgrade a Transitive Dependency?

There are many reasons to upgrade a version of a dependency:

- Bug fixes resolve issues present in older versions.

- Security patches address vulnerabilities to keep the project safe.

- Performance improvements make builds faster and more efficient.

- New features provide additional functionality and better compatibility.

## Setting Dependency Constraints on Transitive Dependencies

Dependency constraints allow you to define the version or version range of both direct dependencies and transitive dependencies.

Dependency constraints can also override transitive dependencies and enforce strict versions, even downgrading if necessary.

To enforce specific versions of transitive dependencies, use the `constraints` block inside `dependencies {}`:

build.gradle.kts

    dependencies {
        implementation("org.apache.httpcomponents:httpclient") // No version specified
        constraints {
            implementation("org.apache.httpcomponents:httpclient:4.5.3") {
                because("previous versions have a bug impacting this application")
            }
            implementation("commons-codec:commons-codec:1.11") {
                because("version 1.9 pulled from httpclient has bugs affecting this application")
            }
        }
    }

build.gradle

    dependencies {
        implementation("org.apache.httpcomponents:httpclient") // No version specified
        constraints {
            implementation("org.apache.httpcomponents:httpclient:4.5.3") {
                because("previous versions have a bug impacting this application")
            }
            implementation("commons-codec:commons-codec:1.11") {
                because("version 1.9 pulled from httpclient has bugs affecting this application")
            }
        }
    }

- The `implementation` dependency omits the version.

- The `constraints` block enforces specific versions for `httpclient` and `commons-codec`.

- The constraint for `commons-codec` only applies if it is pulled transitively.

Running `./gradlew dependencies --configuration runtimeClasspath` showcases the results:

dependencies.out

    > Task :dependencies

    ------------------------------------------------------------
    Root project 'how_to_upgrade_transitive_dependencies'
    ------------------------------------------------------------

    compileClasspath - Compile classpath for source set 'main'.
    +--- org.apache.httpcomponents:httpclient -> 4.5.3
    |    +--- org.apache.httpcomponents:httpcore:4.4.6
    |    +--- commons-logging:commons-logging:1.2
    |    \--- commons-codec:commons-codec:1.9 -> 1.11
    +--- org.apache.httpcomponents:httpclient:4.5.3 (c)
    \--- commons-codec:commons-codec:1.11 (c)

## Summary

Use dependency constraints when:

- You want to override transitive dependencies with a specific version.

- You need to enforce a strict version or range across multiple dependencies.

- You want to prevent dependency conflicts without manually adding transitive dependencies.