Specify dependencies

A package can depend on other packages that are available in Ballerina repositories. By default, Ballerina searches for the dependencies in the repositories below.

• The distribution repository
• The Ballerina Central repository

It also supports a third repository named the local repository, and temporarily overrides dependencies, which is useful for the package-development and bug-fixing phases. Additionally, a predefined set of custom package repositories are also supported, which are useful to bring third-party repositories into dependency management.

Distribution repository

The distribution repository is a file system repository added with the local Ballerina installation. The repository is located at <BALLERINA_HOME>/repo/bala.

Ballerina Central repository

The Ballerina Central is a remote repository and creates a local file system cache at <USER_HOME>/.ballerina/repositories/central.ballerina.io/bala. Ballerina queries the remote repository only if the specified dependency version is not present in its local cache.

Note: If you are connected to the internet via an HTTP proxy, you need to configure the proxy settings to perform operations with the Ballerina Central. For more information on proxy settings, see Configure a network proxy.

Local repository

The local repository is also a file system repository, which will be created in the <USER_HOME> location. The repository location is <USER_HOME>/.ballerina/repositories/local/bala. For more information, see Use dependencies from the local repository.

Custom repositories

Ballerina supports one or more custom remote repositories, which can be configured in the <USER_HOME>/.ballerina/Settings.toml file. A local filesystem cache is maintained per repository at <USER_HOME>/.ballerina/repositories/<REPOSITORY_ID>/bala. Ballerina queries the remote repository only if the specified dependency version is not present in its local cache. For more information, see Use custom repositories for package management.

Import a module

To use exported modules of any package, add an import statement in the Ballerina code. It enables access to all public symbols in the imported module.

The import declaration syntax is as follows.

import [org_name/] module_name [as import_prefix];

• The import_prefix has to be a valid Ballerina identifier, and it is used to refer to public symbols in the declared module.
• The import_prefix is optional. You can use the last part of the module name if an import_prefix is unavailable.

You can import a module by providing the organization name, and the module name. The module name consists of the package name, and the name of the module root directory. The module name of the default module is always the package name.

The following example shows how to import modules from the ballerina/io package.

import ballerina/io; // Imports the default module of io package

public function main() {
	io:println("Hello world!");
}

The following is another example that shows the usage of multiple modules from different libraries.

// Imports the default module from the `ballerina/log` package.
import ballerina/log;
// Imports the default module from the `salesforce` package
// with an import prefix.
import ballerinax/salesforce as sf;
// Imports a non-default module from the `salesforce` package
// with an import prefix.
import ballerinax/salesforce.bulk as sfBulk;

configurable string baseUrl = ?;
configurable string token = ?;

sf:ConnectionConfig sfConfig = {baseUrl, auth: {token}};

public function main() returns error? {
    string contacts = "Name,Email\n"
        + "John,john434@gmail.com\n"
        + "Peter,peter77@gmail.com";

    sfBulk:Client bulkClient = check new (sfConfig);
    sfBulk:BulkJob insertJob = check bulkClient->createJob("insert", "Contact", "CSV");
    sfBulk:BatchInfo batch = check bulkClient->addBatch(insertJob, contacts);

    log:printInfo(batch.id.length() > 0 ? "Batch Added Successfully" : "Failed to add the Batch");
}

Specify dependency versions

When building a package, the compiler figures out the dependency versions automatically. Ballerina searches the latest compatible versions of the package dependencies in the distribution repository, Ballerina Central repository, and the local repository (if specified).

When you execute bal build for the first time on the package, the CLI operation will generate the Dependencies.toml in the package root. This will contain the latest compatible dependency versions. From thereon, the versions locked in the Dependencies.toml are considered as the minimum required versions for the subsequent builds. The Dependencies.toml file is generated and managed by the Ballerina CLI and does not need user intervention.

Update dependency versions

The Dependencies.toml file generated during the compiler will automatically update the versions of the dependencies at the patch level. Therefore, if any patch release is available for a dependency, the compiler will pick the latest patch version.

Note: The automatic update runs only once a day to optimize the time taken during frequent builds. Run the bal clean command if you want to enable automatic updates for the next build.

To update the minor or the major version of a dependency, specify the dependency version in the Ballerina.toml file. The provided version is considered as the minimum required version for compiling the package, which will update the dependency to the latest version that is compatible with the version provided in the Ballerina.toml as well as the version locked in theDependencies.toml.

For example, the minimum version of the ballerinax/mysql dependency can be specified in the following way.

[[dependency]]
org = "ballerinax"
name = "mysql"
version = "1.5.0”

Upgrading packages to use new Swan Lake update distributions

When a new Swan Lake update distribution is released, it may include incompatible language improvements. When upgrading an existing package to use new Swan Lake update distributions, the Ballerina compiler automatically updates the Dependencies.toml file with the latest compatible minor versions of the dependencies of the new distribution. This enables the existing projects to benefit from improvements in the new update releases without requiring significant modifications.

Use dependencies from the local repository

The local repository is useful to test a package in the development phase or to fix bugs. To specify a dependency from the local repository, first, you need to publish it to the local repository by following the steps below.

1. Generate the Ballerina archive after editing the package source files as required.

   $ bal pack
   

2. Publish to the local repository.

   $ bal push --repository local
   

   If you already have the path of Ballerina archive, then you can simply execute the following command.

   $ bal push --repository local <path-to-bala-archive>
   

3. Specify the dependency in the Ballerina.toml file.

   [[dependency]]
   org = "ballerinax"
   name = "googleapis.gmail"
   version = "2.1.1"
   repository = "local"

Once you complete the above steps, the dependency will be picked from the local repository when building the package. Ballerina considers the version specified in the Ballerina.toml file as the minimum required version and uses the local repository to resolve the dependency. However, the compiler gives priority to the latest version if a new patch version is found in the distribution or Ballerina Central repositories. At this point, the compiler resolves the latest version and ignores the dependency version in the local repository.

Use custom repositories for package management

Ballerina supports Maven repositories such as Nexus, Artifactory and Github packages to be set up as custom repositories.

Define the custom repository

You can configure one or multiple custom repositories in the <USER_HOME>/.ballerina/Settings.toml file to integrate them into the package resolution.

[[repository.maven]]
id = "<repository-id>" # This ID is used when pushing/ pulling packages
url = "<repository-url>"
username = "<username>/<userId>"
accesstoken = "<password>/<accesstoken>"

Below is a sample repository configuration.

[[repository.maven]]
id = "github_1" # This ID is used when pushing/ pulling balas
url = "https://maven.pkg.github.com/jackson12/jackson-encrypt-module"
username = "jackson12"
accesstoken = "ghp_nMlJsjshhdtdt5367389920020hHfrdrd"

The sections below show how to configure the above GitHub package repository to resolve a specific dependency.

Publish a Ballerina archive to the custom repository

Follow the steps below to publish a Ballerina archive to the custom repository you configured above.

1. Generate the Ballerina archive.

   $ bal pack
   

2. Publish to the custom repository.

   $ bal push --repository <repository-id>
   

   If you already have the path of the Ballerina archive, execute the command below.

   $ bal push --repository <repository-id> <path-to-bala-archive>
   

Use the package from the custom repository

You can use the package you pushed to the custom repository in the ways below.

Specify the dependency in the Ballerina.toml

Similar to the local repository, dependencies from the custom repository can be specified in the Ballerina.toml file and utilized as shown below.

[[dependency]]
org = "jackson"
name = "encrypter"
version = "2.1.1"
repository = "github_1" # Must match a repository ID configured in the Settings.toml file.

Pull the package from a custom repository

Execute the command below to pull a Ballerina package from a custom repository.

$ bal pull <package-org>/<package-name>:<version> --repository <repository-id>

Achieve reproducible builds

By default, the compiler always looks up the latest compatible versions of the dependencies in the repositories when building a package.

It minimizes the hassle of managing dependency versions to the package developer since the compiler is smart enough to keep the package updated with the latest compatible dependencies all the time. However, if you need to repeat a constant behavior to make the build more predictable, Ballerina facilitates this using offline and sticky modes.

The sticky mode

Using the --sticky flag with bal build will force the compiler to stick to the exact versions locked in the Dependencies.toml. In other words, the CLI disables the automatic-update feature when you provide the --sticky flag.

$ bal build --sticky

Note: The automatic update runs only once a day to optimize the time taken during frequent builds.

The offline mode

Using the –-offline flag will run the compilation offline without connecting to Ballerina Central or any configured Maven repositories. This will save the compilation time since the packages are resolved using the distribution repository, and the file system cache of the Ballerina Central repository/Maven repositories.

Using the --offline flag along with the --sticky flag will ensure a predictable build with optimal time for compilation.

Version compatibility

Abiding by the specifications of Semantic Versioning, Ballerina considers two versions to be compatible if the major versions are equal and not zero.

A few examples would be as follows:

• 0.2.3 and 0.2.4 are considered incompatible since the major version is 0. The major version 0 is unstable.
• 1.2.3, 1.2.4, and 1.4.5 are compatible. 1.4.5 will be considered as the latest.
• 1.2.3-alpha, 1.2.3-alpha.2, and 1.2.3-beta are compatible and 1.2.3-beta is considered the latest.
• 1.2.3-alpha, 1.2.3-beta, 1.2.4-alpha are compatible and 1.2.4-alpha is considered the latest.
• 1.0.0 and 2.0.0 are considered incompatible since the major versions are different.

When building the dependency graph, if there is more than one version for a specific dependency, the versions are chosen according to the following.

• If the versions are compatible, pick the latest version.
• If the versions are incompatible, throw an error with a build failure.

For example, assume one dependency in your package depends on the 1.0.0 version of the ballerina/observe package, and another dependency depends on 0.9.0 of the same. The build fails with the following error message.

error: compilation failed: Two incompatible versions exist in the dependency graph:
ballerina/observe versions: 0.9.0, 1.0.0

Manage platform dependencies

A Ballerina package can depend on JAVA code that is shipped with the JVM, from a remote package repository, or from a JAR file located in the user’s machine. Libraries shipped with the JVM can be used seamlessly and libraries used from other locations must be specified in the Ballerina.toml as shown below.

Specify a Maven dependency

The following example shows how a dependency from a public Maven repository can be specified.

[[platform.java11.dependency]]
# Group ID of the Maven dependency.
groupId = "<group-id>"
# Artifact ID of the Maven dependency.
artifactId = "<artifact-id>"
# Version of the Maven dependency.
version = "<version>"

When building the package, these specified Maven dependencies will be resolved and can be found in the target/platform-libs directory.

Specify a local JAR file path

The following example uses a JAR file located in the user's machine as a platform dependency.

[[platform.java11.dependency]]
# Group ID of the dependency.
groupId = "<group-id>"
# Artifact ID of the dependency.
artifactId = "<artifact-id>"
# Version of the dependency.
version = "<version>"
# Absolute or relative path of the JAR file.
path = "<path-to-jar-file-1>"

The Ballerina compiler will copy the specified JAR file from the provided path when creating the archive.

Info: You can also provide custom package repositories such as GitHub Packages and private Maven repositories. For more information, see Package references.