Developers Guide

Working on OTP in an IDE

Most people writing or modifying OTP code use an Integrated Development Environment (IDE). Some of the most popular IDEs for Java development are Eclipse, IntelliJ IDEA, and NetBeans. All three of these environments are good for working on OTP, and any IDE with Maven build support should also work (ensure that you have the Maven plugins installed and enabled). Git integration is a plus since OTP is under Git version control.

Many of the Core OTP developers use IntelliJ IDEA. It is an excellent IDE, and in my experience is quicker and more stable than the competition. IntelliJ IDEA is a commercial product, but there is an open source "community edition" that is completely sufficient for working on OTP.

Rather than using the version control support in my IDE, I usually find it more straightforward to clone the OTP GitHub repository manually (on the command line or using some other Git interface tool), then import the resulting local OTP repository into my IDE as a Maven project. The IDE should then take care of fetching all the libraries OTP depends on, based on the Maven project description (POM file) in the base of the OTP repository. This step can take a long time because it involves downloading a lot of JAR files.

When running your local copy of the OTP source within an IDE, all command line switches and configuration options will be identical to the ones used when running the OTP JAR from the command line (as described in the basic introduction and configuration reference). The only difference is that you need to manually specify the main class. When you run a JAR from the command line, the JVM automatically knows which class contains the entry point into the program (the main function), but in IDEs you must create a "run configuration".

Both IntelliJ and Eclipse have "run" menus, from which you can select an option to edit the run configurations. You want to create a configuration for a Java Application, specifying the main class org.opentripplanner.standalone.OTPMain. Unlike on the command line, the arguments to the JVM and to the main class you are running are specified separately. In the field for the VM options you'll want to put your maximum memory parameter (-Xmx2G, or whatever limit you want to place on JVM memory usage). The rest of the parameters to OTP itself will go in a different field with a name like "program arguments".

Contributing to the project

OpenTripPlanner is a community based open source project, and we welcome all who wish to contribute. There are several ways to get involved:

Branches and Branch Protection

As of January 2019, we have begun work on OTP 2.x and are using a Git branching model derived from Gitflow. All development will occur on the dev-1.x and dev-2.x branches. Only release commits setting the Maven artifact version to a non-snapshot number should be pushed to the master branch of OTP. All other changes to master should result from fast-forward merges of a Github pull request from the dev-1.x branch. In turn, all changes to dev-1.x should result from a fast-forward merge of a Github pull request for a single feature, fix, or other change. These pull requests are subject to code review. We require two pull request approvals from OTP leadership committee members or designated code reviewers from two different organizations. We also have validation rules ensuring that the code compiles and all tests pass before pull requests can be merged.

The dev-2.x branch is managed similarly to dev-1.x but because it's rapidly changing experimental code worked on by relatively few people, we require only one pull request approval from a different organization than the author. Merges will not occur into master from dev-2.x until that branch is sufficiently advanced and receives approval from the OTP project leadership committee.

Issues and commits

All commits should reference a specific issue number (this was formally decided in issue #175). For example, Simplify module X configuration #9999. If no ticket exists for the feature or bug your code implements or fixes, you should create a new ticket prior to checking in, or ideally even prior to your development work since this provides a place to carry out implementation discussions (in the comments).

GitHub will automatically update issues when commits are merged in: if your commit message includes the text fixes #123, it will automatically append your message as a comment on the isse and close it. If you simply mention #123 in your message, your message will be appended to the issue but it will remain open. Many other expressions exist to close issues via commit messages. See the GitHub help page on this topic.

Code Comments

As a matter of policy, all new methods, classes, and fields should include comments explaining what they are for and any other pertinent information. For Java code, the comments should use the JavaDoc conventions. It is best to provide comments that not only explain what you did but also why you did it while providing some context. Please avoid including trivial Javadoc or the empty Javadoc stubs added by IDEs, such as @param annotations with no description.


Most documentation should be included directly in the OpenTripPlanner repository rather than the GitHub wiki. This allows version control to be applied to documentation as well as program source code. All pull requests that change how OTP is used or configured should include changes to the documentation alongside code modifications. Pages that help organize development teams or serve as scratchpads can still go on the wiki, but all documentation that would be of interest to people configuring or using OTP belong in the repo.

The documentation files are in Markdown format and are in the /docs directory under the root of the project. On every push to the master branch the documentation will be rebuilt and deployed as static pages to our subdomain of ReadTheDocs. MkDocs is a Python program and should run on any major platform. See for information on how to install it and how to generate a live local preview of the documentation while you're working on writing it.

In short:

$ pip install mkdocs
$ mkdocs serve

Debug layers

Adding new renderer is very easy. You just need to create new class (preferably in org.opentripplanner.inspector package) which implements EdgeVertexRenderer. It is best if class name ends with Rendered. To implement this interface you need to write three functions renderEdge, renderVertex and getName. Both render functions accepts EdgeVisualAttributes object in which label of edge/vertex and color can be set. And both return true if edge/vertex should be rendered and false otherwise. getName function should return short descriptive name of the class and will be shown in layer chooser.

For examples how to write renderers you can look into example renderers which are all in org.opentripplanner.inspector package.

After your class is written you only need to add it to TileRenderManager:

//This is how Wheelchair renderer is added
renderers.put("wheelchair", new EdgeVertexTileRenderer(new WheelchairEdgeRenderer()));

wheelchair is internal layer key and should consist of a-zA-Z and -.

By default all the tiles have cache headers to cache them for one hour. This can become problematic if you are changing renderers a lot. To disable this change GraphInspectorTileResource:

//This lines
CacheControl cc = new CacheControl();

//to this:
CacheControl cc = new CacheControl();

Date format

Please use only ISO 8601 date format (YYYY-MM-DD) in documentation, comments, and throughout the project. This avoids the ambiguity that can result from differing local interpretations of date formats like 02/01/12.

Project proposals and decision making

Decisions are made by the OpenTripPlanner community through a proposal and informal voting process on the project mailing list.

While we do vote on proposals, we don't vote in a strict democratic sense, but rather as a way to easily register opinions, foster discussion, and move toward consensus. When responding to a proposal, we use the following system:

A proposal does not need to be a formal or lengthy document; it can and should be a straightforward recommendation of what you want to do, ideally with a brief explanation for why it's a good idea.

Proposals are just messages sent to the list and can be as simple as "I think we should do X because of Y and Z. Deadline for response is 2015-10-29. Assuming I've heard no blocking votes by then, I'll go ahead." Note that you should make sure to include a deadline by which you will go ahead and do what you're proposing if you don't hear any blocking responses. In general, you should leave at least 72 hours for people to respond. This is not a hard-and-fast rule and you should use your best judgement in determining how far in the future the deadline should be depending on the magnitude of the proposal and how much it will affect the overall project and the rest of the community.

Of course you may always fork the OTP repo on GitHub and submit your changes as a pull request, or develop and share whatever features you like on your fork even if they are not included in mainline OTP.

Code style


OpenTripPlanner uses the same code formatting and style as the GeoTools and GeoServer projects. It's a minor variant of the Sun coding convention. Notably, we do not use tabs for indentation and we allow for lines up to 100 characters wide.

The Eclipse formatter configuration supplied by the GeoTools project allows comments up to 150 characters wide. A modified version included in the OpenTripPlanner repository will wrap comments to the same width as lines of code, which makes for easier reading in narrow windows (e.g. when several documents are open side-by-side on a wide display).

If you use Eclipse, you should do the following to make sure your code is automatically formatted correctly:

  1. Open the project Properties (right-click on the project directory in Eclipse and select Properties or choose Project -> Properties).

  2. Select Java, then Code Style, and finally Formatter.

  3. Check the Enable project specific settings checkbox.

  4. Click Import..., select the formatter.xml file in the root of the OpenTripPlanner git repository, and click Open.

  5. Click OK to close the Properties window.


As of #206, we follow Crockford's JavaScript code conventions. Further guidelines include:

     * Configure Class
     * Purpose is to allow a generic configuration object to be read via AJAX/JSON, and inserted into an Ext Store
     * The implementation is TriMet route map specific...but replacing ConfigureStore object (or member variables) with
     * another implementation, will give this widget flexibility for other uses beyond the iMap.
     * @class

Note: There is still a lot of code following other style conventions, but please adhere to consistent style when you write new code, and help clean up and reformat code as you refactor.

Continuous Integration

The OpenTripPlanner project uses the Travis CI continuous integration system. Any time a change is pushed to the main OpenTripPlanner repository on GitHub, this server will compile and test the new code, providing feedback on the stability of the build.

Release Process

This section serves as a checklist for the person performing releases. Note that much of this mimics the actions taken by the Maven release plugin. Based on past experience, the Maven release plugin can fail at various points in the process leaving the repo in a confusing state. Taking each action manually is more tedious, but keeps eyes on each step and is less prone to failure. Releases are performed off the master branch, and are tagged with git annotated tags.

Additional Information on Releases

OpenTripPlanner is released as Maven artifacts to Maven Central. These include compiled and source code JARs as well as a "shaded" JAR containing all dependencies, allowing stand-alone usage. This release process is handled by the Sonatype Nexus Staging plugin, configured in the OpenTripPlanner POM. Typically this final Maven deployment action is performed automatically when the Travis CI build succeeds in building a non-SNAPSHOT version.

Artifact Signing

Maven release artifacts must be digitally signed to prove their origin. This is a safeguard against compromised code from a malicious third party being disguised as a trusted library.

The OTP artifact signing key was created by Conveyal. We export only that signing subkey, with our company's main key blanked out. Therefore, even if someone managed to acquire the decrypted key file and the associated GPG passphrase, they would not have the main key. We could deactivate the signing key and create a new one, without the main key being compromised.

The exported signing key is present in the root of the git repo as the encrypted file maven-artifact-signing-key.asc.enc. When building a tagged release, Travis CI will decrypt this file and import it into GPG on the build machine. The signing key ID and GPG passphrase are also present as encrypted environment variables in the Travis configuration YAML. This only happens on code from non-fork, non-pull-request commits, ensuring that no unreviewed third-party code has access to these files or variables.

OpenTripPlanner's POM is set up to sign artifacts in the verify phase, which means signing will happen for the install and deploy targets, but not the package target. When performing a local test build, if you do mvn clean install site it will test the signing process. If you do not have the certificate installed, you can instead to mvn clean package site to bypass signing, but this provides less certainty that everything is set up correctly for the CI-driven final release.

Documentation Build and Hosting

Three kinds of documentation are built for OTP, all based on information present in the OTP repo itself.

The REST API docs are built by Enunciate from the OTP REST interface. My sense is that this auto-generated documentation has become harder to read and less useful over time, perhaps because of incorrect handling of REST parameters inherited from superclasses.

The Javadoc is built from Javadoc comments in the source code itself.

The main OTP user documentation is built from Markdown files in the /docs directory of the repo.

The REST API docs and Javadoc are built by Maven, then uploaded manually to AWS S3, from which they are served as a web page at The main OTP user documentation is built by Readthedocs and served at

Upload to the S3 bucket requires AWS IAM credentials that can be created by Conveyal (which owns the bucket).