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Guidelines for Contributing

Thank you so much for wanting to contribute to PostgreSQL JDBC Driver!

The purpose of the Guidelines for Contributing is to create a collaboration baseline. Do NOT blindly obey these guidelines, use them (after understanding) where they make sense.

Currently the PgJDBC driver supports the Oracle and OpenJDK Java implementations of versions 8 and higher; and PostgreSQL server versions from 8.4 and higher.

Some PostgreSQL forks might work but are not officially supported, we support vendors of forks that want to improve this driver by sending us pull requests that are not disruptive to the community ecosystem of PostgreSQL.

Issues

Issues are a great way to keep track of tasks, enhancements, and bugs for the PgJDBC project.

How to submit a bug report

If you find a bug in the PgJDBC driver please use an issue to report it, try to be concise and detailed in your report, please ensure to specify at least the following:

  • Use a concise subject.
  • PgJDBC driver version (e.g. 42.2.14)
  • JDK/JRE version or the output of java -version (e.g. OpenJDK Java 8u144, Oracle Java 7u79)
  • PostgreSQL server version or the output of select version() (e.g. PostgreSQL 9.6.2)
  • Context information: what you were trying to achieve with PgJDBC.
  • Simplest possible steps to reproduce
    • More complex the steps are, lower the priority will be.
    • A pull request with failing JUnit test case is most preferred, although it's OK to paste the test case into the issue description.

You can consider a bug: some behaviour that worked before and now it does not; a violation of the JDBC spec in any form, unless it's stated otherwise as an extension.

In the unlikely event that a breaking change is introduced in the driver we will update the major version. We will document this change but please read carefully the changelog and test thoroughly for any potential problems with your app. What is not acceptable is to introduce breaking changes in the minor or patch update of the driver, If you find a regression in a minor patch update, please report an issue.

Bug reports are not isolated only to code, errors in documentation as well as the website source code located in the docs directory also qualify. You are welcome to report issues and send a pull request on these as well. [skip ci] can be added to the commit message to prevent Travis-CI from building a pull request that only changes the documentation.

For enhancements request keep reading the Ideas, enhancements and new features section.

Ideas, enhancements and new features

If you have ideas or proposed changes, please post on the mailing list or open a detailed, specific GitHub issue.

Think about how the change would affect other users, what side effects it might have, how practical it is to implement, what implications it would have for standards compliance and security, etc. Include a detailed use-case description.

Few of the PgJDBC developers have spare time, so it's unlikely that your idea will be picked up and implemented for you. The best way to make sure a desired feature or improvement happens is to implement it yourself. The PgJDBC sources are reasonably clear and they're pure Java, so it's sometimes easier than you might expect.

Contributing code

Here are a few important things you should know about contributing code:

  1. API changes require discussion, use cases, etc. Code comes later.
  2. Pull requests are great for small fixes for bugs, documentation, etc.
  3. Pull request needs to be approved and merged by maintainers into the master branch.
  4. Pull requests needs to fully pass CI tests.

Build requirements

In order to build the source code for PgJDBC you will need the following tools:

  • A Git client
  • A JDK for the JDBC version you'd like to build (Java 17 for pgjdbc 42.7.1, Java 8 for older pgjdbc releases)
  • A running PostgreSQL instance (optional for unit/integration tests)

We use Gradle's Toolchains for JVM projects to separate JDK version used for building and running tests. This means Gradle will automatically find the required JDK version or download it for you.

You could control JDK versions with the following Gradle properties:

  • jdkBuildVersion. Defaults to 17. JDK version to use for building $projectName. If the value is 0, then the current Java is used.
  • jdkBuildVendor. JDK vendor to use building
  • jdkBuildImplementation. Vendor-specific virtual machine implementation to use building
  • jdkTestVersion. Defaults to jdkBuildVersion. JDK version to use for testing.
  • jdkTestVendor. Defaults to jdkBuildVendor. JDK vendor to use testing
  • jdkTestImplementation. Defaults to jdkBuildImplementation. Vendor-specific virtual machine implementation to use testing

Additionally, in order to update translations (not typical), you will need the following additional tools:

  • the gettext package, which contains the commands "msgfmt", "msgmerge", and "xgettext"

Hacking on PgJDBC

The PgJDBC project uses git for version control. You can check out the current code by running:

git clone https://github.com/pgjdbc/pgjdbc.git

Compiling with Gradle on the command line

After checking out the code you can compile and test the PgJDBC driver by running the following on a command line (the outputs are located in the relevant:

./gradlew tasks # lists available tasks

./gradlew build # builds everything
./gradlew assemble # build the artifacts
./gradlew build -x test # build the artifacts, verify code style, skip tests
./gradlew javadoc # build javadoc

./gradlew check # verify code style, execute tests
./gradlew style # update code formatting (for auto-correctable cases) and verify style
./gradlew styleCheck # report code style violations

./gradlew test # execute tests
./gradlew test --tests org.postgresql.test.ssl.SslTest # execute test by class
./gradlew test -PincludeTestTags=!org.postgresql.test.SlowTests # skip slow tests
./gradlew test -PjdkTestVersion=21 --tests org.postgresql.test.ssl.SslTest # execute test with Java 21

./gradlew parameters # list most build parameters like jdkTestVersion above

Note: clean is not required, and the build automatically re-executes the tasks. However, Gradle caches the results of test execution as well, so if you want to re-execute tests even without changes to the source code, you might need to call ./gradlew cleanTest test

PgJDBC uses Gradle for the build system, so IDEs that support Gradle should be able to load, build, and execute PgJDBC tests. It is known that PgJDBC loads automatically and it works in IntelliJ IDEA.

After running the build , and build a .jar file (Java ARchive) depending on which release you have the jar will be named postgresql-<major>.<minor>.<patch>.jar. We use Semantic versioning; as such major, minor, patch refer to the level of change introduced.

Updating translations

From time to time, the translation packages will need to be updated as part of the build process. However, this is atypical, and is generally only done when needed; such as by a project committer before a major release. This process adds additional compile time and generally should not be executed for every build.

Updating translations can be accomplished with the following command:

./gradlew generateGettextSources && git add pgjdbc && git commit -m "Translations updated"

Releasing a snapshot version

Stage Vote Release Plugin is used for releasing artifacts.

Releasing a new version

Prerequisites:

  • Java 17
  • a PostgreSQL instance for running tests; it must have a user named test as well as a database named test
  • ensure that the RPM packaging CI isn't failing at copr web page

Manual release procedure

See details in Stage Vote Release readme

Prepare release candidate:

./gradlew prepareVote -Prc=1 -Pgh

It will create a release candidate tag, push the artifacts to Maven Central and print the announcement draft. The staged repository will become open for smoke testing access at https://oss.sonatype.org/content/repositories/orgpostgresql-1082/

If staged artifacts look fine, release it

./gradlew publishDist -Prc=1 -Pgh

Then update version, and readme as required.

Updating changelog

  • run ./release_notes.sh, edit as desired

Dependencies

PgJDBC has optional dependencies on other libraries for some features. These libraries must also be on your classpath if you wish to use those features; if they aren't, you'll get a PSQLException at runtime when you try to use features with missing libraries.

Gradle will download additional dependencies from the Internet (from Maven repositories) to satisfy build requirements. Whether or not you intend to use the optional features the libraries used to implement them they must be present to compile the driver.

Currently Waffle-JNA and its dependencies are required for SSPI authentication support (only supported on a JVM running on Windows). Unless you're on Windows and using SSPI you can leave them out when you install the driver.

Installing the driver

To install the driver, the postgresql jar file has to be in the classpath. When running standalone Java programs, use the -cp command line option, e.g.

java -cp postgresql-<major>.<minor>.<release>.jre<N>.jar -jar myprogram.jar

If you're using an application server or servlet container, follow the instructions for installing JDBC drivers for that server or container.

For users of IDEs like Eclipse, NetBeans, etc, you should simply add the driver JAR like any other JAR to use it in your program. To use it within the IDE itself (for database browsing etc) you should follow the IDE specific documentation on how to install JDBC drivers.

Bug reports, patches and development

PgJDBC development is carried out on the PgJDBC mailing list and on GitHub.

Set of "backend protocol missing features" is collected in backend_protocol_v4_wanted_features.md

Bug reports

For bug reports please post on pgsql-jdbc or add a GitHub issue. If you include additional unit tests demonstrating the issue, or self-contained runnable test case including SQL scripts etc that shows the problem, your report is likely to get more attention. Make sure you include appropriate details on your environment, like your JDK version, container/appserver if any, platform, PostgreSQL version, etc. Err on the site of excess detail if in doubt.

Bug fixes and new features

If you've developed a patch you want to propose for inclusion in PgJDBC, feel free to send a GitHub pull request or post the patch on the PgJDBC mailing list. Make sure your patch includes additional unit tests demonstrating and testing any new features. In the case of bug fixes, where possible include a new unit test that failed before the fix and passes after it.

For information on working with GitHub, see: https://guides.github.com/activities/forking/ and https://guides.github.com/introduction/flow/.

Testing

Remember to test proposed PgJDBC patches when running against older PostgreSQL versions where possible, not just against the PostgreSQL you use yourself.

You also need to test your changes with older JDKs. PgJDBC must support JDK8 ("Java 1.8") and newer.

You can get old JDK versions from the Oracle Java Archive.

If you have Docker, you can use docker-compose to launch test database (see docker):

cd docker/postgres-server

# Launch the most recent PostgreSQL database with SSL, XA, and SCRAM
docker-compose down && docker-compose up

# Launch PostgreSQL 9.6, with XA, without SSL
docker-compose down && SSL=no XA=yes docker-compose up

Alternatively, to run the test server with Docker in the foreground:

docker/bin/postgres-server

An alternative way is to use a Vagrant script: jackdb/pgjdbc-test-vm. Follow the instructions on that project's README page.

For more information about the unit tests and how to run them, see TESTING.md

Support for IDEs

It's possible to debug and test PgJDBC with various IDEs, not just with mvn on the command line. Projects aren't supplied, but it's easy to prepare them.

IntelliJ IDEA

IDEA imports PgJDBC project just fine. So clone the project whatever way you like and import it (e.g. File -> Open -> build.gradle.kts)

UPD: as of 2020-03, the code style is managed via .editorconfig, so IDEA should configure itself automatically.

  • Configure code style:

Project code style is located at pgjdbc/src/main/checkstyle/pgjdbc-intellij-java-google-style.xml In order to import it, copy the file to $IDEA_CONFIG_LOCATION/codestyles folder, restart IDEA, then choose "GoogleStyle (PgJDBC)" style for the Preferences -> Editor -> CodeStyle setting.

For instance, for macOS it would be ~/Library/Preferences/IntelliJIdeaXX/codestyles. More details here: https://intellij-support.jetbrains.com/hc/en-us/articles/206827437-Directories-used-by-the-IDE-to-store-settings-caches-plugins-and-logs

Eclipse

On Eclipse Mars, to import PgJDBC as an Eclipse Java project with full support for on-demand compile, debugging, etc, you can use the following approach:

  • File -> Import ...
  • Then choose Existing Gradle Project and proceed with the import.
  • Pick git, select https://github.com/pgjdbc/pgjdbc.git URL.
  • Click finish

Configure format configuration:

  • Import "import order" configuration: Eclipse -> Preferences -> Java -> Java Code Style -> Organize Imports -> Import... -> .../workspace-pgjdbc/pgjdbc-aggregate/pgjdbc/src/main/checkstyle/pgjdbc_eclipse.importorder
  • Import "formatter" configuration: Eclipse -> Preferences -> Java -> Java Code Style -> Formatter -> Import... -> .../workspace-pgjdbc/pgjdbc-aggregate/pgjdbc/src/main/checkstyle/pgjdbc-eclipse-java-google-style.xml
  • Configure "trim trailing whitespace": Eclipse -> Preferences -> Java -> Editor -> Save Actions -> "Perform Selected actions on save":
    • Check "Format source code", "Format edited lines"
    • Keep "Optimize Imports" selected
    • Check "Additional actions", click "Configure"
    • Click "Remove trailing whitespace", all lines
    • On "Code Style" tab, check "Use blocks in if/while/... statements", "Always"
    • On "Missing Code" tab, uncheck "Add missing @Override annotation"
    • On "Unnecessary Code" tab, check "Remove unused imports"

Other IDEs

Please submit build instructions for your preferred IDE.

Coding Guidelines

We enforce a style using OpenRewrite, Autostyle, ForbiddenApis, and Checkstyle. The CI will check for the code style, and it will report the deviations. The code style is based on Google style conventions for Java with 100 wide lines.

You might use the following command to fix auto-correctable issues, and report the rest:

./gradlew style

Use 2 spaces for indenting, do not use tabs, trim space at end of lines. Always put braces, even for single-line if. Always put default: case for switch statement.

The style configuration is located at:

  • pgjdbc/src/main/checkstyle
  • config/openrewrite
  • config/forbidden-apis
  • config/checkerframework

Null safety

The project uses the Checker Framework for verification of the null safety (this was introduced in PR 1814).

By default, parameters, return values, and fields are @NonNull, so you need to add @Nullable as required.

To execute the Checker Framework locally please use the following command:

./gradlew -PenableCheckerframework :postgresql:classes

Notable items:

  • The Checker Framework verifies code method by method. That means, it can't account for method execution order. That is why @Nullable fields should be verified in each method where they are used. If you split logic into multiple methods, you might want verify null once, then pass it via non-nullable parameters. For fields that start as null and become non-null later, use @MonotonicNonNull. For fields that have already been checked against null, use @RequiresNonNull.

  • If you are absolutely sure the value is non-null, you might use org.postgresql.util.internal.Nullness.castNonNull(T) or org.postgresql.util.internal.Nullness.castNonNull(T, String).

  • You can configure postfix completion in IntelliJ IDEA via Preferences -> Editor -> General -> Postfix Completion key: cnn, applicable element type: non-primitive, org.postgresql.util.internal.Nullness.castNonNull($EXPR$).

  • The Checker Framework comes with an annotated JDK, however, there might be invalid annotations. In that cases, stub files can be placed to /config/checkerframework to override the annotations. It is important the files have .astub extension otherwise they will be ignored.

  • In array types, a type annotation appears immediately before the type component (either the array or the array component) it refers to. This is explained in the Java Language Specification.

      String nonNullable;
  @Nullable String nullable;

  java.lang.@Nullable String fullyQualifiedNullable;

  // array and elements: non-nullable
  String[] x;

  // array: nullable, elements: non-nullable
  String @Nullable [] x;

  // array: non-nullable, elements: nullable
  @Nullable String[] x;

  // array: nullable, elements: nullable
  @Nullable String @Nullable [] x;

  // arrays: nullable, elements: nullable
  // x: non-nullable
  // x[0]: non-nullable
  // x[0][0]: nullable
  @Nullable String[][] x;

  // x: nullable
  // x[0]: non-nullable
  // x[0][0]: non-nullable
  String @Nullable [][] x;

  // x: non-nullable
  // x[0]: nullable
  // x[0][0]: non-nullable
  String[] @Nullable [] x;

Test

General rule: failing test should look like a good bug report. Thus Assert.fail() is bad.

  • Consider using "single assertion" per test method. Having separate test methods helps manual execution of the tests, and it makes test report cleaner

  • Consider using assertEquals(String message, expected, actual) instead of assertTrue(expected == actual). The former allows you to provide human readable message and it integrates well with IDEs (i.e. it allows to open diff of expected and actual).

If using just assertTrue(expected == actual) all you get is a stacktrace and if such a test fails a developer has to reverse engineer the intention behind that code.

Git Commit Guidelines

We have very precise rules over how our git commit messages can be formatted. This leads to more readable messages that are easy to follow when looking through the project history. But also, we use the git commit messages to generate the change log.

Commit Message Format

Each commit message consists of a header, a body and a footer. The header has a special format that includes a type, and a subject:

<type>: <subject>
<BLANK LINE>
<body>
<BLANK LINE>
<footer>

Any line of the commit message cannot be longer 100 characters! This allows the message to be easier to read on github as well as in various git tools.

Type

Must be one of the following:

  • feat: A new feature
  • fix: A bug fix
  • docs: Documentation only changes
  • style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
  • refactor: A code change that neither fixes a bug or adds a feature
  • perf: A code change that improves performance
  • test: Adding missing tests
  • chore: Changes to the build process or auxiliary tools and libraries such as documentation generation

Subject

The subject contains succinct description of the change:

  • use the imperative, present tense: "change" not "changed" nor "changes"
  • don't capitalize first letter
  • no dot (.) at the end

Body

Just as in the subject, use the imperative, present tense: "change" not "changed" nor "changes" The body should include the motivation for the change and contrast this with previous behavior.

Footer

The footer should contain any information about Breaking Changes and is also the place to reference GitHub issues that this commit Closes.