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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 6, 7, 8 and 9; and PostgreSQL server versions from 8.2 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 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. 42.0.0.jre7)
  • 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 seccion.

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 recent version of Maven (3.x)
  • A JDK for the JDBC version you'd like to build (JDK6 for JDBC 4, JDK7 for JDBC 4.1 or JDK8 for JDBC 4.2)
  • A running PostgreSQL instance (optional for unit/integration tests)

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

This will create a pgjdbc directory containing the checked-out source code. In order do build jre7 or jre6 compatible versions, check out those repositories under pgjdbc

    cd pgjdbc # <-- that is pgjdbc/pgjdbc.git clone
    git clone
    git clone

Note: all the source code is stored in pgjdbc.git repository, so just pgjdbc.git is sufficient for development.

Compiling with Maven 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:

mvn package

Note: if you want to skip test execution, issue mvn package -DskipTests.

Note: in certain cases, proper build requires cleaning the results of previous one. For instance, if you remove a .java file, then clean is required to remove the relevant .class file. In such cases, use mvn clean or mvn clean package.

PgJDBC doesn't natively support building from IDEs like Eclipse, NetBeans or IntelliJ. However you can use the tools Maven support from within the IDE if you wish. You can use regular IDE tools to develop, execute tests, etc, however if you want to build final artifacts you should use mvn.

After running the build , and build a .jar file (Java ARchive) depending on the version of java and which release you have the jar will be named postgresql-...[jre].jar. We use Semantic versioning; as such major, minor, patch refer to the level of change introduced. For Java 6, and Java 7 jre will be appended after the patch level. N corresponds to the version of Java, roughly correlated to the JDBC version number.

The target directory will contain the driver jar. If you need source code, documentation and runtime dependencies use mvn package -P release-artifacts.

NOTE: default build produces Java 8 (JDBC 4.2) driver (in pgjdbc/target folder).

If you need a version for older Java, configure ~/.m2/toolchains.xml. Here's sample configuration for macOS:

<?xml version="1.0" encoding="UTF8"?>
  <!-- JDK toolchains -->


We enforce a style using checkstyle, Travis CI will fail if there are checkstyle errors. It is recommended you run

mvn checkstyle:check 

before creating your pull request ​

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:

mvn -Ptranslate compile && git add pgjdbc && git commit -m "Translations updated"

Note that the maven profile "translate" can safely be called with other profiles, such as -P release-artifacts. Invocation of this command will generate new .po files, a new messages.pot file, and newly translated class files.

Releasing a snapshot version

TravisCI automatically deploys snapshots for each commit to master branch.

Git repository typically contains -SNAPSHOT versions, so you can use the following command:

mvn deploy && (cd pgjdbc-jre7; mvn deploy) && (cd pgjdbc-jre6; mvn deploy)

Releasing a new version


  • JDK 6, JDK 7, and JDK8 configured in ~/.m2/toolchains.xml
  • 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 - possibly bump parent poms or pgjdbc versions in RPM spec file.

Release via Travis

To release a branch via Travis, perform the following:


git checkout -B release/master origin/master
git push origin release/master
  1. Check if pom.xml includes proper -SNAPSHOT versions (release versions would be the ones without -SNAPSHOT)

  2. Push release/master branch to pointing to the commit you want to release.

    Note: master..release/master should be a fast-forward or both branches should point to the same commit.

    Travis would build new version, create a tag, update pom.xml to the next snapshot versions, and update master branch accordingly.

    Note: .jre6 and .jre7 builds will be built and staged to Maven Central automatically

    Note: the artifacts will not be visible in Maven Central before you manually release them.

  3. Navigate to Sonatype Nexus Repository Manager, find staging orgpostgresql repository there and release it

Manual release procedure

Release a version for JDK8

  • From a root folder, perform mvn release:clean release:prepare. That will ask you new version, update pom.xml, commit and push it to git.
  • From a root folder, perform mvn release:perform. That will stage Java 8-compatible PgJDBC version to maven central.

Release a version for JDK7

  • Update pgjdbc submodule in pgjdbc-jre7
cd pgjdbc-jre7/pgjdbc
git checkout master
git reset --hard REL9.4.1208
cd ..
git add pgjdbc
git commit -m "Update pgjdbc"
  • Release pgjdbc-jre7
mvn release:clean release:prepare release:perform

Release a version for JDK6

  • Update pgjdbc submodule in pgjdbc-jre7
  • Release pgjdbc-jre6
mvn release:clean release:prepare release:perform

Close staging repository and release it:

  • From a pgjdbc folder, perform
mvn nexus-staging:close -DstagingRepositoryId=orgpostgresql-1082

The staged repository will become open for smoke testing access at

If staged artifacts look fine, release it

 mvn nexus-staging:release -DstagingRepositoryId=orgpostgresql-1082

Updating changelog

  • run ./, edit as desired


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.

Maven 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

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: and


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 JDK6 ("Java 1.6") and newer. Code that is specific to a particular spec version may use features from that version of the language. i.e. JDBC4.1 specific may use JDK7 features, JDBC4.2 may use JDK8 features. Common code and JDBC4 code needs to be compiled using JDK6.

Three different versions of PgJDBC can be built, the JDBC 4, 4.1 and 4.2 drivers. These require JDK6, JDK7 and JDK8 respectively. The driver to build is auto-selected based on the JDK version used to run the build. The best way to test a proposed change is to build and test with JDK6, 7 and 8.

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

Then, to test against old JDK, run mvn test in pgjdbc-jre6 or pgjdbc-jre7 modules.

An easy way to set up the test PostgreSQL database is to use 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

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 -> pom.xml)

  • 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:


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 -> New -> Project
  • Maven -> Check out Maven Project from SCM
  • Pick git, select URL. Note: if git SCM is missing, just click m2e Marketplace link and search for egit there. Note the letter e.
  • Click finish
  • Eclipse might complain with "Plugin execution not covered by lifecycle configuration: com.igormaznitsa:jcp:6.0.1:preprocess (execution: preprocessSources, phase: generate-sources)", however this error seems to be not that important

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"

Eclipse will interoperate fine with Maven, so you can test and debug with Eclipse then do dist builds with Maven.

Other IDEs

Please submit build instructions for your preferred IDE.

Coding Guidelines


Project uses Google style conventions for java with 100 wide lines. Code style is verified via Travis job. In order to do manual verification, issue

cd pgjdbc && mvn checkstyle:check

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.

Note: there are formatter configurations in pgjdbc/src/main/checkstyle folder.


General rule: failing test should look like a good bug report. Thus 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>

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.


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


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


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.


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

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