# How to contribute

Thank you so much for wanting to contribute to PostgreSQL JDBC Driver! Here are a few important
things you should know about contributing:

  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 requests are not merged directly into the master branch.

## Ideas

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 much 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.

## 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

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"

## Checking out the source code

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
    
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 https://github.com/pgjdbc/pgjdbc-jre7.git
    git clone https://github.com/pgjdbc/pgjdbc-jre6.git

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-<major>.<minor>.<release>.jre<N>.jar. Where major,minor are the PostgreSQL major,minor
version numbers. release is the jdbc release number. N is the version of the JDBC API which 
corresponds to the version of Java used to compile the driver.

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
<?xml version="1.0" encoding="UTF8"?>
<toolchains>
  <!-- JDK toolchains -->
  <toolchain>
    <type>jdk</type>
    <provides>
      <version>1.6</version>
      <vendor>oracle</vendor>
    </provides>
    <configuration>
      <jdkHome>/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home</jdkHome>
    </configuration>
  </toolchain>
  <toolchain>
    <type>jdk</type>
    <provides>
      <version>1.7</version>
      <vendor>oracle</vendor>
    </provides>
    <configuration>
      <jdkHome>/Library/Java/JavaVirtualMachines/jdk1.7.0_55.jdk/Contents/Home</jdkHome>
    </configuration>
  </toolchain>
  <toolchain>
    <type>jdk</type>
    <provides>
      <version>1.8</version>
      <vendor>oracle</vendor>
    </provides>
    <configuration>
      <jdkHome>/Library/Java/JavaVirtualMachines/jdk1.8.0_60.jdk/Contents/Home</jdkHome>
    </configuration>
  </toolchain>
</toolchains>
```

## 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

Prerequisites:
- JDK 6, JDK 7, and JDK8 configured in `~/.m2/toolchains.xml`
- a PostgreSQL instance for running tests
- ensure that the RPM packaging CI isn't failing at
  [copr web page](https://copr.fedorainfracloud.org/coprs/g/pgjdbc/pgjdbc-travis/builds/) -
  possibly bump `parent poms` or `pgjdbc` versions in RPM [spec file](packaging/rpm/postgresql-jdbc.spec).

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 https://oss.sonatype.org/content/repositories/orgpostgresql-1082/

If staged artifacts look fine, release it

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

Update 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.

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](https://jdbc.postgresql.org/community/mailinglist.html) and on [GitHub](https://github.com/pgjdbc/pgjdbc).

Set of "backend protocol missing features" is collected in [backend_protocol_v4_wanted_features.md](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: http://help.github.com/articles/fork-a-repo and http://learn.github.com/p/intro.html.

### 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 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](http://www.oracle.com/technetwork/java/archive-139210.html).

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

For information about the unit tests and how to run them, see
  [org/postgresql/test/README](pgjdbc/src/test/java/org/postgresql/test/README.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 -> `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: 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 -> New -> Project
* Maven -> Check out Maven Project from SCM
* Pick `git`, select `https://github.com/pgjdbc/pgjdbc.git` 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.

## <a name="tests"></a> Coding Guidelines

### Java

Project uses [Google style](https://google.github.io/styleguide/javaguide.html) 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.

### 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.

## <a name="commit"></a> 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**.
