# PostgreSQL JDBC driver

This is a simple readme describing how to compile and use the Postgresql JDBC driver.

• Commit Message Guidelines

Info

This isn't a guide on how to use JDBC - for that refer to Oracle's website and the JDBC tutorial.

For problems with this driver, refer to driver's home page and associated mailing list.

Downloading pre-built drivers

Most people do not need to compile PgJDBC. You can download prebuilt versions of the driver from the Postgresql JDBC site.

Compiling with Ant on the command line

PgJDBC doesn't natively support compilation from IDEs like Eclipse, NetBeans or IntelliJ. You should compile with ant on the command line or create your own IDE project. Tips for use with some IDEs follow below.

Before you can compile the driver you must download the source code from git. You cannot compile from a jar or a .zip distribution. Run:

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

to download the source code. (You'll need git installed, of course).

To compile you will need to have a Java 5 or newer JDK and will need to have Ant installed. To obtain Ant go to http://ant.apache.org/index.html and download the binary. Being pure Java it will run on virtually all Java platforms. If you have any problems please email the pgsql-jdbc list.

Once you have Ant, simply run ant using 'ant -lib lib' in the top level directory.
This will compile the correct driver for your JVM, and build a .jar file (Java ARchive) depending on the version of java and which release you have the jar will be named postgresql-.-.jdbc.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.

REMEMBER: Once you have compiled the driver, it will work on ALL platforms that support that version of the API. You don't need to build it for each platform.

Creating a distribution zip

To create a package of the driver jar, sources, and dependencies, run:

ant dist

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.

Ant will download additional dependencies from the Internet (from Maven respositories) to satisfy build requirements. Whether or not you intend to use the optional features the libraries used to implement them 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-9.4-1200.jdbc4.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 its self (for database browsing etc) you should follow the IDE specific documentation on how to install JDBC drivers.

Using the driver

Java 6 and above do not need any special action to enable the driver - if it's on the classpath it is automatically detected and loaded by the JVM.

For Java 1.5 and below, use Class.forName or a system parameter. See the main documentation and the JDBC tutorial for details - take a look at "more information" below.

JDBC URL syntax

The driver recognises JDBC URLs of the form:

jdbc:postgresql/

jdbc:postgresql:database

jdbc:postgresql://host/database

jdbc:postgresql://host/

jdbc:postgresql://host:port/database

jdbc:postgresql://host:port/

When the parameter database is omitted it defaults to the username.

Also, you can supply both username and passwords as arguments, by appending them to the URL. e.g.:

jdbc:postgresql:database?user=me
jdbc:postgresql:database?user=me&password=mypass

Notes:

• If you are connecting to localhost or 127.0.0.1 you can leave it out of the URL. i.e.: jdbc:postgresql://localhost/mydb can be replaced with jdbc:postgresql:mydb

• The port defaults to 5432 if it's left out.

There are many options you can pass on the URL to control the driver's behaviour. See the full JDBC driver documentation for details.

More information

For more information see the the PgJDBC driver documentation and the JDBC tutorial.

Bug reports, patches and development

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

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 JDK5 ("Java 1.5") and newer. Code that's JDBC4 specific may use JDK6 features, and code that's JDBC4.1 specific may use JDK7 features. Common code and JDBC3 code needs to stick to Java 1.5.

Two different versions of PgJDBC can be built, the JDBC 3 and JDBC 4 drivers. The former may be built with JDK 5, while building JDBC4 requires JDK 6 or 7. 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 with both the JDBC3 and JDBC4 drivers is to build and test with both JDK5 and JDK6 or 7.

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

Typically you can test against an old JDK with:

export JAVA_HOME=/path/to/jdk_1_5
export PATH=$JAVA_HOME/bin:$JAVA_HOME/jre/bin:
ant clean test

For information about the unit tests and how to run them, see org/postgresql/test/README

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.

Support for IDEs

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

Eclipse

On Eclipse Luna, to import PgJDBC as an Eclipse Java project with full support for on-demand compile, debugging, etc, you must:

• Perform a git clone of PgJDBC on the command line

• Use Ant to fetch the dependency JARs:

      ant -lib lib snapshot-version maven-dependencies
  

• In Eclipse, File -> New -> Java Project

• Uncheck "Use default location" and find your git clone of PgJDBC then press Next

• Under Source, open "configure inclusion and exclusion filters"

• Add the exclusion filters: org/postgresql/jdbc3/Jdbc3*.java org/postgresql/jdbc3g/Jdbc3g*.java ... and accept the dialog.

• Under Libraries, choose Add JARs and add everything under lib

• Click finish to create the project

Note that unlike a JDBC4 JAR an Eclipse project will not be auto-detected using service discovery, so you'll have to use an explicit load:

Class.forName("org.postgresql.Driver")

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

Other IDEs

Please submit build instructions for your preferred IDE.

Coding Guidelines

Java

Use 4 spaces for indenting. Always put braces, even for single-line if. Always put default: case for switch statement.

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.

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