docs/source/java/quickstart.rst

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==========
Quickstart
==========

Here we'll briefly tour basic features of ADBC with Java :doc:`JNI driver manager <./jni>` and the PostgreSQL driver.

Installation
============

To include ADBC in your Maven project, add the following dependency:

.. code-block:: xml

   <dependency>
       <groupId>org.apache.arrow.adbc</groupId>
       <artifactId>adbc-driver-jni</artifactId>
       <version>${adbc.version}</version>
   </dependency>

Installing Drivers
------------------

See :ref:`driver-table-install` for instructions on installing ADBC drivers for
the database you want to connect to. For the example below, you could install
`dbc <https://docs.columnar.tech/dbc>`__ and then install the PostgreSQL driver with:

.. code-block:: shell

   dbc install postgresql

Imports
-------

For the examples in this section, the following imports are required:

.. code-block:: java

   import java.util.HashMap;
   import java.util.Map;
   import org.apache.arrow.adbc.core.AdbcConnection;
   import org.apache.arrow.adbc.core.AdbcDatabase;
   import org.apache.arrow.adbc.core.AdbcDriver;
   import org.apache.arrow.adbc.core.AdbcException;
   import org.apache.arrow.adbc.core.AdbcStatement;
   import org.apache.arrow.adbc.driver.jni.JniDriver;
   import org.apache.arrow.memory.BufferAllocator;
   import org.apache.arrow.memory.RootAllocator;

Basic Usage
===========

.. code-block:: java

   Map<String, Object> parameters = new HashMap<>();
   JniDriver.PARAM_DRIVER.set(parameters, "postgresql");
   AdbcDriver.PARAM_URI.set(parameters, "postgresql://localhost:5432/postgres");
   try (
       BufferAllocator allocator = new RootAllocator();
       AdbcDatabase db = new JniDriver(allocator).open(parameters);
       AdbcConnection adbcConnection = db.connect();
       AdbcStatement stmt = adbcConnection.createStatement();
   ) {
       stmt.setSqlQuery("select * from foo");
       try (AdbcStatement.QueryResult queryResult = stmt.executeQuery()) {
           while (queryResult.getReader().loadNextBatch()) {
               // process batch
           }
       }
   } catch (AdbcException e) {
       // throw
   }

In application code, the connection must be closed after usage or memory may leak.
It is recommended to wrap the connection in a try-with-resources block for automatic
resource management. In this example, we are connecting to a PostgreSQL database,
specifically the default database "postgres".

Note that creating a statement is also wrapped in the try-with-resources block.
Assuming we have a table "foo" in the database, an example for setting and executing the
query is also provided.

Next Steps
==========

- Check out the :doc:`Java API documentation <index>` for more details
- See the :doc:`drivers </driver/index>` to see which databases are supported
- Explore more examples in the `adbc-quickstarts repository <https://github.com/columnar-tech/adbc-quickstarts/tree/main/java>`_
- Explore the `Java source code <https://github.com/apache/arrow-adbc/tree/main/java>`_ for additional examples