Avatica is a framework for building JDBC and ODBC drivers for databases, and an RPC wire protocol.
Avatica's Java binding has very few dependencies. Even though it is part of Apache Calcite it does not depend on other parts of Calcite. It depends only on JDK 1.7+ and Jackson.
Avatica's wire protocol is JSON over HTTP. The Java implementation uses Jackson to convert request/response command objects to/from JSON.
Avatica-Server is a Java implementation of Avatica RPC.
Core concepts:
Avatica implements JDBC by means of Factory. Factory creates implementations of the JDBC classes (Driver, Connection, Statement, PreparedStatement, ResultSet) on top of a Meta.
Work has not started on Avatica ODBC.
Avatica ODBC would use the same wire protocol and could use the same server implementation in Java. The ODBC client would be written in C or C++.
Since the Avatica protocol abstracts many of the differences between providers, the same ODBC client could be used for different databases.
Avatica-server embeds the Jetty HTTP server, providing a class [HttpServer]({{ site.apiRoot }}/org/apache/calcite/avatica/server/HttpServer.html) that implements the Avatica RPC protocol and can be run as a standalone Java application.
Connectors in HTTP server can be configured if needed by extending HttpServer
class and overriding its configureConnector()
method. For example, user can set requestHeaderSize
to 64K bytes as follows:
{% highlight java %} HttpServer server = new HttpServer(handler) { @Override protected ServerConnector configureConnector( ServerConnector connector, int port) { HttpConnectionFactory factory = (HttpConnectionFactory) connector.getDefaultConnectionFactory(); factory.getHttpConfiguration().setRequestHeaderSize(64 << 10); return super.configureConnector(connector, port); } }; server.start(); {% endhighlight %}
We know that it is important that client libraries have minimal dependencies.
Avatica is currently part of Apache Calcite. It does not depend upon any other part of Calcite. At some point Avatica could become a separate project.
Packages: