baeeq / olap4j

Open Java API for OLAP

olap4j

Olap4j is an open Java API for accessing OLAP data.

It is an extension to JDBC. For example, its OlapConnection class extends java.sql.Connection, from which you can create an OlapStatement, and execute to create a CellSet (analogous to a java.sql.ResultSet). There are also similar mechanisms for browsing metadata. As a result, olap4j is easy to learn if you have JDBC experience and know a little about OLAP.

Prerequisites

Olap4j requires ant (version 1.7 or later) and JDK 1.7 to build. (Once built, it also runs under JDK 1.5 and 1.6.)

Download and build

$ git clone git://github.com/olap4j/olap4j.git
$ cd olap4j
$ ant

Writing a simple program

You can now write and run a simple program against olap4j. For example, you can write:

import org.olap4j.*;
import org.olap4j.metadata.Member;
import java.sql.*;

Class.forName("org.olap4j.driver.xmla.XmlaOlap4jDriver");
Connection connection =
    DriverManager.getConnection(
        "jdbc:xmla:Server=http://example.com:8080/mondrian/xmla");
OlapConnection olapConnection = connection.unwrap(OlapConnection.class);
OlapStatement statement = olapConnection.createStatement();
CellSet cellSet =
    statement.executeOlapQuery(
        "SELECT {[Measures].[Unit Sales]} ON 0,\n"
        + "{[Product].Children} ON 1\n"
        + "FROM [Sales]");
for (Position row : cellSet.getAxes().get(1)) {
    for (Position column : cellSet.getAxes().get(0)) {
        for (Member member : row.getMembers()) {
            System.out.println(member.getUniqueName());
        }
        for (Member member : column.getMembers()) {
            System.out.println(member.getUniqueName());
        }
        final Cell cell = cellSet.getCell(column, row);
        System.out.println(cell.getFormattedValue());
        System.out.println();
    }
}

Or, if you are using the in-process mondrian driver, include mondrian.jar and its dependencies in your classpath, and change the appropriate lines in the above code to the following:

Class.forName("mondrian.olap4j.MondrianOlap4jDriver");
Connection connection =
    DriverManager.getConnection(
        "jdbc:mondrian:"
        + "Jdbc='jdbc:odbc:MondrianFoodMart';"
        + "Catalog='file://c:/open/mondrian/demo/FoodMart.xml';"
        + "JdbcDrivers=sun.jdbc.odbc.JdbcOdbcDriver;");

Packages and Roadmap

The core API of olap4j version 1.0 is a Long Term Support (LTS) release, but some parts of the olap4j project will remain considered as experimental, thus subject to change in future releases.

Core packages are as follows:

• org.olap4j.driver.xmla - Generic XML/A driver.
• org.olap4j.mdx - Core objects of the MDX model.
• org.olap4j.mdx.parser - Parser for the MDX query language.
• org.olap4j.metadata - Discovery of an OLAP server's metadata.
• org.olap4j.type - System for the core MDX object model and the metadata package.

The following packages are considered experimental and are subject to change:

• org.olap4j.query - Programmatic Query Model.
• org.olap4j.transform - Core MDX object model transformation utilities.
• org.olap4j.layout - Utility classes to display CellSets.
• org.olap4j.CellSetListener and all associated classes - Event-based system for real time updates of CellSet objects.
• org.olap4j.Scenario and all associated classes - Statistical simulations module.

Version 2.0

Olap4j version 2.0 is currently under development. Goals are:

• Support metadata and API changes in recent SSAS (Microsoft SQL Server Analysis Services) and XMLA (XML for Analysis)
• Support metadata and API changes in Mondrian version 4

We aim to be backwards compatible in the same way that each JDBC release is backwards compatible:

• Applications developed against earlier versions will work against 2
• Drivers supporting version 2 will also serve as 1.x drivers (JDBC version 4 broke this rule, and it was painful for driver developers)
• Some work will be required to convert a version 1.x driver to a version 2 driver

Version 2 specification is here.

More information

General project information:

• License: Apache License, Version 2.0.
• Lead developers: Julian Hyde, Luc Boudreau.
• Project page: http://www.olap4j.org
• Specification: HTML, PDF, history.
• Javadoc: http://www.olap4j.org/api
• Source code: http://github.com/julianhyde/olap4j
• Developers list: https://lists.sourceforge.net/lists/listinfo/olap4j-devel
• Forum: http://sourceforge.net/p/olap4j/discussion/577988/

Related projects:

• Mondrian
• olap4j-xmlaserver

If you have downloaded a release:

• README.txt describes the release structure.
• CHANGES.txt describes what has changed in the release.
• The VERSION.txt file holds the version number of the release.