BarChartOLAPDataModel: Basic Requirements

The main responsibility of a BarChartOLAPDataModel is to map data members from an OLAP data structure to variable roles in a bar chart.

In your code, you can explicitly select measures in the OLAP data, or allow the component's OLAP data model to select measures by default.

A bar chart's primary variable roles are

CategoryVariable

Specifies a classification variable whose values determine the number and arrangement of bars in the chart. A unique bar element is produced for each unique classification value or combination of values when other variable roles are specified. A BarChartOLAPDataModel maps this role to an OLAP column or row level, depending on the OLAP structure.

ResponseVariable

Specifies an analysis variable whose values determine the height of each bar. A BarChartOLAPDataModel maps this role to one or more OLAP measures, depending on the OLAP structure.

SubgroupVariable

Divides bars into subgroup segments, based on the values of a categorical variable. A BarChartOLAPDataModel uses this role if the OLAP axis that supplies the CategoryVariable role has more than one level and the BarChart's subgroupEnabled field is true.

To access OLAP data for a graph, you must know the name of the OLAP host server and connect to that server with a valid username and password. To use the OLAP data in a BarChart, you must

• create an OLAPDataSet, either from the result set of a query that is executed on an OLAP provider or from the metadata that has been mapped to the OLAP data
• assign the OLAPDataSet to a BarChartOLAPDataModel
• assign the BarChartOLAPDataModel to a BarChart.

The following code fragment generates a bar chart that shows product sums for selected products, years, and countries.

// Create strings to store an SQL query, the OLAP server name,
// and the connection port.
   String OLAP_QUERY="SELECT CROSSJOIN({[GEOGRAPHIC].[COUNTRY].MEMBERS},"
                   + "{[PRODUCTLINE].[PRODUCT].MEMBERS}) ON COLUMNS,"
                   + "{[TIME].[YEAR].MEMBERS} ON ROWS "
                   + "FROM MYOLAPCUBE WHERE ([Measures].[ACTUAL_SUM])"; // specify valid OLAP source
   String OLAP_SERVER="myOlapServer.com"; // use a valid server name
   int OLAP_PORT=8800;                    // use a valid port

// Create a BarChartOLAPDataModel from an OLAPDataSet. The final argument
// on the model constructor sets the chart's subgroupEnabled field to true.
   BarChartOLAPDataModel olapDataModel = null;
   try {
        // OLAPDataSet arguments: host, port, username, pwd, query
           olapDataModel=new BarChartOLAPDataModel(
           new OLAPDataSet(OLAP_SERVER, OLAP_PORT, "myUsername", "myPwd",
                           OLAP_QUERY), true);
       } catch (Exception ex) { ex.printStackTrace(); }

// Create a BarChart that uses the BarChartOLAPDataModel as its data model
   BarChart barChart=new BarChart();
   barChart.setDataModel(olapDataModel);