While
BIRT offers many ways to connect to Cassandra, including using the Cassandra
JDBC driver, this post focuses on using a Scripted data source to call the
Hector Client Java client. A BIRT scripted
data source allows external Java classed to be called to retrieve data for a
BIRT report and can be written in Java or JavaScript. The examples below will use JavaScript. For this post we used the DataStax
community edition which is available here, and created a keyspace with the name users and a column
family named User. The User column
family contains three string columns for first name, last name and age. The script used to load the sample data is
available in the example download.
Set Designer Classpath
The first thing that you will need to do is set the
classpath for the designer to access the following set of jars.
-
hector-core-version.jar
- hector-object-mapper-version.jar
- slf4j-api-version.jar
- libthrift-version.jar
- apache-cassandra-thrift-version.jar
- guava-rversion.jar
- commons-lang-version.jar
All of these jars, with the exception of the two Hector jars
are available in the /install-directory/DataStax Community/apache-cassandra/lib
directory. To get the Hector jars you
can download and build the hector source or just download them from a maven
repository.
The Hector-object-mapper jar file can be downloaded from
here.
The Hector core jar file can be downloaded from here.
One way to setup the classpath is to create a libs directory
in your Report Project and then copy all of the jars above to this folder.
Next Select Window->Preferences. Select the Report Design->Classpath
preference and click on the Configure project specific settings link.
Select the BIRT Project that you will be using Hector with
and click on ok.
Select
the enable project specific settings checkbox and add the jars in the lib
folder you created earlier.
Creating a Scripted Data Source using Hector
You can now create a report that calls the Hector APIs
directly. To do this first create a new
report. Select the data explorer view
and right click on the data sources node and click on New Data Source. Select the Scripted Data Source option and
click on finish.
Next right click on the Data Sets node and choose the New
Data Set option. Make sure to select the
Scripted Data Source that you just created as the data source for this data
set.
Click on the Next button and enter each column name and data
type for the data set.
Click on the Finish button.
You can now enter script for the data set. To do this first make sure the data set is
selected in data explorer view and click on the script tab at the bottom of the
report canvas.
In the script editor you will have many events that could be
scripted, but in this example all we need is an open script and a fetch
script. First select open from the
script drop down list and enter a script similar to the following.
importPackage(Packages.java.util);
importPackage(Packages.me.prettyprint.cassandra.serializers);
importPackage(Packages.me.prettyprint.cassandra.service);
importPackage(Packages.me.prettyprint.hector.api);
importPackage(Packages.me.prettyprint.hector.api.beans);
importPackage(Packages.me.prettyprint.hector.api.factory);
importPackage(Packages.me.prettyprint.hector.api.query);
var cluster =
HFactory.getOrCreateCluster("Test Cluster",new
CassandraHostConfigurator("localhost:9160"));
var keyspace =
HFactory.createKeyspace("users", cluster);
var rangeSlicesQuery =
HFactory.createRangeSlicesQuery(keyspace, StringSerializer.get(),
StringSerializer.get(), StringSerializer.get())
.setColumnFamily("User").setRange(null, null, false,
10).setRowCount(100);
var result =
rangeSlicesQuery.execute();
myrows = result.get();
rowsIterator = myrows.iterator();
Hector also supports using
CQL so you could also use the following open script
importPackage(Packages.java.util);
importPackage(Packages.me.prettyprint.cassandra.serializers);
importPackage(Packages.me.prettyprint.cassandra.service);
importPackage(Packages.me.prettyprint.hector.api);
importPackage(Packages.me.prettyprint.hector.api.beans);
importPackage(Packages.me.prettyprint.hector.api.factory);
importPackage(Packages.me.prettyprint.hector.api.query);
importPackage(Packages.me.prettyprint.cassandra.model);
var cluster =
HFactory.getOrCreateCluster("Test Cluster",new
CassandraHostConfigurator("localhost:9160"));
var keyspace =
HFactory.createKeyspace("users", cluster);
var cqlQuery = new CqlQuery(keyspace,
StringSerializer.get(), StringSerializer.get(), StringSerializer.get());
cqlQuery.setQuery("select * from
User");
var resultCQL =
cqlQuery.execute();
rowsIterator = resultCQL.get().iterator();
Next add a fetch script like the following.
if
(rowsIterator.hasNext()) {
var myrow =
rowsIterator.next();
var cols =
myrow.getColumnSlice().getColumns();
for( ii=0; ii <
cols.size(); ii++ ){
row[cols.get(ii).getName()] =
cols.get(ii).getValue();
}
return true;
}else{
return false;
}
In the above fetch the script assumes you
have named your scripted data set columns the same as the columns in Cassandra. You should now be able to preview the data
set. Double click on the data set in the
data explorer view and select preview.
You
can now use the data set within your report.
Deploying a Report that Uses the Hector API
If you are using the BIRT Viewer and deploy a report that
calls the Hector API, verify that all the jars discussed in the beginning of
this Post (Set Designer Classpath) are placed in WEB-INF/lib directory of the
Viewer. If you are running BIRT reports
using the BIRT APIs verify that the above jars are also in the classpath.
More information on CQL and Hector is available here. The example in this post is available on
Birt-Exchange.
