5:14 p.m.
I’ve been trying out the DROOLS-TEMPLATES project, really impressed so far, surprised
there isn’t more buzz about this project.
I wrote a new version of the DataProviderCompiler that takes a SQL ResultSet instead of a
org.drools.template.DataProvider.
I don’t think it will be useful to that many people, so I’m not going to try and add it to
the code base, but I’ll provide it here. I used it for testing out templates, but for our
actual production code, I will naturally be using Hibernate to retrieve the rules from the
DB (so I can take advantage of Hibernate cache.) It is much quicker to set up a template
test with this compiler though.
It also allows you to put the data in whatever types you like in the database, as long as
you add a String converter for that type in processData(), like:
<pre>
case java.sql.Types.DOUBLE:
cell = String.valueOf(rs.getInt(cellNum));
break;
</pre>
Calling Code (based on
drools-examples\drools-examples-drl\src\main\java\org\drools\examples\DataDrivenTemplateExample.java)
<pre>
ResultSet rs;
try {
Statement sta = conn.createStatement();
rs = sta.executeQuery("SELECT * FROM RulePricingPolicy");
// TODO: you need to catch or handle
} catch (SQLException e) {
}
final ResultSetCompiler converter = new ResultSetCompiler();
final String drl = converter.compile(rs, getTemplate());
</pre>
Here is the ResultSet Compiler:
<pre>
import org.drools.template.parser.TemplateContainer;
import org.drools.template.parser.DefaultTemplateContainer;
import org.drools.template.parser.TemplateDataListener;
import org.drools.template.parser.DataListener;
import java.io.InputStream;
import java.util.List;
import java.util.ArrayList;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
/**
* <p> A Drools template compiler which takes a ResultSet and compiles it into
* a template using DefaultTemplateContainer.
* </p>
*
* @author bxt, Aug 19, 2009 1:53:38 PM
* <br>
* Copyright © 2008 Customized Services Administrators, Inc.
* All Rights Reserved.
*/
public class ResultSetCompiler {
/**
* Generates DRL from a data provider for the spreadsheet data and templates.
*
* @param rs the resultset for the table data
* @param template the string containing the template resource name
* @return the generated DRL text as a String
*/
public String compile(final ResultSet rs,
final String template) {
final InputStream templateStream = this.getClass().getResourceAsStream(template);
return compile(rs,
templateStream);
}
/**
* Generates DRL from a data provider for the spreadsheet data and templates.
*
* @param rs the resultset for the table data
* @param templateStream the InputStream for reading the templates
* @return the generated DRL text as a String
*/
public String compile(final ResultSet rs,
final InputStream templateStream) {
TemplateContainer tc = new DefaultTemplateContainer(templateStream);
closeStream(templateStream);
return compile(rs,
new TemplateDataListener(tc));
}
/**
* Generates DRL from a data provider for the spreadsheet data and templates.
*
* @param rs the resultset for the table data
* @param listener a template data listener
* @return the generated DRL text as a String
*/
public String compile(final ResultSet rs,
final TemplateDataListener listener) {
List<DataListener> listeners = new ArrayList<DataListener>();
listeners.add(listener);
processData(rs,
listeners);
return listener.renderDRL();
}
/**
* Iterate through the resultset.
* @param rs the resultset for the table data
* @param listeners list of template data listener
*/
private void processData(final ResultSet rs,
List<DataListener> listeners) {
try {
ResultSetMetaData rsmd = rs.getMetaData();
int colCount = rsmd.getColumnCount();
int i = 0;
while (rs.next()) {
newRow(listeners, i, colCount);
for (int cellNum = 1; cellNum < colCount + 1; cellNum++) {
String cell;
int sqlType = rsmd.getColumnType(cellNum);
switch (sqlType) {
case java.sql.Types.DATE:
cell = rs.getDate(cellNum).toString();
break;
case java.sql.Types.INTEGER:
case java.sql.Types.DOUBLE:
cell = String.valueOf(rs.getInt(cellNum));
break;
default:
cell = rs.getString(cellNum);
}
newCell(listeners,
i,
cellNum -1,
cell,
DataListener.NON_MERGED);
}
i++;
}
//TODO: you need to throw or handle
} catch (SQLException e) {
}
finishData(listeners);
}
private void finishData(List<DataListener> listeners) {
for (DataListener listener : listeners) {
listener.finishSheet();
}
}
private void newRow(List<DataListener> listeners,
int row,
int cols) {
for (DataListener listener : listeners) {
listener.newRow(row,
cols);
}
}
public void newCell(List<DataListener> listeners,
int row,
int column,
String value,
int mergedColStart) {
for (DataListener listener : listeners) {
listener.newCell(row,
column,
value,
mergedColStart);
}
}
protected void closeStream(final InputStream stream) {
try {
stream.close();
} catch (final Exception e) {
System.err.print("WARNING: Wasn't able to correctly close stream for rule
template. " + e.getMessage());
}
}
}
</pre>