/*
* This program is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
* Foundation.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* or from the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Lesser General Public License for more details.
*
* Copyright (c) 2001 - 2013 Object Refinery Ltd, Pentaho Corporation and Contributors.. All rights reserved.
*/
package org.pentaho.reporting.engine.classic.core.modules.misc.beanshell;
import bsh.EvalError;
import bsh.Interpreter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.pentaho.reporting.engine.classic.core.function.AbstractExpression;
import org.pentaho.reporting.engine.classic.core.function.Expression;
import org.pentaho.reporting.libraries.base.util.ObjectUtilities;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.Reader;
/**
* An expression that uses the BeanShell scripting framework to perform a scripted calculation. The expression itself is
* contained in a function called
* <p/>
* <code>Object getValue()</code>
* <p/>
* and this function is defined in the <code>expression</code> property. You have to overwrite the function
* <code>getValue()</code> to begin and to end your expression, but you are free to add your own functions to the
* script.
* <p/>
* By default, base Java core and extension packages are imported for you. They are:
* <ul>
* <li><code>java.lang<code>
* <li><code>java.io</code>
* <li><code>java.util</code>
* <li><code>java.net</code>
* <li><code>java.awt</code>
* <li><code>java.awt.event</code>
* <li><code>javax.swing</code>
* <li><code>javax.swing.event</code>
* </ul>
* <p/>
* An example in the XML format: (from report1.xml)
* <p/>
*
* <pre>
* <expression name="expression" class="org.pentaho.reporting.engine.classic.core.modules.misc.beanshell
* .BSHExpression">
* <properties>
* <property name="expression">
* // you may import packages and classes or use the fully qualified name of the class
* import org.pentaho.reporting.engine.classic.core.*;
* <p/>
* String userdefinedFunction (String parameter, Date date)
* {
* return parameter + " - the current date is " + date);
* }
* <p/>
* // use simple java code to perform the expression. You may use all classes
* // available in your classpath as if you write "real" java code in your favourite
* // IDE.
* // See the www.beanshell.org site for more information ...
* //
* // A return value of type "Object" is alway implied ...
* getValue ()
* {
* return userdefinedFunction ("Hello World :) ", new Date());
* }
* </property>
* </properties>
* </expression>
* </pre>
*
* @author Thomas Morgner
*/
public class BSHExpression extends AbstractExpression {
private static final Log logger = LogFactory.getLog( BSHExpression.class );
/**
* The headerfile with the default initialisations.
*/
public static final String BSHHEADERFILE =
"org/pentaho/reporting/engine/classic/core/modules/misc/beanshell/BSHExpressionHeader.txt"; //$NON-NLS-1$
/**
* The beanshell-interpreter used to evaluate the expression.
*/
private transient Interpreter interpreter;
private transient boolean invalid;
private String expression;
/**
* default constructor, create a new BeanShellExpression.
*/
public BSHExpression() {
}
/**
* This method tries to create a new and fully initialized BeanShell interpreter.
*
* @return the interpreter or null, if there was no way to create the interpreter.
*/
protected Interpreter createInterpreter() {
try {
final Interpreter interpreter = new Interpreter();
initializeInterpreter( interpreter );
return interpreter;
} catch ( Throwable e ) {
logger.warn( "Unable to initialize the expression", e ); //$NON-NLS-1$
return null;
}
}
/**
* Initializes the bean-shell interpreter by executing the code in the BSHExpressionHeader.txt file.
*
* @param interpreter
* the interpreter that should be initialized.
* @throws EvalError
* if an BeanShell-Error occured.
* @throws IOException
* if the beanshell file could not be read.
*/
protected void initializeInterpreter( final Interpreter interpreter ) throws EvalError, IOException {
final InputStream in = ObjectUtilities.getResourceRelativeAsStream( "BSHExpressionHeader.txt", BSHExpression.class ); //$NON-NLS-1$
// read the header, creates a skeleton
final Reader r = new InputStreamReader( new BufferedInputStream( in ) );
try {
interpreter.eval( r );
} finally {
r.close();
}
// now add the userdefined expression
// the expression is given in form of a function with the signature of:
//
// Object getValue ()
//
if ( getExpression() != null ) {
interpreter.eval( expression );
}
}
/**
* Evaluates the defined expression. If an exception or an evaluation error occures, the evaluation returns null and
* the error is logged. The current datarow and a copy of the expressions properties are set to script-internal
* variables. Changes to the properties will not alter the expressions original properties and will be lost when the
* evaluation is finished.
* <p/>
* Expressions do not maintain a state and no assumptions about the order of evaluation can be made.
*
* @return the evaluated value or null.
*/
public Object getValue() {
if ( invalid ) {
return null;
}
if ( interpreter == null ) {
interpreter = createInterpreter();
if ( interpreter == null ) {
invalid = true;
return null;
}
}
try {
interpreter.set( "runtime", getRuntime() ); //$NON-NLS-1$
interpreter.set( "dataRow", getDataRow() ); //$NON-NLS-1$
return interpreter.eval( "getValue ();" ); //$NON-NLS-1$
} catch ( Exception e ) {
if ( logger.isWarnEnabled() ) {
logger.warn( "Evaluation error: " + //$NON-NLS-1$
e.getClass() + " - " + e.getMessage() ); //$NON-NLS-1$
} else if ( logger.isDebugEnabled() ) {
logger.debug( "Evaluation error: " + //$NON-NLS-1$
e.getClass() + " - " + e.getMessage(), e ); //$NON-NLS-1$
}
return null;
} finally {
try {
interpreter.set( "runtime", null ); //$NON-NLS-1$
interpreter.set( "dataRow", null ); //$NON-NLS-1$
} catch ( EvalError er ) {
// ignored ..
}
}
}
/**
* Return a new instance of this expression. The copy is initialized and uses the same parameters as the original, but
* does not share any objects.
*
* @return a copy of this function.
*/
public Expression getInstance() {
final BSHExpression ex = (BSHExpression) super.getInstance();
ex.interpreter = null;
return ex;
}
/**
* Serialisation support. The transient child elements were not saved.
*
* @param in
* the input stream.
* @throws IOException
* if there is an I/O error.
* @throws ClassNotFoundException
* if a serialized class is not defined on this system.
*/
private void readObject( final ObjectInputStream in ) throws IOException, ClassNotFoundException {
in.defaultReadObject();
}
/**
* Sets the beanshell script as string.
*
* @return the script.
*/
public String getExpression() {
return expression;
}
/**
* Sets the beanshell script that should be executed. The script should define a getValue() method which returns a
* single object.
*
* @param expression
* the script.
*/
public void setExpression( final String expression ) {
this.expression = expression;
this.invalid = false;
this.interpreter = null;
}
}