Package org.pentaho.reporting.engine.classic.core.modules.misc.beanshell

Class BSHExpression

java.lang.Object

org.pentaho.reporting.engine.classic.core.function.AbstractExpression

org.pentaho.reporting.engine.classic.core.modules.misc.beanshell.BSHExpression

All Implemented Interfaces:

Serializable, Cloneable, Expression

public class BSHExpression
extends AbstractExpression

An expression that uses the BeanShell scripting framework to perform a scripted calculation. The expression itself is contained in a function called

Object getValue()

and this function is defined in the expression property. You have to overwrite the function getValue() to begin and to end your expression, but you are free to add your own functions to the script.

By default, base Java core and extension packages are imported for you. They are:

• java.lang
• java.io
• java.util
• java.net
• java.awt
• java.awt.event
• javax.swing
• javax.swing.event

An example in the XML format: (from report1.xml)

 
 
 
 // you may import packages and classes or use the fully qualified name of the class
 import org.pentaho.reporting.engine.classic.core.*;
 

 String userdefinedFunction (String parameter, Date date)
 {
 return parameter + " - the current date is " + date);
 }
 

 // 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());
 }
 
 
 
 

Author:

Thomas Morgner

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static String	BSHHEADERFILE	The headerfile with the default initialisations.

Constructor Summary

Constructors

Constructor	Description
BSHExpression()	default constructor, create a new BeanShellExpression.

Method Summary

Modifier and Type	Method	Description
protected bsh.Interpreter	createInterpreter()	This method tries to create a new and fully initialized BeanShell interpreter.
String	getExpression()	Sets the beanshell script as string.
Expression	getInstance()	Return a new instance of this expression.
Object	getValue()	Evaluates the defined expression.
protected void	initializeInterpreter(bsh.Interpreter interpreter)	Initializes the bean-shell interpreter by executing the code in the BSHExpressionHeader.txt file.
void	setExpression(String expression)	Sets the beanshell script that should be executed.

Methods inherited from class org.pentaho.reporting.engine.classic.core.function.AbstractExpression

clone, getDataRow, getDependencyLevel, getName, getReportConfiguration, getResourceBundleFactory, getRuntime, isActive, isDeepTraversing, isPreserve, setActive, setDependencyLevel, setName, setPreserve, setRuntime

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BSHHEADERFILE

public static final String BSHHEADERFILE

The headerfile with the default initialisations.

See Also:

Constant Field Values

Constructor Detail

BSHExpression

public BSHExpression()

default constructor, create a new BeanShellExpression.

Method Detail

createInterpreter

protected bsh.Interpreter createInterpreter()

This method tries to create a new and fully initialized BeanShell interpreter.

Returns:

the interpreter or null, if there was no way to create the interpreter.

initializeInterpreter

protected void initializeInterpreter(bsh.Interpreter interpreter)
                              throws bsh.EvalError,
                                     IOException

Initializes the bean-shell interpreter by executing the code in the BSHExpressionHeader.txt file.

Parameters:

interpreter - the interpreter that should be initialized.

Throws:

bsh.EvalError - if an BeanShell-Error occured.

IOException - if the beanshell file could not be read.

getValue

public Object getValue()

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.

Expressions do not maintain a state and no assumptions about the order of evaluation can be made.

Returns:

the evaluated value or null.

getInstance

public Expression getInstance()

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.

Specified by:

getInstance in interface Expression

Overrides:

getInstance in class AbstractExpression

Returns:

a copy of this function.

getExpression

public String getExpression()

Sets the beanshell script as string.

Returns:

the script.

setExpression

public void setExpression(String expression)

Sets the beanshell script that should be executed. The script should define a getValue() method which returns a single object.

Parameters:

expression - the script.