Class 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.util
    • 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 site for more information ... // // A return value of type "Object" is alway implied ... getValue () { return userdefinedFunction ("Hello World :) ", new Date()); }

    Thomas Morgner
    See Also:
    Serialized Form
    • Field Detail


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

        protected void initializeInterpreter​(bsh.Interpreter interpreter)
                                      throws bsh.EvalError,
        Initializes the bean-shell interpreter by executing the code in the BSHExpressionHeader.txt file.
        interpreter - the interpreter that should be initialized.
        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.

        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
        getInstance in class AbstractExpression
        a copy of this function.
      • getExpression

        public String getExpression()
        Sets the beanshell script as string.
        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.
        expression - the script.