org.jfree.report.modules.misc.beanshell: public class: BSHExpression

org.jfree.report.modules.misc.beanshell
public class: BSHExpression [javadoc | source]

java.lang.Object
   org.jfree.report.function.AbstractExpression
      org.jfree.report.modules.misc.beanshell.BSHExpression

All Implemented Interfaces:
Expression, Serializable

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.jfree.report.*;

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









    







    
Field Summary
public static final   String  BSHHEADERFILE    The headerfile with the default initialisations. 











    
Constructor:
 public BSHExpression() {

}
default constructor, create a new BeanShellExpression.











    Method from org.jfree.report.modules.misc.beanshell.BSHExpression Summary:

createInterpreter,   getExpression,   getInstance,   getValue,   initializeInterpreter,   setExpression
Methods from org.jfree.report.function.AbstractExpression:

clone,   getDataRow,   getDependencyLevel,   getInstance,   getName,   getReportConfiguration,   getResourceBundleFactory,   getRuntime,   isActive,   isDeepTraversing,   isPreserve,   setActive,   setDependencyLevel,   setName,   setPreserve,   setRuntime
Methods from java.lang.Object:

equals,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from org.jfree.report.modules.misc.beanshell.BSHExpression Detail:
 protected Interpreter createInterpreter() {
    try
    {
      final Interpreter interpreter = new Interpreter();
      initializeInterpreter(interpreter);
      return interpreter;
    }
    catch (Exception e)
    {
      BSHExpression.logger.error("Unable to initialize the expression", e); //$NON-NLS-1$
      return null;
    }
}
This method tries to create a new and fully initialized BeanShell interpreter.
 public String getExpression() {
    return expression;
}
Sets the beanshell script as string.
 public Expression getInstance() {
    final BSHExpression ex = (BSHExpression) super.getInstance();
    ex.interpreter = null;
    return ex;
}
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.
 public Object getValue() {
    if (invalid)
    {
      return null;
    }
    if (interpreter == null)
    {
      interpreter = createInterpreter();
      if (interpreter == null)
      {
        invalid = true;
        return null;
      }
    }
    try
    {
      interpreter.set("dataRow", getDataRow()); //$NON-NLS-1$
      return interpreter.eval("getValue ();"); //$NON-NLS-1$
    }
    catch (Exception e)
    {
      BSHExpression.logger.warn("Evaluation error: " + //$NON-NLS-1$
          e.getClass() + " - " + e.getMessage(), e); //$NON-NLS-1$
      return null;
    }
}
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.
 protected  void initializeInterpreter(Interpreter interpreter) throws IOException, EvalError {
    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);
    }
}
Initializes the bean-shell interpreter by executing the code in
the BSHExpressionHeader.txt file.
 public  void setExpression(String expression) {
    this.expression = expression;
    this.invalid = false;
    this.interpreter = null;
}
Sets the beanshell script that should be executed. The script should
define a getValue() method which returns a single object.