MessageFunction.java example

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pentaho-reporting-master
package org.pentaho.reporting.libraries.formula.function.text;

import org.pentaho.reporting.libraries.formula.EvaluationException;
import org.pentaho.reporting.libraries.formula.FormulaContext;
import org.pentaho.reporting.libraries.formula.LibFormulaErrorValue;
import org.pentaho.reporting.libraries.formula.function.Function;
import org.pentaho.reporting.libraries.formula.function.ParameterCallback;
import org.pentaho.reporting.libraries.formula.lvalues.TypeValuePair;
import org.pentaho.reporting.libraries.formula.typing.Type;
import org.pentaho.reporting.libraries.formula.typing.coretypes.TextType;

import java.text.MessageFormat;

public class MessageFunction implements Function {
  public String getCanonicalName() {
    return "MESSAGE";
  }

  public TypeValuePair evaluate( final FormulaContext context, final ParameterCallback parameters )
    throws EvaluationException {
    final int parameterCount = parameters.getParameterCount();
    if ( parameterCount < 1 ) {
      throw EvaluationException.getInstance( LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE );
    }
    final Type type1 = parameters.getType( 0 );
    final Object value1 = parameters.getValue( 0 );
    final String message = context.getTypeRegistry().convertToText( type1, value1 );

    final MessageFormat format = new MessageFormat( message, context.getLocalizationContext().getLocale() );
    final Object[] args = new Object[ parameterCount - 1 ];
    for ( int i = 1; i < parameterCount; i += 1 ) {
      args[ i - 1 ] = parameters.getValue( i );
    }
    return new TypeValuePair( TextType.TYPE, format.format( args ) );
  }
}