adding the ability to evaluate groovy expressions

src/groovy/pl/touk/excel/export/Formatters.groovy

@@ -3,6 +3,7 @@ package pl.touk.excel.export
 import pl.touk.excel.export.getters.Getter
 import pl.touk.excel.export.getters.PropertyGetter
 import pl.touk.excel.export.getters.AsIsPropertyGetter
+import pl.touk.excel.export.getters.AsClosurePropertyGetter
 import pl.touk.excel.export.getters.LongToDatePropertyGetter
 
 class Formatters {
@@ -14,14 +15,20 @@ class Formatters {
         return new AsIsPropertyGetter(propertyName)
     }
 
+    static PropertyGetter asClosure(Closure closure) {
+        return new AsClosurePropertyGetter(closure)
+    }
+
     static List<Getter> convertSafelyToGetters(List properties) {
         properties.collect {
             if (it instanceof Getter) {
                 return it
             } else if(it instanceof String) {
                 return asIs(it)
+            } else if(it instanceof Closure) {
+                return asClosure(it)
             } else {
-                throw IllegalArgumentException('List of properties, which should be either String, a Getter. Found: ' +
+                throw IllegalArgumentException('List of properties, which should be either String, a Getter or a Groovy Closure. Found: ' +
                         it?.toString() + ' of class ' + it?.getClass())
             }
         }

src/groovy/pl/touk/excel/export/getters/AsClosurePropertyGetter.groovy

@@ -0,0 +1,19 @@
+package pl.touk.excel.export.getters
+
+class AsClosurePropertyGetter extends PropertyGetter<Object, Object> {
+
+	def closure
+
+    AsClosurePropertyGetter(Closure closure) {
+        super(null)
+        this.closure = closure
+    }
+
+    def getFormattedValue(Object object) {
+    	closure.call(object)
+    }
+
+    def format(Object value) {
+        null
+    }
+}

test/unit/pl/touk/excel/export/XlsxExporterRowTest.groovy

@@ -73,6 +73,31 @@ class XlsxExporterRowTest extends XlsxExporterTest {
         testObject.verifyRowHasSelectedProperties(xlsxReporter.withDefaultSheet(), 3)
     }
 
+    @Test
+    void shouldFillRowEvaluatingPropertyList() {
+        //given
+        SampleObject testObject = new SampleObject()
+        def propertyExpressions = [
+           'stringValue',
+           { it.stringValue },
+           { it.child.stringValue.toUpperCase() },
+           { it.booleanValue?" it is true ":"it is false " },
+           { it.shortValue + it.integerValue },
+           { Math.sqrt(it.doubleValue) }
+        ]
+
+        //when
+        xlsxReporter.add(testObject, propertyExpressions, 0)
+
+        //then
+        assert xlsxReporter.getCellAt(0, 0).getStringCellValue() == testObject.stringValue
+        assert xlsxReporter.getCellAt(0, 1).getStringCellValue() == testObject.stringValue
+        assert xlsxReporter.getCellAt(0, 2).getStringCellValue() == testObject.child.stringValue.toUpperCase()
+        assert xlsxReporter.getCellAt(0, 3).getStringCellValue() == testObject.booleanValue?" it is true ":"it is false "
+        assert xlsxReporter.getCellAt(0, 4).getNumericCellValue() == testObject.integerValue + testObject.shortValue
+        assert xlsxReporter.getCellAt(0, 5).getNumericCellValue() == Math.sqrt(testObject.doubleValue)
+    }
+
     @Test
     void shouldFillRows() {
         //given