add keeping whitespaces option

build.gradle

@@ -16,7 +16,7 @@ plugins {
 }
 
 group 'name.velikodniy.vitaliy'
-version '0.12'
+version '0.13'
 
 repositories {
     mavenLocal()

src/main/java/name/velikodniy/vitaliy/fixedlength/FixedLength.java

@@ -326,7 +326,7 @@ private boolean acceptFieldContent(String content, FixedField fieldAnnotation) {
         if (content == null) {
             return false;
         }
-        if (content.trim().isEmpty()) {
+        if (content.trim().isEmpty() && !fieldAnnotation.allowEmptyStrings()) {
             return false;
         }
         if (fieldAnnotation.ignore().isEmpty()) {

src/main/java/name/velikodniy/vitaliy/fixedlength/annotation/FixedField.java

@@ -57,4 +57,12 @@
      * @return pattern matching content to ignore
      */
     String ignore() default "";
+
+    /**
+     * Allows empty string as value, by default it is false.
+     * If true - values will be kept as is
+     * If false - value will be null
+     * @return allows empty string as value boolean
+     */
+    boolean allowEmptyStrings() default false;
 }

src/test/java/name/velikodniy/vitaliy/fixedlength/ParserTest.java

@@ -230,4 +230,16 @@ void testParseMixedLineTypeCustomPredicate() throws FixedLengthException {
 
         assertEquals(2, parse.size());
     }
+
+    @Test
+    @DisplayName("Parse object with whitespaces preventing it to cast as null")
+    void testParseWhitespaceNonNull() throws FixedLengthException {
+
+        List<StringHolder> holders = new FixedLength<StringHolder>()
+                .registerLineType(StringHolder.class)
+                .parse(new ByteArrayInputStream("   some text to drop".getBytes()));
+
+        assertEquals(1, holders.size());
+        assertEquals("   ", holders.get(0).value);
+    }
 }

src/test/java/name/velikodniy/vitaliy/fixedlength/StringHolder.java

@@ -0,0 +1,8 @@
+package name.velikodniy.vitaliy.fixedlength;
+
+import name.velikodniy.vitaliy.fixedlength.annotation.FixedField;
+
+public class StringHolder {
+    @FixedField(offset = 1, length = 3, padding = Character.MIN_VALUE, allowEmptyStrings = true)
+    public String value;
+}