add experimental java records support

README.md

@@ -243,6 +243,24 @@ There is a `startsWith` parameter for easy-to-use identifying the class to deser
 
 This class will be initialized just once and cached. 
 
+## Java records support
+
+There is an experimental support of Java 14+ records with no breaking of Java 8 support.
+
+Just annotate record's constructor as follows:
+
+```java
+record Employee (
+    @FixedField(offset = 1, length = 10, align = Align.LEFT)
+    String firstName,
+
+    @FixedField(offset = 10, length = 10, align = Align.LEFT)
+    String lastName
+){}
+```
+
+and it works the same way as annotated class.
+
 ## Benchmark
 
 There is a benchmark, you can run it with `gradle jmh` command. Also, you can change running parameters of it in file `src/jmh/java/name/velikodniy/vitaliy/fixedlength/benchmark/BenchmarkRunner.java`. 

build.gradle

@@ -16,7 +16,7 @@ plugins {
 }
 
 group 'name.velikodniy.vitaliy'
-version '0.11'
+version '0.12'
 
 repositories {
     mavenLocal()

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

@@ -245,11 +245,13 @@ private FixedFormatRecord fixedFormatLine(String line) {
     private T lineToObject(FixedFormatRecord fixedFormatRecord) {
         Class<? extends T> clazz = fixedFormatRecord.fixedFormatLine.clazz;
         String line = fixedFormatRecord.rawLine;
-        T lineAsObject;
+        T lineAsObject = null;
+        boolean useEmptyConstructor = true;
         try {
             lineAsObject = clazz.getDeclaredConstructor().newInstance();
         } catch (NoSuchMethodException e) {
-            throw new FixedLengthException("No empty constructor in class", e);
+            LOGGER.fine("No empty constructor in class");
+            useEmptyConstructor = false;
         } catch (IllegalAccessException
                  | InstantiationException
                  | InvocationTargetException e) {
@@ -258,6 +260,8 @@ private T lineToObject(FixedFormatRecord fixedFormatRecord) {
             );
         }
 
+        Object[] args = new Object[fixedFormatRecord.fixedFormatLine.fixedFormatFields.size()];
+        int index = 0;
         for (FixedFormatField fixedFormatField : fixedFormatRecord.fixedFormatLine.fixedFormatFields) {
             FixedField fieldAnnotation = fixedFormatField.getFixedFieldAnnotation();
             Field field = fixedFormatField.getField();
@@ -271,7 +275,23 @@ private T lineToObject(FixedFormatRecord fixedFormatRecord) {
                     endOfFieldIndex
             ), fieldAnnotation.padding());
             if (acceptFieldContent(str, fieldAnnotation)) {
-                fillField(field, lineAsObject, str, fieldAnnotation);
+                if (useEmptyConstructor) {
+                    fillField(field, lineAsObject, str, fieldAnnotation);
+                } else {
+                    args[index++] = Formatter.instance(FORMATTERS, field.getType()).asObject(str, fieldAnnotation);
+                }
+            }
+        }
+        if (!useEmptyConstructor) {
+            try {
+                if (clazz.getDeclaredConstructors().length != 1) {
+                    throw new FixedLengthException("There should be only one matching constructor");
+                }
+                lineAsObject = (T) clazz.getDeclaredConstructors()[0].newInstance(args);
+            } catch (IllegalAccessException
+                     | InstantiationException
+                     | InvocationTargetException e) {
+                throw new FixedLengthException("Unable to instantiate " + clazz.getName(), e);
             }
         }
         return lineAsObject;

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

@@ -9,7 +9,7 @@
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 
 @Retention(RUNTIME)
-@Target(ElementType.FIELD)
+@Target({ElementType.FIELD, ElementType.PARAMETER})
 public @interface FixedField {
     /**
      * Offset of the field

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

@@ -0,0 +1,42 @@
+package name.velikodniy.vitaliy.fixedlength;
+
+import name.velikodniy.vitaliy.fixedlength.annotation.FixedField;
+
+import java.math.BigDecimal;
+import java.time.LocalDate;
+
+/**
+ * this class emulates built java 14+'s record as follows
+ *  record EmployeeRecord(
+ *         @FixedField(offset = 1, length = 10, align = Align.LEFT)
+ *         String firstName,
+ *         @FixedField(offset = 11, length = 10, align = Align.LEFT)
+ *         String lastName,
+ *         @FixedField(offset = 21, length = 10, align = Align.LEFT)
+ *         String title,
+ *         @FixedField(offset = 31, length = 6, padding = '0')
+ *         BigDecimal salary,
+ *         @FixedField(offset = 37, length = 8, format = "MMddyyyy")
+ *         LocalDate hireDate
+ * ){}
+ */
+class EmployeeRecord{
+        @FixedField(offset = 1, length = 10, align = Align.LEFT)
+        public String firstName;
+        @FixedField(offset = 11, length = 10, align = Align.LEFT)
+        public String lastName;
+        @FixedField(offset = 21, length = 10, align = Align.LEFT)
+        public String title;
+        @FixedField(offset = 31, length = 6, padding = '0')
+        public BigDecimal salary;
+        @FixedField(offset = 37, length = 8, format = "MMddyyyy")
+        public LocalDate hireDate;
+
+        public EmployeeRecord(String firstName, String lastName, String title, BigDecimal salary, LocalDate hireDate) {
+                this.firstName = firstName;
+                this.lastName = lastName;
+                this.title = title;
+                this.salary = salary;
+                this.hireDate = hireDate;
+        }
+}

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

@@ -67,6 +67,20 @@ void testParseInheritedOneLineType() throws FixedLengthException {
         });
     }
 
+    @Test
+    @DisplayName("Parse as input stream with default charset and one line type with record emulation class")
+    void testParseInheritedOneLineTypeRecord() throws FixedLengthException {
+        List<EmployeeRecord> parse = new FixedLength<EmployeeRecord>()
+                .registerLineType(EmployeeRecord.class)
+                .parse(new ByteArrayInputStream(singleTypeExample.getBytes()));
+
+        assertEquals(2, parse.size());
+        parse.forEach(e -> {
+            assertNotNull(e.firstName);
+            assertNotNull(e.lastName);
+        });
+    }
+
     @Test
     @DisplayName("Parse as input stream with default charset and one line type")
     void testParseOneLineType() throws FixedLengthException {