diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/Address.java b/generator/src/main/java/net/codecrete/qrbill/generator/Address.java
index 0ffdab1..9f23317 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/Address.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/Address.java
@@ -45,14 +45,23 @@ public enum Type {
 
     private static final long serialVersionUID = -8833174154173397772L;
 
+    /** Address type */
     private Type type = Type.UNDETERMINED;
+    /** Name of person or company */
     private String name;
+    /** Address line 1 */
     private String addressLine1;
+    /** Address line 2 */
     private String addressLine2;
+    /** Street */
     private String street;
+    /** House or building number */
     private String houseNo;
+    /** Postal code */
     private String postalCode;
+    /** Town */
     private String town;
+    /** ISO country code */
     private String countryCode;
 
     /**
diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/AlternativeScheme.java b/generator/src/main/java/net/codecrete/qrbill/generator/AlternativeScheme.java
index 9b25a4d..fc3de34 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/AlternativeScheme.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/AlternativeScheme.java
@@ -17,7 +17,9 @@ public class AlternativeScheme implements Serializable {
 
     private static final long serialVersionUID = -8304082204378228870L;
 
+    /** Scheme name */
     private String name;
+    /** Payment instruction */
     private String instruction;
 
     /**
diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/Bill.java b/generator/src/main/java/net/codecrete/qrbill/generator/Bill.java
index 1c8acb9..1361efb 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/Bill.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/Bill.java
@@ -42,17 +42,29 @@ public enum Version {
         V2_0
     }
 
+    /** Version of QR bill standard */
     private Version version = Version.V2_0;
+    /** Payment amount */
     private BigDecimal amount = null;
+    /** Payment currency (ISO code) */
     private String currency = "CHF";
+    /** Creditor's account number */
     private String account = null;
+    /** Creditor address */
     private Address creditor = new Address();
+    /** Payment reference type */
     private String referenceType = REFERENCE_TYPE_NO_REF;
+    /** Payment reference (number) */
     private String reference = null;
+    /** Debtor address */
     private Address debtor = null;
+    /** Unstructured message */
     private String unstructuredMessage = null;
+    /** Structured bill information */
     private String billInformation = null;
+    /** Alternative schemes */
     private AlternativeScheme[] alternativeSchemes = null;
+    /** Bill format */
     private BillFormat format = new BillFormat();
 
     /**
diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/BillFormat.java b/generator/src/main/java/net/codecrete/qrbill/generator/BillFormat.java
index e83be73..1caaa0b 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/BillFormat.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/BillFormat.java
@@ -22,13 +22,21 @@ public class BillFormat implements Serializable {
 
     private static final long serialVersionUID = -2874086922578292745L;
 
+    /** Output size */
     private OutputSize outputSize = OutputSize.QR_BILL_ONLY;
+    /** Language */
     private Language language = Language.EN;
+    /** Separator type */
     private SeparatorType separatorType = SeparatorType.DASHED_LINE_WITH_SCISSORS;
+    /** Font family */
     private String fontFamily = "Helvetica,Arial,\"Liberation Sans\"";
+    /** Graphics format */
     private GraphicsFormat graphicsFormat = GraphicsFormat.SVG;
+    /** Resolution, in dpi */
     private int resolution = 144;
+    /** Left margin, in mm */
     private double marginLeft = DEFAULT_MARGIN_WIDTH;
+    /** Right margin, in mm */
     private double marginRight = DEFAULT_MARGIN_WIDTH;
 
     /**
diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/QRBillValidationError.java b/generator/src/main/java/net/codecrete/qrbill/generator/QRBillValidationError.java
index d04dd09..118d59f 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/QRBillValidationError.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/QRBillValidationError.java
@@ -13,6 +13,7 @@ public class QRBillValidationError extends RuntimeException {
 
     private static final long serialVersionUID = -959460901342010774L;
 
+    /** Validation result */
     private final ValidationResult validationResult;
 
     /**
diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/ValidationMessage.java b/generator/src/main/java/net/codecrete/qrbill/generator/ValidationMessage.java
index 60af12b..6826516 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/ValidationMessage.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/ValidationMessage.java
@@ -36,9 +36,13 @@ public enum Type {
         ERROR
     }
 
+    /** Message type */
     private Type type;
+    /** Affected data field */
     private String field;
+    /** Message key */
     private String messageKey;
+    /** Message parameters for placeholders */
     private String[] messageParameters;
 
     /**
diff --git a/generator/src/main/java/net/codecrete/qrbill/generator/ValidationResult.java b/generator/src/main/java/net/codecrete/qrbill/generator/ValidationResult.java
index 1f9e09c..df34dce 100644
--- a/generator/src/main/java/net/codecrete/qrbill/generator/ValidationResult.java
+++ b/generator/src/main/java/net/codecrete/qrbill/generator/ValidationResult.java
@@ -23,7 +23,9 @@ public class ValidationResult implements Serializable {
     private static final long serialVersionUID = -791181851684443602L;
     private static final List<ValidationMessage> EMPTY_LIST = Collections.emptyList();
 
+    /** Validation messages */
     private List<ValidationMessage> validationMessages;
+    /** Cleaned bill data */
     private Bill cleanedBill;
 
     /**