RecipientInformation: Updates to toString method

SirNate · SirNate · commit 3005dcfbfc8e · 2018-06-25T16:11:37.000+02:00
Updated toString method to return fields and their
values in alphabetical order based on the field name.

Also added Javadoc to explain this behaviour and
the use of a TreeMap.
diff --git a/src/main/java/com/trustly/api/data/request/requestdata/RecipientInformation.java b/src/main/java/com/trustly/api/data/request/requestdata/RecipientInformation.java
@@ -24,6 +24,10 @@
 
 package com.trustly.api.data.request.requestdata;
 
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.stream.Collectors;
+
 import com.google.gson.annotations.SerializedName;
 
 public class RecipientInformation {
@@ -64,27 +68,37 @@ public RecipientInformation setDateOfBirth(final String dateOfBirth) {
         return this;
     }
 
+    /**
+     * Method for returning a String representation of the
+     * RecipientInformation object. Used for serialization.
+     * <p>
+     * Uses a TreeMap for automatically sorting the object's
+     * field values in an alphabetical order, which is required
+     * for generating a valid signature from the serialized string.
+     */
     @Override
     public String toString() {
-        final StringBuilder stringBuilder = new StringBuilder();
+        final Map<String, String> attributes = new TreeMap<>();
 
-        stringBuilder.append("Partytype").append(partyType);
-        stringBuilder.append("Firstname").append(firstName);
-        stringBuilder.append("Lastname").append(lastName);
-        stringBuilder.append("CountryCode").append(countryCode);
+        attributes.put("Partytype", partyType);
+        attributes.put("Firstname", firstName);
+        attributes.put("Lastname", lastName);
+        attributes.put("CountryCode", countryCode);
 
         if (customerId != null) {
-            stringBuilder.append("CustomerID").append(customerId);
+            attributes.put("CustomerID", customerId);
         }
 
         if (address != null) {
-            stringBuilder.append("Address").append(address);
+            attributes.put("Address", address);
         }
 
         if (dateOfBirth != null) {
-            stringBuilder.append("DateOfBirth").append(dateOfBirth);
+            attributes.put("DateOfBirth", dateOfBirth);
         }
 
-        return stringBuilder.toString();
+        return attributes.entrySet().stream()
+                .map(entry -> entry.getKey() + entry.getValue())
+                .collect(Collectors.joining());
     }
 }
