Support customizing date format in model (de)serialization in Java client

and update the default date format to conform to RFC3339

modules/swagger-codegen/src/main/resources/Java/ApiClient.mustache

@@ -55,13 +55,15 @@ public class ApiClient {
   private DateFormat dateFormat;
 
   public ApiClient() {
-    // Use ISO 8601 format for date and datetime.
-    // See https://en.wikipedia.org/wiki/ISO_8601
-    this.dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
+    // Use RFC3339 format for date and datetime.
+    // See http://xml2rfc.ietf.org/public/rfc/html/rfc3339.html#anchor14
+    this.dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
 
     // Use UTC as the default time zone.
     this.dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
 
+    this.json.setDateFormat((DateFormat) dateFormat.clone());
+
     // Set default User-Agent.
     setUserAgent("Java-Swagger");
 
@@ -74,6 +76,13 @@ public class ApiClient {
     authentications = Collections.unmodifiableMap(authentications);
   }
 
+  /**
+   * Gets the JSON instance to do JSON serialization and deserialization.
+   */
+  public JSON getJSON() {
+    return json;
+  }
+
   public String getBasePath() {
     return basePath;
   }
@@ -227,6 +236,8 @@ public class ApiClient {
    */
   public ApiClient setDateFormat(DateFormat dateFormat) {
     this.dateFormat = dateFormat;
+    // also set the date format for model (de)serialization with Date properties
+    this.json.setDateFormat((DateFormat) dateFormat.clone());
     return this;
   }
 

modules/swagger-codegen/src/main/resources/Java/JSON.mustache

@@ -4,6 +4,8 @@ import com.fasterxml.jackson.annotation.*;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.datatype.joda.*;
 
+import java.text.DateFormat;
+
 import java.io.IOException;
 
 {{>generatedAnnotation}}
@@ -20,6 +22,13 @@ public class JSON {
     mapper.registerModule(new JodaModule());
   }
 
+  /**
+   * Set the date format for JSON (de)serialization with Date properties.
+   */
+  public void setDateFormat(DateFormat dateFormat) {
+    mapper.setDateFormat(dateFormat);
+  }
+
   /**
    * Serialize the given Java object into JSON string.
    */