#631 - Partial Response : Implement Field to json conversion

partial-response/src/main/java/com/iluwatar/partialresponse/FieldJsonMapper.java

@@ -24,6 +24,8 @@
 
 package com.iluwatar.partialresponse;
 
+import java.lang.reflect.Field;
+
 /**
  * Map a video to json
  */
@@ -34,7 +36,25 @@ public class FieldJsonMapper {
    * @param fields fields information to get
    * @return json of required fields from video
    */
-  public String toJson(Video video, String[] fields) {
-    return null;
+  public String toJson(Video video, String[] fields) throws Exception {
+    StringBuilder json = new StringBuilder().append("{");
+
+    for (int i = 0, fieldsLength = fields.length; i < fieldsLength; i++) {
+      json.append(getString(video, Video.class.getDeclaredField(fields[i])));
+      if (i != fieldsLength - 1) {
+        json.append(",");
+      }
+    }
+    json.append("}");
+    return json.toString();
+  }
+
+  private String getString(Video video, Field declaredField) throws IllegalAccessException {
+    declaredField.setAccessible(true);
+    Object value = declaredField.get(video);
+    if (declaredField.get(video) instanceof Integer) {
+      return "\"" + declaredField.getName() + "\"" + ": " + value;
+    }
+    return "\"" + declaredField.getName() + "\"" + ": " + "\"" + value.toString() + "\"";
   }
 }

partial-response/src/main/java/com/iluwatar/partialresponse/Video.java

@@ -59,7 +59,7 @@ public class Video {
   @Override
   public String toString() {
     return "{"
-        + "\"id\": \"" + id + "\","
+        + "\"id\": " + id + ","
         + "\"title\": \"" + title + "\","
         + "\"length\": " + length + ","
         + "\"description\": \"" + description + "\","

partial-response/src/main/java/com/iluwatar/partialresponse/VideoResource.java

@@ -48,7 +48,7 @@ public class VideoResource {
    * @param fields fields to get information about
    * @return json of specified fields of particular video by id
    */
-  public String getDetails(Integer id, String... fields) {
+  public String getDetails(Integer id, String... fields) throws Exception {
     if (fields.length == 0) {
       return videos.get(id).toString();
     }