Added PlayerSkin#fromUuid and PlayerSkin#fromUsername

src/main/java/net/minestom/server/entity/PlayerSkin.java

@@ -1,5 +1,14 @@
 package net.minestom.server.entity;
 
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import net.minestom.server.utils.url.URLUtils;
+
+import java.io.IOException;
+import java.util.Iterator;
+
 /**
  * Contains all the data required to store a skin
  */
@@ -30,4 +39,56 @@ public class PlayerSkin {
     public String getSignature() {
         return signature;
     }
+
+    /**
+     * Get a skin from a Mojang UUID
+     *
+     * @param uuid Mojang UUID
+     * @return a player skin based on the UUID
+     */
+    public static PlayerSkin fromUuid(String uuid) {
+        final String url = "https://sessionserver.mojang.com/session/minecraft/profile/" + uuid + "?unsigned=false";
+
+        try {
+            final String response = URLUtils.getText(url);
+            JsonObject jsonObject = (new JsonParser()).parse(response).getAsJsonObject();
+            JsonArray propertiesArray = jsonObject.get("properties").getAsJsonArray();
+
+            Iterator<JsonElement> iterator = propertiesArray.iterator();
+            while (iterator.hasNext()) {
+                JsonObject propertyObject = iterator.next().getAsJsonObject();
+                final String name = propertyObject.get("name").getAsString();
+                if (!name.equals("textures"))
+                    continue;
+                final String textureValue = propertyObject.get("value").getAsString();
+                final String signatureValue = propertyObject.get("signature").getAsString();
+                return new PlayerSkin(textureValue, signatureValue);
+            }
+            return null;
+        } catch (IOException e) {
+            e.printStackTrace();
+            return null;
+        }
+    }
+
+    /**
+     * Get a skin from a Minecraft username
+     *
+     * @param username the Minecraft username
+     * @return a skin based on a Minecraft username
+     */
+    public static PlayerSkin fromUsername(String username) {
+        final String url = "https://api.mojang.com/users/profiles/minecraft/" + username;
+
+        try {
+            final String response = URLUtils.getText(url);
+            JsonObject jsonObject = (new JsonParser()).parse(response).getAsJsonObject();
+            final String uuid = jsonObject.get("id").getAsString();
+            return fromUuid(uuid);
+        } catch (IOException e) {
+            e.printStackTrace();
+            return null;
+        }
+    }
+
 }

src/main/java/net/minestom/server/utils/url/URLUtils.java

@@ -0,0 +1,40 @@
+package net.minestom.server.utils.url;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URL;
+
+public class URLUtils {
+
+    public static String getText(String url) throws IOException {
+        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
+        //add headers to the connection, or check the status if desired..
+
+        // handle error response code it occurs
+        int responseCode = connection.getResponseCode();
+        InputStream inputStream;
+        if (200 <= responseCode && responseCode <= 299) {
+            inputStream = connection.getInputStream();
+        } else {
+            inputStream = connection.getErrorStream();
+        }
+
+        BufferedReader in = new BufferedReader(
+                new InputStreamReader(
+                        inputStream));
+
+        StringBuilder response = new StringBuilder();
+        String currentLine;
+
+        while ((currentLine = in.readLine()) != null)
+            response.append(currentLine);
+
+        in.close();
+
+        return response.toString();
+    }
+
+}