We'll stay with LWJGL backend for the examples.

spine-libgdx/.classpath

@@ -2,7 +2,7 @@
 <classpath>
 	<classpathentry kind="src" path="src"/>
 	<classpathentry kind="src" path="test"/>
-	<classpathentry combineaccessrules="false" exported="true" kind="src" path="/gdx-backend-jglfw"/>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.6"/>
+	<classpathentry combineaccessrules="false" exported="true" kind="src" path="/gdx-backend-lwjgl"/>
 	<classpathentry kind="output" path="bin"/>
 </classpath>

spine-libgdx/src/com/esotericsoftware/spine/AttachmentLoader.java

@@ -2,5 +2,6 @@
 package com.esotericsoftware.spine;
 
 public interface AttachmentLoader {
+	/** @return May be null to not load any attachment. */
 	public Attachment newAttachment (AttachmentType type, String name);
 }

spine-libgdx/src/com/esotericsoftware/spine/SkeletonJson.java

@@ -103,7 +103,7 @@ public class SkeletonJson {
 					int slotIndex = skeletonData.findSlotIndex(slotEntry.key);
 					for (Entry<String, OrderedMap> attachmentEntry : ((OrderedMap<String, OrderedMap>)slotEntry.value).entries()) {
 						Attachment attachment = readAttachment(attachmentEntry.key, attachmentEntry.value);
-						skin.addAttachment(slotIndex, attachmentEntry.key, attachment);
+						if (attachment != null) skin.addAttachment(slotIndex, attachmentEntry.key, attachment);
 					}
 				}
 				skeletonData.addSkin(skin);

spine-libgdx/test/com/esotericsoftware/spine/MixTest.java

@@ -3,8 +3,8 @@ package com.esotericsoftware.spine;
 
 import com.badlogic.gdx.ApplicationAdapter;
 import com.badlogic.gdx.Gdx;
-import com.badlogic.gdx.backends.jglfw.JglfwApplication;
-import com.badlogic.gdx.backends.jglfw.JglfwApplicationConfiguration;
+import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
+import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.GL10;
 import com.badlogic.gdx.graphics.g2d.SpriteBatch;
@@ -113,10 +113,6 @@ public class MixTest extends ApplicationAdapter {
 	}
 
 	public static void main (String[] args) throws Exception {
-		JglfwApplicationConfiguration config = new JglfwApplicationConfiguration();
-		config.title = "Mix Test";
-		config.width = 640;
-		config.height = 480;
-		new JglfwApplication(new MixTest(), config);
+		new LwjglApplication(new MixTest());
 	}
 }

spine-libgdx/test/com/esotericsoftware/spine/SkeletonTest.java

@@ -5,8 +5,8 @@ import com.badlogic.gdx.ApplicationAdapter;
 import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.Input.Keys;
 import com.badlogic.gdx.InputAdapter;
-import com.badlogic.gdx.backends.jglfw.JglfwApplication;
-import com.badlogic.gdx.backends.jglfw.JglfwApplicationConfiguration;
+import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
+import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;
 import com.badlogic.gdx.files.FileHandle;
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.GL10;
@@ -114,10 +114,6 @@ public class SkeletonTest extends ApplicationAdapter {
 	}
 
 	public static void main (String[] args) throws Exception {
-		JglfwApplicationConfiguration config = new JglfwApplicationConfiguration();
-		config.title = "Skeleton Test";
-		config.width = 640;
-		config.height = 480;
-		new JglfwApplication(new SkeletonTest(), config);
+		new LwjglApplication(new SkeletonTest());
 	}
 }