making ReferenceResolver null-tolerant

Author: erosb

core/src/main/java/org/everit/json/schema/loader/internal/ReferenceResolver.java

@@ -37,7 +37,12 @@ public final class ReferenceResolver {
    * @return the resolved URI
    */
   public static URI resolve(final URI parentScope, final String encounteredSegment) {
-    return parentScope.resolve(encounteredSegment);
+    try {
+      return new URI(resolve(parentScope == null ? null : parentScope.toString(),
+          encounteredSegment));
+    } catch (URISyntaxException e) {
+      throw new RuntimeException(e);
+    }
   }
 
   /**
@@ -52,11 +57,13 @@ public static URI resolve(final URI parentScope, final String encounteredSegment
    */
   public static String resolve(final String parentScope, final String encounteredSegment) {
     try {
+      if (parentScope == null) {
+        return encounteredSegment;
+      }
       return new URI(parentScope).resolve(encounteredSegment).toString();
     } catch (URISyntaxException e) {
       throw new RuntimeException(e);
     }
-    // return new ReferenceResolver(parentScope, encounteredSegment).resolve();
   }
 
   private ReferenceResolver() {

core/src/test/java/org/everit/json/schema/loader/internal/ReferenceResolverTest.java

@@ -15,6 +15,8 @@
  */
 package org.everit.json.schema.loader.internal;
 
+import java.net.URI;
+import java.net.URISyntaxException;
 import java.util.Arrays;
 import java.util.List;
 
@@ -38,7 +40,8 @@ public static List<Object[]> params() {
         parList("file name after folder path", "http://x.y.z/schema/child.json",
             "http://x.y.z/schema/", "child.json"),
         parList("new root", "http://bserver.com", "http://aserver.com/",
-            "http://bserver.com"));
+            "http://bserver.com"),
+                    parList("null parent", "http://a.b.c", null, "http://a.b.c"));
   }
 
   private static Object[] parList(final String... params) {
@@ -65,4 +68,15 @@ public void test() {
     Assert.assertEquals(expectedOutput, actual);
   }
 
+  @Test
+  public void testURI() {
+    URI parentScopeURI;
+    try {
+      parentScopeURI = new URI(parentScope);
+    } catch (URISyntaxException | NullPointerException e) {
+      parentScopeURI = null;
+    }
+    URI actual = ReferenceResolver.resolve(parentScopeURI, encounteredSegment);
+  }
+
 }