escaping json pointers in ValidationException

Author: erosb

core/src/main/java/org/everit/json/schema/ValidationException.java

@@ -126,7 +126,7 @@ public ValidationException(final Schema violatedSchema, final String message) {
    *          a (possibly empty) list of validation failures. It is used if multiple schema
    *          violations are found by violatedSchema
    */
-  public ValidationException(final Schema violatedSchema, final StringBuilder pointerToViolation,
+  ValidationException(final Schema violatedSchema, final StringBuilder pointerToViolation,
       final String message,
       final List<ValidationException> causingExceptions) {
     super(message);
@@ -153,6 +153,10 @@ private ValidationException(final StringBuilder pointerToViolation,
     this(violatedSchema, pointerToViolation, message, causingExceptions);
   }
 
+  private String escapeFragment(final String fragment) {
+    return fragment.replace("~", "~0").replace("/", "~1");
+  }
+
   public List<ValidationException> getCausingExceptions() {
     return causingExceptions;
   }
@@ -201,10 +205,11 @@ public ValidationException prepend(final String fragment) {
    * @return the new {@code ViolationException} instance
    */
   public ValidationException prepend(final String fragment, final Schema violatedSchema) {
-    Objects.requireNonNull(fragment, "fragment cannot be null");
-    StringBuilder newPointer = this.pointerToViolation.insert(1, '/').insert(2, fragment);
+    String escapedFragment = escapeFragment(
+        Objects.requireNonNull(fragment, "fragment cannot be null"));
+    StringBuilder newPointer = this.pointerToViolation.insert(1, '/').insert(2, escapedFragment);
     List<ValidationException> prependedCausingExceptions = causingExceptions.stream()
-        .map(exc -> exc.prepend(fragment))
+        .map(exc -> exc.prepend(escapedFragment))
         .collect(Collectors.toList());
     return new ValidationException(newPointer, violatedSchema, super.getMessage(),
         prependedCausingExceptions);

core/src/test/java/org/everit/json/schema/ValidationExceptionTest.java

@@ -37,6 +37,24 @@ private ValidationException createDummyException(final String pointer) {
         "stuff went wrong", Collections.emptyList());
   }
 
+  @Test
+  public void fragmentEscapingBoth() {
+    ValidationException subject = createDummyException("#/aaa").prepend("x~y/z");
+    Assert.assertEquals("#/x~0y~1z/aaa", subject.getPointerToViolation());
+  }
+
+  @Test
+  public void fragmentEscapingSlash() {
+    ValidationException subject = createDummyException("#/aaa").prepend("x/y");
+    Assert.assertEquals("#/x~1y/aaa", subject.getPointerToViolation());
+  }
+
+  @Test
+  public void fragmentEscapingTilde() {
+    ValidationException subject = createDummyException("#/aaa").prepend("x~y");
+    Assert.assertEquals("#/x~0y/aaa", subject.getPointerToViolation());
+  }
+
   @Test
   public void getMessageAfterPrepend() {
     ValidationException subject = createDummyException("#/a").prepend("obj");