Use LinkedHashSets for ValidationMessages

For things that might be read by humans, maintaining order can be
valuable. This change uses LinkedHashSet rather than HashSet to
maintain the iteration order of error in the order they're encountered.

Additionally, there are a few optimzations in validators:
- Using singletonSet and emptySet rather than a *HashSet when
  appropriate
- Map iteration optimization
- StringBuilder optimization

Author: ehrmann

src/main/java/com/networknt/schema/AdditionalPropertiesValidator.java

@@ -66,7 +66,7 @@ public AdditionalPropertiesValidator(String schemaPath, JsonNode schemaNode, Jso
     public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String at) {
         if (logger.isDebugEnabled()) debug(logger, node, rootNode, at);
 
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
+        Set<ValidationMessage> errors = new LinkedHashSet<ValidationMessage>();
         if (!node.isObject()) {
             // ignore no object
             return errors;
@@ -97,7 +97,7 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
                 }
             }
         }
-        return errors;
+        return Collections.unmodifiableSet(errors);
     }
 
 }

src/main/java/com/networknt/schema/AllOfValidator.java

@@ -22,7 +22,8 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
-import java.util.HashSet;
+import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
@@ -43,13 +44,13 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
         debug(logger, node, rootNode, at);
 
         int size = schemas.size();
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
+        Set<ValidationMessage> errors = new LinkedHashSet<ValidationMessage>();
 
         for (int i = 0; i < size; i++) {
             errors.addAll(schemas.get(i).validate(node, rootNode, at));
         }
 
-        return errors;
+        return Collections.unmodifiableSet(errors);
     }
 
 }

src/main/java/com/networknt/schema/AnyOfValidator.java

@@ -22,7 +22,8 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
-import java.util.HashSet;
+import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
@@ -43,7 +44,7 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
         debug(logger, node, rootNode, at);
 
         int size = schemas.size();
-        Set<ValidationMessage> allErrors = new HashSet<ValidationMessage>();
+        Set<ValidationMessage> allErrors = new LinkedHashSet<ValidationMessage>();
 
         for (int i = 0; i < size; i++) {
             Set<ValidationMessage> errors = schemas.get(i).validate(node, rootNode, at);
@@ -53,7 +54,7 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
             allErrors.addAll(errors);
         }
 
-        return allErrors;
+        return Collections.unmodifiableSet(allErrors);
     }
 
 }

src/main/java/com/networknt/schema/DependenciesValidator.java

@@ -55,7 +55,7 @@ public DependenciesValidator(String schemaPath, JsonNode schemaNode, JsonSchema
     public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String at) {
         debug(logger, node, rootNode, at);
 
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
+        Set<ValidationMessage> errors = new LinkedHashSet<ValidationMessage>();
 
         for (Iterator<String> it = node.fieldNames(); it.hasNext(); ) {
             String pname = it.next();
@@ -73,7 +73,7 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
             }
         }
 
-        return errors;
+        return Collections.unmodifiableSet(errors);
     }
 
 }

src/main/java/com/networknt/schema/EnumValidator.java

@@ -22,7 +22,8 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
-import java.util.HashSet;
+import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
@@ -57,13 +58,13 @@ public EnumValidator(String schemaPath, JsonNode schemaNode, JsonSchema parentSc
     public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String at) {
         debug(logger, node, rootNode, at);
 
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
+        Set<ValidationMessage> errors = new LinkedHashSet<ValidationMessage>();
 
         if (!nodes.contains(node)) {
             errors.add(buildValidationMessage(at, error));
         }
 
-        return errors;
+        return Collections.unmodifiableSet(errors);
     }
 
 }

src/main/java/com/networknt/schema/FormatValidator.java

@@ -21,8 +21,9 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.Collections;
 import java.util.HashMap;
-import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
 import java.util.regex.Matcher;
@@ -74,7 +75,7 @@ public FormatValidator(String schemaPath, JsonNode schemaNode, JsonSchema parent
     public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String at) {
         debug(logger, node, rootNode, at);
 
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
+        Set<ValidationMessage> errors = new LinkedHashSet<ValidationMessage>();
 
         JsonType nodeType = TypeFactory.getValueNodeType(node);
         if (nodeType != JsonType.STRING) {
@@ -93,7 +94,7 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
             }
         }
 
-        return errors;
+        return Collections.unmodifiableSet(errors);
     }
 
 }

src/main/java/com/networknt/schema/ItemsValidator.java

@@ -22,7 +22,8 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
-import java.util.HashSet;
+import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
@@ -61,7 +62,7 @@ public ItemsValidator(String schemaPath, JsonNode schemaNode, JsonSchema parentS
     public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String at) {
         debug(logger, node, rootNode, at);
 
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
+        Set<ValidationMessage> errors = new LinkedHashSet<ValidationMessage>();
 
         if (!node.isArray()) {
             // ignores non-arrays
@@ -93,7 +94,7 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
 
             i++;
         }
-        return errors;
+        return Collections.unmodifiableSet(errors);
     }
 
 }

src/main/java/com/networknt/schema/MaxItemsValidator.java

@@ -21,7 +21,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.HashSet;
+import java.util.Collections;
 import java.util.Set;
 
 public class MaxItemsValidator extends BaseJsonValidator implements JsonValidator {
@@ -41,15 +41,13 @@ public MaxItemsValidator(String schemaPath, JsonNode schemaNode, JsonSchema pare
     public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String at) {
         debug(logger, node, rootNode, at);
 
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
-
         if (node.isArray()) {
             if (node.size() > max) {
-                errors.add(buildValidationMessage(at, "" + max));
+                return Collections.singleton(buildValidationMessage(at, "" + max));
             }
         }
 
-        return errors;
+        return Collections.emptySet();
     }
 
 }

src/main/java/com/networknt/schema/MaxLengthValidator.java

@@ -21,7 +21,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.HashSet;
+import java.util.Collections;
 import java.util.Set;
 
 public class MaxLengthValidator extends BaseJsonValidator implements JsonValidator {
@@ -43,15 +43,14 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
         debug(logger, node, rootNode, at);
 
         JsonType nodeType = TypeFactory.getValueNodeType(node);
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
         if (nodeType != JsonType.STRING) {
             // ignore no-string typs
-            return errors;
+            return Collections.emptySet();
         }
         if (node.textValue().codePointCount(0, node.textValue().length()) > maxLength) {
-            errors.add(buildValidationMessage(at, "" + maxLength));
+            return Collections.singleton(buildValidationMessage(at, "" + maxLength));
         }
-        return errors;
+        return Collections.emptySet();
     }
 
 }

src/main/java/com/networknt/schema/MaxPropertiesValidator.java

@@ -21,7 +21,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.HashSet;
+import java.util.Collections;
 import java.util.Set;
 
 public class MaxPropertiesValidator extends BaseJsonValidator implements JsonValidator {
@@ -42,15 +42,13 @@ public MaxPropertiesValidator(String schemaPath, JsonNode schemaNode, JsonSchema
     public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String at) {
         debug(logger, node, rootNode, at);
 
-        Set<ValidationMessage> errors = new HashSet<ValidationMessage>();
-
         if (node.isObject()) {
             if (node.size() > max) {
-                errors.add(buildValidationMessage(at, "" + max));
+                return Collections.singleton(buildValidationMessage(at, "" + max));
             }
         }
 
-        return errors;
+        return Collections.emptySet();
     }
 
 }