Initial Work on Modular Design

JSON is widespread and many applications leverage it already. Adding support for Schemas to a existing Solution might cause some hindrance due to the various Json Implementations (e.g. Gson, org.json, jackson) currently existing. Relying on a specific JSON implementation requires consuming parties to choose between libraries that support their own library or write conversion code from and to a library of their choice.

This work tries to introduce a new modular design, without breaking any existing code relying on org.json. After rewriting the Infrastructure it might be a good idea to remove some/all deprecation though.

Signed-off-by: Bjoern Heinrichs <bjoern@heinrichs.pro>

Author: BjoernAkAManf

core/pom.xml

@@ -143,11 +143,13 @@
         </plugins>
     </build>
     <dependencies>
+        <!-- TODO: Move into own artifact-->
         <dependency>
             <groupId>org.json</groupId>
             <artifactId>json</artifactId>
             <version>20180130</version>
         </dependency>
+        <!-- -->
         <dependency>
             <groupId>com.google.guava</groupId>
             <artifactId>guava</artifactId>

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

@@ -18,6 +18,7 @@ class ArraySchemaValidatingVisitor extends Visitor {
 
     private final ValidatingVisitor owner;
 
+    // TODO: New API (JsonArray)
     private JSONArray arraySubject;
 
     private ArraySchema arraySchema;
@@ -30,6 +31,7 @@ public ArraySchemaValidatingVisitor(Object subject, ValidatingVisitor owner) {
     }
 
     @Override void visitArraySchema(ArraySchema arraySchema) {
+        // TODO: New API (JsonArray)
         if (owner.passesTypeCheck(JSONArray.class, arraySchema.requiresArray(), arraySchema.isNullable())) {
             this.arraySubject = (JSONArray) subject;
             this.subjectLength = arraySubject.length();

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

@@ -18,10 +18,13 @@
 public class EnumSchema extends Schema {
 
     static Object toJavaValue(Object orig) {
+        // TODO: New API (JsonArray)
         if (orig instanceof JSONArray) {
             return ((JSONArray) orig).toList();
+        // TODO: New API (JsonObject)
         } else if (orig instanceof JSONObject) {
             return ((JSONObject) orig).toMap();
+        // TODO: New API (Null)
         } else if (orig == JSONObject.NULL) {
             return null;
         } else {

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

@@ -206,7 +206,7 @@ void describePropertiesTo(JSONPrinter writer) {
         try {
             writer.ifPresent("exclusiveMinimum", exclusiveMinimumLimit);
             writer.ifPresent("exclusiveMaximum", exclusiveMaximumLimit);
-        } catch (JSONException e) {
+        } catch (JSONException e) { // TODO: New API (JsonException)
             throw new IllegalStateException("overloaded use of exclusiveMinimum or exclusiveMaximum keyword");
         }
     }

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

@@ -1,78 +1,29 @@
 package org.everit.json.schema;
 
-import java.util.Arrays;
-import java.util.Objects;
-
+import org.everit.json.schema.facade.Facade;
 import org.json.JSONArray;
-import org.json.JSONObject;
 
 /**
- * Deep-equals implementation on primitive wrappers, {@link JSONObject} and {@link JSONArray}.
+ * Deep-equals implementation on primitive wrappers,
+ * {@link org.everit.json.schema.facade.JsonObject} and
+ * {@link JSONArray}.
  */
+@Deprecated
 public final class ObjectComparator {
-
     /**
-     * Deep-equals implementation on primitive wrappers, {@link JSONObject} and {@link JSONArray}.
+     * Deep-equals implementation on primitive wrappers,
+     * {@link org.everit.json.schema.facade.JsonObject} and
+     * {@link JSONArray}.
      *
-     * @param obj1
-     *         the first object to be inspected
-     * @param obj2
-     *         the second object to be inspected
+     * @param obj1 the first object to be inspected
+     * @param obj2 the second object to be inspected
      * @return {@code true} if the two objects are equal, {@code false} otherwise
      */
     public static boolean deepEquals(Object obj1, Object obj2) {
-        if (obj1 instanceof JSONArray) {
-            if (!(obj2 instanceof JSONArray)) {
-                return false;
-            }
-            return deepEqualArrays((JSONArray) obj1, (JSONArray) obj2);
-        } else if (obj1 instanceof JSONObject) {
-            if (!(obj2 instanceof JSONObject)) {
-                return false;
-            }
-            return deepEqualObjects((JSONObject) obj1, (JSONObject) obj2);
-        }
-        return Objects.equals(obj1, obj2);
-    }
-
-    private static boolean deepEqualArrays(JSONArray arr1, JSONArray arr2) {
-        if (arr1.length() != arr2.length()) {
-            return false;
-        }
-        for (int i = 0; i < arr1.length(); ++i) {
-            if (!deepEquals(arr1.get(i), arr2.get(i))) {
-                return false;
-            }
-        }
-        return true;
-    }
-
-    private static String[] sortedNamesOf(JSONObject obj) {
-        String[] raw = JSONObject.getNames(obj);
-        if (raw == null) {
-            return null;
-        }
-        Arrays.sort(raw, String.CASE_INSENSITIVE_ORDER);
-        return raw;
-    }
-
-    private static boolean deepEqualObjects(JSONObject jsonObj1, JSONObject jsonObj2) {
-        String[] obj1Names = sortedNamesOf(jsonObj1);
-        if (!Arrays.equals(obj1Names, sortedNamesOf(jsonObj2))) {
-            return false;
-        }
-        if (obj1Names == null) {
-            return true;
-        }
-        for (String name : obj1Names) {
-            if (!deepEquals(jsonObj1.get(name), jsonObj2.get(name))) {
-                return false;
-            }
-        }
-        return true;
+        return Facade.getInstance().comparator()
+            .deepEquals(obj1, obj2);
     }
 
     private ObjectComparator() {
     }
-
 }

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

@@ -14,6 +14,7 @@ class ObjectSchemaValidatingVisitor extends Visitor {
 
     private final Object subject;
 
+    // TODO: New API (JsonObject)
     private JSONObject objSubject;
 
     private ObjectSchema schema;
@@ -28,6 +29,7 @@ public ObjectSchemaValidatingVisitor(Object subject, ValidatingVisitor owner) {
     }
 
     @Override void visitObjectSchema(ObjectSchema objectSchema) {
+        // TODO: New API (JsonObject)
         if (owner.passesTypeCheck(JSONObject.class, objectSchema.requiresObject(), objectSchema.isNullable())) {
             objSubject = (JSONObject) subject;
             objectSize = objSubject.length();
@@ -129,6 +131,7 @@ private boolean matchesAnyPattern(String key) {
     }
 
     @Override void visitPatternPropertySchema(Regexp propertyNamePattern, Schema schema) {
+        // TODO: New API (JsonObject)
         String[] propNames = JSONObject.getNames(objSubject);
         if (propNames == null || propNames.length == 0) {
             return;

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

@@ -3,8 +3,9 @@
 import java.io.StringWriter;
 import java.util.Objects;
 
+import org.everit.json.schema.facade.JsonWriter;
 import org.everit.json.schema.internal.JSONPrinter;
-import org.json.JSONWriter;
+import org.json.JSONPointer;
 
 /**
  * Superclass of all other schema validator classes of this package.
@@ -237,14 +238,14 @@ public Boolean isWriteOnly() {
      * Describes the instance as a JSONObject to {@code writer}.
      * <p>
      * First it adds the {@code "title} , {@code "description"} and {@code "id"} properties then calls
-     * {@link #describePropertiesTo(JSONPrinter)}, which will add the subclass-specific properties.
+     * {@link #describePropertiesTo(JsonWriter)}, which will add the subclass-specific properties.
      * <p>
      * It is used by {@link #toString()} to serialize the schema instance into its JSON representation.
      *
      * @param writer
      *         it will receive the schema description
      */
-    public void describeTo(JSONPrinter writer) {
+    public void describeTo(JsonWriter writer) {
         writer.object();
         writer.ifPresent("title", title);
         writer.ifPresent("description", description);
@@ -257,16 +258,26 @@ public void describeTo(JSONPrinter writer) {
         writer.endObject();
     }
 
+    @Deprecated // See new API
+    public void describeTo(JSONPrinter writer) {
+        this.describeTo((JsonWriter) writer);
+    }
+
     /**
      * Subclasses are supposed to override this method to describe the subclass-specific attributes.
-     * This method is called by {@link #describeTo(JSONPrinter)} after adding the generic properties if
+     * This method is called by {@link #describeTo(JsonWriter)} after adding the generic properties if
      * they are present ({@code id}, {@code title} and {@code description}). As a side effect,
-     * overriding subclasses don't have to open and close the object with {@link JSONWriter#object()}
-     * and {@link JSONWriter#endObject()}.
+     * overriding subclasses don't have to open and close the object with {@link JsonWriter#object()}
+     * and {@link JsonWriter#endObject()}.
      *
      * @param writer
      *         it will receive the schema description
      */
+    void describePropertiesTo(JsonWriter writer) {
+        this.describePropertiesTo(new JSONPrinter(writer));
+    }
+
+    @Deprecated // See new API
     void describePropertiesTo(JSONPrinter writer) {
 
     }

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

@@ -8,6 +8,8 @@
 import java.util.Objects;
 import java.util.stream.Collectors;
 
+import org.everit.json.schema.facade.Facade;
+import org.everit.json.schema.facade.JsonObject;
 import org.json.JSONArray;
 import org.json.JSONObject;
 
@@ -426,21 +428,27 @@ public String getKeyword() {
      *
      * @return a JSON description of the validation error
      */
+    // TODO: New API (Easy)
+    @Deprecated
     public JSONObject toJSON() {
-        JSONObject rval = new JSONObject();
-        rval.put("keyword", keyword);
+        return toJson().unsafe(JSONObject.class);
+    }
+
+    public JsonObject toJson() {
+        JsonObject rval = Facade.getInstance().object();
+        rval.set("keyword", keyword);
         if (pointerToViolation == null) {
-            rval.put("pointerToViolation", JSONObject.NULL);
+            rval.set("pointerToViolation", Facade.getInstance().NULL());
         } else {
-            rval.put("pointerToViolation", getPointerToViolation());
+            rval.set("pointerToViolation", getPointerToViolation());
         }
-        rval.put("message", super.getMessage());
-        List<JSONObject> causeJsons = causingExceptions.stream()
-                .map(ValidationException::toJSON)
-                .collect(Collectors.toList());
-        rval.put("causingExceptions", new JSONArray(causeJsons));
+        rval.set("message", super.getMessage());
+        List<Object> causeJsons = causingExceptions.stream()
+            .map(ValidationException::toJson)
+            .collect(Collectors.toList());
+        rval.set("causingExceptions", new JSONArray(causeJsons));
         if (schemaLocation != null) {
-            rval.put("schemaLocation", schemaLocation);
+            rval.set("schemaLocation", schemaLocation);
         }
         return rval;
     }

core/src/main/java/org/everit/json/schema/facade/Facade.java

@@ -0,0 +1,54 @@
+package org.everit.json.schema.facade;
+
+import org.everit.json.schema.facade.orgjson.JsonOrg;
+
+import java.io.Writer;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.ServiceLoader;
+
+public final class Facade {
+    private static final ServiceLoader<FacadeImpl> LOADER = ServiceLoader.load(FacadeImpl.class);
+    private static FacadeImpl instance;
+
+    private Facade() { // Utility Class
+        throw new Error();
+    }
+
+    // TODO: Document
+    // Allows overriding when ServiceLoader is not feasible.
+    public static void setInstance(FacadeImpl instance) {
+        Facade.instance = instance;
+    }
+
+    public static FacadeImpl getInstance() {
+        if (instance == null) {
+            load();
+        }
+        return instance;
+    }
+
+    private static void load() {
+        LOADER.reload();
+        Iterator<FacadeImpl> it = LOADER.iterator();
+        if (!it.hasNext()) {
+            // TODO: Remove
+            instance = new JsonOrg();
+            return;
+            // throw new IllegalStateException("Missing Json Implementation. Are you sure it is on the classpath?");
+        }
+        instance = it.next();
+    }
+
+    public interface FacadeImpl {
+        Object NULL();
+
+        JsonObject object();
+
+        JsonArray array(Collection<Object> elements);
+
+        JsonWriter writer(Writer writer);
+
+        JsonComparator comparator();
+    }
+}

core/src/main/java/org/everit/json/schema/facade/JsonArray.java

@@ -0,0 +1,4 @@
+package org.everit.json.schema.facade;
+
+public interface JsonArray extends JsonElement {
+}