Support "const" keyword

Author: reda-alaoui

core/src/main/java/com/cosium/json_schema_to_java_record/JsonSchemaContent.java

@@ -35,7 +35,8 @@ record JsonSchemaContent(
     @Nullable JsonSchemaContent items,
     @Nullable List<Object> enumeration,
     Map<String, JsonSchemaContent> properties,
-    Set<String> required) {
+    Set<String> required,
+    @Nullable String constValue) {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(JsonSchemaContent.class);
 
@@ -48,7 +49,8 @@ record JsonSchemaContent(
       @JsonProperty("items") @Nullable JsonSchemaContent items,
       @JsonProperty("enum") @Nullable List<Object> enumeration,
       @JsonProperty("properties") @Nullable Map<String, JsonSchemaContent> properties,
-      @JsonProperty("required") @Nullable Set<String> required) {
+      @JsonProperty("required") @Nullable Set<String> required,
+      @JsonProperty("const") @Nullable String constValue) {
     this(
         $schema,
         $id,
@@ -57,7 +59,8 @@ record JsonSchemaContent(
         items,
         enumeration,
         Optional.ofNullable(properties).orElseGet(Map::of),
-        Optional.ofNullable(required).orElseGet(Set::of));
+        Optional.ofNullable(required).orElseGet(Set::of),
+        constValue);
   }
 
   public TypeName writeJavaType(
@@ -66,6 +69,10 @@ public TypeName writeJavaType(
       ClassName fallbackClassName,
       boolean preferPrimitive) {
 
+    if (constValue != null) {
+      return ClassName.get(String.class);
+    }
+
     final TypeName processedTypeName =
         switch (type()) {
           case STRING -> {
@@ -137,6 +144,20 @@ public TypeName writeJavaType(
         String propertyName = property.getKey();
         JsonSchemaContent propertySchema = property.getValue();
 
+        String propertyConstValue = propertySchema.constValue();
+        if (propertyConstValue != null) {
+          typeBuilder.addMethod(
+              addNotNullRelatedAnnotations(
+                      javaTypes,
+                      addJsonRelatedAnnotations(
+                          MethodSpec.methodBuilder(propertyName), propertyName))
+                  .addModifiers(Modifier.PUBLIC)
+                  .returns(String.class)
+                  .addStatement("return $S", propertyConstValue)
+                  .build());
+          continue;
+        }
+
         TypeName propertyType =
             propertySchema.writeJavaType(
                 javaTypes,
@@ -211,10 +232,16 @@ private boolean isList(TypeName type) {
     return className.canonicalName().equals(List.class.getCanonicalName());
   }
 
-  private void addJsonRelatedAnnotations(
-      ParameterSpec.Builder parameterBuilder, String propertyName) {
+  private void addJsonRelatedAnnotations(ParameterSpec.Builder builder, String propertyName) {
 
-    parameterBuilder.addAnnotation(
+    builder.addAnnotation(
+        AnnotationSpec.builder(JsonProperty.class).addMember("value", "$S", propertyName).build());
+  }
+
+  private MethodSpec.Builder addJsonRelatedAnnotations(
+      MethodSpec.Builder builder, String propertyName) {
+
+    return builder.addAnnotation(
         AnnotationSpec.builder(JsonProperty.class).addMember("value", "$S", propertyName).build());
   }
 
@@ -239,6 +266,14 @@ private void addNullRelatedAnnotations(
     }
   }
 
+  private MethodSpec.Builder addNotNullRelatedAnnotations(
+      JavaTypes javaTypes, MethodSpec.Builder builder) {
+    if (!javaTypes.existsOnClassPath(ClassName.get(NonNull.class))) {
+      return builder;
+    }
+    return builder.addAnnotation(NonNull.class);
+  }
+
   private void addRecordBuilderRelatedAnnotations(
       JavaTypes javaTypes, TypeSpec.Builder typeBuilder) {
 

tests/src/test/resources/com/cosium/json_schema_to_java_record_tests/case1/address.json

@@ -1,5 +1,5 @@
 {
-  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$schema": "https://json-schema.org/draft-06/schema",
   "$id": "address",
   "type": "object",
   "properties": {
@@ -11,6 +11,9 @@
     },
     "country": {
       "$ref": "classpath:/com/cosium/json_schema_to_java_record_tests/case1/country.json"
+    },
+    "planet": {
+      "const": "earth"
     }
   },
   "required": [ "streetNumber", "streetName" ]