refactor: add DiscriminatorUtils for handling discriminator properties in schemas

Author: Mattias-Sehlstedt

modules/swagger-core/src/main/java/io/swagger/v3/core/jackson/DiscriminatorUtils.java

@@ -0,0 +1,79 @@
+package io.swagger.v3.core.jackson;
+
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.databind.JavaType;
+import io.swagger.v3.core.converter.AnnotatedType;
+import io.swagger.v3.core.converter.ModelConverterContext;
+import io.swagger.v3.core.util.AnnotationsUtils;
+import io.swagger.v3.oas.annotations.media.DiscriminatorMapping;
+import io.swagger.v3.oas.models.media.Discriminator;
+import io.swagger.v3.oas.models.media.JsonSchema;
+import io.swagger.v3.oas.models.media.Schema;
+import io.swagger.v3.oas.models.media.StringSchema;
+import org.apache.commons.lang3.StringUtils;
+
+import static io.swagger.v3.core.util.RefUtils.constructRef;
+
+class DiscriminatorUtils {
+
+    private DiscriminatorUtils() {
+    }
+
+    private static final int SCHEMA_COMPONENT_PREFIX = "#/components/schemas/".length();
+    private static final String TYPE_STRING = "string";
+
+    public static void resolveDiscriminatorProperty(JavaType type,
+                                                    ModelConverterContext context,
+                                                    Schema model,
+                                                    boolean openapi31) {
+        // add JsonTypeInfo.property if not member of bean
+        JsonTypeInfo typeInfo = type.getRawClass().getDeclaredAnnotation(JsonTypeInfo.class);
+        if (typeInfo != null) {
+            String typeInfoProp = typeInfo.property();
+            if (StringUtils.isNotBlank(typeInfoProp)) {
+                Schema modelToUpdate = model;
+                if (StringUtils.isNotBlank(model.get$ref())) {
+                    modelToUpdate = context.getDefinedModels().get(model.get$ref().substring(SCHEMA_COMPONENT_PREFIX));
+                }
+                if (modelToUpdate.getProperties() == null || !modelToUpdate.getProperties().keySet().contains(typeInfoProp)) {
+                    Schema discriminatorSchema = openapi31 ? new JsonSchema().typesItem(TYPE_STRING).name(typeInfoProp) : new StringSchema().name(typeInfoProp);
+                    modelToUpdate.addProperties(typeInfoProp, discriminatorSchema);
+                    if (modelToUpdate.getRequired() == null || !modelToUpdate.getRequired().contains(typeInfoProp)) {
+                        modelToUpdate.addRequiredItem(typeInfoProp);
+                    }
+                }
+            }
+        }
+    }
+
+    public static Discriminator resolveDiscriminator(JavaType type, ModelConverterContext context) {
+        io.swagger.v3.oas.annotations.media.Schema declaredSchemaAnnotation = AnnotationsUtils.getSchemaDeclaredAnnotation(type.getRawClass());
+
+        String disc = (declaredSchemaAnnotation == null) ? "" : declaredSchemaAnnotation.discriminatorProperty();
+
+        if (disc.isEmpty()) {
+            // longer method would involve AnnotationIntrospector.findTypeResolver(...) but:
+            JsonTypeInfo typeInfo = type.getRawClass().getDeclaredAnnotation(JsonTypeInfo.class);
+            if (typeInfo != null) {
+                disc = typeInfo.property();
+            }
+        }
+        if (!disc.isEmpty()) {
+            Discriminator discriminator = new Discriminator()
+                    .propertyName(disc);
+            if (declaredSchemaAnnotation != null) {
+                DiscriminatorMapping[] mappings = declaredSchemaAnnotation.discriminatorMapping();
+                if (mappings != null && mappings.length > 0) {
+                    for (DiscriminatorMapping mapping : mappings) {
+                        if (!mapping.value().isEmpty() && !mapping.schema().equals(Void.class)) {
+                            discriminator.mapping(mapping.value(), constructRef(context.resolve(new AnnotatedType().type(mapping.schema())).getName()));
+                        }
+                    }
+                }
+            }
+
+            return discriminator;
+        }
+        return null;
+    }
+}