content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.beam.sdk.schemas;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.Field;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  import java.util.List;
  import java.util.Optional;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  import javax.annotation.Nullable;
  import org.apache.beam.sdk.schemas.annotations.SchemaIgnore;
  import org.apache.beam.sdk.schemas.utils.ByteBuddyUtils.DefaultTypeConversionsFactory;
  import org.apache.beam.sdk.schemas.utils.FieldValueTypeSupplier;
  import org.apache.beam.sdk.schemas.utils.JavaBeanUtils;
  import org.apache.beam.sdk.schemas.utils.POJOUtils;
  import org.apache.beam.sdk.schemas.utils.ReflectUtils;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Lists;
  import org.checkerframework.checker.nullness.qual.NonNull;
  
  /**
   * A {@link SchemaProvider} for Java POJO objects.
   *
   * <p>This provider finds all public fields (recursively) in a Java object, and creates schemas and
   * rows that bind to those fields. The field order in the schema is not guaranteed to match the
   * field order in the class. The Java object is expected to have implemented a correct .equals() and
   * .hashCode() methods. The equals method must be completely determined by the schema fields. i.e.
   * if the object has hidden fields that are not reflected in the schema but are compared in equals,
   * then results will be incorrect.
   *
   * <p>TODO: Validate equals() method is provided, and if not generate a "slow" equals method based
   * on the schema.
   */
  public class JavaFieldSchema extends GetterBasedSchemaProviderV2 {
    /** {@link FieldValueTypeSupplier} that's based on public fields. */
    @VisibleForTesting
    public static class JavaFieldTypeSupplier implements FieldValueTypeSupplier {
      public static final JavaFieldTypeSupplier INSTANCE = new JavaFieldTypeSupplier();
  
      @Override
      public List<FieldValueTypeInformation> get(TypeDescriptor<?> typeDescriptor) {
        List<Field> fields =
            ReflectUtils.getFields(typeDescriptor.getRawType()).stream()
                .filter(m -> !m.isAnnotationPresent(SchemaIgnore.class))
                .collect(Collectors.toList());
        List<FieldValueTypeInformation> types = Lists.newArrayListWithCapacity(fields.size());
        for (int i = 0; i < fields.size(); ++i) {
          types.add(FieldValueTypeInformation.forField(typeDescriptor, fields.get(i), i));
        }
        types.sort(JavaBeanUtils.comparingNullFirst(FieldValueTypeInformation::getNumber));
        validateFieldNumbers(types);
  
        // If there are no creators registered, then make sure none of the schema fields are final,
        // as we (currently) have no way of creating classes in this case.
        if (ReflectUtils.getAnnotatedCreateMethod(typeDescriptor.getRawType()) == null
            && ReflectUtils.getAnnotatedConstructor(typeDescriptor.getRawType()) == null) {
          Optional<Field> finalField =
              types.stream()
                  .flatMap(
                      fvti ->
                          Optional.ofNullable(fvti.getField()).map(Stream::of).orElse(Stream.empty()))
                  .filter(f -> Modifier.isFinal(f.getModifiers()))
                  .findAny();
          if (finalField.isPresent()) {
            throw new IllegalArgumentException(
                "Class "
                    + typeDescriptor
                    + " has final fields and no "
                    + "registered creator. Cannot use as schema, as we don't know how to create this "
                    + "object automatically");
          }
        }
        return types;
      }
    }
  
    private static void validateFieldNumbers(List<FieldValueTypeInformation> types) {
      for (int i = 0; i < types.size(); ++i) {
        FieldValueTypeInformation type = types.get(i);
        @Nullable Integer number = type.getNumber();
        if (number == null) {
          throw new RuntimeException("Unexpected null number for " + type.getName());
        }
        Preconditions.checkState(
            number == i,
            "Expected field number "
                + i
                + " for field + "
                + type.getName()
                + " instead got "
                + number);
      }
    }
  
    @Override
    public <T> Schema schemaFor(TypeDescriptor<T> typeDescriptor) {
      return POJOUtils.schemaFromPojoClass(typeDescriptor, JavaFieldTypeSupplier.INSTANCE);
    }
  
    @Override
    public <T> List<FieldValueGetter<@NonNull T, Object>> fieldValueGetters(
        TypeDescriptor<T> targetTypeDescriptor, Schema schema) {
      return POJOUtils.getGetters(
          targetTypeDescriptor,
          schema,
          JavaFieldTypeSupplier.INSTANCE,
          new DefaultTypeConversionsFactory());
    }
  
    @Override
    public List<FieldValueTypeInformation> fieldValueTypeInformations(
        TypeDescriptor<?> targetTypeDescriptor, Schema schema) {
      return POJOUtils.getFieldTypes(targetTypeDescriptor, schema, JavaFieldTypeSupplier.INSTANCE);
    }
  
    @Override
    public SchemaUserTypeCreator schemaTypeCreator(
        TypeDescriptor<?> targetTypeDescriptor, Schema schema) {
      // If a static method is marked with @SchemaCreate, use that.
      Method annotated = ReflectUtils.getAnnotatedCreateMethod(targetTypeDescriptor.getRawType());
      if (annotated != null) {
        return POJOUtils.getStaticCreator(
            targetTypeDescriptor,
            annotated,
            schema,
            JavaFieldTypeSupplier.INSTANCE,
            new DefaultTypeConversionsFactory());
      }
  
      // If a Constructor was tagged with @SchemaCreate, invoke that constructor.
      Constructor<?> constructor =
          ReflectUtils.getAnnotatedConstructor(targetTypeDescriptor.getRawType());
      if (constructor != null) {
        return POJOUtils.getConstructorCreator(
            (TypeDescriptor) targetTypeDescriptor,
            constructor,
            schema,
            JavaFieldTypeSupplier.INSTANCE,
            new DefaultTypeConversionsFactory());
      }
  
      return POJOUtils.getSetFieldCreator(
          targetTypeDescriptor,
          schema,
          JavaFieldTypeSupplier.INSTANCE,
          new DefaultTypeConversionsFactory());
    }
  }
  