JacksonConverterRegistrar.java

/*
 * Copyright 2017-2020 original authors
 *
 * Licensed 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
 *
 * https://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 io.micronaut.jackson.databind.convert;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategies;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ContainerNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import com.fasterxml.jackson.databind.type.TypeFactory;
import io.micronaut.context.BeanProvider;
import io.micronaut.context.annotation.Prototype;
import io.micronaut.core.annotation.Internal;
import io.micronaut.core.annotation.NonNull;
import io.micronaut.core.annotation.Nullable;
import io.micronaut.core.convert.ArgumentConversionContext;
import io.micronaut.core.convert.ConversionService;
import io.micronaut.core.convert.MutableConversionService;
import io.micronaut.core.convert.TypeConverter;
import io.micronaut.core.convert.TypeConverterRegistrar;
import io.micronaut.core.convert.value.ConvertibleValues;
import io.micronaut.core.naming.NameUtils;
import io.micronaut.core.type.Argument;
import io.micronaut.core.util.StringUtils;
import io.micronaut.jackson.JacksonConfiguration;
import jakarta.inject.Inject;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Map;
import java.util.Optional;

/**
 * Converter registrar for Jackson.
 *
 * @author graemerocher
 * @since 2.0
 */
@Prototype
@Internal
public class JacksonConverterRegistrar implements TypeConverterRegistrar {

    private final BeanProvider<ObjectMapper> objectMapper;
    private final ConversionService conversionService;

    /**
     * Default constructor.
     *
     * @param objectMapper The object mapper provider
     * @param conversionService The conversion service
     */
    @Inject
    protected JacksonConverterRegistrar(
        BeanProvider<ObjectMapper> objectMapper,
        ConversionService conversionService) {
        this.objectMapper = objectMapper;
        this.conversionService = conversionService;
    }

    @Override
    public void register(MutableConversionService conversionService) {
        conversionService.addConverter(
            ArrayNode.class,
            Object[].class,
            arrayNodeToObjectConverter()
        );
        conversionService.addConverter(
            ArrayNode.class,
            Iterable.class,
            arrayNodeToIterableConverter()
        );
        conversionService.addConverter(
            JsonNode.class,
            Object.class,
            jsonNodeToObjectConverter()
        );
        conversionService.addConverter(
            ObjectNode.class,
            ConvertibleValues.class,
            objectNodeToConvertibleValuesConverter()
        );
        conversionService.addConverter(
            Object.class,
            JsonNode.class,
            objectToJsonNodeConverter()
        );
        conversionService.addConverter(
            CharSequence.class,
            PropertyNamingStrategy.class,
            (charSequence, targetType, context) -> {

                Optional<PropertyNamingStrategy> propertyNamingStrategy = resolvePropertyNamingStrategy(charSequence);

                if (propertyNamingStrategy.isEmpty()) {
                    context.reject(charSequence, new IllegalArgumentException("Unable to convert '%s' to a com.fasterxml.jackson.databind.PropertyNamingStrategy".formatted(charSequence)));
                }

                return propertyNamingStrategy;
            }
        );
    }

    /**
     * @return A converter that converts an object to a json node
     */
    protected TypeConverter<Object, JsonNode> objectToJsonNodeConverter() {
        // same as in JsonConverterRegistrar, but with JsonNode
        return (object, targetType, context) -> {
            try {
                return Optional.of(objectMapper.get().valueToTree(object));
            } catch (IllegalArgumentException e) {
                context.reject(e);
                return Optional.empty();
            }
        };
    }

    /**
     * @return A converter that converts object nodes to convertible values
     */
    protected TypeConverter<ObjectNode, ConvertibleValues> objectNodeToConvertibleValuesConverter() {
        return (object, targetType, context) -> Optional.of(new ObjectNodeConvertibleValues<>(object, conversionService));
    }

    /**
     * @return The JSON node to object converter
     */
    protected TypeConverter<JsonNode, Object> jsonNodeToObjectConverter() {
        return (node, targetType, context) -> {
            try {
                if (CharSequence.class.isAssignableFrom(targetType) && node instanceof ObjectNode) {
                    return Optional.of(node.toString());
                } else {
                    Argument<Object> argument = null;
                    if (node instanceof ContainerNode && context instanceof ArgumentConversionContext conversionContext && targetType.getTypeParameters().length != 0) {
                        argument = conversionContext.getArgument();
                    }
                    Object result;
                    if (argument != null) {
                        ObjectMapper om = this.objectMapper.get();
                        JsonParser jsonParser = om.treeAsTokens(node);
                        TypeFactory typeFactory = om.getTypeFactory();
                        JavaType javaType = JacksonConfiguration.constructType(argument, typeFactory);
                        result = om.readValue(jsonParser, javaType);
                    } else {
                        result = this.objectMapper.get().treeToValue(node, targetType);
                    }
                    return Optional.ofNullable(result);
                }
            } catch (IOException e) {
                context.reject(e);
                return Optional.empty();
            }
        };
    }

    /**
     * @return Converts array nodes to iterables.
     */
    protected TypeConverter<ArrayNode, Iterable> arrayNodeToIterableConverter() {
        return (node, targetType, context) -> {
            Map<String, Argument<?>> typeVariables = context.getTypeVariables();
            Class<?> elementType = typeVariables.isEmpty() ? Map.class : typeVariables.values().iterator().next().getType();
            var results = new ArrayList<>();
            node.elements().forEachRemaining(jsonNode -> {
                Optional<?> converted = conversionService.convert(jsonNode, elementType, context);
                if (converted.isPresent()) {
                    results.add(converted.get());
                }
            });
            return Optional.of(results);
        };
    }

    /**
     * @return Converts array nodes to objects.
     */
    protected TypeConverter<ArrayNode, Object[]> arrayNodeToObjectConverter() {
        return (node, targetType, context) -> {
            try {
                Object[] result = objectMapper.get().treeToValue(node, targetType);
                return Optional.of(result);
            } catch (JsonProcessingException e) {
                context.reject(e);
                return Optional.empty();
            }
        };
    }

    @NonNull
    private Optional<PropertyNamingStrategy> resolvePropertyNamingStrategy(@Nullable CharSequence charSequence) {
        if (charSequence != null) {
            String stringValue = NameUtils.environmentName(charSequence.toString());
            if (StringUtils.isNotEmpty(stringValue)) {
                return switch (stringValue) {
                    case "SNAKE_CASE" -> Optional.of(PropertyNamingStrategies.SNAKE_CASE);
                    case "UPPER_CAMEL_CASE" -> Optional.of(PropertyNamingStrategies.UPPER_CAMEL_CASE);
                    case "LOWER_CASE" -> Optional.of(PropertyNamingStrategies.LOWER_CASE);
                    case "KEBAB_CASE" -> Optional.of(PropertyNamingStrategies.KEBAB_CASE);
                    case "LOWER_CAMEL_CASE" -> Optional.of(PropertyNamingStrategies.LOWER_CAMEL_CASE);
                    case "LOWER_DOT_CASE" -> Optional.of(PropertyNamingStrategies.LOWER_DOT_CASE);
                    default -> Optional.empty();
                };
            }
        }
        return Optional.empty();
    }
}