JSONMapper.java

package core.framework.impl.json;

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.MapperFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.cfg.MapperConfig;
import com.fasterxml.jackson.databind.introspect.AnnotatedMember;
import com.fasterxml.jackson.databind.jsontype.TypeResolverBuilder;
import com.fasterxml.jackson.databind.type.MapType;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.fasterxml.jackson.databind.util.ISO8601DateFormat;
import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.module.afterburner.AfterburnerModule;
import com.fasterxml.jackson.module.jaxb.JaxbAnnotationIntrospector;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.lang.reflect.Type;
import java.util.Map;
import java.util.Optional;

/**
 * used internally, performance is top priority in design
 *
 * @author neo
 */
public final class JSONMapper {
    public static final ObjectMapper OBJECT_MAPPER = createObjectMapper();

    private static ObjectMapper createObjectMapper() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(new Jdk8Module());
        mapper.registerModule(new JavaTimeModule());
        mapper.registerModule(new AfterburnerModule());
        mapper.setDateFormat(new ISO8601DateFormat());
        mapper.setAnnotationIntrospector(new JAXBAnnotationIntrospector());
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        mapper.configure(MapperFeature.USE_WRAPPER_NAME_AS_PROPERTY_NAME, true);
        return mapper;
    }

    public static <T> T fromMapValue(Type instanceType, Map<String, String> map) {
        ObjectMapper objectMapper = OBJECT_MAPPER;
        JavaType type = objectMapper.getTypeFactory().constructType(instanceType);
        try {
            byte[] json = objectMapper.writeValueAsBytes(map);
            return objectMapper.readValue(json, type);
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    public static Map<String, String> toMapValue(Object instance) {
        ObjectMapper objectMapper = OBJECT_MAPPER;
        MapType type = objectMapper.getTypeFactory().constructMapType(Map.class, String.class, String.class);
        try {
            byte[] json = objectMapper.writeValueAsBytes(instance);
            return objectMapper.readValue(json, type);
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    public static <T> T fromJSON(Type instanceType, byte[] json) {
        return fromJSON(instanceType, json, 0, json.length);
    }

    // jackson detects encoding and default to utf-8, works with our scenario, so there not to specify charset
    public static <T> T fromJSON(Type instanceType, byte[] json, int offset, int length) {
        JavaType type = OBJECT_MAPPER.getTypeFactory().constructType(instanceType);
        try {
            return OBJECT_MAPPER.readValue(json, offset, length, type);
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    public static byte[] toJSON(Object instance) {
        try {
            return OBJECT_MAPPER.writeValueAsBytes(instance);
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    private static class JAXBAnnotationIntrospector extends JaxbAnnotationIntrospector {
        private static final long serialVersionUID = 9089203444578006521L;

        JAXBAnnotationIntrospector() {
            super(TypeFactory.defaultInstance());
        }

        @Override
        public TypeResolverBuilder<?> findPropertyContentTypeResolver(MapperConfig<?> config, AnnotatedMember am, JavaType containerType) {
            if (!containerType.hasRawClass(Optional.class) && !containerType.isContainerType()) {
                throw new IllegalArgumentException("expect container type (got " + containerType + ")");
            }
            return _typeResolverFromXmlElements(am);
        }
    }
}