AnnotatedClassBuilder.java

package io.katharsis.resource.field;

import com.fasterxml.jackson.databind.AnnotationIntrospector;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.SerializationConfig;
import com.fasterxml.jackson.databind.introspect.AnnotatedClass;
import io.katharsis.errorhandling.exception.InternalException;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * Since Jackson 2.7 there is a change in internal method {@link AnnotatedClass#construct} definition. Since Jackson
 * 2.7 there is <i>AnnotatedClass#construct(JavaType, MapperConfig, ClassIntrospector.MixInResolver)</i>
 * and before there is <i>AnnotatedClass#construct(Class, AnnotationIntrospector, ClassIntrospector.MixInResolver)</i>.
 * <p>
 * This builder purpose is to create an instance of {@link AnnotatedClass} no matter which Jackson version is available.
 */
public class AnnotatedClassBuilder {
    private static final String CONSTRUCT_METHOD_NAME = "construct";
    private static final String CANNOT_FIND_PROPER_METHOD = "Couldn't find proper AnnotatedClass#construct method";

    public static AnnotatedClass build(Class<?> declaringClass, SerializationConfig serializationConfig) {

        for (Method method : AnnotatedClass.class.getMethods()) {
            if (CONSTRUCT_METHOD_NAME.equals(method.getName()) &&
                method.getParameterTypes().length == 3) {
                try {
                    return buildAnnotatedClass(method, declaringClass, serializationConfig);
                } catch (InvocationTargetException | IllegalAccessException e) {
                    throw new InternalException("Exception while building " + AnnotatedClass.class.getCanonicalName(), e);
                }
            }
        }

        throw new InternalException(CANNOT_FIND_PROPER_METHOD);
    }

    private static AnnotatedClass buildAnnotatedClass(Method method, Class<?> declaringClass,
                                                      SerializationConfig serializationConfig)
        throws InvocationTargetException, IllegalAccessException {
        if (method.getParameterTypes()[0] == Class.class) {
            return buildOldAnnotatedClass(method, declaringClass, serializationConfig);
        } else if (method.getParameterTypes()[0] == JavaType.class) {
            return buildNewAnnotatedClass(method, declaringClass, serializationConfig);
        } else {
            throw new InternalException(CANNOT_FIND_PROPER_METHOD);
        }
    }

    private static AnnotatedClass buildNewAnnotatedClass(Method method, Class<?> declaringClass,
                                                         SerializationConfig serializationConfig)
        throws InvocationTargetException, IllegalAccessException {
        JavaType declaringType = serializationConfig.constructType(declaringClass);
        return AnnotatedClass.class.cast(method.invoke(null, declaringType, serializationConfig, serializationConfig));
    }

    private static AnnotatedClass buildOldAnnotatedClass(Method method, Class<?> declaringClass,
                                                         SerializationConfig serializationConfig)
        throws InvocationTargetException, IllegalAccessException {
        boolean useAnnotations = serializationConfig.isAnnotationProcessingEnabled();
        AnnotationIntrospector aintr = useAnnotations ? serializationConfig.getAnnotationIntrospector() : null;
        return AnnotatedClass.class.cast(method.invoke(null, declaringClass, aintr, serializationConfig));
    }
}