TupleMapper.java

/*
 * Copyright (c) 2011-2020 Contributors to the Eclipse Foundation
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 * which is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 */
package io.vertx.sqlclient.templates;

import io.vertx.codegen.annotations.VertxGen;
import io.vertx.core.json.JsonObject;
import io.vertx.sqlclient.Tuple;
import io.vertx.sqlclient.templates.impl.JsonTuple;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.function.Function;

/**
 * Map an arbitrary {@code T} object to a {@link Tuple}.
 */
@VertxGen
@FunctionalInterface
public interface TupleMapper<T> {

  /**
   * Create a mapper that associates a parameters object to a map of named parameters to
   * their respective value.
   *
   * @param fn the function turning a parameters object into a map
   * @return the mapper
   */
  static <T> TupleMapper<T> mapper(Function<T, Map<String, Object>> fn) {
    return (mapping, size, params) -> {
      Map<String, Object> args = fn.apply(params);
      Object[] array = new Object[size];
      for (int i = 0;i < array.length;i++) {
        String column = mapping.apply(i);
        array[i] = args.get(column);
      }
      return Tuple.wrap(array);
    };
  }

  /**
   * Create a mapper that converts a parameters object of the given {@code type} to a map of named parameters.
   *
   * <p>This feature relies on {@link io.vertx.core.json.JsonObject#mapFrom} feature. This likely requires
   * to use Jackson databind in the project.
   *
   * @param type the parameters class
   * @return the mapper
   */
  static <T> TupleMapper<T> mapper(Class<T> type) {
    return mapper(params -> {
      JsonObject jsonObject = JsonObject.mapFrom(params);
      Map<String, Object> map = new LinkedHashMap<>(jsonObject.size());
      for (String fieldName : jsonObject.fieldNames()) {
        map.put(fieldName, jsonObject.getValue(fieldName));
      }
      return map;
    });
  }

  /**
   * Map a {@link JsonObject} to a {@link Tuple}.
   */
  static TupleMapper<JsonObject> jsonObject() {
    return JsonTuple::new;
  }

  /**
   * The internal mapper contract that builds a tuple.
   *
   * @param mapping associates an index to template parameter name
   * @param size the tuple size
   * @param params the parameters object
   * @return the tuple
   */
  Tuple map(Function<Integer, String> mapping, int size, T params);

}