DbImpl.java 文件源码

/**
 * Finds and return mapper by type. Uses registered mappers map if not null to search for candidates and register results in this map.
 */
@Nullable
public static <T> DbMapper<T> findOrResolveMapperByType(@NotNull Class<T> type, @Nullable Map<Class, DbMapper> registeredMappers) {
    DbMapper<T> mapper = registeredMappers == null ? null : registeredMappers.get(type);
    if (mapper == null) {
        // search for a field marked as mapper with valid parameter type
        for (Field f : type.getDeclaredFields()) {
            int mods = f.getModifiers();
            if (Modifier.isStatic(mods) && Modifier.isPublic(mods) && Modifier.isFinal(mods) && f.getType().isAssignableFrom(DbMapper.class)) {
                AnnotatedType at = f.getAnnotatedType();
                if (at instanceof AnnotatedParameterizedType) {
                    AnnotatedParameterizedType apt = (AnnotatedParameterizedType) at;
                    AnnotatedType[] args = apt.getAnnotatedActualTypeArguments();
                    if (args.length == 1 && args[0].getType() == type) {
                        Mapper a = f.getAnnotation(Mapper.class);
                        if (a != null) {
                            try {
                                //noinspection unchecked
                                mapper = (DbMapper<T>) f.get(type);
                                if (mapper == null) {
                                    throw new IllegalArgumentException("Mapper must not be null: " + f);
                                }
                            } catch (IllegalAccessException ignored) { // already checked for 'isPublic' before
                            }
                            if (registeredMappers != null) {
                                if (registeredMappers.containsKey(type)) {
                                    throw new IllegalArgumentException("Found multiple mappers per type: m1: " + mapper + ", m2: " + registeredMappers.get(type));
                                }
                                registeredMappers.put(type, mapper);
                            }
                        }
                    }
                }
            } else {
                if (f.getAnnotation(Mapper.class) != null) {
                    throw new IllegalArgumentException("@Mapper field must be public, static final and have valid parametrized type type: " + f);
                }
            }
        }
    }
    return mapper;
}