Import Reader

The reader is designed to go through a file to return chunks of its contents as objects without a high memory usage.

Installation

composer require dmt-software/import-reader

Usage

Create a reader

The reader can be created manually or the reader builder can be used to create a (default) reader or a pre-configured one.

use DMT\Import\Reader\Decorators\DecoratorInterface;
use DMT\Import\Reader\Decorators\Handler\GenericHandlerDecorator;
use DMT\Import\Reader\Handlers\JsonReaderHandler;
use DMT\Import\Reader\Reader;
use DMT\Import\Reader\Handlers\Sanitizers\SanitizerInterface;
use pcrov\JsonReader\JsonReader;

$internalReader = new JsonReader();
$internalReader->open('/path/to/some.json');

/** @var DecoratorInterface[] $decorators */
/** @var SanitizerInterface[] $sanitizers */
$reader = new Reader(
    new JsonReaderHandler($internalReader, ...$sanitizers),
    new GenericHandlerDecorator(), 
    ...$decorators
);

Visit the reader handler documentation for more information on the handlers internal readers and sanitizers.

Adding decorators

Once a default reader is created, it is possible to add extra decorators to apply on each object that is returned by the read method.

use DMT\Import\Reader\Decorators\ToObjectDecorator;
use DMT\Import\Reader\Reader;

/** @var Reader $reader */
$reader->addDecorator(new ToObjectDecorator(Customer::class, ['id' => 'id', 'name' => 'fullName', ]));

foreach ($reader->read() as $customer) {
    // import customer;
}

More on decorators see the documentation.

Adding filters

Besides controlling the output by using a decorator a part of the object stream the reader returns can be skipped or filtered.

use DMT\Import\Reader\Reader;

/** start on item 4 */ 
$skip = 3;
/** skip all objects that has no id */
$filter = function (object $current) { 
    return isset($current->id); 
}

foreach ($reader->read($skip, $filter) as $item) {
    // import item
}

Visit the filters section for more information about filter callbacks.

Error Handling

UnreadableException

This is thrown when the given file can not be read. This can have several causes:

• file is unreadable
• can not set file pointer
• end of file reached whilst set file pointer
• file pointer is set to the wrong return type

use DMT\Import\Reader\Exceptions\UnreadableException;

try {
    $readerBuilder->build($file, $options = []);
} catch (UnreadableException $exception) {
    // file can not be processed
}

ReaderReadException

This can happen when a single chunk can not be read from the file. It will stop execution of the reading process.

use DMT\Import\Reader\Exceptions\ReaderReadException;

try {
    foreach ($reader->read() as $n => $object) {
        // import object
    }
} catch (ReaderReadException $exception) {
    // execution stopped, after $n rows
}

DecoratorException

This exception happens silently. It triggers a user warning and continues the reading process. Depending on you server configuration this warning is ignored or send to STDOUT or STDERR.

Other Exceptions or Errors

Any other kind of failures are (most likely) problems that are caused by configuration faults or when this software is implemented incorrect.