A robust JSON decoder/encoder with support for schema validation.

1.2.2 2016-01-14 12:11 UTC

README

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Latest release: 1.2.2

A robust wrapper for json_encode()/json_decode() that normalizes their behavior across PHP versions, throws meaningful exceptions and supports schema validation by default.

Installation

Use Composer to install the package:

$ composer require webmozart/json

Encoding

Use the JsonEncoder to encode data as JSON:

use Webmozart\Json\JsonEncoder;

$encoder = new JsonEncoder();

// Store JSON in string
$string = $encoder->encode($data);

// Store JSON in file
$encoder->encodeFile($data, '/path/to/file.json');

By default, the JSON schema stored in the $schema property of the JSON document is used to validate the file. You can also pass the path to the schema in the last optional argument of both methods:

use Webmozart\Json\ValidationFailedException;

try {
    $string = $encoder->encode($data, '/path/to/schema.json');
} catch (ValidationFailedException $e) {
    // data did not match schema 
}

Decoding

Use the JsonDecoder to decode a JSON string/file:

use Webmozart\Json\JsonDecoder;

$decoder = new JsonDecoder();

// Read JSON string
$data = $decoder->decode($string);

// Read JSON file
$data = $decoder->decodeFile('/path/to/file.json');

Like JsonEncoder, the decoder accepts the path to a JSON schema in the last optional argument of its methods:

use Webmozart\Json\ValidationFailedException;

try {
    $data = $decoder->decodeFile('/path/to/file.json', '/path/to/schema.json');
} catch (ValidationFailedException $e) {
    // data did not match schema 
}

Validation

Sometimes it is necessary to separate the steps of encoding/decoding JSON data and validating it against a schema. In this case, you can omit the schema argument during encoding/decoding and use the JsonValidator to validate the data manually later on:

use Webmozart\Json\JsonDecoder;
use Webmozart\Json\JsonValidator;
use Webmozart\Json\ValidationFailedException;

$decoder = new JsonDecoder();
$validator = new JsonValidator();

$data = $decoder->decodeFile('/path/to/file.json');

// process $data...

$errors = $validator->validate($data, '/path/to/schema.json');

if (count($errors) > 0) {
    // data did not match schema 
}

Note: This does not work if you use the $schema property to set the schema (see next section). If that property is set, the schema is always used for validation during encoding and decoding.

Schemas

You are encouraged to store the schema of your JSON documents in the $schema property:

{
    "$schema": "http://example.org/schemas/1.0/schema"
}

The utilities in this package will load the schema from the URL and use it for validating the document. Obviously, this has a hit on performance and depends on the availability of the server and an internet connection. Hence you are encouraged to ship the schema with your package. Use the LocalUriRetriever to map the URL to your local schema file:

$uriRetriever = new UriRetriever();
$uriRetriever->setUriRetriever(new LocalUriRetriever(
    // base directory
    __DIR__.'/../res/schemas',
    // list of schema mappings
    array(
        'http://example.org/schemas/1.0/schema' => 'schema-1.0.json',
    )
));

$validator = new JsonValidator(null, $uriRetriever);
$encoder = new JsonEncoder($validator);
$decoder = new JsonDecoder($validator);

// ...

Conversion

You can implement JsonConverter to encapsulate the conversion of objects from and to JSON structures in a single class:

use stdClass;
use Webmozart\Json\Conversion\JsonConverter;

class ConfigFileJsonConverter implements JsonConverter
{
    const SCHEMA = 'http://example.org/schemas/1.0/schema';
    
    public function toJson($configFile, array $options = array())
    {
        $jsonData = new stdClass();
        $jsonData->{'$schema'} = self::SCHEMA;
         
        if (null !== $configFile->getApplicationName()) {
            $jsonData->application = $configFile->getApplicationName();
        }
        
        // ...
        
        return $jsonData;
    }
    
    public function fromJson($jsonData, array $options = array())
    {
        $configFile = new ConfigFile();
        
        if (isset($jsonData->application)) {
            $configFile->setApplicationName($jsonData->application);
        }
        
        // ...
        
        return $configFile;
    }
}

Loading and dumping ConfigFile objects is very simple now:

$converter = new ConfigFileJsonConverter();

// Load config.json as ConfigFile object
$jsonData = $decoder->decodeFile('/path/to/config.json');
$configFile = $converter->fromJson($jsonData);

// Save ConfigFile object as config.json
$jsonData = $converter->toJson($configFile);
$encoder->encodeFile($jsonData, '/path/to/config.json');

You can automate the schema validation of your ConfigFile by wrapping the converter in a ValidatingConverter:

use Webmozart\Json\Validation\ValidatingConverter;

$converter = new ValidatingConverter(new ConfigFileJsonConverter());

You can also validate against an explicit schema by passing the schema to the ValidatingConverter:

use Webmozart\Json\Validation\ValidatingConverter;

$converter = new ValidatingConverter(
    new ConfigFileJsonConverter(),
    __DIR__.'/../res/schema/config-schema.json'
);

Versioning and Migration

When you continuously develop an application, you will enter the situation that you need to change your JSON schemas. Updating JSON files to match their changed schemas can be challenging and time consuming. This package supports a versioning mechanism to automate this migration.

Imagine config.json files in three different versions: 1.0, 2.0 and 3.0. The name of a key changed between those versions:

config.json (version 1.0)

{
    "$schema": "http://example.org/schemas/1.0/schema",
    "application": "Hello world!"
}

config.json (version 2.0)

{
    "$schema": "http://example.org/schemas/2.0/schema",
    "application.name": "Hello world!"
}

config.json (version 3.0)

{
    "$schema": "http://example.org/schemas/3.0/schema",
    "application": {
        "name": "Hello world!"
    }
}

You can support files in any of these versions by implementing:

  1. A converter compatible with the latest version (e.g. 3.0)

  2. Migrations that migrate older versions to newer versions (e.g. 1.0 to 2.0 and 2.0 to 3.0.

Let's look at an example of a ConfigFileJsonConverter for version 3.0:

use stdClass;
use Webmozart\Json\Conversion\JsonConverter;

class ConfigFileJsonConverter implements JsonConverter
{
    const SCHEMA = 'http://example.org/schemas/3.0/schema';
    
    public function toJson($configFile, array $options = array())
    {
        $jsonData = new stdClass();
        $jsonData->{'$schema'} = self::SCHEMA;
         
        if (null !== $configFile->getApplicationName()) {
            $jsonData->application = new stdClass();
            $jsonData->application->name = $configFile->getApplicationName();
        }
        
        // ...
        
        return $jsonData;
    }
    
    public function fromJson($jsonData, array $options = array())
    {
        $configFile = new ConfigFile();
        
        if (isset($jsonData->application->name)) {
            $configFile->setApplicationName($jsonData->application->name);
        }
        
        // ...
        
        return $configFile;
    }
}

This converter can be used as described in the previous section. However, it can only be used with config.json files in version 3.0.

We can add support for older files by implementing the JsonMigration interface. This interface contains four methods:

  • getSourceVersion(): returns the source version of the migration
  • getTargetVersion(): returns the target version of the migration
  • up(stdClass $jsonData): migrates from the source to the target version
  • down(stdClass $jsonData): migrates from the target to the source version
use Webmozart\Json\Migration\JsonMigration;

class ConfigFileJson20To30Migration implements JsonMigration
{
    const SOURCE_SCHEMA = 'http://example.org/schemas/2.0/schema';
    
    const TARGET_SCHEMA = 'http://example.org/schemas/3.0/schema';
    
    public function getSourceVersion()
    {
        return '2.0';
    }
    
    public function getTargetVersion()
    {
        return '3.0';
    }
    
    public function up(stdClass $jsonData)
    {
        $jsonData->{'$schema'} = self::TARGET_SCHEMA;
        
        if (isset($jsonData->{'application.name'})) {
            $jsonData->application = new stdClass();
            $jsonData->application->name = $jsonData->{'application.name'};
            
            unset($jsonData->{'application.name'});
        )
    }
    
    public function down(stdClass $jsonData)
    {
        $jsonData->{'$schema'} = self::SOURCE_SCHEMA;
        
        if (isset($jsonData->application->name)) {
            $jsonData->{'application.name'} = $jsonData->application->name;
            
            unset($jsonData->application);
        )
    }
}

With a list of such migrations, we can create a MigratingConverter that decorates our ConfigFileJsonConverter:

use Webmozart\Json\Migration\MigratingConverter;
use Webmozart\Json\Migration\MigrationManager;

// Written for version 3.0
$converter = new ConfigFileJsonConverter();

// Support for older versions. The order of migrations does not matter.
$migrationManager = new MigrationManager(array(
    new ConfigFileJson10To20Migration(),
    new ConfigFileJson20To30Migration(),
));

// Decorate the converter
$converter = new MigratingConverter($converter, $migrationManager);

The resulting converter is able to load and dump JSON files in any of the versions 1.0, 2.0 and 3.0.

// Loads a file in version 1.0, 2.0 or 3.0
$jsonData = $decoder->decodeFile('/path/to/config.json');
$configFile = $converter->fromJson($jsonData);

// Writes the file in the latest version by default (3.0)
$jsonData = $converter->toJson($configFile);
$encoder->encodeFile($jsonData, '/path/to/config.json');

// Writes the file in a specific version
$jsonData = $converter->toJson($configFile, array(
    'targetVersion' => '2.0',
));
$encoder->encodeFile($jsonData, '/path/to/config.json');

Validation of Different Versions

If you want to add schema validation, wrap your encoder into a ValidatingConverter. You can wrap both the inner and the outer converter to make sure that both the JSON before and after running the migrations complies to the corresponding schemas.

// Written for version 3.0
$converter = new ConfigFileJsonConverter();

// Decorate to validate against the schema at version 3.0
$converter = new ValidatingConverter($converter);

// Decorate to support different versions
$converter = new MigratingConverter($converter, $migrationManager);

// Decorate to validate against the old schema
$converter = new ValidatingConverter($converter);

If you store the version in a version field (see below) and want to use a custom schema depending on that version, you can pass schema paths or closures for resolving the schema paths:

// Written for version 3.0
$converter = new ConfigFileJsonConverter();

// Decorate to validate against the schema at version 3.0
$converter = new ValidatingConverter($converter, __DIR__.'/../res/schema/config-schema-3.0.json');

// Decorate to support different versions
$converter = new MigratingConverter($converter, $migrationManager);

// Decorate to validate against the old schema
$converter = new ValidatingConverter($converter, function ($jsonData) {
    return __DIR__.'/../res/schema/config-schema-'.$jsonData->version.'.json'
});

Using Custom Schema Versioning

By default, the version of the schema is stored in the schema name:

{
    "$schema": "http://example.com/schemas/1.0/my-schema"
}

The version must be enclosed by slashes. Appending the version to the schema, for example, won't work:

{
    "$schema": "http://example.com/schemas/my-schema-1.0"
}

You can however customize the format of the schema URI by creating a SchemaUriVersioner with a custom regular expression:

use Webmozart\Json\Versioning\SchemaUriVersioner;

$versioner = new SchemaUriVersioner('~(?<=-)\d+\.\d+(?=$)~');

$migrationManager = new MigrationManager(array(
    // migrations...
), $versioner);

// ...

The regular expression must match the version only. Make sure to wrap characters before and after the version in look-around assertions ((?<=...), (?=...)).

Storing the Version in a Field

Instead of storing the version in the schema URI, you could also store it in a separate field. For example, the field "version":

{
    "version": "1.0"
}

This use case is supported by the VersionFieldVersioner class:

use Webmozart\Json\Versioning\VersionFieldVersioner;

$versioner = new VersionFieldVersioner();

$migrationManager = new MigrationManager(array(
    // migrations...
), $versioner);

// ...

The constructor of VersionFieldVersioner optionally accepts a custom field name used to store the version. The default field name is "version".

Authors

Contribute

Contributions to the package are always welcome!

Support

If you are having problems, send a mail to bschussek@gmail.com or shout out to @webmozart on Twitter.

License

All contents of this package are licensed under the MIT license.