cweiske / Jsonmapper
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JsonMapper - map nested JSON structures onto PHP classes
.. image:: https://api.travis-ci.com/cweiske/jsonmapper.svg :target: https://travis-ci.com/github/cweiske/jsonmapper :align: right
Takes data retrieved from a JSON__ web service and converts them into nested object and arrays - using your own model classes.
Starting from a base object, it maps JSON data on class properties, converting them into the correct simple types or objects.
It's a bit like the native SOAP parameter mapping PHP's SoapClient
gives you, but for JSON.
It does not rely on any schema, only your PHP class definitions.
Type detection works by parsing @var docblock annotations of
class properties, as well as type hints in setter methods.
You do not have to modify your model classes by adding JSON specific code; it works automatically by parsing already-existing docblocks.
Keywords: deserialization, hydration
.. contents::
============ Pro & contra
Benefits
- Autocompletion in IDEs
- It's easy to add comfort methods to data model classes
- Your JSON API may change, but your models can stay the same - not breaking applications that use the model classes.
Drawbacks
-
Model classes need to be written by hand
Since JsonMapper does not rely on any schema information (e.g. from
json-schema__), model classes cannot be generated automatically.
===== Usage
Basic usage
#. Register an autoloader that can load PSR-0__ compatible classes.
#. Create a JsonMapper object instance
#. Call the map or mapArray method, depending on your data
Map a normal object:
.. code:: php
<?php
require 'autoload.php';
$mapper = new JsonMapper();
$contactObject = $mapper->map($jsonContact, new Contact());
?>
Map an array of objects:
.. code:: php
<?php
require 'autoload.php';
$mapper = new JsonMapper();
$contactsArray = $mapper->mapArray(
$jsonContacts, array(), 'Contact'
);
?>
Instead of array() you may also use ArrayObject and descending classes.
__ http://www.php-fig.org/psr/psr-0/
Example
JSON from an address book web service:
.. code:: javascript
{
'name':'Sheldon Cooper',
'address': {
'street': '2311 N. Los Robles Avenue',
'city': 'Pasadena'
}
}
Your local Contact class:
.. code:: php
<?php
class Contact
{
/**
* Full name
* @var string
*/
public $name;
/**
* @var Address
*/
public $address;
}
?>
Your local Address class:
.. code:: php
<?php
class Address
{
public $street;
public $city;
public function getGeoCoords()
{
//do something with $street and $city
}
}
?>
Your application code:
.. code:: php
<?php
$json = json_decode(file_get_contents('http://example.org/sheldon.json'));
$mapper = new JsonMapper();
$contact = $mapper->map($json, new Contact());
echo "Geo coordinates for " . $contact->name . ": "
. var_export($contact->address->getGeoCoords(), true);
?>
Property type mapping
JsonMapper uses several sources to detect the correct type of
a property:
#. The setter method (set + ucwords($propertyname)) is inspected.
Underscores "_" and hyphens "-" make the next letter uppercase.
Property foo_bar-baz leads to setter method setFooBarBaz.
#. If it has a type hint in the method signature then its type used::
public function setPerson(Contact $person) {...}
#. The method's docblock is inspected for @param $type annotations::
/**
* @param Contact $person Main contact for this application
*/
public function setPerson($person) {...}
#. If no type could be detected, the plain JSON value is passed to the setter method.
#. Class property types (since PHP 7.4)::
public Contact $person;
#. @var $type docblock annotation of class properties::
/**
* @var \my\application\model\Contact
*/
public $person;
The property has to be public to be used directly.
You may also use $bIgnoreVisibility__ to utilize
protected and private properties.
.. __: #prop-bignorevisibility
If no type could be detected, the property gets the plain JSON value set.
If a property can not be found, JsonMapper tries to find the property
in a case-insensitive manner.
A JSON property isempty would then be mapped to a PHP property
isEmpty.
.. note:: You have to provide the fully qualified namespace for the type to work. Relative class names are evaluated in the context of the current classes namespace, NOT respecting any imports that may be present.
PHP does not provide the imports via Reflection; the comment text only
contains the literal text of the type.
For performance reasons JsonMapper does not parse the source code on its
own to detect and expand any imports.
Supported type names
-
Simple types
string-
bool,boolean -
int,integer -
double,float arrayobject
-
Class names, with and without namespaces
-
Contact- exception will be thrown if the JSON value isnull
-
-
Arrays of simple types and class names:
int[]Contact[]
-
Multidimensional arrays:
int[][]TreeDeePixel[][][]
-
ArrayObjects of simple types and class names:
ContactList[Contact]NumberList[int]
-
Nullable types:
-
int|null- will benullif the value in JSON isnull, otherwise it will be an integer -
Contact|null- will benullif the value in JSON isnull, otherwise it will be an object of typeContact
-
ArrayObjects and extending classes are treated as arrays.
Variables without a type or with type mixed will get the
JSON value set directly without any conversion.
See phpdoc's type documentation__ for more information.
__ http://phpdoc.org/docs/latest/references/phpdoc/types.html
Simple type mapping
When an object shall be created but the JSON contains a simple type only (e.g. string, float, boolean), this value is passed to the classes' constructor. Example:
PHP code:
.. code:: php
/**
* @var DateTime
*/
public $date;
JSON:
.. code:: js
{"date":"2014-05-15"}
This will result in new DateTime('2014-05-15') being called.
Class map
When variables are defined as objects of abstract classes or interfaces, JsonMapper would normally try to instantiate those directly and crash.
Using JsonMapper's $classMap property, you can specify which classes
shall get instantiated instead:
.. code:: php
$jm = new JsonMapper();
$jm->classMap['Foo'] = 'Bar';
$jm->map(...);
This would create objects of type Bar when a variable is defined to be
of type Foo.
It is also possible to use a callable in case the actual implementation class needs to be determined dynamically (for example in case of a union). The mapped class ('Foo' in the example below) and the Json data are passed as parameters into the call.
.. code:: php
$mapper = function ($class, $jvalue) {
// examine $class and $jvalue to figure out what class to use...
return 'DateTime';
};
$jm = new JsonMapper();
$jm->classMap['Foo'] = $mapper;
$jm->map(...);
Nullables
JsonMapper throws an exception when a JSON property is null,
unless the PHP class property has a nullable type - e.g. Contact|null.
If your API contains many fields that may be null and you do not want
to make all your type definitions nullable, set:
.. code:: php
$jm->bStrictNullTypes = false;
Logging
JsonMapper's setLogger() method supports all PSR-3__ compatible
logger instances.
Events that get logged:
- JSON data contain a key, but the class does not have a property or setter method for it.
- Neither setter nor property can be set from outside because they are protected or private
__ http://www.php-fig.org/psr/psr-3/
Handling invalid or missing data
During development, APIs often change. To get notified about such changes, JsonMapper can be configured to throw exceptions in case of either missing or yet unknown data.
Unknown properties
When JsonMapper sees properties in the JSON data that are
not defined in the PHP class, you can let it throw an exception
by setting $bExceptionOnUndefinedProperty:
.. code:: php
$jm = new JsonMapper();
$jm->bExceptionOnUndefinedProperty = true;
$jm->map(...);
You may also choose to handle those properties yourself by setting
a callable__ to $undefinedPropertyHandler:
__ http://php.net/manual/en/language.types.callable.php
.. code:: php
/**
* Handle undefined properties during JsonMapper::map()
*
* @param object $object Object that is being filled
* @param string $propName Name of the unknown JSON property
* @param mixed $jsonValue JSON value of the property
*
* @return void
*/
function setUndefinedProperty($object, $propName, $jsonValue)
{
$object->{'UNDEF' . $propName} = $jsonValue;
}
$jm = new JsonMapper();
$jm->undefinedPropertyHandler = 'setUndefinedProperty';
$jm->map(...);
Missing properties
Properties in your PHP classes can be marked as "required" by
putting @required in their docblock:
.. code:: php
/**
* @var string
* @required
*/
public $someDatum;
When the JSON data do not contain this property, JsonMapper will throw
an exception when $bExceptionOnMissingData is activated:
.. code:: php
$jm = new JsonMapper();
$jm->bExceptionOnMissingData = true;
$jm->map(...);
Option $bRemoveUndefinedAttributes causes JsonMapper to remove properties
from the final object if they have not been in the JSON data:
.. code:: php
$jm = new JsonMapper();
$jm->bRemoveUndefinedAttributes = true;
$jm->map(...);
.. _prop-bignorevisibility:
Private properties and functions
You can allow mapping to private and protected properties and
setter methods by setting $bIgnoreVisibility to true:
.. code:: php
$jm = new JsonMapper();
$jm->bIgnoreVisibility = true;
$jm->map(...);
Simple types instead of objects
When a variable's type is a class and JSON data is a simple type
like string, JsonMapper passes this value to the class' constructor.
If you do not want this, set $bStrictObjectTypeChecking to true:
.. code:: php
$jm = new JsonMapper();
$jm->bStrictObjectTypeChecking = true;
$jm->map(...);
An exception is then thrown in such cases.
Passing arrays to map()
You may wish to pass array data into map() that you got by calling
.. code:: php
json_decode($jsonString, true)
By default, JsonMapper will throw an exception because map() requires
an object as first parameter.
You can circumvent that by setting $bEnforceMapType to false:
.. code:: php
$jm = new JsonMapper();
$jm->bEnforceMapType = false;
$jm->map(...);
Post-mapping callback
JsonMapper is able to call a custom method directly on each object after mapping it is finished:
.. code:: php
$jm = new JsonMapper();
$jm->postMappingMethod = 'afterMapping';
$jm->map(...);
Now afterMapping() is called on each mapped object
(if the class has that method).
============ Installation
Via Composer from Packagist__::
$ composer require netresearch/jsonmapper
__ https://packagist.org/packages/netresearch/jsonmapper
================ Related software
Alternatives
-
Jackson's data binding__ for Java -
Johannes Schmitt Serializer__ for PHP -
metassione__ for PHP -
Cartographer__ for PHP -
Data Transfer Object__ for PHP
__ https://fasterxml.github.io/jackson-databind/ __ http://jmsyst.com/libs/serializer __ https://github.com/drbonzo/metassione __ https://github.com/jonjomckay/cartographer __ https://github.com/spatie/data-transfer-object
================ About JsonMapper
License
JsonMapper is licensed under the OSL 3.0__.
__ http://opensource.org/licenses/osl-3.0
Coding style
JsonMapper follows the PEAR Coding Standards__.
__ http://pear.php.net/manual/en/standards.php
Author
Christian Weiske, cweiske.de
__ mailto:[email protected] __ http://cweiske.de/