# flask-json-pattern
Decorator for REST endpoints in flask. Validate JSON request data.
## Installation
Use pip to install the package:
```bash
pip install flask-json-pattern
```
## Usage
This package provides a flask route decorator to validate json payload.
```python
from flask import Flask, jsonify
from flask_json_pattern import json_pattern
app = Flask(__name__)
@app.route('/greet', methods=['POST'])
@json_pattern({
'name': {'type': str},
'surname': {'type': str}
})
def greet():
return jsonify({"msg": "Hello %(name)s %(surname)s" % request.json})
```
## Required fields
By default all fields are required, If you want you can change this behavior by adding `required: False` in the field you want
```python
@app.route('/greet', methods=['POST'])
@json_pattern({
'name': {'type': str},
'surname': {'type': str, 'required': False}
})
def greet():
return ""
```
## Default values
When the field is optional `required: False`, you could set the default value of it using the `default` property.
```python
@app.route('/greet', methods=['POST'])
@json_pattern({
'name': {'type': str},
'surname': {'type': str, "default": 'unknown'}
})
def greet():
return ""
```
## Empty values
By default the fields can be empty, you could change this if you set the `empty` property to false.
```python
@app.route('/greet', methods=['POST'])
@json_pattern({
'name': {'type': str},
'surname': {'type': str, "empty": False}
})
def greet():
return ""
```
Also, you could change the empty and default properties, so that when the property is empty assign a value.
```python
@app.route('/greet', methods=['POST'])
@json_pattern({
'name': {'type': str, "empty": False, 'default': "unknown"},
'surname': {'type': str}
})
def greet():
return ""
```
## Skip validation methods
If you want to skip the validation for some HTTP methods, can you set `ignore_methods=[]`. By default methods that do not expect a body are GET, HEAD and DELETE.
```python
@app.route('/greet', methods=['GET', 'POST'])
@json_pattern({
'name': {'type': str},
'surname': {'type': str}
}, ignore_methods=['GET'])
def greet():
return ""
```
## Tuple and list
If you want, you can validate the data type of each position of a simple list
```python
@app.route('/greet', methods=['GET', 'POST'])
@json_pattern({
'name': {'type': str},
'surname': {'type': str},
'skills': {
'type': list,
'of': str
}
}, ignore_methods=['GET'])
def greet():
return ""
```
Also, If you want you could validate lists of objects, and the fields of each object.
```python
@app.route('/greet', methods=['GET', 'POST'])
@json_pattern({
'name': {'type': str},
'surname': {'type': str},
'skills': {
'type': list,
"schema": {
"name": {"type": str}
}
}
}, ignore_methods=['GET'])
def greet():
return ""
```
## Error handling
On validation failure the library calls `flask.abort` and passes an 400 error code and instance of the ValidationError.
```python
from flask import make_response, jsonify
from flask_json_pattern import ValidationError
@app.errorhandler(400)
def bad_request(error):
if isinstance(error.description, ValidationError):
return make_response(jsonify({'msg': error.description.message}), 400)
return error
```
