Serializers把querysets和model instances这些复杂的数据结构转化为native Python 以便于以json,xml或其它内容类型的形式render出去。
- 类似于Django的 Form 和ModelForm
- Serializer和ModelSerializer
序列化对象
from datetime import datetime
class Comment(object):
def __init__(self, email, content, created=None):
self.email = email
self.content = content
self.created = created or datetime.now()
from rest_framework import serializers
class CommentSerializer(serializers.Serializer):
email = serializers.EmailField()
content = serializers.CharField(max_length=200)
created = serializers.DateTimeField()
comment = Comment(email='leila@example.com', content='foo bar')
serializer = CommentSerializer(comment)
serializer.data
# {'email': 'leila@example.com', 'content': 'foo bar', 'created': '2016-01-27T15:17:10.375877'}
把数据转化为json格式
from rest_framework.renderers import JSonRenderer
json = JSonRenderer().render(serializer.data)
json
# b'{"email":"leila@example.com","content":"foo bar","created":"2016-01-27T15:17:10.375877"}'
反序列化对象
把json数据转化为本地数据类型，也就是Django rest framework可以使用的数据类型
from django.utils.six import BytesIO from rest_framework.parsers import JSonParser stream = BytesIO(json) data = JSonParser().parse(stream)
让后进一步把这些数据绑定到serializers上面，serializer = CommentSerializer(data=data)之后使用serializer.is_valid()验证传进来的数据（上段代码的data是否符合CommentSerializer的格式，这里可以写一个try-exception.现在可以在serializer.validated_data找到传进来的数据。
在访问validated data或板寸validated data之前一定要检查serializer.is_valid()是否为true。如果为false的话错误信息包含在serializer.errors里。
serializer = CommentSerializer(data=data)
serializer.is_valid()
# True
serializer.validated_data
# {'content': 'foo bar', 'email': 'leila@example.com', 'created': datetime.datetime(2012, 08, 22, 16, 20, 09, 822243)}
保存instances
我们应该实现基本的create和update方法，把数据写入数据库
def create(self, validated_data):
return Comment.objects.create(**validated_data)
def update(self, instance, validated_data):
instance.email = validated_data.get('email', instance.email)
instance.content = validated_data.get('content', instance.content)
instance.created = validated_data.get('created', instance.created)
instance.save()
return instance
如果不需要写入数据库，可以直接放回数据就好了
class CommentSerializer(serializers.Serializer):
email = serializers.EmailField()
content = serializers.CharField(max_length=200)
created = serializers.DateTimeField()
def create(self, validated_data):
return Comment(**validated_data)
def update(self, instance, validated_data):
instance.email = validated_data.get('email', instance.email)
instance.content = validated_data.get('content', instance.content)
instance.created = validated_data.get('created', instance.created)
return instance
在命令行中的编写如下：
创建一个新的对象
serializer = CommentSerializer(data=data)
serializer.is_valid()
# True
serializer.validated_data
# {'content': 'foo bar', 'email': 'leila@example.com', 'created': datetime.datetime(2012, 08, 22, 16, 20, 09, 822243)}
comment = serializer.save()
更新已经存在的comment实例
serializer = CommentSerializer(comment, data=data)
serializer.is_valid()
# True
serializer.validated_data
# {'content': 'foo bar', 'email': 'leila@example.com', 'created': datetime.datetime(2012, 08, 22, 16, 20, 09, 822243)}
comment = serializer.save()
在save的时候添加其它内容比如
serializer.save(owner=request.user)
owner数据被绑定在serializer.validated_data对象上，当create或update的时候就会被添加进数据库。
直接重写save()方法
有时候并不需要保存或则返回数据，这个时候save()方法就需要重写。比如执行发送邮件的任务。
class ContactForm(serializers.Serializer):
email = serializers.EmailField()
message = serializers.CharField()
def save(self):
email = self.validated_data['email']
message = self.validated_data['message']
send_email(from=email, message=message)
请注意，在上述情况下，我们现在必须直接访问serializer_date属性。
验证
serializer = CommentSerializer(data={'email': 'foobar', 'content': 'baz'})
serializer.is_valid()
# False
serializer.errors
# {'email': [u'Enter a valid e-mail address.'], 'created': [u'This field is required.']}
non_field_errors关键字有可能出现，可以在REST framework 框架的设置文件里面设置NON_FIELD_ERRORS_KEY。
is_valid()有默认的异常处理机制，raise_exception标志默认为true,框架自动帮你抛异常（serializers.ValidationError）。
# Return a 400 response if the data was invalid. serializer.is_valid(raise_exception=True)
自定义验证
类似于Django表单的clean_
from rest_framework import serializers
class BlogPostSerializer(serializers.Serializer):
title = serializers.CharField(max_length=100)
content = serializers.CharField()
def validate_title(self, value):
"""
Check that the blog post is about Django.
"""
if 'django' not in value.lower():
raise serializers.ValidationError("Blog post is not about Django")
return value
注意：如果你不希望这个验证方法被使用，你可以在serializer上声明required=False，那么如果这个field没有包括进来这个验证步骤就不会起作用。（这里有点不清晰）
对象级验证
如果你的验证需要访问多个fileds,你可以添加serializer的子类validate().这个方法接收一个字典参数，你需要使用的多个fileds应该包含在这个字典参数里面。报错类型为serializers.ValidationError
from rest_framework import serializers
class EventSerializer(serializers.Serializer):
description = serializers.CharField(max_length=100)
start = serializers.DateTimeField()
finish = serializers.DateTimeField()
def validate(self, data):
"""
Check that the start is before the stop.
"""
if data['start'] > data['finish']:
raise serializers.ValidationError("finish must occur after start")
return data
验证器
- 通过在字段实例上声明使用验证器
def multiple_of_ten(value):
if value % 10 != 0:
raise serializers.ValidationError('Not a multiple of ten')
class GameRecord(serializers.Serializer):
score = IntegerField(validators=[multiple_of_ten])
...
- 作用于全部字段的验证器
下载meta里面
class EventSerializer(serializers.Serializer):
name = serializers.CharField()
room_number = serializers.IntegerField(choices=[101, 102, 103, 201])
date = serializers.DateField()
class meta:
# Each room only has one event per day.
validators = UniqueTogetherValidator(
queryset=Event.objects.all(),
fields=['room_number', 'date']
)
