如何配置Tastypie使字段视为唯一？

Question

我该如何配置Tastypie，让某个字段被视为唯一的呢？我希望如果我尝试插入重复的条目，系统能给我一个非500的错误提示（可能是409冲突？）作为回应。

---

我查阅了文档，感觉应该很简单，但不知道为什么我没有得到我期待的回应。

这是文档链接：

http://readthedocs.org/docs/django-tastypie/en/latest/fields.html?highlight=unique

---

下面是示例代码：

urls.py

v1_api = Api(api_name='v1')
v1_api.register(CompanyResource())

urlpatterns = patterns('',
    (r'^api/', include(v1_api.urls)),
)

resource.py

class CompanyResource(ModelResource):

    CompanyName = fields.CharField(attribute='company_name')
    CompanyId = fields.CharField(attribute='company_id', unique=True)
    Contact = fields.CharField(attribute='contact')
    Email = fields.CharField(attribute='email')
    Phone = fields.CharField(attribute='phone')

    class Meta:
        queryset = Company.objects.all()
        authentication = BasicAuthentication()
        authorization = Authorization()
        allowed_methods = ['get', 'post']

models.py

class Company(models.Model):

    company_name = models.TextField(default=None, blank=True, null=True)
    company_id = models.CharField(default='', unique=True, db_index=True, max_length=20)
    contact = models.TextField(default=None, blank=True, null=True)
    email = models.EmailField(default=None, blank=True, null=True)
    phone = models.TextField(default=None, blank=True, null=True)

---

我收到的错误信息是这样的（使用curl访问我的本地服务）：

curl --dump-header - -H "Content-Type: application/json" -X POST --user user:password --data '{"CompanyName": "company", "CompanyId": "1234567890", "Contact": "John", "Email": "example@example.com", "Phone": "555-555-5555"}' http://localhost:8000/api/v1/company/
HTTP/1.0 500 INTERNAL SERVER ERROR
Date: Thu, 15 Sep 2011 18:25:20 GMT
Server: WSGIServer/0.1 Python/2.7.1
Content-Type: application/json; charset=utf-8

{"error_message": "(1062, \"Duplicate entry '1234567890' for key 'api_company_company_id_uniq'\")", 
...<snip>...
raise errorclass, errorvalue\n\nIntegrityError: (1062, \"Duplicate entry '1234567890' for key 'api_company_company_id_uniq'\")\n"}

当我从Company模型中移除unique=True, db_index=True,时，我没有收到完整性错误，而是创建了一个新的重复资源。再次强调，这不是我期待的结果，因为我希望唯一性能够进行一些验证，并导致一些非500的响应。

Answer 1

我想说的是，我找到了一种稍微不同的解决方案，对我来说效果更好。这是基于thoslin的回答。

我发现e.args[0] == 1062这个检查对我来说不管用。我很确定这是MySQL的错误，而我用的是Postgres。

我还把这个实现放在了obj_create方法里，这样它就可以处理所有对象的创建，而不仅仅是通过post_list创建的对象。

from tastypie.exceptions import ImmediateHttpResponse
from tastypie.http import HttpConflict
from django.db import IntegrityError

...

class MyBaseResource(ModelResource):
    def obj_create(self, bundle, **kwargs):
        try:
            return super(MyBaseResource, self).obj_create(bundle, **kwargs)
        except IntegrityError, e:
            if e.args[0] == 1062 or e.args[0].startswith('duplicate key'):
                raise ImmediateHttpResponse(HttpConflict())

...

class MyResource(MyBaseResource):
    [usual resource stuff]

Answer 2

我今天也遇到了同样的问题。这里是我解决它的方法：

在你的资源定义中，重写 [request_method]_[request_type] 方法。例如，我在 FooResource 中重写了 post_list：

def post_list(self, request, **kwargs):
    from django.db import IntegrityError
    try:
        return super(FooResource, self).post_list(request, **kwargs)
    except IntegrityError, e:
        if e.args[0] == 1062:
            return http.HttpConflict()

希望这个方法对你有用。

Answer 3

这是我解决问题的方法：

根据验证的文档，我实现了一个自定义的验证器，用来检查字段的唯一性。

在CompanyResource类中，我在类的元信息里添加了一个CustomValidation。我把CustomValidation的实现放在了一个叫validations.py的文件里。如果isValid返回错误，API就会返回一个400的错误码，并且会把错误信息包含在返回的消息里。

class CompanyResource(ModelResource):
    """
    CompanyIds should be unique
    """     
    CompanyName = fields.CharField(attribute='company_name')     
    CompanyId = fields.CharField(attribute='company_id', unique=True)     
    Contact = fields.CharField(attribute='contact')     
    Email = fields.CharField(attribute='email')     
    Phone = fields.CharField(attribute='phone')    

    class Meta:        
        queryset = Company.objects.all()        
        authentication = BasicAuthentication()        
        authorization = Authorization()        
        allowed_methods = ['get', 'post']                
        validation = CustomValidation()

validations.py

class CustomValidation(Validation):
    """
    The custom validation checks two things:
       1) that there is data
       2) that the CompanyId exists (unique check)
    """
    def is_valid(self, bundle, request=None):
        if not bundle.data:
            return {'__all__': 'Missing data, please include CompanyName, CompanyId, Contact, Email, and Phone.'}

        errors = {}                                    
        company_id=bundle.data.get('CompanyId', None)

        # manager method, returns true if the company exists, false otherwise
        if Company.objects.company_exists(company_id):
            errors['CompanyId']='Duplicate CompanyId, CompanyId %s already exists.' % company_id
        return errors