django 序列化器 非空1检验

序列化器：

params = serializers.CharField(max_length=500, allow_blank=True,allow_null=True)

class TestCase(models.Model):
    case_name = models.CharField(max_length=50, null=False)
    method = models.CharField(max_length=10, null=False)
    url = models.CharField(max_length=500, null=False)
    params = models.CharField(max_length=500, null=True)