什么是做ServiceStack补丁部分更新推荐的方式？ [英] What is the recommended way to do partial updates with PATCH in ServiceStack?

问题描述

我建立使用ServiceStack框架一个RESTful API。很多我需要更新的资源是相当大的，每个班最多40个属性，所以我想这样做的部分更新而不是更换整个资源。通常情况下，客户端只需要更新了40中的一个或两个属性，所以我想只发送一个JSON体由为数不多的属性。

I am building a RESTful API using the ServiceStack framework. A lot of the resources that I need to update are quite big, with up to 40 attributes per class, so I would like to do partial updates instead of replacing the entire resource. Often the client will only need to update one or two attributes out of the 40, so I would like to just send a JSON body consisting of the few attributes.

由于属性的所有组合都是可能的，这是不可行的，使每类中的更新类作为这里建议：https://github.com/ServiceStack/ServiceStack/wiki/New-Api#patch-request-example

Since all combinations of attributes are possible, it is not feasible to make an "Update" class per class as suggested here: https://github.com/ServiceStack/ServiceStack/wiki/New-Api#patch-request-example

在微软ASP.NET的WebAPI的OData包有一个三角洲类，它的类的子集，并更新基于此子集资源（的http://www.strathweb.com/2013/01/easy-asp-net-web-api-resource-updates-with-delta/).这是我想拥有的功能，我将有相当多的类，所以通用的方法是最好的。

In the Microsoft ASP.NET WebAPI OData package there is a Delta class that takes a subset of a class and updates the resource based on this subset (http://www.strathweb.com/2013/01/easy-asp-net-web-api-resource-updates-with-delta/). This is the functionality I would like to have, as I will be having quite a few classes so a generic method would be best.

基本上，如果我有一个类

Basically, if I have a class

public class MyClass {
   public int a { get; set; }
   public int b { get; set; }
   ...
   public int z { get; set; }
}

我想更新的MyClass资源与身体修补请求

I would like to update a resource of MyClass with a PATCH request with body

{"a":42,"c":42}

有没有办法做到这一点与ServiceStack标准或推荐的方式？

Is there a standard or recommended way to accomplish this with ServiceStack?

推荐答案

在声明DTO的任何标量值为空。这将允许您以确定哪些字段在请求中实际发送的：

Declare any scalar values in your DTO as nullable. This will allow you to determine which fields were actually sent in the request:

public class MyClass {
    public int? a { get; set; }
    public int? b { get; set; }
    public int? c { get; set; }
    // etc.
    // object-type properties are already nullable of course
    public string MyString { get; set; }
}

如果客户端发送一个请求部分，像这样

现在

Now if a client sends a partial request, like so:

{ "a": 1, "b": 0 }

您将能够确定检查您的DTO时哪些属性实际发送：

You'll be able to determine which properties were actually sent when inspecting your DTO:

myClass.a == 1
myClass.b == 0
myClass.c == null
myClass.MyString == null
etc.

设置 PATCH 路线为您的DTO和服务实施补丁方法：

Set up a PATCH route for your DTO and implement a Patch method in your service:

public object Patch(MyClass request)
{
    var existing = GetMyClassObjectFromDatabase();
    existing.PopulateWithNonDefaultValues(request);
    SaveToDatabase(existing);
    ...
}

PopulateWithNonDefaultValues​​ 这里是关键。它会从你的请求对象中的值复制到数据库实体，而只会复制不属于默认值的属性。因此，如果一个值为null，它不会复制，因为客户端没有为它发送的值。请注意，这将复制的零整数值，但因为我们做它一个可空int和可空INT的默认值是通过这种方法被认为是空，而不是0。声明你的DTO属性为空的应该不会造成太大的麻烦，在code的其余部分。

PopulateWithNonDefaultValues is key here. It will copy values from your request object onto the database entity, but will only copy properties that are not the default values. Thus, if a value is null, it won't copy it, because the client didn't send a value for it. Notice that it will copy an integer value of zero though, because we made it a nullable int, and the default value for a nullable int is considered by this method to be null, not zero. Declaring your DTO properties as nullable shouldn't cause much of a hassle in the rest of your code.

请注意，这种方法使用JSON工作很容易。如果您需要支持XML请求/响应，则可能需要需要做一些额外的工作 DataContract /数据成员属性，以确保空的正确处理。

Note that this approach works easily with JSON. If you need to support XML requests/responses, you may need need to do some additional work with DataContract/DataMember attributes to insure that nulls are handled correctly.

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