在MongoDb上序列化只读属性 [英] Serialize get-only properties on MongoDb

问题描述

使用C#6，我可以编写:

With C# 6 I can write:

public class Person
{
    public Guid Id { get; }
    public string Name { get; }
    public Person(Guid id, string name)
    {
        Id = id;
        Name = name;
    }
}

不幸的是，像这样的类没有被MongoDb驱动程序正确地序列化，属性没有被序列化.

Unfortunately a class like this is not serialized correctly by MongoDb driver, properties are not serialized.

MongoDb仅在默认情况下使用getter和setter序列化属性.我知道您可以手动更改类映射，并告诉序列化程序为

MongoDb only serialize by default properties with getter and setter. I known that you can manually change the class mapping and tell serializer to include get-only properties but I was looking for a generic way to avoid customizing each mapping.

我当时正在考虑创建类似于

I was thinking to create a custom convention similar to ReadWriteMemberFinderConvention but without the CanWrite check.

还有其他解决方案吗?构造函数会自动被调用，还是我需要其他一些自定义?

There are other solutions? Constructor will be called automatically or I need some other customization?

推荐答案

我试图通过创建一个约定来映射所有与构造函数匹配的只读属性以及匹配的构造函数的约定来解决此问题.

I have tried to solve this problem by creating a convention that map all read only properties that match a constructor and also the matched constructor.

假设您有一个不变的类，如:

Assume that you have an immutable class like:

public class Person
{
    public string FirstName { get; }
    public string LastName { get; }
    public string FullName => FirstName + LastName;
    public ImmutablePocoSample(string lastName)
    {
        LastName = lastName;
    }

    public ImmutablePocoSample(string firstName, string lastName)
    {
        FirstName = firstName;
        LastName = lastName;
    }
}

这是约定的代码:

using MongoDB.Bson.Serialization;
using MongoDB.Bson.Serialization.Conventions;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

/// <summary>
/// A convention that map all read only properties for which a matching constructor is found.
/// Also matching constructors are mapped.
/// </summary>
public class ImmutablePocoConvention : ConventionBase, IClassMapConvention
{
    private readonly BindingFlags _bindingFlags;

    public ImmutablePocoConvention()
            : this(BindingFlags.Instance | BindingFlags.Public)
    { }

    public ImmutablePocoConvention(BindingFlags bindingFlags)
    {
        _bindingFlags = bindingFlags | BindingFlags.DeclaredOnly;
    }

    public void Apply(BsonClassMap classMap)
    {
        var readOnlyProperties = classMap.ClassType.GetTypeInfo()
            .GetProperties(_bindingFlags)
            .Where(p => IsReadOnlyProperty(classMap, p))
            .ToList();

        foreach (var constructor in classMap.ClassType.GetConstructors())
        {
            // If we found a matching constructor then we map it and all the readonly properties
            var matchProperties = GetMatchingProperties(constructor, readOnlyProperties);
            if (matchProperties.Any())
            {
                // Map constructor
                classMap.MapConstructor(constructor);

                // Map properties
                foreach (var p in matchProperties)
                    classMap.MapMember(p);
            }
        }
    }

    private static List<PropertyInfo> GetMatchingProperties(ConstructorInfo constructor, List<PropertyInfo> properties)
    {
        var matchProperties = new List<PropertyInfo>();

        var ctorParameters = constructor.GetParameters();
        foreach (var ctorParameter in ctorParameters)
        {
            var matchProperty = properties.FirstOrDefault(p => ParameterMatchProperty(ctorParameter, p));
            if (matchProperty == null)
                return new List<PropertyInfo>();

            matchProperties.Add(matchProperty);
        }

        return matchProperties;
    }


    private static bool ParameterMatchProperty(ParameterInfo parameter, PropertyInfo property)
    {
        return string.Equals(property.Name, parameter.Name, System.StringComparison.InvariantCultureIgnoreCase)
               && parameter.ParameterType == property.PropertyType;
    }

    private static bool IsReadOnlyProperty(BsonClassMap classMap, PropertyInfo propertyInfo)
    {
        // we can't read 
        if (!propertyInfo.CanRead)
            return false;

        // we can write (already handled by the default convention...)
        if (propertyInfo.CanWrite)
            return false;

        // skip indexers
        if (propertyInfo.GetIndexParameters().Length != 0)
            return false;

        // skip overridden properties (they are already included by the base class)
        var getMethodInfo = propertyInfo.GetMethod;
        if (getMethodInfo.IsVirtual && getMethodInfo.GetBaseDefinition().DeclaringType != classMap.ClassType)
            return false;

        return true;
    }
}

您可以使用以下方式注册我:

You can register i using:

ConventionRegistry.Register(
    nameof(ImmutablePocoConvention),
    new ConventionPack { new ImmutablePocoConvention() },
    _ => true);

这篇关于在MongoDb上序列化只读属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！