之前看过MVC4.0的源码，里面就有Binder。作用是将前台页面传递过来的键值对/字典表绑定到特定的对象。此处的Binder几乎是同样的作用——将IConfiguration映射为特定的类型<T>.
我们进入正文之前还是看一个例子比较好，这样能充分了解Binder。
public class ComplexOptions
{
public ComplexOptions()
{
Virtual = "complex";
}
public int Integer { get; set; }
public bool Boolean { get; set; }
public virtual string Virtual { get; set; }
}
public class Test
{
public IConfiguration BuildConfiguration()
{
var dic = new Dictionary<string, string>
{
{"Integer", "-2"},
{"Boolean", "TRUe"},
{"Nested:Integer", "11"}
};
var builder = new ConfigurationBuilder(new MemoryConfigurationSource(dic));
return config = builder.Build();
}
public void BinderTest()
{
var config = BuildConfiguration();
var options = ConfigurationBinder.Bind<ComplexOptions>(config);
Assert.True(options.Boolean);
Assert.Equal(-2, options.Integer);
}
}
上面例子比较简单，实际上对象可能是复合对象（对象的属性还是对象），也可能是数组、枚举、结构体等。所以我们创建的过程中需要对属性遍历，如果是复合对象，还涉及到递归的过程，所以我把整个过程绘制成类似流程图的图标。如下图所示：
下面我们正式介绍工程的源码，按照惯例还是上工程结构图（就那么一个文件，搞什么搞）
整个工程只有ConfigurationBinder这一个类，调用过程上面“流程图”已经画出来了。
public static class ConfigurationBinder
{
public static TModel Bind<TModel>(IConfiguration configuration) where TModel : new()
{
var model = new TModel();
Bind(model, configuration);
return model;
}
public static void Bind(object model, IConfiguration configuration)
{
if (model == null)
{
return;
}
BindObjectProperties(model, configuration);
}
private static void BindObjectProperties(object obj, IConfiguration configuration)
{
foreach (var property in GetAllProperties(obj.GetType().GetTypeInfo()))
{
BindProperty(property, obj, configuration);
}
}
private static void BindProperty(PropertyInfo property, object propertyOwner, IConfiguration configuration)
{
configuration = configuration.GetConfigurationSection(property.Name);
if (property.GetMethod == null || !property.GetMethod.IsPublic)
{
// We don‘t support set only properties
return;
}
var propertyValue = property.GetValue(propertyOwner);
var hasPublicSetter = property.SetMethod != null && property.SetMethod.IsPublic;
if (propertyValue == null && !hasPublicSetter)
{
// Property doesn‘t have a value and we cannot set it so there is no
// point in going further down the graph
return;
}
propertyValue = BindType(
property.PropertyType,
propertyValue,
configuration);
if (propertyValue != null && hasPublicSetter)
{
property.SetValue(propertyOwner, propertyValue);
}
}
private static object BindType(Type type, object typeInstance, IConfiguration configuration)
{
var configValue = configuration.Get(null);
var typeInfo = type.GetTypeInfo();
if (configValue != null)
{
// Leaf nodes are always reinitialized
return CreateValueFromConfiguration(type, configValue, configuration);
}
else
{
var subkeys = configuration.GetConfigurationSections();
if (subkeys.Count() != 0)
{
if (typeInstance == null)
{
if (typeInfo.IsInterface || typeInfo.IsAbstract)
{
throw new InvalidOperationException(Resources.FormatError_CannotActivateAbstractOrInterface(type));
}
bool hasParameterlessConstructor = typeInfo.DeclaredConstructors.Any(ctor => ctor.IsPublic && ctor.GetParameters().Length == 0);
if (!hasParameterlessConstructor)
{
throw new InvalidOperationException(Resources.FormatError_MissingParameterlessConstructor(type));
}
try
{
typeInstance = Activator.CreateInstance(type);
}
catch (Exception ex)
{
throw new InvalidOperationException(Resources.FormatError_FailedToActivate(type), ex);
}
}
var collectionInterface = GetGenericOpenInterfaceImplementation(typeof(IDictionary<,>), type);
if (collectionInterface != null)
{
// Dictionary
BindDictionary(typeInstance, collectionInterface, configuration);
}
else
{
collectionInterface = GetGenericOpenInterfaceImplementation(typeof(ICollection<>), type);
if (collectionInterface != null)
{
// ICollection
BindCollection(typeInstance, collectionInterface, configuration);
}
else
{
// Something else
BindObjectProperties(typeInstance, configuration);
}
}
}
return typeInstance;
}
}
private static void BindDictionary(object dictionary, Type iDictionaryType, IConfiguration configuration)
{
var iDictionaryTypeInfo = iDictionaryType.GetTypeInfo();
// It is guaranteed to have a two and only two parameters
// because this is an IDictionary<K,V>
var keyType = iDictionaryTypeInfo.GenericTypeArguments[0];
var valueType = iDictionaryTypeInfo.GenericTypeArguments[1];
if (keyType != typeof(string))
{
// We only support string keys
return;
}
var addMethod = iDictionaryTypeInfo.GetDeclaredMethod("Add");
var subkeys = configuration.GetConfigurationSections().ToList();
foreach (var keyProperty in subkeys)
{
var keyConfiguration = keyProperty.Value;
var item = BindType(
type: valueType,
typeInstance: null,
configuration: keyConfiguration);
if (item != null)
{
addMethod.Invoke(dictionary, new[] { keyProperty.Key, item });
}
}
}
private static void BindCollection(object collection, Type iCollectionType, IConfiguration configuration)
{
var iCollectionTypeInfo = iCollectionType.GetTypeInfo();
// It is guaranteed to have a one and only one parameter
// because this is an ICollection<T>
var itemType = iCollectionTypeInfo.GenericTypeArguments[0];
var addMethod = iCollectionTypeInfo.GetDeclaredMethod("Add");
var subkeys = configuration.GetConfigurationSections().ToList();
foreach (var keyProperty in subkeys)
{
var keyConfiguration = keyProperty.Value;
try
{
var item = BindType(
type: itemType,
typeInstance: null,
configuration: keyConfiguration);
if (item != null)
{
addMethod.Invoke(collection, new[] { item });
}
}
catch
{
}
}
}
private static object CreateValueFromConfiguration(Type type, string value, IConfiguration configuration)
{
var typeInfo = type.GetTypeInfo();
if (typeInfo.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
{
return CreateValueFromConfiguration(Nullable.GetUnderlyingType(type), value, configuration);
}
var configurationValue = configuration.Get(key: null);
try
{
if (typeInfo.IsEnum)
{
return Enum.Parse(type, configurationValue);
}
else
{
return Convert.ChangeType(configurationValue, type);
}
}
catch (Exception ex)
{
throw new InvalidOperationException(Resources.FormatError_FailedBinding(configurationValue, type), ex);
}
}
private static Type GetGenericOpenInterfaceImplementation(Type expectedOpenGeneric, Type actual)
{
var interfaces = actual.GetTypeInfo().ImplementedInterfaces;
foreach (var interfaceType in interfaces)
{
if (interfaceType.GetTypeInfo().IsGenericType &&
interfaceType.GetGenericTypeDefinition() == expectedOpenGeneric)
{
return interfaceType;
}
}
return null;
}
private static IEnumerable<PropertyInfo> GetAllProperties(TypeInfo type)
{
var allProperties = new List<PropertyInfo>();
do
{
allProperties.AddRange(type.DeclaredProperties);
type = type.BaseType.GetTypeInfo();
}
while (type != typeof(object).GetTypeInfo());
return allProperties;
}
}
ConfigurationBinder
我们对其中几个方法，进行简单的说明：
- GetAllProperties。系统获取属性的时候，不光要获取当前类的属性也要获取基类的属性。
- 绑定属性时，将需要被绑定的对象作为参数传入进去，由于是引用类型，所以不用返回值也能更改其属性、类似的还有ArrayList等。
- BindProperty(PropertyInfo property, object propertyOwner, IConfiguration configuration)。此处的propertyOwner值会被调用方法中修改。
- 将字符串转换成枚举的方法：
- Enum.Parse(type, configurationValue);、
- 将对象转变类型的方法：
- Convert.ChangeType(configurationValue, type);
- 判断泛型的方法
-
private static Type GetGenericOpenInterfaceImplementation(Type expectedOpenGeneric, Type actual) { var interfaces = actual.GetTypeInfo().ImplementedInterfaces; foreach (var interfaceType in interfaces) { if (interfaceType.GetTypeInfo().IsGenericType && interfaceType.GetGenericTypeDefinition() == expectedOpenGeneric) { return interfaceType; } } return null; }
-
时间： 2024-08-06 03:45:05