Spring.NET学习笔记9——打造简易的依赖注入框架(练习篇)

　我们在第三篇中学习里一个简易的IoC框架。今天我们接着上次的程序，实现带参数构造函数对象的实例和属性的注入 。
　　我们知道可以通过反射获取类的构造函数及参数(GetConstructors方法)；可以获取属性和属性的类型(GetProperties方法)。通过Activator的CreateInstance(Type type, params object[] args)方法可以创建带参数构造函数的实例。通过SetValue方法可以给属性赋值，这样一来，我们就上次的代码稍加改造就可以实现属性的注入了。

　　下面是完成的代码：

public class Person
{
public string Name { get; set; }
public int Age { get; set; }
}

public class PersonDao
{
private int intProp;

public PersonDao(int intProp)
{
this.intProp = intProp;
}

public Person Entity { get; set; }

public override string ToString()
{
return "构造函数参数intProp为：" + this.intProp;
}
}

public class ObjectFactory
{
private IDictionary<string, object> objectDefine = new Dictionary<string, object>();

private ObjectFactory(string fileName)
{
InstanceObjects(fileName);  // 实例IoC容器
DiObjects(fileName);  // 属性注入
}

private static ObjectFactory instance;

private static object lockHelper = new object();

public static ObjectFactory Instance(string fileName)
{
if (instance == null)
{
lock (lockHelper)
{
instance = instance ?? new ObjectFactory(fileName);
}
}
return instance;
}

/**//// <summary>
/// 实例IoC容器
/// </summary>
/// <param name="fileName"></param>
private void InstanceObjects(string fileName)
{
XElement root = XElement.Load(fileName);
var objects = from obj in root.Elements("object")
select obj;

//无参构造函数
objectDefine = objects.Where(obj =>
obj.Element("constructor-arg") == null).ToDictionary(
k => k.Attribute("id").Value,
v =>
{
string typeName = v.Attribute("type").Value;
Type type = Type.GetType(typeName);
return Activator.CreateInstance(type);
}
);

//有参构造函数
foreach (XElement item in objects.Where(obj =>
obj.Element("constructor-arg") != null))
{
string id = item.Attribute("id").Value;
string typeName = item.Attribute("type").Value;
Type type = Type.GetType(typeName);
var args = from property in type.GetConstructors()[0].GetParameters()
join el in item.Elements("constructor-arg")
on property.Name equals el.Attribute("name").Value
select Convert.ChangeType(el.Attribute("value").Value,
property.ParameterType);
object obj = Activator.CreateInstance(type, args.ToArray());
objectDefine.Add(id, obj);
}
}

/**//// <summary>
/// 属性注入
/// </summary>
/// <param name="fileName"></param>
private void DiObjects(string fileName)
{
XElement root = XElement.Load(fileName);
var objects = from obj in root.Elements("object")
select obj;

foreach (KeyValuePair<string,object> item in objectDefine)
{
foreach (var el in objects.Where(e =>
e.Attribute("id").Value == item.Key).Elements("property"))
{
Type type = item.Value.GetType();
//获取属性
foreach (PropertyInfo property in type.GetProperties())
{
if (property.Name == el.Attribute("name").Value)
{
if (el.Attribute("value") != null)
{
//设置属性值
property.SetValue(item.Value,
Convert.ChangeType(el.Attribute("value").Value,
property.PropertyType), null);
}
else if (el.Attribute("ref") != null)
{
object refObject = null;

if (objectDefine.ContainsKey(el.Attribute("ref").Value))
{
refObject = objectDefine[el.Attribute("ref").Value];
}
//设置关联对象属性
property.SetValue(item.Value, refObject, null);
}
}
}
}
}
}

/**//// <summary>
/// 获取对象
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public object GetObject(string id)
{
object result = null;

if (objectDefine.ContainsKey(id))
{
result = objectDefine[id];
}

return result;
}
}

<?xml version="1.0" encoding="utf-8" ?>

<objects>

<object id="person" type="SpringNetMyDi.Person, SpringNetMyDi">
<!--属性值类型注入-->
<property name="Name" value="Liu Dong"/>
<property name="Age" value="27"/>

</object>

<object id="personDao" type="SpringNetMyDi.PersonDao, SpringNetMyDi">
<!--构造器注入-->
<constructor-arg name="intProp" value="1"/>

<property name="Entity" ref="person" />

</object>

</objects>

class Program
{
static void Main(string[] args)
{
ObjectFactory factory = ObjectFactory.Instance(@"F:/Exercise/SpringNet/Step1/SpringNet_Lesson9/SpringNetMyDi/Objects.xml");

PersonDao dao = (PersonDao)factory.GetObject("personDao");

Console.WriteLine("姓名：" + dao.Entity.Name);
Console.WriteLine("年龄：" + dao.Entity.Age);
Console.WriteLine(dao);

Console.ReadLine();
}
}