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(); } }