Spring.Net学习笔记十(打造简易的依赖注入框架)

      之前我们学习里一个简易的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 。原文地址：http://www.cnblogs.com/GoodHelper/archive/2009/11/02/SpringNet_MyDi.html

      我感觉这个很有必要对应IOC框架的理解，知道注入的工作原理，对应实际的应用是很有帮助的。

　　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:ExerciseSpringNetStep1SpringNet_Lesson9SpringNetMyDiObjects.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();
        }
    }