用Java創建簡單的依賴注入容器，動態創建對象

Question

我想在java中創建一個簡單的依賴注入容器。我的東西可以通過以下方式使用：

DI.register(ITheInterface, ClassImplementingInterface); 
obj = DI.create(ITheInterface); 

如何可能實際的代碼實現register & create樣子？

UPDATE

爲什麼我試着去理解由@Bill提供的鏈接，我想知道什麼是錯我的嘗試：

public class Container { 

    protected static Container instance; 
    protected Hashtable<Class<?>, Class<?>> classMap; 

    protected Container() { 
     this.classMap = new Hashtable<Class<?>, Class<?>>(); 
    } 

    public static Container getInstance() { 
     if (Container.instance == null) 
      Container.instance = new Container(); 
     return Container.instance; 
    } 

    public void register(Class<?> forInterface, Class<?> toUse) { 
     this.classMap.put(forInterface, toUse); 
    } 

    public Object create(Class<?> forInterface) throws Exception { 
     if (!this.classMap.containsKey(forInterface)) 
      throw new Exception("Dependency Ingection Container does not have a class registered for use with " + forInterface.getName()); 
     return this.classMap.get(forInterface).newInstance(); 
    } 
} 

測試代碼：

interface ITest { 
    public String getName(); 
    public void setName(String name); 
} 

class Test1 implements ITest { 

    protected String name; 

    @Override 
    public String getName() { 
     return this.name; 
    } 

    @Override 
    public void setName(String name) { 
     this.name = name; 
    } 

} 

public class Test { 
    public static void main(String[] args) throws Exception { 
     Container di = Container.getInstance(); 
     di.register(ITest.class, Test1.class); 
     ITest t1 = (ITest)di.create(ITest.class); 
     t1.setName("Yay!!!"); 
     System.out.println(t1.getName()); 
    } 
} 

我得到的錯誤：

Exception in thread "main" java.lang.IllegalAccessException: Class dependencyinjection.Container can not access a member of class Test1 with modifiers "" 
    at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:95) 
    at java.lang.Class.newInstance0(Class.java:366) 
    at java.lang.Class.newInstance(Class.java:325) 
    at dependencyinjection.Container.create(Container.java:27) 
    at Test.main(Test.java:32) 

更新2

我想，當我把課public它會奏效。還有一個問題，我想創建基於通用接口的類。例如。

• IDataMapper<Event> ==>EventDataMapper
• IDataMapper<Venue> ==>VenueDataMapper

目前，如果我做

di.register(IDataMapper<Event>.class, EventDataMapper.class); 

我得到IDataMapper和Event都沒有解決一個變量

Answer 1

你可以找到一個簡單的實現JSR 330 here

這很容易理解。

爲了回答您的編輯：

Test1的是包私有類Container是另一個軟件包中沒有訪問Test1的構造。您可以解決此通過執行以下操作：

Constructor c = this.classMap.get(forInterface).getDeclaredConstructor(); 
c.setAccessible(true); 
return c.newInstance();