我想在java中创建一个简单的依赖注入容器。我可以通过以下方式使用的东西:
DI.register(ITheInterface, ClassImplementingInterface);
obj = DI.create(ITheInterface);
实施register
&的实际代码怎么样? create
看起来像?
更新
为什么我试着理解@Bill提供的链接,我想知道我的尝试有什么不对:
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();
}
}
测试代码:
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());
}
}
我得到的错误:
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
我认为当我上课public
时它会起作用。还有一个问题,我想基于通用接口创建类。例如
IDataMapper<Event>
==&gt; EventDataMapper
IDataMapper<Venue>
==&gt; VenueDataMapper
目前,如果我这样做
di.register(IDataMapper<Event>.class, EventDataMapper.class);
我得到IDataMapper
而Event
未解析为变量
答案 0 :(得分:3)
您可以找到JSR 330 here
的简单实现这很容易理解。
回答您的修改:
Test1是一个包私有类Container在另一个包中没有访问Test1构造函数。您可以通过执行以下操作来解决此问题:
Constructor c = this.classMap.get(forInterface).getDeclaredConstructor();
c.setAccessible(true);
return c.newInstance();