spring IoC

控制反转（ IoC  =  Inversion  of  Control ），即用容器控制程序间的（关联、继承等）关系。IoC的目标是为了提升组件重用，降低耦合。

下面用一个简单的例子说明其用途。

1、接口：

public interface Action {

public String execute(String msg);

}

2、子类：

public class UpperAction implements Action{

@Override

public String execute(String msg) {

return "Upper : " + msg.toUpperCase();

}

}

public class LowerAction implements Action {

@Override

public String execute(String msg) {

return "Lower : " + msg.toLowerCase();

}

}

3、容器：

import java.util.HashMap;

import java.util.Map;

public class BeanFactory {

private Map<String, String>  mapping = new HashMap<String, String>();

public BeanFactory() {

refresh();

}

/**

* 读取配置文件，缓存所有的bean

*/

private void refresh() {

mapping.put("1", "test.ioc.UpperAction");

mapping.put("2", "test.ioc.LowerAction");

// cacheBean("1", "test.ioc.UpperAction");

// cacheBean("2", "test.ioc.LowerAction");

}

public Object getInstance(String className) {

Class<?> clazz = null;

Object obj = null;

try {

clazz = Class.forName(className);

obj = clazz.newInstance();

} catch (ClassNotFoundException e) {

e.printStackTrace();

} catch (InstantiationException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

return obj;

}

public Object cacheBean(String id, String className) {

if(!mapping.containsKey(id)) {

mapping.put(id, className);

}

return getInstance(className);

}

public Object getBean(String id) {

Object obj = cacheBean(id, mapping.get(id));

if(obj == null) {

System.out.println("没有找到相关的bean...");

}

return obj;

}

}

4、测试用例：

public class TestCase {

public static void main(String[] args) {

BeanFactory ioc = new BeanFactory();

Action action = (Action) ioc.getBean("1");

System.out.println(action.execute("hahahHHH"));

}

}