一． 控制反转和容器的思想
1. 面向对象设计里，讲究“接口与实现分离”
//定义接口
publicinterfaceIPingJiaDaoForSpring {
//插入一条记录
publicbooleaninsert(PingJia pingJia);
}
//接口实现
publicclassPingJiaDaoImplForSpringimplementsIPingJiaDaoForSpring {
@Override
publicbooleaninsert(PingJia pingJia) {
//实现insert的具体方法
}
2. 在代码当中调用
publicclassStoreServiceForSpring {
//在此处写死了实现是PingJiaDaoImplForSpring()
privateIPingJiaDaoForSpringpingJiaDao=newPingJiaDaoImplForSpring();
publicbooleanaddPingJia(PingJia pingJia) {
returnpingJiaDao.insert(pingJia);
}
}
3. 不同组织有不同的实现方式
privateIPingJiaDaoForSpringpingJiaDao=new其他实现();
问题：需要维护多个StoreServiceForSpring，每个各自创建和管理自己的依赖，对象之间的耦合性很高。
4. 使用一个容器来管理这些组件
publicclassContainer {
publicstaticContainerinstance;
privateMap<String, Object>components;
publicContainer() {
components=newHashMap<String, Object>();
instance=this;
IPingJiaDaoForSpring pinjiaDao =newPingJiaDaoImplForSpring();
components.put("pinjiaDao", pinjiaDao);
IStoreServiceForSpring storeService =newStoreServiceForSpring();
components.put("storeService", storeService);
}
publicObject getComponent(String id) {
returncomponents.get(id);
}
}
在组件中使用容器生成组件：privateIPingJiaDaoForSpringpingJiaDao= (IPingJiaDaoForSpring) Container.instance
.getComponent("pinjiaDao");
5. 使用容器后，可以用容器来生成需要的组件：
publicclassMain {
publicstaticvoidmain(String args[]) {
IStoreServiceForSpring storeService = (IStoreServiceForSpring) Container.instance
.getComponent("storeservice");
PingJia pingJia =newPingJia();
pingJia.setPingJiaId("123456");
storeService.addPingJia(pingJia);
}
}
6. 使用服务定位器查找组件（主动查找）
publicclassServiceLocator {
publicstaticContainercontainer= Container.instance;
publicstaticIPingJiaDaoForSpring getPingJiaDao() {
return(IPingJiaDaoForSpring)container.getComponent("pinjiaDao");
}
}
在组件中使用查找器：privateIPingJiaDaoForSpringpingJiaDao= ServiceLocator.getPingJiaDao();
7. 应用控制反转和依赖注入
在组件中使用查找器查找组件时，组件依旧需要知道如何查找资源，然后向容器发起请求查找资源，容器返回资源，
使用控制反转原则：容器主动将资源推送到所管理的组件中，组件只是选择一种合适的方式接受资源。
publicContainer() {
//components = new HashMap<String, Object>();
//instance = this;
IPingJiaDaoForSpring pingJiaDao =newPingJiaDaoImplForSpring();
components.put("pinjiaDao", pingJiaDao);
StoreServiceForSpringstoreService =newStoreServiceForSpring();
StoreServiceForSpring storeService1 =newStoreServiceForSpring(pingJiaDao);
storeService.setPingJiaDao(pingJiaDao);//设置资源
components.put("storeService", storeService);
components.put("storeService1", storeService1);
}
依赖注入的三种方式：接口注入，setter注入，构造器注入
8. 使用配置文件来配置容器
publicContainer() {
components=newHashMap<String, Object>();
// instance = this;
Properties properties =newProperties();
try{
properties.load(newFileInputStream("components.properties"));
for(Map.Entryentry : properties.entrySet()) {
String key = (String) entry.getKey();
String value = (String) entry.getValue();
processEntry(key, value);
}
}catch(Exception e) {
e.printStackTrace();
}
IPingJiaDaoForSpring pingJiaDao =newPingJiaDaoImplForSpring();
components.put("pinjiaDao", pingJiaDao);
StoreServiceForSpring storeService =newStoreServiceForSpring();
StoreServiceForSpring storeService1 =newStoreServiceForSpring(
pingJiaDao);
storeService.setPingJiaDao(pingJiaDao);
components.put("storeService", storeService);
components.put("storeService1", storeService1);
}
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