Sprig 之 模拟Spring IOC
IOC是Spring的核心,其他的我也不多说了,直接进入主题。
1. 创建实体类User.java
public class User {
private int id;
private String name;
private String age;
// ….舍略getter/setter
}
2. 创建Dao层UserDao.java/UserDaoImpl.java
public interface UserDao {
public void add();
}
public class UserDaoImpl implements UserDao {
@Override
public void add() {
}
}
3. 创建Service层UserService..java
public class UserService {
private UserDao userDao;
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
}
4. 定义一个BeanFactory接口和Spring的取名一样
public interface BeanFactory {
public Object getBean(String name);
}
5. 定义ClassPathXmlApplicationContext 实现BeanFactory接口
这也是和Spring中的取名相同,具体实现如下:
在初始化的时候读取配置文件,根据反射机制实例化相应的对象及注入相关的依赖对象。
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
public class ClassPathXmlApplicationContext implements BeanFactory {
private Map<String,Object> beans = new HashMap<String, Object>();
public ClassPathXmlApplicationContext() throws Exception{
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(this.getClass().getClassLoader().getResourceAsStream("bean.xml"));
Element root = doc.getRootElement(); //获取根元素
List list = (List) root.getChildren("bean"); //获取名字为bean的所有元素
for(int i = 0;i<list.size();i++){
Element element = (Element)list.get(i);
String id = element.getAttributeValue("id");
String clazz = element.getAttributeValue("class");
System.out.println(id + ":" + clazz);
Object o = Class.forName(clazz).newInstance();
beans.put(id, o);
for(Element propertyElement : (List<Element>)element.getChildren("property")){
String name = propertyElement.getAttributeValue("name");
String bean = propertyElement.getAttributeValue("bean");
Object beanObject = beans.get(bean);
String methodName = "set" + name.substring(0,1).toUpperCase() + name.substring(1);
System.out.println("method name = " + methodName);
Method m = o.getClass().getMethod(methodName,beanObject.getClass().getInterfaces()[0]);
m.invoke(o, beanObject);
}
}
}
@Override
public Object getBean(String name) {
return beans.get(name);
}
}
6. 配置文件bean.xml如下:
<beans>
<bean id="user" class="com.zsw.spring.ioc.User" />
<bean id="userDao" class="com.zsw.spring.ioc.UserDaoImpl"></bean>
<bean id="userService" class="com.zsw.spring.ioc.UserService">
<property name="userDao" bean="userDao" />
</bean>
</beans>
7. 最后编写测试类
public class UserServiceTest {
public static void main(String[] args) throws Exception {
BeanFactory factory = new ClassPathXmlApplicationContext();
UserDao service = (UserDao) factory.getBean("userDao");
}
}