Spring 架构主要有两大特点:
IOC /DI: 控制反转/依赖注入
AOP 切面编程 .
今天主要是实现IOC这一特点.
主要的逻辑如下:
User 用户类.
UserDAO User类的访问接口.
UserDAOImpl 实现UserDAO 接口以实现拓展.
UserService 包含一系列的用户功能 ,如addUser
关于以上类的代码:
package com.bjsxt.model; public class User { private String username; private String password; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } }
package com.bjsxt.dao; import com.bjsxt.model.User; public interface UserDAO { public void save(User user); }
package com.bjsxt.dao.impl; import com.bjsxt.dao.UserDAO; import com.bjsxt.model.User; public class UserDAOImpl implements UserDAO { public void save(User user) { //Hibernate //JDBC //XML //NetWork System.out.println("user saved!"); } }
package com.bjsxt.service; import com.bjsxt.dao.UserDAO; import com.bjsxt.model.User; public class UserService { private UserDAO userDAO; public void add(User user) { userDAO.save(user); } public UserDAO getUserDAO() { return userDAO; } public void setUserDAO(UserDAO userDAO) { this.userDAO = userDAO; } }
import com.bjsxt.dao.UserDAO; import com.bjsxt.dao.impl.UserDAOImpl; import com.bjsxt.model.User; import com.bjsxt.service.UserService; import com.bjsxt.spring.BeanFactory; import com.bjsxt.spring.ClassPathXmlApplicationContext; public class Test { public static void main(String[] args)throws Exception{ UserService service =new UserService(); UserDAO userdao =new UserDAOImpl(); service.setUserDAO(userdao); User u =new User(); service.add(u); } }
为了实现IOC 的装配功能, 比如说我不想在 代码中体现new 的是哪种UserDAO的实现, 而是直接在配置文件中进行设置.
配置文件beans.xml如下:
<beans> <bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl" /> <bean id="userService" class="com.bjsxt.service.UserService" > <property name="userDAO" bean="u"/> </bean> </beans>
这里可以根据bean 的id userService 找到 所属的UserService类, 在属性userDAO中 ,设置其为id 为 "u"的bean . 而上述文件中的 id 为"u"的bean , 就是UserDAOImp .
当然, 需要借助Factory 接口 和该接口的实现类 ClassPathXmlApplicationContext .
package com.bjsxt.spring; public interface BeanFactory { public Object getBean(String id); }
package com.bjsxt.spring; 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>(); //IOC Inverse of Control DI Dependency Injection public ClassPathXmlApplicationContext() throws Exception { SAXBuilder sb=new SAXBuilder(); Document doc=sb.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml")); //构造文档对象 Element root=doc.getRootElement(); //获取根元素HD List list=root.getChildren("bean");//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"); Object o = Class.forName(clazz).newInstance(); System.out.println(id); System.out.println(clazz); beans.put(id, o); for(Element propertyElement : (List<Element>)element.getChildren("property")) { String name = propertyElement.getAttributeValue("name"); //userDAO String bean = propertyElement.getAttributeValue("bean"); //u Object beanObject = beans.get(bean);//UserDAOImpl instance 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); } } } public Object getBean(String id) { return beans.get(id); } }
ClassPathXmlApplicationContext 利用反射机制, 在构造函数中根据xml文件内容实现装配功能.
新的test函数:
import com.bjsxt.dao.UserDAO; import com.bjsxt.dao.impl.UserDAOImpl; import com.bjsxt.model.User; import com.bjsxt.service.UserService; import com.bjsxt.spring.BeanFactory; import com.bjsxt.spring.ClassPathXmlApplicationContext; public class Test { public static void main(String[] args)throws Exception{ BeanFactory factory =new ClassPathXmlApplicationContext(); UserService service =(UserService)factory.getBean("userService"); // UserDAO userdao =new UserDAOImpl(); // service.setUserDAO(userdao); User u =new User(); service.add(u); } }
Spring 架构的简单模拟实现,布布扣,bubuko.com
原文地址:http://blog.csdn.net/ltianchao/article/details/26586831