Spring开始学习了。我是跟着马士兵的视频自学的。
首先模拟Spring对配置文件的操作。
需要的额外的包:
jdom.jar,junit.jar.
源码:
model:
User.java
public class User { private String name; 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; } }
DAO:
UserDAO.java
package com.bjsxt.dao; import com.bjsxt.model.User; public interface UserDAO { public void save(User u); }
Implments:
UserDAOImpl.java
package com.bjsxt.dao.impl; import com.bjsxt.dao.UserDAO; import com.bjsxt.model.User; public class UserDAOImpl implements UserDAO{ @Override public void save(User u) { System.out.println("user saved!"); } }
Service:
UserService.java
package com.bjsxt.service; import com.bjsxt.dao.UserDAO; import com.bjsxt.dao.impl.UserDAOImpl; import com.bjsxt.model.User; public class UserService { private UserDAO userDAO; //依赖于beans.xml通过ClassPathXmlApplicationContext.java注入 public UserDAO getUserDAO() { return userDAO; } public void setUserDAO(UserDAO userDAO) { this.userDAO = userDAO; } public void add(User user){ this.userDAO.save(user); } }
这个是beans.xml,也是Spring框架的配置文件:
<bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl"/> <bean id ="userService" class="com.bjsxt.service.UserService"> <property name="userDAO" bean="u"></property> </bean> </beans>
BeanFactory.java
下面就是模拟Spring对beans.xml的读取和对其内容的操作:
package com.bjsxt.spring; public interface BeanFactory { public Object getBean(String name); }
ClassPathXMLApplication.java
对BeanFactory.java的interface的实现:
package com.bjsxt.spring; import java.lang.reflect.Method; import java.util.HashMap; import java.util.List; import java.util.Map; import org.jdom2.Document; import org.jdom2.Element; import org.jdom2.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("beans.xml")); Element root = doc.getRootElement();//获取根元素 List list = root.getChildren("bean"); 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); System.out.println(""); Object o = Class.forName(clazz).newInstance(); 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]);//setUserDAO m.invoke(o, beanObject); } } } @Override public Object getBean(String name) { return beans.get(name); } }
下面是测试类,另外再建立一个源文件test的文件夹:
package com.bjsxt.service; import org.junit.Test; import com.bjsxt.model.User; import com.bjsxt.spring.BeanFactory; import com.bjsxt.spring.ClassPathXmlApplicationContext; public class UserServiceTest { @Test public void testAdd() throws Exception { BeanFactory applicationContext = new ClassPathXmlApplicationContext(); UserService service = (UserService)applicationContext.getBean("userService"); User u = new User(); u.setUsername("zhangsan"); u.setPassword("zhangsan"); service.add(u); } }
至此视频上的代码,结束,我觉得有些许收获。
此小项目的核心是:ClassPathXMLApplication.java的内容。实现了对XML文件的处理,将<key,value>的值放到Map中,当在main中 ,执行到:
时,new ClassPathXMLApplicationContext();调用构造方法的时候,就已经对XML进行读取了,并且对每一个<id,class>做了反射。
所以当调用applicationContext.getBean("UserService");的时候,就会生成UserService类 并且其变量名为 service。
将User的类的变量add到service中,就OK了。
这是我对上述源码的一个分析,暂时就这么多了吧。