01_2_模拟spring装载bean
1. xml配置文件内容
beans.xml
<beans> <bean id="u" class="com.wysj.dao.impl.UserDAOImpl"></bean> <bean id="userService" class="com.wysj.service.UserService"> <property name="userDAO" bean="u"></property> </bean> </beans>
2. 实体类
User.java
package com.wysj.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;
}
}
3. dao及其实现
UserDAO.java
package com.wysj.dao;
import com.wysj.model.User;
public interface UserDAO {
public void save(User u);
}
UserDAOImpl.java
package com.wysj.dao.impl;
import com.wysj.dao.UserDAO;
import com.wysj.model.User;
public class UserDAOImpl implements UserDAO{
@Override
public void save(User u) {
System.out.println("user saved!");
}
}
4. 业务逻辑类
UserService.java
package com.wysj.service;
import com.wysj.dao.UserDAO;
import com.wysj.dao.impl.UserDAOImpl;
import com.wysj.model.User;
public class UserService {
private UserDAO userDAO;
public void add(User u) {
this.userDAO.save(u);
}
public UserDAO getUserDAO() {
return userDAO;
}
public void setUserDAO(UserDAO userDAO) {
this.userDAO = userDAO;
}
}
5. spring读取bean工厂及其实现类
BeanFactory.java
package com.wysj.spring;
public interface BeanFactory {
public Object getBean(String name);
}
ClassPathXmlApplicationContext.java
package com.wysj.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 static final int Element = 0;
private Map<String, Object> beans = new HashMap<String, Object>();
@Override
public Object getBean(String name) {
// TODO Auto-generated method stub
return beans.get(name);
}
public ClassPathXmlApplicationContext() throws Exception {
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(ClassPathXmlApplicationContext.class.getClassLoader().getResourceAsStream("beans.xml"));
Element root = doc.getRootElement();
List list = root.getChildren("bean");
for (int i = 0; i < list.size(); i++) {
Element e = (Element) list.get(i);
String id = e.getAttributeValue("id");
String clazz = e.getAttributeValue("class");
System.out.println(id + ":" + clazz);
Object o = Class.forName(clazz).newInstance();
beans.put(id, o);
for(Element propertyElement : (List<Element>)e.getChildren("property")) {
String name = propertyElement.getAttributeValue("name");//userDAO
String bean = propertyElement.getAttributeValue("bean"); //u
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]);//setUserDAO
m.invoke(o, beanObject);
}
}
}
}