[Spring系列01]Spring IOC/DI模拟

package com.ctsh.dao;

import com.ctsh.model.User;

public interface UserDAO {
    public void save(User user);
}

package com.ctsh.dao.impl;

import com.ctsh.dao.UserDAO;
import com.ctsh.model.User;

public class UserDAOImpl implements UserDAO {

    public void save(User user) {
        System.out.println("user saved!");
    }

}

package com.ctsh.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.ctsh.service;

import com.ctsh.dao.UserDAO;
import com.ctsh.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;
    }
}

package com.ctsh.spring;

public interface BeanFactory {
    public Object getBean(String id);
}

package com.ctsh.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();
        List<Element> 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");
            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);
                Method m = o.getClass().getMethod(methodName,beanObject.getClass().getInterfaces()[0]);
                //对对象o（即com.ctsh.service.UserService）调用m方法（即setUserDAO（com.ctsh.dao.UserDAO）方法），
                //其中传入参数为beanObject（即com.ctsh.dao.impl.UserDAOImpl）
                m.invoke(o, beanObject);
                
            }
        }

    }

    public Object getBean(String id) {
        return beans.get(id);
    }

}

<beans>
    <bean id="u" class="com.ctsh.dao.impl.UserDAOImpl" />
    <bean id="userService" class="com.ctsh.service.UserService" >
        <property name="userDAO" bean="u"/>
    </bean>
</beans>

package com.ctsh.service;
import org.junit.Test;

import com.ctsh.model.User;
import com.ctsh.service.UserService;
import com.ctsh.spring.BeanFactory;
import com.ctsh.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("123456");
        service.add(u);
    }

}