public interface BookDao {
public void save();
}
public class BookDaoImpl implements BookDao {
public void save() {
System.out.println("book dao save ...");
}
}
public interface BookService {
public void save();
}
public class BookServiceImpl implements BookService {
private BookDao bookDao = new BookDaoImpl();
public void save() {
System.out.println("book service save ...");
bookDao.save();
}
}
public class App {
public static void main(String[] args) {
//获取IOC容器
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
}
}
从容器中获取对象进行方法调用
java复制代码
public class App {
public static void main(String[] args) {
//获取IOC容器
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
// BookDao bookDao = (BookDao) ctx.getBean("bookDao");
// bookDao.save();
BookService bookService = (BookService) ctx.getBean("bookService");
bookService.save();
}
}
public interface BookDao {
public void save();
}
public class BookDaoImpl implements BookDao {
public void save() {
System.out.println("book dao save ...");
}
}
public class AppForInstanceBook {
public static void main(String[] args) {
ApplicationContext ctx = new
ClassPathXmlApplicationContext("applicationContext.xml");
BookDao bookDao = (BookDao) ctx.getBean("bookDao");
bookDao.save();
}
}
④类中提供构造函数测试
java复制代码
public class BookDaoImpl implements BookDao {
public BookDaoImpl() {
System.out.println("book dao constructor is running ....");
}
public void save() {
System.out.println("book dao save ...");
}
}
通过控制台的输出可以说明Spring容器在创建对象时走的是构造函数
将构造函数改为private进行测试：
从上图中可以看出Spring能访问到类中的私有构造方法，所以Spring的底层用的是反射
在构造函数中添加一个参数进行测试：
程序报错，则Spring底层使用的是无参构造
2.1.2实例工厂实例化
搭建实例工厂
①准备UserDao接口和UserDaoImpl实现类
java复制代码
public interface UserDao {
public void save();
}
public class UserDaoImpl implements UserDao {
public void save() {
System.out.println("user dao save ...");
}
}
②创建工厂类OrderDaoFactory并提供一个普通方法
java复制代码
public class UserDaoFactory {
public UserDao getUserDao(){
return new UserDaoImpl();
}
}
③编写AppForInstanceUser运行类，在类中通过工厂获取对象
java复制代码
public class AppForInstanceUser {
public static void main(String[] args) {
//创建实例工厂对象
UserDaoFactory userDaoFactory = new UserDaoFactory();
//通过实例工厂对象创建对象
UserDao userDao = userDaoFactory.getUserDao();
userDao.save();
}
