Spring 入门之注解开发 IOC 与 DI

案例演示：

1. 创建Spring配置类代替原来的applicationContext.xml

package com.daidai.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.daidai.impl")
public class SpringConfig {
}

@Configuration 表明是spring配置文件
@ComponentScan 表明要扫描bean的位置

2. 创建BookService接口及其实现类

package com.daidai;

public interface BookService {
    void startService();
}


package com.daidai.impl;

import com.daidai.BookService;
import org.springframework.stereotype.Component;

@Component("bookService")
public class BookServiceImpl implements BookService {

    @Override
    public void startService() {
        System.out.println("bookservice...");
    }
}

@Component(“bookService”) 相当于 < bean id=“bookService” class=“com.daidai.impl.BookServiceImpl”/>

3. 创建测试

package com.daidai.app;

import com.daidai.impl.BookServiceImpl;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class App1 {
    public static void main(String[] args) {

        ApplicationContext context = new AnnotationConfigApplicationContext(com.daidai.config.SpringConfig.class);
        BookServiceImpl bookService = context.getBean("bookService", BookServiceImpl.class);
        bookService.startService();
    }
}

案例演示：

1. 创建Spring配置文件

package com.daidai.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.daidai.impl")
public class SpringConfig {
}

2. 创建BookDao、BookService接口及其实现类

package com.daidai;

public interface BookDao {
    void save();
}


package com.daidai;

public interface BookService {
    void startService();
}


package com.daidai.impl;

import com.daidai.BookDao;
import org.springframework.stereotype.Component;

@Component("bookDao")
public class BookDaoImpl implements BookDao {
    @Override
    public void save() {
        System.out.println("bookdao...");
    }
}


package com.daidai.impl;

import com.daidai.BookDao;
import com.daidai.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component("bookService")
public class BookServiceImpl implements BookService {

    @Autowired
    BookDao bookDao;

    @Override
    public void startService() {
        System.out.println("bookservice...");
        bookDao.save();
    }
}

1. @Autowired是按照类型注入，可以写在属性上，也可也写在setter方法上，最简单的处理方式是写在属性上并将setter方法删除掉
2. 为什么setter方法可以删除呢?
   自动装配基于反射设计创建对象并通过暴力反射为私有属性进行设值普通反射只能获取public修饰的内容，暴力反射除了获取public修饰的内容还可以获

3. 创建测试

package com.daidai.app;

import com.daidai.impl.BookServiceImpl;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class App1 {
    public static void main(String[] args) {

        ApplicationContext context = new AnnotationConfigApplicationContext(com.daidai.config.SpringConfig.class);
        BookServiceImpl bookService = context.getBean("bookService", BookServiceImpl.class);
        bookService.startService();


    }
}