@Autowired自动装配

自动装配：Spring利用依赖注入(DI),完成对IOC容器中各个组件的依赖关系的赋值。
新建controller,service,dao包，在各个包下，分别新建BookController,BookService,BookRepository类。

package com.ljessie.controller;

import com.ljessie.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;

@Controller
public class BookController {
    @Autowired
    private BookService bookService;
}

package com.ljessie.service;

import com.ljessie.dao.BookRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import javax.inject.Inject;

@Service
public class BookService {

    @Autowired
    private BookRepository bookRepository;

    public void print(){
        System.out.println(bookRepository);
    }

    @Override
    public String toString() {
        return "BookService{" +
                "bookRepository=" + bookRepository +
                '}';
    }
}

package com.ljessie.dao;

import org.springframework.stereotype.Repository;

//名字是默认的首字母小写
@Repository
public class BookRepository {

    private String lable = "1";

    public String getLable() {
        return lable;
    }

    public void setLable(String lable) {
        this.lable = lable;
    }

    @Override
    public String toString() {
        return "BookRepository{" +
                "lable='" + lable + '\'' +
                '}';
    }
}

新建MainConfigOfAutowired类

package com.ljessie.config;

import com.ljessie.bean.Car;
import com.ljessie.bean.Color;
import com.ljessie.dao.BookRepository;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

@Configuration
@ComponentScan({"com.ljessie.service","com.ljessie.controller","com.ljessie.dao"})
public class MainConfigOfAutowired {
}

新建IOCTest_Autowired

package com.ljessie.test;

import com.ljessie.bean.Boss;
import com.ljessie.bean.Car;
import com.ljessie.bean.Color;
import com.ljessie.config.MainConfigOfAutowired;
import com.ljessie.config.MainConfigOfLifeCycle;
import com.ljessie.dao.BookRepository;
import com.ljessie.service.BookService;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class IOCTest_Autowired {

    @Test
    public void test01(){
        //创建IOC容器
        AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfigOfAutowired.class);
        System.out.println("容器创建完成");
        BookService bean = annotationConfigApplicationContext.getBean(BookService.class);
        BookRepository bean1 = annotationConfigApplicationContext.getBean(BookRepository.class);
        System.out.println(bean1.toString());
        System.out.println(bean.toString());
        System.out.println(annotationConfigApplicationContext);
        //关闭容器
        annotationConfigApplicationContext.close();
    }
}

运行test01()

容器创建完成
BookRepository{lable='1'}
BookService{bookRepository=BookRepository{lable='1'}}
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 10:52:38 CST 2020]; root of context hierarchy
一月 19, 2020 10:52:38 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 10:52:38 CST 2020]; root of context hierarchy

Autowired自动注入：
1.默认优先按照类型去容器中找对应的组件，annotationConfigApplicationContext.getBean(BookRepository.class);如果找到，就赋值。
2.如果找到多个相同类型的组件，再将属性的名称作为组件的id去容器中查找annotationConfigApplicationContext.getBean("bookRepository")
@Qualifier("bookRepository")：使用@Qualifier指定需要装配组件的id，而不是使用属性。
在MainConfigOfAutowired添加方法

@Bean("bookRepository2")
    public BookRepository bookRepository(){
        BookRepository bookRepository = new BookRepository();
        bookRepository.setLable("2");
        return  bookRepository;
    }

在BookService里面，给bookRepository添加@Qualifier注解，指定装配bookRepository

    @Qualifier("bookRepository")
    @Autowired(required = false)
    private BookRepository bookRepository;

注掉test01()获取bookRepository组件代码，否则会报错

//BookRepository bean1 = annotationConfigApplicationContext.getBean(BookRepository.class);
//System.out.println(bean1.toString());

运行test01()

容器创建完成
BookService{bookRepository=BookRepository{lable='1'}}
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:00:14 CST 2020]; root of context hierarchy
一月 19, 2020 11:00:15 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:00:14 CST 2020]; root of context hierarchy

给BookService里面注入的BookRepository的id为bookRepository。修改@Qualifier为@Qualifier("bookRepository2")

    @Qualifier("bookRepository2")
    @Autowired(required = false)
    private BookRepository bookRepository;

再运行test01()，给BookService里面注入的BookRepository为MainConfigOfAutowired里面bookRepository()方法配置的BookRepository。

容器创建完成
BookService{bookRepository=BookRepository{lable='2'}}
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:02:32 CST 2020]; root of context hierarchy
一月 19, 2020 11:02:32 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:02:32 CST 2020]; root of context hierarchy

@Primary:让Spring进行自动装配的时候，默认使用首选的Bean。也可以继续使用@Qualifier指定需要装配的bean的名字。
注掉BookService里面的@Qualifier注解

    //@Qualifier("bookRepository2")
    @Autowired(required = false)
    private BookRepository bookRepository;

MainConfigOfAutowired类的bookRepository()方法添加@Primary注解

    @Primary
    @Bean("bookRepository2")
    public BookRepository bookRepository(){
        BookRepository bookRepository = new BookRepository();
        bookRepository.setLable("2");
        return  bookRepository;
    }

运行test01()，此时给BookService注入的BookRepository是bookRepository()方法配置的BookRepository。

容器创建完成
BookService{bookRepository=BookRepository{lable='2'}}
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:07:09 CST 2020]; root of context hierarchy
一月 19, 2020 11:07:09 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:07:09 CST 2020]; root of context hierarchy

@Resource：Spring还支持使用@Resource(JSR250)注解，可以和Autowired一样进行自动装配，默认是按照组件名称进行装配。没有@Primary功能，也没有@Autowired(required=false)功能。
修改BookService代码

//    @Qualifier("bookRepository2")
//    @Autowired(required = false)
    @Resource(name="bookRepository2")
    private BookRepository bookRepository;

运行test01()

容器创建完成
BookService{bookRepository=BookRepository{lable='2'}}
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:12:08 CST 2020]; root of context hierarchy
一月 19, 2020 11:12:08 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:12:08 CST 2020]; root of context hierarchy

@Inject:需要导入javax.inject包，和@Autowired功能一样，支持@Primary功能，没有@Autowired(required=false)
添加Maven依赖

<!-- https://mvnrepository.com/artifact/javax.inject/javax.inject -->
        <dependency>
            <groupId>javax.inject</groupId>
            <artifactId>javax.inject</artifactId>
            <version>1</version>
        </dependency>

修改BookService代码

//    @Qualifier("bookRepository2")
//    @Autowired(required = false)
//    @Resource(name="bookRepository2")
    @Inject
    private BookRepository bookRepository;

运行test01()

容器创建完成
BookService{bookRepository=BookRepository{lable='2'}}
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:15:24 CST 2020]; root of context hierarchy
一月 19, 2020 11:15:25 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 19 11:15:24 CST 2020]; root of context hierarchy

@Autowired是Spring定义的，@Resource和@Inject是JAVA规范。
@Autowired标注在方法上
新建Car

package com.ljessie.bean;

import org.springframework.stereotype.Component;

@Component
public class Car {
    public Car(){
        System.out.println("Car Constructor......");
    }

    public void init(){
        System.out.println("Car init......");
    }

    public void destroy(){
        System.out.println("Car destroy......");
    }
}

新建Boss

package com.ljessie.bean;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

/**
 * 默认加载IOC容器中的组件，容器启动会调用无参构造器创建对象，再进行初始化赋值操作。
 */
@Component
public class Boss {

    private Car car;
    public Car getCar() {
        return car;
    }

    @Override
    public String toString() {
        return "Boss{" +
                "car=" + car +
                '}';
    }

    /**
     * 标注在方法上，Spring容器创建当前对象，就会调用此方法，完成赋值
     * @param car 从IOC容器中获取
     */
//    @Autowired
    public void setCar(Car car) {
        this.car = car;
    }
}

在MainConfigOfAutowired类中，添加ComponentScan里面的数组，扫描bean包

@Configuration
@ComponentScan({"com.ljessie.service","com.ljessie.controller","com.ljessie.dao","com.ljessie.bean"})
public class MainConfigOfAutowired {
  //省略其他代码
}

修改IOCTest_Autowired,test01()代码

@Test
    public void test01(){
        //创建IOC容器
        AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfigOfAutowired.class);
        System.out.println("容器创建完成");
//        BookService bean = annotationConfigApplicationContext.getBean(BookService.class);
//        BookRepository bean1 = annotationConfigApplicationContext.getBean(BookRepository.class);
//        System.out.println(bean1.toString());
//        System.out.println(bean.toString());

        Boss boss = annotationConfigApplicationContext.getBean(Boss.class);
        Car car = annotationConfigApplicationContext.getBean(Car.class);
        System.out.println(boss);
        System.out.println(car);
//
//        Color color = annotationConfigApplicationContext.getBean(Color.class);
//        System.out.println(color);

        System.out.println(annotationConfigApplicationContext);
        //关闭容器
        annotationConfigApplicationContext.close();
    }

运行test01()

Car Constructor......
容器创建完成
Boss{car=null}
com.ljessie.bean.Car@7ea37dbf
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 26 14:23:28 CST 2020]; root of context hierarchy
一月 26, 2020 2:23:28 下午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 26 14:23:28 CST 2020]; root of context hierarchy

在Boss中的setCar(Car car)方法上面，添加@Autowired注释

@Autowired
    public void setCar(Car car) {
        this.car = car;
    }

再次运行test01()：Boss中的Car属性已经被赋值

Car Constructor......
容器创建完成
Boss{car=com.ljessie.bean.Car@27c86f2d}
com.ljessie.bean.Car@27c86f2d
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 26 14:27:40 CST 2020]; root of context hierarchy
一月 26, 2020 2:27:40 下午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 26 14:27:40 CST 2020]; root of context hierarchy

@Autowired标注在构造器上：如果组件只有一个有参构造器，可以省略@Autowired，参数位置的组件还是从容器中获取。
在Boss中添加构造方法

 /**
     * 构造器要用的组件，也是从容器中获取
     */
    @Autowired
    public BossCar car){
        this.car = car;
        System.out.println("Boss....有参构造器");
    }

运行test01():Spring调用Boss中的有参构造器，完成Car的赋值

Car Constructor......
Boss....有参构造器
容器创建完成
Boss{car=com.ljessie.bean.Car@6a01e23}
com.ljessie.bean.Car@6a01e23
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 26 14:30:05 CST 2020]; root of context hierarchy

@Autowired标注在参数上：修改Boss中的构造方法

/**
     * 构造器要用的组件，也是从容器中获取
     */
//    @Autowired
    public Boss(@Autowired Car car){
        this.car = car;
        System.out.println("Boss....有参构造器");
    }

运行test01():同样可以完成赋值操作。

Car Constructor......
Boss....有参构造器
容器创建完成
Boss{car=com.ljessie.bean.Car@1df82230}
com.ljessie.bean.Car@1df82230
org.springframework.context.annotation.AnnotationConfigApplicationContext@7a46a697: startup date [Sun Jan 26 14:33:46 CST 2020]; root of context hierarchy