Spring之注解实现依赖注入

1.使用@Autowired注解按类型自动装配引用数据类型

注：自动装配（按类型和名称）基于反射设计创建对象并暴力反射对应属性为私有属性初始化数据，因此无需提供setter方法。自动装配建议使用无参构造方法创建对象，如果不提供对应的构造方法，应提供唯一的构造方法

package domain;

import org.springframework.stereotype.Component;

@Component
public class Animal {
    private String name;
    private Integer age;
}

package domain;

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

@Component
public class People {
    @Autowired
    private Animal animal;

}

package config;

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

@Configuration
@ComponentScan("domain")
public class SpringConfig {
}

import config.SpringConfig;
import domain.People;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Demo {
    public static void main(String[] args) {
        ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig.class);
        People people = ctx.getBean(People.class);
        System.out.println(people);

    }
}

2.使用@Autowired和@Qualifier注解按名称自动装配引用数据类型（不推荐使用）

注：@Qualifier注解无法单独使用，必须配合@Autowired注解使用

package domain;

import org.springframework.stereotype.Component;

@Component("animal")
public class Animal {
    private String name;
    private Integer age;
}

package domain;

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

@Component
public class People {
    @Autowired
    @Qualifier("animal")
    private Animal animal;

}

package config;

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

@Configuration
@ComponentScan("domain")
public class SpringConfig {
}

import config.SpringConfig;
import domain.People;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Demo {
    public static void main(String[] args) {
        ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig.class);
        People people = ctx.getBean(People.class);
        System.out.println(people);

    }
}

3.使用@Value注解实现简单数据类型的注入

package domain;

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

@Component
public class Animal {
    @Value("maomi")
    private String name;
    @Value("123")
    private Integer age;
}