Spring @Autowired为属性注入值

@Autowired实现对象属性值的注入默认是按照属性类型进行值的注入，假如提供了与此属性有对应关系的构造函数则执行这个构造函数直接对属性进行初始化，如果没有，底层通过反射获得属性的类型以后，从容器中查找与此类型匹配的对象再为期注入值。

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.spring</groupId>
    <artifactId>spring-ioc-autowired</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.10.RELEASE</version>
        </dependency>
    </dependencies>
</project>

spring-configs.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans 
    default-lazy-init="true"
    xmlns="http://www.springframework.org/schema/beans"
    xmlns:p="http://www.springframework.org/schema/p" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:util="http://www.springframework.org/schema/util" xmlns:jpa="http://www.springframework.org/schema/data/jpa"
    xsi:schemaLocation="  
       http://www.springframework.org/schema/beans   
       http://www.springframework.org/schema/beans/spring-beans-4.3.xsd  
       http://www.springframework.org/schema/mvc   
       http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd   
       http://www.springframework.org/schema/tx   
       http://www.springframework.org/schema/tx/spring-tx-4.3.xsd   
       http://www.springframework.org/schema/aop 
       http://www.springframework.org/schema/aop/spring-aop-4.3.xsd
       http://www.springframework.org/schema/util 
       http://www.springframework.org/schema/util/spring-util-4.3.xsd
       http://www.springframework.org/schema/data/jpa 
       http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context-4.3.xsd">
       <context:component-scan base-package="project"/>       
</beans>

package project.dao;

public interface CarDao {
    void insertCar(String car);
}

package project.dao.impl;

import org.springframework.stereotype.Repository;

import project.dao.CarDao;
/**
 * 数据持久层对象(封装jdbc操作的对象)
 */
@Repository
public class CarDaoImpl implements CarDao{
    public CarDaoImpl() {
        System.out.println("CarDaoImpl.CarDaoImpl()");
    }

    @Override
    public void insertCar(String car) {
        System.out.println("CarDaoImpl.insertCar()");
        System.out.println("insert car "+car);
    }

}

package project.service;

public interface CarService {
    void saveCar(String car);
}

package project.service.impl;

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

import project.dao.CarDao;
import project.service.CarService;
@Service
public class CarServiceImpl implements CarService{
    @Autowired
    private CarDao carDao;
    
    public CarServiceImpl(CarDao carDao) {
        this.carDao = carDao;
        System.out.println("CarServiceImpl.CarServiceImpl(CarDao carDao)");
    }

    public void setCarDao(CarDao carDao) {
        this.carDao = carDao;
        System.out.println("CarServiceImpl.setCarDao(CarDao carDao)");
    }

    @Override
    public void saveCar(String car) {
        System.out.println("CarServiceImpl.saveCar()");
        carDao.insertCar(car);
    }

}

package test;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import project.service.CarService;

public class TestProject {
    private static ClassPathXmlApplicationContext ctx;
    public static void init(){
        ctx=new ClassPathXmlApplicationContext("spring-configs.xml");
    }
    public static void close(){
        ctx.close();
    }
    public static void main(String[] args) {
        init();
        CarService carService=ctx.getBean("carServiceImpl",CarService.class);
        carService.saveCar("bmw");
        close();
    }
}

运行结果

CarDaoImpl.CarDaoImpl()
CarServiceImpl.CarServiceImpl(CarDao carDao)
CarServiceImpl.saveCar()
CarDaoImpl.insertCar()
insert car bmw