文章示例环境配置信息

jdk版本:1.8

开发工具：Intellij iDEA 2020.1

springboot:2.3.9.RELEASE

前言

在Spring依赖注入（一）：字段注入的方式是如何工作的？中主要分享了Spring bean依赖注入方式中的字段注入方式及其工作过程，这篇文章来分享一下SPrng bean依赖注入的第二种方式：setter方法注入，从名字来猜也能猜出一个大概，就是通过调用bean的setter方法进行注入，根本原理是java的反射技术。

settter注入方法

以@Autowired注解为例，即把@Autowired注解标记在目标bean的引用bean的setter方法上；

setter注入示例

示例主要内容：1、定义Teachert类; 2、定义Student类；3、在Student类中依赖Teacher；4、使用@Autowired注解标记在Student#setTeacher()上，即在Student对象中以setter方法注入的方式注入Teacher对象；

@Slf4j
@Component
public class Teacher {
    private String name = "李老师";
    private Student student;

    public Teacher() {
        log.info("----teacher的无参数构造方法被执行");
    }

    public Teacher(Student student) {
        this.student = student;
        log.info("----teacher的有参数构造方法被执行");
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        log.info("----teacher中的setStudent方法被调用");
        this.student = student;
    }
}

@Slf4j
@Component
public class Student {
    private String name = "小明";
    private Teacher teacher;

    public Student() {
        log.info("----student的无参数构造方法被执行");
    }

    public Student(Teacher teacher) {
        this.teacher = teacher;
        log.info("----student的有参数构造方法（teacher）被执行");
    }

    public Student(String name, Teacher teacher) {
        this.name = name;
        this.teacher = teacher;
        log.info("----student的有参数构造方法（name，teacher）被执行");
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Teacher getTeacher() {
        return teacher;
    }

    @Autowired
    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
        log.info("----student中的setTeacher方法被调用");
    }

}

@Component
@Slf4j
public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (beanName.equals("student")) {
            Student student = (Student) bean;
            log.info("----student属性注入完成,student.name:" + student.getName());
        }
        return bean;
    }
}

@Component
@Slf4j
public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor {
    @Override
    public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
        if (beanName.equals("student")||beanName.equals("teacher")) {
            log.info("----bean实例化完成，beanName：" + beanName);
        }
        return true;
    }
}

@Test
public void test4() {
    log.info("----单元测试执行开始");
    AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext("com.fanfu");
    Student bean = context.getBean(Student.class);
    log.info("----bean:"+bean.getName());
    log.info("----单元测试执行完毕");
}

单元测试执行日志：