Spring框架依赖注入DI顺序

Spring 依赖注入的顺序

  1. 构造器方法注入
  2. 字段注入
  3. 属性或普通方法注入

注意：后面的注入会覆盖前面的值

测试代码

package com.jade.spring.context.annotation7;

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

@Configuration
public class ConfigForRegister {

    @Bean
    String fieldInject() {
        return "属性注入值";
    }

    @Bean
    String constructorInject() {
        return "构造器注入值";
    }
    
    @Bean
    String methodInject() {
        return "方法注入值";
    }
    
    @Bean
    String anotherMethodInject() {
        return "另一个方法注入值";
    }
}

package com.jade.spring.context.annotation7;

import javax.inject.Named;

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

@Component
public class InjectOrder {
    
    @Autowired
    @Named("fieldInject")
    String log;
    {
        log = "手动属性赋值";
        System.out.println(log);
    }
    
    @Autowired
    public InjectOrder(@Named("constructorInject") String log) {
        System.out.println();
        System.out.println("进入构造器《="+this.log);
        System.out.println("第一步：构造器注入=》"+log);
        this.log = "手动构造器赋值";
        System.out.println(this.log);
    }
    
    @Autowired
    public void setValue(@Named("methodInject") String log) {
        System.out.println();
        System.out.println("进入方法《="+this.log);
        System.out.println("第三步：方法注入=》"+log);
        this.log = "手动方法赋值";
        System.out.println(this.log);
    }

    @Autowired
    public void setValue2(@Named("anotherMethodInject") String log) {
        System.out.println();
        System.out.println("再次进入方法《="+this.log);
        System.out.println("再次方法注入=》"+log);
        this.log = "再次手动方法赋值";
        System.out.println(this.log);
    }

    public String getValue() {
        return log;
    }
}

package com.jade.spring.context.annotation;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.jade.spring.context.annotation7.ConfigForRegister;
import com.jade.spring.context.annotation7.InjectOrder;

public class InjectionOrderTest {

    @Test
    public void testInjectionOrder() {
        @SuppressWarnings("resource")
        ApplicationContext context = new AnnotationConfigApplicationContext(InjectOrder.class, ConfigForRegister.class);
        InjectOrder bean = context.getBean(InjectOrder.class);
        System.out.println(bean.getValue());
    }
}

结果如下：

手动属性赋值

进入构造器《=手动属性赋值
第一步：构造器注入=》构造器注入值
手动构造器赋值

进入方法《=属性注入值
第三步：方法注入=》方法注入值
手动方法赋值

再次进入方法《=手动方法赋值
再次方法注入=》另一个方法注入值
再次手动方法赋值

再次手动方法赋值