Spring学习（二）——IOC创建对象方式及Spring配置

桃扇骨 2022-12-30 10:34 157阅读 0赞

### IOC创建对象方式 ###

*  默认使用无参构造创建对象
 *  使用有参构造
 *   *  1、根据下标构造
     *  2、根据参数类型匹配
     *  3、直接根据参数名构造
 *  Spring配置
 *   *  使用别名
     *  bean的配置
     *  import

**在配置文件加载的时候，容器中管理的对象就已经初始化了**

# 默认使用无参构造创建对象 #

**是创建ApplicationContext的时候实例就已经被创建了，getBean只是获得了引用**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 2]  
如果将无参构造改为有参构造  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 3]

# 使用有参构造 #

## 1、根据下标构造 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 4]

<bean id="user" class="com.my.pojo.User">
            <constructor-arg index="0" value="啦啦啦啦啦"/>
        </bean>

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 5]

## 2、根据参数类型匹配 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 6]

![在这里插入图片描述][20201224202935753.png]

<bean id="user" class="com.my.pojo.User">
            <constructor-arg type="java.lang.String" value="hahahaha"/>
        </bean>

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 7]  
**但是如果有两个参数且类型相同就会按照参数的顺序依次构造**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 8]

## 3、直接根据参数名构造 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 9]

<bean id="user" class="com.my.pojo.User">
            <constructor-arg name="name" value="hehe"/>
            <constructor-arg name="pwd" value="12346"/>
    
        </bean>

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 10]

# Spring配置 #

## 使用别名 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 11]

## bean的配置 ##

> 类型 变量名 = new 类型（）;  
> Hello hello = new Hello();  
> id = 变量名  
> class = new 的对象  
> property 相当于给对象中的某个属性设置一个值  
> name： 也是别名 可以同时起多个别名

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 12]

**name可以同时起多个别名**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 13]

## import ##

一般用于团队开发使用，可以将多个配置文件整合到一起

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 14]

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[20201224202935753.png]: https://img-blog.csdnimg.cn/20201224202935753.png
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