前言

什麼是IOC，IOC是控制反轉，打個比方，本來你自己new一隻火雞，現在讓控制權交給spring，它使用依賴注入的技術做給你吃。

一、IOC——setter注入

1、準備dmo

首先準備一隻火雞

public class Turkey {
    private int id;
    private String name;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

然後準備一個廚房， 屬性包含火雞

public class Cookhouse {
    private int id;
    private String name;
    private Turkey turkey;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public Turkey getTurkey() {
        return turkey;
    }

    public void setTurkey(Turkey turkey) {
        this.turkey = turkey;
    }

    @Override
    public String toString() {
        return "Cookhouse{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}
 

2、applicationContext.xml配置

給bean起個名字，class就是dmo類，property name是屬性名，value和ref是屬性值，如果屬性是物件要使用"ref="

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
   http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <bean name="t" class="Turkey">
        <property name="name" value="usaTurkey"/>
    </bean>

    <bean name="c" class="Cookhouse">
        <property name="name" value="cnCookhouse"/>
        <property name="turkey" ref="t"/>
    </bean>
</beans>
 

3、新增spring的相關JAR包

JAR包以及其它知識詳見網上一個大神的專案：自學網站

4、spring幫我們在廚房做火雞

讓spring幫我在廚房做火雞吃，spring根據核心配置檔案applicationContext.xml建立了一箇中國廚房，然後做了只美國火雞。

public class TestSpring {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
        Cookhouse c = (Cookhouse)applicationContext.getBean("c");
        System.out.println(c.getName()+"做了只"+c.getTurkey().getName());
    }
}

執行結果：

二、IOC——註解注入

有小夥伴說：火雞做太慢，等餓了
spring說：那我來用註解注入的方式給你做火雞

1、@Autowired對屬性的註解

首先優化物件的注入方式，applicationContext.xml新增<context:annotation-config/>，表示告訴Spring要用註解的方式進行注入，<property name="turkey" ref="t"/>就可以註釋掉了，我們只需要在Cookhouse類的屬性Turkey上面加上@Autowired就可以注入火雞了

@Autowired
    private Turkey turkey;

2、@Component對Bean的註解

然後優化Bean的注入方式，applicationContext.xml的Bean注入看上去還是比較繁瑣，我們再簡化下，只新增：

<context:component-scan base-package="com.fantasy.dmo"/>
其作用是告訴Spring，bean都放在這個包下

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
   http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!--bean都放在這個包下-->
    <context:component-scan base-package="com.fantasy.dmo"/>
</beans>

因為Bean移到dmo了，所以在dmo分別給Cookhouse和Turkey加上註解@Component，然後給它們的屬性name命名。

@Component("c")
public class Cookhouse {
    private int id;
    private String name="cnCookhouse";
    @Autowired
    private Turkey turkey;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public Turkey getTurkey() {
        return turkey;
    }

    public void setTurkey(Turkey turkey) {
        this.turkey = turkey;
    }

    @Override
    public String toString() {
        return "com.fantasy.dmo.Cookhouse{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

@Component("t")
public class Turkey {
    private int id;
    private String name="usaTurkey";

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

執行程式發現結果一樣，又省去很多配置，香噴噴的火雞做的更快了呢~

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