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???????????????????????????????????????????????????????????? Java ?????????????????????????

???????

????????????????????????????????????????????????????????????????????????????????????????

???????????????????????????????????????

public class Xiaoer {
    public void saodi() {
        System.out.println("??????????");
    }
}
public class Laowang {
    public void mingling() {
        new Xiaoer().saodi();
    }
}

?????????

public class Test {
    public static void main(String[] args) {
        Laowang laowang = new Laowang();
        laowang.mingling();
    }
}

???????Laowang ?? mingling ????? new ???????? Xiaoer ?????????????????????

??????????????????????????????????????

public class Xiaosan {
    public void saodi() {
        System.out.println("??????????");
    }
}
public class Laowang {
    public void mingling() {
        new Xiaoer().saodi();
    }
    public void mingling1() {
        new Xiaosan().saodi();
    }
}

??????????????????????????????????????????????????

????????

??????????????????????????????????????????????????????

????????????????

public interface Heshang {
    void saodi();
}

??????????

public class Xiaoer implements Heshang {
    @Override
    public void saodi() {
        System.out.println("??????????");
    }
    public boolean isYijinjing() {
        return false;
    }
}

??????????

public class Xiaosan implements Heshang {
    @override
    public void saodi() {
        System.out.println("??????????");
    }
}

????????????

public class Laofang {
    public static Heshang getSaodiseng() {
        Xiaoer xiaoer = new Xiaoer();
        if (xiaoer.isYijinjing()) {
            return new Xiaosan();
        }
        return xiaoer;
    }
}

???????????????

public class Laowang {
    public void mingling() {
        Laofang.getSaodiseng().saodi();
    }
}

?????????????????????????????????????Inversion of Control?IoC????????????????????????

????????

?????Dependency Injection??? DI??????????????????????? A ????????????? B ?????????????????????????????????????????

public class Laowang {
    private Heshang saodiseng;
    public Laowang(Heshang saodiseng) {
        this.saodiseng = saodiseng;
    }
    public void mingling() {
        this.saodiseng.saodi();
    }
}

2. ?? set ?????????? public set ?????????????????????

public class Laowang {
    private Heshang saodiseng;
    public Heshang getSaodiseng() {
        return saodiseng;
    }
    public void setSaodiseng(Heshang saodiseng) {
        this.saodiseng = saodiseng;
    }
    public void mingling() {
        this.getSaodiseng().saodi();
    }
}

3. ??????????????????????????????????????????????

????????????????????????????????????????

??? Spring ???

?????????????????????????? Spring ???Spring ???????????????????????????????set ?????????????????????

???? pom.xml ????? Spring ?????

     
    
      
       org.springframework
      
    
      
       spring-context-support
      
    
      
       4.3.2.RELEASE
      
     

???? Laowang ?????

public class Laowang {
    private Heshang saodiseng;
    public Laowang(Heshang saodiseng) {
        this.saodiseng = saodiseng;
    }
    public void mingling() {
        this.saodiseng.saodi();
    }
}

???? Spring ???? application.xml?

?????????????????????????????????????

??????????

public class Test {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("application.xml");
        Laowang laowang = (Laowang) context.getBean("laowang");
        laowang.mingling();
    }
}

????????????? IoC ?? Spring????????????????

????

4. ????????????????????????????????????????????????????

5. ?????????????????????????set ???????????????????????

6. Spring ????????????????????????????????????????

?????????????????????????????????? Spring ???????