cgb2107-day17

一,IOC的xml方式–了解

–1,專案結構

–2,創建Hello類

package cn.tedu.spring;

public class Hello {
    public void hi(){
        System.out.println("hello springioc~");
    }
}

–3,創建User類

package cn.tedu.spring;

public class User {
    public void eat(){
        System.out.println(123);
    }
}

–4,創建組態檔

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

    <!--spring認為萬物皆是bean,配置bean的位置,spring自動完成ioc
        class屬性用來描述類的全路徑, id屬性用來作為bean的唯一標識
        scope="prototype"用來設定物件是多例的,默認是singleton單例的
        IOC底層是Map結構,Map<id的值,類的物件>,資料結類似: {"hello",new Hello()}
        spring只能用反射創建物件:
        {"hello",Class.forName("cn.tedu.spring.Hello").newInstance() }
    -->
    <bean class="cn.tedu.spring.Hello" id="hello"></bean>

    <bean class="cn.tedu.spring.User" id="user"></bean>

</beans>

–5,創建測驗類

package cn.tedu.spring;
import org.junit.jupiter.api.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test1 {
    //測驗IOC(創建類+配置類)
    @Test//junit單元測驗方法:@Test void public 沒有引數
    public void ioc(){
        //1,讀取組態檔--引數是組態檔的路徑
        ClassPathXmlApplicationContext spring =
                new ClassPathXmlApplicationContext(
                        "spring-config.xml");
        //2,獲取spring創建好的物件--引數是組態檔里bean標簽的id的值
        Object o = spring.getBean("hello");
        System.out.println(o);//cn.tedu.spring.Hello@43bc63a3
        Hello h = (Hello) o;
        h.hi();

        //單例物件:節省記憶體和時間,spring框架默認的創建單例物件的方式
        Hello h2 = (Hello) spring.getBean("hello");
//        System.out.println(o2);//cn.tedu.spring.Hello@43bc63a3
        h2.hi();

//java.lang.ClassCastException:cn.tedu.spring.Hello cannot be cast to cn.tedu.spring.User
        //User uu = (User) spring.getBean("hello");
        //System.out.println(uu);

        Object o3 = spring.getBean("user");
        System.out.println(o3);//cn.tedu.spring.User@38425407
        //向下轉型:把父型別別變成子型別別,目的要用子類的功能
        User u = (User) o3 ;
        u.eat();
    }
}

二,IOC的注解方式–重點

1, 創建類, 類上使用IOC的注解
2, 創建組態檔, 指定包掃描的路徑
3, 直接getBean(“類名首字母要變成小寫”)

spring認為萬物皆是bean,配置bean的位置,spring自動完成ioc
class屬性用來描述類的全路徑, id屬性用來作為bean的唯一標識
scope="prototype"用來設定物件是多例的,默認是singleton單例的
IOC底層是Map結構,Map<id的值,類的物件>,資料結類似: {"hello",new Hello()}
spring只能用反射創建物件:
{"hello",Class.forName("cn.tedu.spring.Hello").newInstance() }

–0,專案結構

–1,創建類

package cn.tedu.spring;

import org.springframework.stereotype.Component;
@Component //用來讓spring完成ioc {"person"=new Person()}
public class Student {
    public void study(){
        System.out.println("Student.study()");
    }
}

package cn.tedu.spring;
import org.springframework.stereotype.Component;

@Component //用來讓spring完成ioc {"person"=new Person()}
public class Person {
    public void show(){
        System.out.println("Person.show()");
    }
}

–2,配置包掃描

<?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:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

   <!--包掃描:掃描 指定包 以及 子包里的所有資源,找到有IOC注解的類就進行new
        IOC的注解包括: @Component   @Service  @Controller
        base-package 用來指定包路徑,范圍越小越好,性能高
    -->
    <context:component-scan base-package="cn.tedu"></context:component-scan>

</beans>

–3,測驗

package cn.tedu.spring;

import org.junit.jupiter.api.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test1 {
    //單元測驗方法
    @Test
    public void ioc(){
        //1,讀取組態檔---引數是組態檔的路徑
        ClassPathXmlApplicationContext spring =
                new ClassPathXmlApplicationContext(
                        "spring.xml");
        //2,getBean()---引數是類名,首字母小寫
        Object o = spring.getBean("person");
        System.out.println(o);//cn.tedu.spring.Person@7e5afaa6
        Object o1 = spring.getBean("student");
        System.out.println(o1);

        Object o2 = spring.getBean("animal");
        System.out.println(o2);
    }
}

三,模擬 DI依賴注入

–1,概述

維護了兩個物件間的關系,方便在使用A的同時可以看到關聯的B的資料

–2,測驗

創建Emp類

package cn.tedu.di;

public class Emp {
    String name = "吳謙";
    //系結了兩個類的關系--依賴
    private Dept d;
    //get set
    public Dept getD() {
        return d;
    }
    public void setD(Dept d) {
        this.d = d;
    }
    @Override
    public String toString() {
        return "Emp{" +
                "name='" + name + '\'' +
                ", d=" + d +
                '}';
    }
}

創建Dept 類

package cn.tedu.di;
public class Dept {
    String name = "java軟體開發一部";
    @Override
    public String toString() {
        return "Dept{" +
                "name='" + name + '\'' +
                '}';
    }
}

創建測驗類

package cn.tedu.di;
import org.junit.Test;
public class TestDi {
    @Test
    public void di(){
        //1,創建物件
        Emp e = new Emp();
        Dept d = new Dept();
        //Emp{name='吳謙', d=null}
        System.out.println(e);

        //2,di維護了兩個物件間的關系-set()
        e.setD(d);
//Emp{name='吳謙', d=Dept{name='java軟體開發一部'}}
        System.out.println(e);
    }
}

四,Spring提供的DI依賴注入

–1,創建UserInfo 類

package cn.tedu.di2;

import org.springframework.stereotype.Component;
@Component//ioc -- {"userInfo"=new UserInfo()}
public class UserInfo {
    String name="jack";
    @Override
    public String toString() {
        return "UserInfo{" +
                "name='" + name + '\'' +
                '}';
    }
}

–2,創建Order 類

package cn.tedu.di2;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component//ioc--{"order"=new Order()}
public class Order {
    String name = "iphone13";
    //get set
    @Autowired //di
    private UserInfo ui;

    @Override
    public String toString() {

        return "Order{" +
                "name='" + name + '\'' +
                ", ui=" + ui +
                '}';
    }
}

–3,測驗類

package cn.tedu.di2;
import org.junit.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestDI {
    @Test
    public void di(){
        //1,讀取組態檔
        ClassPathXmlApplicationContext spring =
                new ClassPathXmlApplicationContext(
                        "spring.xml");
        //2,getBean()--DI:獲取A的同時也獲取到B的資訊
        Object o = spring.getBean("order");
//Order{name='iphone13',ui=UserInfo{name='jack'}}
        System.out.println(o);
    }
}

–4,總結

IOC: 控制翻轉,Spring框架創建物件.
使用步驟: 1, 在類上使用注解@Component @Service @Controller 2, 配置包掃描
DI: 依賴注入,把兩個物件之間的關系依賴.
使用步驟: 1, 先完成IOC 2, 用注解@Autowired

擴展：SpringMVC原始碼里的核心方法