java项目实战-spring-基本用法01-day24

目录

• 1. spring 简单介绍
• 2. IOC/DI --控制反转--是啥
• 3. 实现
• 3. 如果 对象的 属性为引用数据类型 如何 实例化对象
• 4 如何用注解的方式 以少量的代码实现对象的创建于获取

1. spring 简单介绍

https://spring.io

什么事 SSM？

spring-mvc

spring-framework -- web服务层

mybatis --数据持久化

2. IOC/DI --控制反转--是啥

控制反转 Inversion of Control

依赖注入 DI dependency inject

创建对象的权利或者决定位置 转移到 spring，由spring容器来创建对象

演变：

举个例子：

对所有商品打打5折

查出所有的商品 将价格打五折 保存

再次演变 接口以及实现

业务接口没变但是 实现由多种形式 可以根据需要切换到不同的实现

同样的举个例子：

对所有商品打打5折

直接一条sql就能实现 不用查找再更新

接着演进 创建对象也由spring来完成



原理的同属理解：

根据xml配置文件创建对象

将对象放入容器 （map)

根据需要 通过名字 获取对象

3. 实现

package com.msb.pojo;

/**
 * @Auther: jack.chen
 * @Date: 2023/11/12 - 11 - 12 - 15:46
 * @Description: com.msb.pojo
 * @version: 1.0
 */
public class Book {
    private int id;
    String name;
    String author;
    double price;

    public Book() {
    }

    public Book(int id, String name, String author, double price) {
        this.id = id;
        this.name = name;
        this.author = author;
        this.price = price;
    }

    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 String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

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

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

    <bean id="b" class="com.msb.pojo.Book" ></bean>

</beans>

public class Test01 {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Book b = (Book)context.getBean("b");
        System.out.println(b);

    }
}

上面的实现确实能实例化一个Book对象

但是如何传参 实例化对象？

1. 使用setter方法
2. 使用构造器
   
   

    <bean id="b" class="com.msb.pojo.Book" >
        <property name="id" value="4"></property>
        <property name="name" value="水浒传"></property>
        <property name="author" value="施耐庵"></property>
        <property name="price" value="39.98"></property>
    </bean>

说明：这里通过setter的方式来设置属性 name="xxx" 实际上是调用setterxxxx方法来实现

    <bean id="b2" class="com.msb.pojo.Book" >
        <constructor-arg name="id" value="5"></constructor-arg>
        <constructor-arg name="name" value="时间简史"></constructor-arg>
        <constructor-arg name="author" value="霍金"></constructor-arg>
        <constructor-arg name="price" value="25.5"></constructor-arg>
    </bean>

说明：这里通过调用构造器的方式来实例化对象 name=xxx 实际上是 构造器里面形参的名称

public class Test01 {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Book b = (Book)context.getBean("b2");
        System.out.println(b);

    }
}

3. 如果 对象的 属性为引用数据类型 如何 实例化对象

Girl Boy girl的boyfriend是boy

package com.msb.pojo;

/**
 * @Auther: jack.chen
 * @Date: 2023/11/12 - 11 - 12 - 20:42
 * @Description: com.msb.pojo
 * @version: 1.0
 */
public class Boy {

    private String name;
    private int age;

    public Boy() {
    }

    public Boy(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

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

package com.msb.pojo;

/**
 * @Auther: jack.chen
 * @Date: 2023/11/12 - 11 - 12 - 20:40
 * @Description: com.msb.pojo
 * @version: 1.0
 */
public class Girl {
    private int age;
    private String name;
    private Boy boyfriend;

    public Girl() {
    }

    public Girl(int age, String name) {
        this.age = age;
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public Girl(int age, String name, Boy boyfriend) {
        this.age = age;
        this.name = name;
        this.boyfriend = boyfriend;
    }

    @Override
    public String toString() {
        return "Girl{" +
                "age=" + age +
                ", name='" + name + '\'' +
                ", boyfriend=" + boyfriend +
                '}';
    }
}

public class Test02 {

    public static void main(String[] args) {
        Boy boy = new Boy("小刚", 27);

        Girl lili = new Girl(25, "lili", boy);
        System.out.println(lili);
    }
}

很简单的一个例子 但是 如何用注解来实现创建对象？

    <bean id="boy1" class="com.msb.pojo.Boy">
        <property name="name" value="小帅aaa"></property>
        <property name="age" value="27"></property>
    </bean>

    <bean id="girl1" class="com.msb.pojo.Girl">
        <property name="age" value="25"></property>
        <property name="name" value="小美1"></property>
        <property name="boyfriend" ref="boy1"></property>
    </bean>

    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Girl girl1 = (Girl)context.getBean("girl1");
        System.out.println(girl1);
    }

4 如何用注解的方式 以少量的代码实现对象的创建于获取

复习一下 什么是注解

定义扫描的位置：

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

    <context:component-scan base-package="com.msb.pojo"></context:component-scan>
</beans>

public class Test03 {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Girl girl1 = (Girl)context.getBean("girl");
        System.out.println(girl1);
    }
}

其他的注解 不同之处 是使用的层 不同 加以区分 @Component 不区分层

@value 实力化对象将基本数据类型的属性注入 不易依赖setter方法

@Autoaired 将引用数据类型的属性设置

@Component
public class Boy {
    @Value("小帅11111")
    private String name;
    @Value("18")
    private int age;

    public Boy() {
    }

@Component
public class Girl {
    @Value("18")
    private int age;

    @Value("xiaomei111")
    private String name;

    @Autowired
    private Boy boyfriend;

    public Girl() {
    }

    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Girl girl1 = (Girl)context.getBean("girl");
        System.out.println(girl1);
    }