Spring Bean的作用域有哪些？

可以通过scope属性来指定bean的作用域
    singleton：默认值。当IOC容器一创建就会创建bean的实例，而且是单例的，每次得到的都是同一个
    prototype：原型的。当IOC容器一创建不再实例化该bean，每次调用getBean方法时再实例化该bean，而且每调用一次创建一个对象
    request：每次请求实例化一个bean
    session：在一次会话中共享一个bean

核心代码

• beans.xml

<?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 http://www.springframework.org/schema/context/spring-context-4.0.xsd">

	<!-- ★bean的作用域
		可以通过scope属性来指定bean的作用域
			-singleton：默认值。当IOC容器一创建就会创建bean的实例，而且是单例的，每次得到的都是同一个
			-prototype：原型的。当IOC容器一创建不再实例化该bean，每次调用getBean方法时再实例化该bean，而且每调用一次创建一个对象
			-request：每次请求实例化一个bean
			-session：在一次会话中共享一个bean
	 -->
	<bean id="book" class="cn.wangzengqiang.interview.atguigu2019.javaee.spring.beans.Book" scope="prototype">
	 	<property name="id" value="8"></property>
	 	<property name="title" value="红高粱"></property>
	 	<property name="author" value="莫言"></property>
	 	<property name="price" value="10.00"></property>
	 	<property name="sales" value="800"></property>
	</bean>
	
</beans>

• Book.java

public class Book {

    private Integer id;
    private String title;
    private String author;
    private double price;
    private Integer sales;

    public Book() {
        System.out.println("Book对象被创建了");
    }

    public Book(Integer id, String title, String author, double price, Integer sales) {
        super();
        this.id = id;
        this.title = title;
        this.author = author;
        this.price = price;
        this.sales = sales;
        System.out.println("全参的构造器被调用");
    }

    public Book(Integer id, String title, String author, double price) {
        super();
        this.id = id;
        this.title = title;
        this.author = author;
        this.price = price;
        System.out.println("不含销量的构造器被调用");
    }

    public Book(Integer id, String title, String author, Integer sales) {
        super();
        this.id = id;
        this.title = title;
        this.author = author;
        this.sales = sales;
        System.out.println("不含价格的构造器被调用");
    }

    public Integer getId() {
        return id;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    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;
    }

    public Integer getSales() {
        return sales;
    }

    public void setSales(Integer sales) {
        this.sales = sales;
    }

    @Override
    public String toString() {
        return "Book [id=" + id + ", title=" + title + ", author=" + author + ", price=" + price + ", sales=" + sales
                + "]";
    }

}

• SpringTest.java

public class SpringTest {

    //01.Spring Bean的作用域之间有什么区别

    //创建IOC容器对象
    ApplicationContext ioc = new ClassPathXmlApplicationContext("beans.xml");

    @Test
    public void testBook() {
        Book book = (Book) ioc.getBean("book");
        Book book2 = (Book) ioc.getBean("book");
        System.out.println(book == book2);
    }
}
/**
 * 1.Invalid test class 'cn.wangzengqiang.interview.atguigu2019.javaee.spring.test.SpringTest':
 *   1. Method testBook() should be public
 *   junit测试方法前面应该加个public
 * 2.junit方法主类应该是public，否则没有运行按钮
 * 3.org.springframework.beans.factory.BeanDefinitionStoreException: IOException parsing XML document from class path resource [beans.xml]; nested exception is java.io.FileNotFoundException: class path resource [beans.xml] cannot be opened because it does not exist
 * 在maven工程中，config应该设置为source folder
 * 4.非maven工程引入jar包，可以新建一个lib目录，然后设置为source folder，然后添加到类路径
 */

代码结构图

代码地址

代码地址