5.1、bean的作用域

5.1.1、单例(默认且常用)

5.1.1.1、配置bean

注意：当bean不配置scope属性时，默认是singleton（单例）

<?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">

    <bean id="student" class="org.rain.spring.pojo.Student"></bean>

</beans>

5.1.1.2、测试

由控制台日志可知，此时ioc获取到的两个bean本质上是同一个对象

    @Test
    public void testScope() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-scope.xml");
        Student student1 = applicationContext.getBean(Student.class);
        Student student2 = applicationContext.getBean(Student.class);
        System.out.println(student1 == student2);
    }

5.1.2、多例

5.1.2.1、配置bean

<?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">

    <!--
    scope属性：设置bean的作用域
        当属性值为singleton时，在IOC容器中这个bean的对象始终为单实例；且创建对象的时机是IOC容器初始化时
        当属性值为prototype时，在IOC容器中这个bean的对象有多个实例；且创建对象的时机是获取bean时
    -->
    <bean id="student" class="org.rain.spring.pojo.Student" scope="prototype"></bean>

</beans>

5.1.2.2、测试

由控制台日志可知，此时ioc获取到的两个bean本质上是不同的对象

5.1.3、其他作用域

如果是在WebApplicationContext环境下还会有另外两个作用域（但不常用）：

• request：在一个请求范围内有效

• session：在一个会话范围内有效

5.2、bean的生命周期

5.2.1、创建User类

package org.rain.spring.pojo;

/**
 * @author liaojy
 * @date 2023/8/3 - 23:59
 */
public class User {

    private Integer id;
    private String username;
    private String password;
    private Integer age;

    public User() {
        System.out.println("生命周期1：创建对象");
    }

    public User(Integer id, String username, String password, Integer age) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.age = age;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        System.out.println("生命周期2：依赖注入");
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Integer getAge() {
        return age;
    }

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

    public void initMethod(){
        System.out.println("生命周期3：初始化");
    }

    public void destroyMethod(){
        System.out.println("生命周期4：销毁");
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                '}';
    }
}

5.2.2、配置bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi=&qu