一文搞懂Spring Bean中的作用域和生命周期

public class Dept {
    //部门编号
    private int deptNo;
    //部门名称
    private String deptName;
}

<bean id="dept" class="com.bighorn.pojo.Dept" scope="singleton">
</bean>

public static void main(String[] args) {
    //获取IoC容器
    ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
    //从容器中获取对象
    Dept dept1 = context.getBean("dept", Dept.class);
    Dept dept2 = context.getBean("dept", Dept.class);
    //打印对象
    System.out.println(dept1);
    System.out.println(dept2);
}

<bean id="dept" class="com.bighorn.pojo.Dept" scope="prototype">
</bean>

//获取 ClassPathXmlApplicationContext 容器
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
//调用close方法关闭容器
context.close();

//获取 ClassPathXmlApplicationContext 容器
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
//调用注册狗子关闭容器
context.registerShutdownHook();

/**
 * 继承接口，程序初始化回调和销毁回调方法
 */
public class User implements InitializingBean, DisposableBean {
    String name;
    int age;

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

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

    //初始化回调方法
    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("这是初始化回调方法");
    }

    //销毁回调方法
    @Override
    public void destroy() throws Exception {
        System.out.println("这是销毁回调方法");
    }

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

<bean id="user" class="com.bighorn.pojo.User">
    <property name="name" value="bighorn"/>
    <property name="age" value="18"/>
</bean>

public class App {
    public static void main(String[] args) {
        //获取 ClassPathXmlApplicationContext 容器
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        //从容器中获取对象
        User user = context.getBean("user", User.class);
        //使用bean
        System.out.println(user);
        //调用close方法关闭容器
        context.close();
    }
}

/**
 * 通过XML配置指定回调方法
 */
public class User {
    String name;
    int age;

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

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

    //初始化回调方法
    public void init() throws Exception {
        System.out.println("这是初始化回调方法");
    }

    //销毁回调方法
    public void destroy() throws Exception {
        System.out.println("这是销毁回调方法");
    }

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

<!--通过XML配置指定回调方法-->
<bean id="user" class="com.bighorn.pojo.User" init-method="init" destroy-method="destroy">
    <property name="name" value="bighorn"/>
    <property name="age" value="18"/>
</bean>