Whether the bean instance created in Spring is a single instance or multiple instances

In Spring, beans are single-instance objects by default

public class Student {
    
    
}

    <bean id="student" class="iocbean.byxml.example.Student">

    </bean>

public class DemoTest {
    
    
    @Test
    public void test1(){
    
    
        ApplicationContext context = new ClassPathXmlApplicationContext("iocbean/byxml/example/bean.xml");

        Student student1 = context.getBean("student", Student.class);
        Student student2 = context.getBean("student", Student.class);

        System.out.println(student1);
        System.out.println(student2);
    }
}

Result: (You can see that the address values ​​of the two objects are the same)

iocbean.byxml.example.Student@5bd03f44
iocbean.byxml.example.Student@5bd03f44

Process finished with exit code 0

There are attributes (scope) in the bean tag of the spring configuration file to set single instance or multiple instances

• The default value, singleton, means a single-instance object
• prototype, which means it is a multi-instance object

    <bean id="student" class="iocbean.byxml.example.Student" scope="prototype">

    </bean>

Result: (You can see that the address values ​​of the two objects are not the same)

iocbean.byxml.example.Student@470f1802
iocbean.byxml.example.Student@63021689

Process finished with exit code 0

The difference between singleton and prototype creating instance objects:

• When the scope value is set to singleton, a single instance object will be created when the spring configuration file is loaded
• When setting the scope value to prototype, instead of creating an object when loading the spring configuration file, create a multi-instance object when calling the getBean method