Spring Issues with bean aliases in XML configuration

Spring version - 5.3.22

Aliases overwrite the ID property, moreover they are not verifying for presence of duplicate beans. The case remains same with Name.

Please have a look at below code for better understanding.

Bean Definition

<bean id="string_bean" class="java.lang.String">
        <constructor-arg value="Sample" />
    </bean>

    <bean id="string_bean1" class="java.lang.String">
        <constructor-arg value="Sample 1" />
    </bean>

    <alias name="string_bean" alias="string_bean1" />
    <alias name="string_bean1" alias="string" />

Java File

ApplicationContext context = new ClassPathXmlApplicationContext("\\config\\basics.xml");
        String[] beanNames = {
            "string_bean",
            "string_bean1",
            "string"
        };

        for(String beanName : beanNames) {
            String str = context.getBean(beanName, String.class);
            System.out.println("For " + beanName + " => " + str);
        }

Output

For string_bean => Sample
For string_bean1 => Sample
For string => Sample

Comment From: sbrannen

I would not suggest defining an alias such as string_bean1 that conflicts with an existing bean ID/name.

Are you expecting Spring to throw an exception if that occurs?

Also, what exactly are you trying to achieve?

Comment From: spring-projects-issues

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

Comment From: Abhi4281

If this is the expected behavior then its fine.

However, while handling large amount of configuration details this could possibly lead to a Logical error, which would be very difficult to debug for the users.

Not trying to achieve anything, just learning Spring :)

Comment From: snicoll

Yes it's the expected behavior. Spring Boot has an option to prevent bean overriding by default, which would prevent the use case from happening. On an AbstractRefreshableBeanFactory you can call setAllowBeanDefinitionOverriding to disallow bean overriding.