Spring中的构造函数注入如何促进不变性？

Question

I am new to spring and reading the on line spring reference. One of the advantages of using constructor injection(CI) is because CI is immutable?I know it means that it cannot be modified. But how does that happen, any simple example please to show how CI promote immutability? thanks

Answer 1

this is an immutable bean, thanking to CI

class B1 {
    private final int x;

    B1(int x) {
        this.x = x;
    }
}

context.xml

<bean id="b1" class="test.B1">
    <constructor-arg value="1"/>
</bean>