Spring injection issue with constructor-arg overload

Question

I would like to ask about the Spring Constructor Injection. So in the class, I have two constructors with different number of arguments.

public class MyClassHello() {
    public MyClassHello(String A) {
        // do sth
    }

    public MyClassHello(String A, int B){
        // do sth
    }
}

If I try to inject like this to access the 1st constructor, Spring can not work since there is ambiguity.

<bean id="injectQuestion" class="MyClassHello">
    <constructor-arg index="0" value="A String"/>
</bean>

The debug code is like this:

Unsatisfied dependency expressed through constructor argument with index 1 of type [java.lang.String]: Ambiguous constructor argument types.

I think it means, Spring needs to know if the index 1 argument exists?

It is not like the usual case where we have two constructors with same number of arguments. Like that, I could set the type in order to distinguish when injecting.

In my case, is there anyway to force Spring to choose the first constructor?

Thanks a lot!!

While I find this odd that your current setup will cause any ambiguity, add a `type` attribute to your constructor definition to clear up any remaining ambiguity. You should then have `` — kolossus, Sep 17 '14 at 17:21
@kolossus That won't help, I already tried but still the same result. For both constructor the 1st argument is a string. The problem I think is how the injection know whether the 2nd argument exists. — user2152814, Sep 17 '14 at 18:46

Random42 · Answer 1 · 2014-09-17T18:50:19.253

0

You can use the name:

<bean id= "InjectQuestion" class = "MyClassHello">
    <constructor-arg name = "A" value="A String"/>
</bean>

<bean id= "InjectQuestion" class = "MyClassHello">
    <constructor-arg name = "A" value="A String"/>
    <constructor-arg name = "B" value="42"/>
</bean>

Note that your syntax in declaring the class is not valid; and also when defining the bean, in class="..." you should use the fully qualified name of the class (for example packageName.subPackage.MyClassHello not just MyClassHello)

edited Sep 17 '14 at 18:50

answered Sep 17 '14 at 18:40

Random42

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Thanks. I will have a try. Sorry for the syntax. – user2152814 Sep 17 '14 at 18:49

Spring injection issue with constructor-arg overload

1 Answers1