Question

I have the following xml:

<parameters>
    <parameter >value1</param>
    <parameter >value2</param>
</parameters>

with the following class:

@XmlRootElement
public class Parameters {
    @XmlElement public String parameter;
}

How can I get warned (exception?) of the duplicate values when unmarshaling the xml to object?

Answer 1

You should have a schema a make a schema validation. If your schema permits duplicates then maybe you should switch from String to a Collection type.

If you don’t have a schema, you could use schemagen tool to generate it from your java classes.
You could even generate a schema at runtime, maybe cache it together with the JaxbContext and then use it for validation.