JAXB - Annotations, Annotations for Enums: XmlEnum, XmlEnumValue

An enum type is annotated with

XmlEnum

. It has an optional element

value

of type

java.lang.Class

which defines the class used for the values used in the XML representation. Usually, and by default, this is

java.lang.String

but other types, even numeric ones, are equally possible. For a straightforward enum type, this is sufficient:

@XmlEnum
public enum SubElemType {
//...(enum definition)
}

Individual enum constants have to be annotated if there is a difference between the Java name and the string used to represent the value in XML. This is defined with an

@XmlEnumValue

annotation that is attached to individual enum constants. Its required element defines the XML representation string. If it might be useful for the Java application to have support for the conversion between Java values and XML representations as well, the enum type might define the XML representation as a parameter for the constructor, provide a getter for the XML string and perhaps even a lookup function (

fromValue

) to convert a string to the enum constant. Such a deluxe version of an enum type is shown below.

@XmlEnum
public enum SubElemType {
@XmlEnumValue("PrMaSig")
PR_MA_SIG("PrMaSig"),
@XmlEnumValue("Track1")
TRACK_1("Track1"),
// ...(more enum constant definitions)

private final String value;

SubElemType(String v) {
value = v;
}

public String value() {
return value;
}

public static SubElemType fromValue(String v) {
for (SubElemType c: SubElemType.values()) {
if (c.value.equals(v)) {
return c;
}
}
throw new IllegalArgumentException(v.toString());
}
}