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34.3. Enumerations

Overview
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In XML Schema, enumerated types are simple types that are defined using the xsd:enumeration facet. Unlike atomic simple types, they are mapped to Java enums.

Defining an enumerated type in XML Schema
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Enumerations are a simple type using the xsd:enumeration facet. Each xsd:enumeration facet defines one possible value for the enumerated type.
Example 34.5, “XML Schema Defined Enumeration” shows the definition for an enumerated type. It has the following possible values:
  • big
  • large
  • mungo
  • gargantuan

Example 34.5. XML Schema Defined Enumeration

<simpleType name="widgetSize">
  <restriction base="xsd:string">
    <enumeration value="big"/>
    <enumeration value="large"/>
    <enumeration value="mungo"/>
    <enumeration value="gargantuan"/>
  </restriction>
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Mapping to Java
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XML Schema enumerations where the base type is xsd:string are automatically mapped to Java enum type. You can instruct the code generator to map enumerations with other base types to Java enum types by using the customizations described in Section 38.4, “Customizing Enumeration Mapping”.
The enum type is created as follows:
  1. The name of the type is taken from the name attribute of the simple type definition and converted to a Java identifier.
    In general, this means converting the first character of the XML Schema's name to an uppercase letter. If the first character of the XML Schema's name is an invalid character, an underscrore (_) is prepended to the name.
  2. For each enumeration facet, an enum constant is generated based on the value of the value attribute.
    The constant's name is derived by converting all of the lowercase letters in the value to their uppercase equivalent.
  3. A constructor is generated that takes the Java type mapped from the enumeration's base type.
  4. A public method called value() is generated to access the facet value that is represented by an instance of the type.
    The return type of the value() method is the base type of the XML Schema type.
  5. A public method called fromValue() is generated to create an instance of the enum type based on a facet value.
    The parameter type of the value() method is the base type of the XML Schema type.
  6. The class is decorated with the @XmlEnum annotation.
The enumerated type defined in Example 34.5, “XML Schema Defined Enumeration” is mapped to the enum type shown in Example 34.6, “Generated Enumerated Type for a String Bases XML Schema Enumeration”.

Example 34.6. Generated Enumerated Type for a String Bases XML Schema Enumeration

@XmlType(name = "widgetSize")
@XmlEnum
public enum WidgetSize {

    @XmlEnumValue("big")
    BIG("big"),
    @XmlEnumValue("large")
    LARGE("large"),
    @XmlEnumValue("mungo")
    MUNGO("mungo"),
    @XmlEnumValue("gargantuan")
    GARGANTUAN("gargantuan");
    private final String value;

    WidgetSize(String v) {
        value = v;
    }

    public String value() {
        return value;
    }

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

}
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