Added MessageState enumeration and XJB file for message schema

src/main/java/envoy/schema/MessageState.java

@@ -0,0 +1,22 @@
+package envoy.schema;
+
+import javax.xml.bind.annotation.XmlEnum;
+import javax.xml.bind.annotation.XmlType;
+
+/**
+ * Project: <strong>envoy-common</strong><br>
+ * File: <strong>MessageState.java</strong><br>
+ * Created: <strong>11 Oct 2019</strong><br>
+ * 
+ * @author Kai S. K. Engelbart
+ */
+@XmlType(name = "")
+@XmlEnum
+public enum MessageState {
+
+	Waiting, Sent, Received, Read;
+
+	public String value() { return name(); }
+
+	public static MessageState fromValue(String v) { return valueOf(v); }
+}

src/main/resources/message_schema.xsd

@@ -21,7 +21,16 @@
 						<xs:element name="Sender" type="xs:long" />
 						<xs:element name="Recipient" type="xs:long" />
 						<xs:element name="Date" type="xs:date" />
-						<xs:element name="State" type="xs:boolean" />
+						<xs:element name="State">
+							<xs:simpleType>
+								<xs:restriction base="xs:string">
+									<xs:enumeration value="Waiting"/>
+									<xs:enumeration value="Sent"/>
+									<xs:enumeration value="Received"/>
+									<xs:enumeration value="Read"/>
+								</xs:restriction>
+							</xs:simpleType>
+						</xs:element>
 					</xs:sequence>
 				</xs:complexType>
 			</xs:element>

src/main/xjb/bindings.xml

@@ -0,0 +1,15 @@
+<jaxb:bindings xmlns:xs="http://www.w3.org/2001/XMLSchema"
+	xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
+	xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
+	jaxb:extensionBindingPrefixes="xjc" version="2.1">
+	<jaxb:globalBindings generateIsSetMethod="true"
+		fixedAttributeAsConstantProperty="true">
+		<xjc:serializable />
+	</jaxb:globalBindings>
+	<jaxb:bindings schemaLocation="../resources/message_schema.xsd">
+		<jaxb:bindings
+			node="//xs:element[@name='State']/xs:simpleType">
+			<jaxb:typesafeEnumClass name="MessageState" />
+		</jaxb:bindings>
+	</jaxb:bindings>
+</jaxb:bindings>