https://github.com/mybatis/mybatis-3/issues/2541

Author: mavegaart

src/main/java/org/apache/ibatis/builder/xml/mybatis-3-mapper.dtd

@@ -61,7 +61,7 @@ extends CDATA #IMPLIED
 autoMapping (true|false) #IMPLIED
 >
 
-<!ELEMENT constructor (idArg*,arg*)>
+<!ELEMENT constructor ((idArg|arg)*)>
 
 <!ELEMENT id EMPTY>
 <!ATTLIST id

src/main/java/org/apache/ibatis/builder/xml/mybatis-mapper.xsd

@@ -108,10 +108,10 @@
   </xs:element>
   <xs:element name="constructor">
     <xs:complexType>
-      <xs:sequence>
-        <xs:element minOccurs="0" maxOccurs="unbounded" ref="idArg"/>
-        <xs:element minOccurs="0" maxOccurs="unbounded" ref="arg"/>
-      </xs:sequence>
+      <xs:choice minOccurs="0" maxOccurs="unbounded">
+        <xs:element ref="idArg"/>
+        <xs:element ref="arg"/>
+      </xs:choice>
     </xs:complexType>
   </xs:element>
   <xs:element name="id">