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Generate JAXB class with constant from XML schema file and XJB binding

Currently i have to hard-code the schema version (or parse it) manually in java code when working with generated JAXB classes. This can easily lead to mistakes when changing the XML schema version and feels wrong.
What i want is to specify the schema version in the schema and let xjc generate a constant in the corresponding root element class.
I haven't found a JAXB plugin or binding mechanism which i can use to meet these requirements.
example.xsd
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:my="my:namespace:v1"
targetNamespace="my:namespace:v1"
xmlns="my:namespace:v1"
elementFormDefault="qualified"
attributeFormDefault="unqualified"
<!-- Use this version information in generated class! -->
version="1.0">
<xs:element name="root" type="RootType"/>
<xs:complexType name="RootType">
<xs:sequence>
<xs:element name="name" type="xs:string" minOccurs="0" maxOccurs="1"/>
</xs:sequence>
<xs:attribute name="xsdVersion" type="xs:string" use="required"/>
[...]
</xs:schema>
Generated RootType.class:
[...]
public class RootType {
protected String name;
protected String xsdVersion;
// This shall be generated too
public static final GENERATED_WITH_VERSION = "1.0";
[...]
}

Create XML on JAVA

I need to create an XML on JAVA but for multi fields on one element:
<cities>
<city_insert city_id="123" city_name="São Paulo" />
<city_insert city_id="456" city_name="Rio de Janeiro"/>
</cities>
As you can see on the example above, the element city_insert need to have city_id, and city_name , one element can have multiples fields.
How this can be done on Java?
I've searched for DOM and JDOM parsers but still don't know how this works.
Thank you!

Refer to this question for creating an XML using DOM parser.
Create XML file using java
In order to create an attribute (which you mentioned as fields), call setAttribute() method.
nodelist = doc.getElementsByTagName("city_insert");
for (Element element : nodelist) {
Element parent = element.getParentNode()
parent.setAttribute("city_id", "123");
parent.setAttribute("city_name", "São Paulo");
}

I allways do this things using jaxb
First, generate an xsd from your xml (there are many free online generators on the net)
For your xml, an online generated xsd look as follows:
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="cities">
<xs:complexType>
<xs:sequence>
<xs:element name="city_insert" maxOccurs="unbounded" minOccurs="0">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute type="xs:short" name="city_id" use="optional"/>
<xs:attribute type="xs:string" name="city_name" use="optional"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
Then, using jaxb (many IDE's like Eclipse have an easy way of doing it) generate jaxb classes from an xsd:
Click finish, then this is java console output:
parsing a schema...
compiling a schema...
com\erax\xml\test\xsd\Cities.java
com\erax\xml\test\xsd\ObjectFactory.java
And the generated classes:
Then just use jaxb marshalling to serialize and deserialize

JAXB Unmarshall error

I'm using JAXB on my project, but from time to time, I face some problems that I can't solve. I have setup my environment like this:
Armor Class
package com.fortresswars.entity.component;
#XmlType(name = "armor", namespace = "http://fortresswars.com")
public class ArmorComponent extends AbstractComponent
package-info.java
#XmlSchema(xmlns = #XmlNs(namespaceURI = "http://fortresswars.com", prefix = "fw"), elementFormDefault = XmlNsForm.UNQUALIFIED, namespace = "http://fortresswars.com")
package com.fortresswars.entity.component;
The generated schema header is almost correct:
<xs:schema elementFormDefault="unqualified" version="1.0" targetNamespace="http://fortresswars.com" xmlns:fw="http://fortresswars.com" xmlns:tns="http://fortresswars.com" xmlns:xs="http://www.w3.org/2001/XMLSchema">
The only thing I didn't like is that TNS prefix that JAXB puts there and I can't remove. I'm using an ant task (com.sun.tools.jxc.SchemaGenTask), and I remember reading somewhere that this was the problem.
The rest of the generated scheme follows below. I'll show only the relevant part about armor:
<xs:complexType name="armor">
<xs:complexContent>
<xs:extension base="tns:abstractComponent">
<xs:sequence>
<xs:element name="value" type="xs:short" minOccurs="0"/>
<xs:element name="type" type="tns:armor-type" minOccurs="0"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
And the element that is using the armor component:
<xs:complexType name="character">
<xs:complexContent>
<xs:extension base="tns:thing">
<xs:sequence>
<xs:choice minOccurs="0" maxOccurs="unbounded">
<xs:element name="armor" type="tns:armor"/>
<xs:element name="model" type="tns:model"/>
<xs:element name="status" type="tns:status"/>
<xs:element name="costs" type="tns:costs"/>
</xs:choice>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
To test this, I created a XML Document (see the TNS prefix, I need to put it, or the fw prefix, along with the xmlns:fw also).
<?xml version="1.0" encoding="UTF-8"?><tns:character xmlns:tns="http://fortresswars.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="/home/shirkit/jMonkeyProjects/Fortress Wars/Core/schema/full.xsd">
<armor>
<value>5</value>
<type>NORMAL</type>
</armor>
</tns:character>
But when I'm unmarshalling this document, here's the error I get:
Exception: unexpected element (uri:"", local:"armor"). Expected elements are <{http://fortresswars.com}armor>,<{http://fortresswars.com}attacks>,<{http://fortresswars.com}costs>,<{http://fortresswars.com}model>,<{http://fortresswars.com}abilities>,<{http://fortresswars.com}status>,<{http://fortresswars.com}movement>
I have setup elementFormDefault to UNQUALIFIED, and even though this doesn't work. Why I'm getting this exception? And can I remove TNS prefix from the generated schema?

when you define a namespace prefix for elements of http://fortresswars.com you need to prefix all elements with it, not only character. So this should work
<?xml version="1.0" encoding="UTF-8"?>
<tns:character
xmlns:tns="http://fortresswars.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="/home/shirkit/jMonkeyProjects/Fortress Wars/Core/schema/full.xsd">
<tns:armor>
<tns:value>5</tns:value>
<tns:type>NORMAL</tns:type>
</tns:armor>
</tns:character>
The tns prefix used in the schema is unrelated to what you use as prefix for XML text that you unmarshal. You may choose any other in xmlns:whatyoulike="http://fortresswars.com". The key that connects the elements in the XML document to the definitions in the schema file is the namespace URI, in your case "http://fortresswars.com". If you define your namespace as default namespace, you can omit the prefix on every element:
<?xml version="1.0" encoding="UTF-8"?>
<character
xmlns="http://fortresswars.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="/home/shirkit/jMonkeyProjects/Fortress Wars/Core/schema/full.xsd">
<armor>
<value>5</value>
<type>NORMAL</type>
</armor>
</character>
The namespace prefix in the XSD file helps to avoid name clashes if you wan't to use the schema file together with other schema files that define types or elements with the same name. It does not force you to use it in the xml files you want to unmarshal.
On the other hand, when you marhshal objects to XML, the file package-info.java defines what prefix JAXB uses, but this only works in recent versions of JAXB and it's not always easy to assure that the correct version is in use when your code runs. But you may use a NamespacePrefixMapper to control that.

Generating JAXB class from XSDs with similar attribute names

I use maven-jaxb2-plugin to generate jaxb annotated classes from xsd. I have many xsd files like those:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="A3">
<xs:complexType>
<xs:sequence>
<xs:element name="loginPartner">
<xs:complexType>
<xs:sequence>
<xs:element type="xs:string" name="login"/>
<xs:element type="xs:string" name="password"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="A3">
<xs:complexType>
<xs:sequence>
<xs:element type="xs:string" name="errorCode"/>
<xs:element type="xs:string" name="errorDescription"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
When I run maven plugin it gives me an error:
[ERROR] Error while parsing schema(s).Location [
file:schema1.xsd{10,16}]. org.xml.sax.SAXParseException: 'A3' is already
defined
Is there any way to fix this?
Actually I have many XSDs representing request/response messages to/from server. I want to simplify creating, validating, parsing messages. Maybe is there another solution for this?

I had a similar problem; I had two separate and independent WSDL (each with several schema definitions in each) that I was running through JAXB (via the maven-jaxb2-plugin) to generate mapping classes.
My WSDL's shared a duplicate schema definition that was causing XJC to choke.
Because they were both independent, I was able to generate JAXB mappings by running two separate executions of the maven-jaxb2-plugin - one for each WSDL (covered here - How can I tell jaxb / Maven to generate multiple schema packages?).

You cannot have conflicting element definitions within the same namespace. This is same as not allowing multiple classes with the same name in a given package in Java. Your best bet is to define them with different names or in different namespaces.

you can rename the second or the first A3 of your xsd in your jaxb binding file
<jaxb:bindings schemaLocation="filePath.xsd" node="/xs:schema">
<jaxb:bindings node="//xs:element[#name='A3']">
<jaxb:property name="SecondA3"/>
</jaxb:bindings>
</jaxb:bindings>

How to generate Java code from an XSD that includes MSFT Serialization: GUID datatypes?

I have used the Jaxme 2 libraries before to generate Java code from .XSD files without a problem. I'm currently encountering a problem generating Java from an XSD file that contains a http://schemas.microsoft.com/2003/10/Serialization/ namespace.
Some sample code from my .XSD is:
<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:tns="http://schemas.datacontract.org/2004/07/MyMessagingTypes"
xmlns:ser="http://schemas.microsoft.com/2003/10/Serialization/"
elementFormDefault="qualified"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:import namespace="http://schemas.microsoft.com/2003/10/Serialization/" />
<xs:complexType name="MyMessage">
<xs:sequence>
...
<xs:element minOccurs="0" name="MyPlanID" type="ser:guid" />
...
</xs:sequence>
</xs:complexType>
<xs:element name="MyMessage" nillable="true" type="tns:MyMessage" />
</xs:schema>
The Error I'm getting is:
Invalid element: The type {http://schemas.microsoft.com/2003/10/Serialization/}guid is not defined.
Any ideas what the problem is or how I can generate Java code from this xsd?

I don't know where the schema for http://schemas.microsoft.com/2003/10/Serialization/ is located, but you would have to find it, and make sure that Java sees both schemas. Alternatively, you could edit the XSD to include your own GUID type instead.