read Xml file with JAXB

Question

I want to read a xml file (like below) but I get an Execption. Could you please help me how can I fix this problem?

Answer 1

When you describing an XML model, you need to begin with a root entity (in your case it's the<config> element).

@XmlRootElement(name="config")
class Config implements Serializable {
   private Log log;
   private Env env;

   @XmlElement(name="log")
   public Log getLog() {
      return this.log;
   }

   @XmlElement(name="env")
   public Env getEnv() {
      return this.env;
   }

   // Setters are omitted
}

And then you parse the XML like the following:

JAXBContext jaxbContext = JAXBContext.newInstance(Config.class);
Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
Config config = (Config) jaxbUnmarshaller.unmarshal(file);
if (config != null && config.getLog() != null) {
   customer = config.getLog().getProperties();
}

Answer 2

javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"config"). Expected elements are (none)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:631)

You need to ensure that you associate a class with the root element of the XML document using @XmlRootElement or @XmlElementDecl (see: http://blog.bdoughan.com/2012/07/jaxb-and-root-elements.html). Alternatively you can use one of the unmarshal methods that take a Class parameter to tell JAXB what type of object you are unmarshalling.

---

Domain Model (Config)

I would recommend having a domain class like the following from which you could obtain the two lists of Property objects.

import java.util.*;
import javax.xml.bind.annotation.*;

@XmlRootElement
public class Config {

    private List<Property> logProperties = new ArrayList<Property>();
    private List<Property> envProperties = new ArrayList<Property>();

    @XmlElementWrapper(name="log")
    @XmlElement(name="property")
    public List<Property> getLogProperties() {
        return logProperties;
    }

    @XmlElementWrapper(name="env")
    @XmlElement(name="property")
    public List<Property> getEnvProperties() {
        return envProperties;
    }

}

Demo

import java.io.File;
import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Config.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum17059227/input.xml");
        Config config = (Config) unmarshaller.unmarshal(xml);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty(Marshaller.JAXB_NO_NAMESPACE_SCHEMA_LOCATION, "file:///C:/Documents%20and%20Settings/mojalal/Desktop/FirstXSD.xml");
        marshaller.marshal(config, System.out);
    }

}

input.xml/Output

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="file:///C:/Documents%20and%20Settings/mojalal/Desktop/FirstXSD.xml">
    <env>
        <property key="firstenv" value="fo"/>
        <property key="123" value="333"/>
    </env>
    <log>
        <property key="firstKey" value="firstValue"/>
        <property key="secoundKey" value="secoundKey"/>
        <property key="thirdKey" value="thirdValue"/>
    </log>
</config>