We know that JAXB(Java Architecture for XML Binding) allows Java developers to map Java classes to XML representations. JAXB provides two main features: the ability to marshal Java objects into XML and the inverse, i.e. to unmarshal XML back into Java objects. JAXB mostly is used while implementing webservices or any other such client interface for an application where data needs to be transferred in XML format instead of HTML format which is the default in the case of the visual clients like web browsers.
A good example is Facebook APIs. Facebook has exposed its services through some open endpoints in the form of RESTful webservices where you hit a URL and post some parameters, and the API returns the data in xml format. Now it is upto you, how you use that data.
In this post, I am giving an example of marshalling and unmarshalling of Map object e.g. HashMap. These map objects usually represent the mapping between some simple keys to complex data.
1. Maven
Start with adding the latest ‘jakarta‘ dependencies for adding the JAXB support (Java 11 onwards).
<dependencies>
<dependency>
<groupId>jakarta.xml.bind</groupId>
<artifactId>jakarta.xml.bind-api</artifactId>
<version>4.0.0</version>
</dependency>
</dependencies>
<dependencies>
<dependency>
<groupId>com.sun.xml.bind</groupId>
<artifactId>jaxb-impl</artifactId>
<version>4.0.3</version>
<scope>runtime</scope>
</dependency>
</dependencies>2. Model
I have created a model class “Employee.java” which has some common fields. I want to build code that could parse maps of objects where key is sequence code and value is Employee object itself.
@XmlRootElement(name = "employee")
@XmlAccessorType (XmlAccessType.FIELD)
public class Employee
{
private Integer id;
private String firstName;
private String lastName;
private double income;
//Getters and Setters
}@XmlRootElement (name="employees")
@XmlAccessorType(XmlAccessType.FIELD)
public class EmployeeMap {
private Map<Integer, Employee> employeeMap = new HashMap<Integer, Employee>();
public Map<Integer, Employee> getEmployeeMap() {
return employeeMap;
}
public void setEmployeeMap(Map<Integer, Employee> employeeMap) {
this.employeeMap = employeeMap;
}
}3. Marshal Map to XML Example
Java example to marshal or convert java map to xml representation. In below example code, I am writing the map of employees first in console, and then in a file.
public static void main(String[] args) throws JAXBException
{
HashMap<Integer, Employee> map = new HashMap<Integer, Employee>();
Employee emp1 = new Employee();
emp1.setId(1);
emp1.setFirstName("Lokesh");
emp1.setLastName("Gupta");
emp1.setIncome(100.0);
Employee emp2 = new Employee();
emp2.setId(2);
emp2.setFirstName("John");
emp2.setLastName("Mclane");
emp2.setIncome(200.0);
map.put( 1 , emp1);
map.put( 2 , emp2);
//Add employees in map
EmployeeMap employeeMap = new EmployeeMap();
employeeMap.setEmployeeMap(map);
/******************** Marshalling example *****************************/
JAXBContext jaxbContext = JAXBContext.newInstance(EmployeeMap.class);
Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
jaxbMarshaller.marshal(employeeMap, System.out);
jaxbMarshaller.marshal(employeeMap, new File("c:/temp/employees.xml"));
}The program output:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<employees>
<employeeMap>
<entry>
<key>1</key>
<value>
<id>1</id>
<firstName>Lokesh</firstName>
<lastName>Gupta</lastName>
<income>100.0</income>
</value>
</entry>
<entry>
<key>2</key>
<value>
<id>2</id>
<firstName>John</firstName>
<lastName>Mclane</lastName>
<income>200.0</income>
</value>
</entry>
</employeeMap>
</employees>4. Unmarshal XML to Map Example
Java example to convert xml to Java map object. Let’s see the example of our EmployeeMap class.
JAXBContext jaxbContext = JAXBContext.newInstance(EmployeeMap.class);
Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
EmployeeMap empMap = (EmployeeMap) jaxbUnmarshaller.unmarshal( new File("c:/temp/employees.xml") );
for(Integer empId : empMap.getEmployeeMap().keySet())
{
System.out.println(empMap.getEmployeeMap().get(empId).getFirstName());
System.out.println(empMap.getEmployeeMap().get(empId).getLastName());
}
The program output:
Lokesh
Gupta
John
MclaneHappy Learning !!
how to use only the name of xml file without giving the full path address in unMarshalingExample() ?
what to do if wanna call xml file only by its name not by full path address?
i want learn Data Structures and Algorithms and I want know which algorithm is better for which Data Structures also….. please give me Best Reference to learn Time Complexity and Space Complexity also…..
Not sure. I still have not gone through any resource/book which I can recommend.
Ok But as per your point of view you can prefer one book, so Just give me any one based on your experience level to refer, it could be Commercial also fine or Open Source also fine…
I want grow up my Skills, i am trying for 6 months but i did’t find So please help me ……
Hi Lokesh good evening ,
thank you for Sharing Content here and giving reply for to US.
i got one Business case, that I have to Develop one Web Service and That Web Service Will have to as SOAP(JAX-RS) Web Service and as well as REST full web Service, to get the Solution i am referring JAX-RS Spec and SOAP(JAX-RS) Spec, But i could n’t able to find the Solution . So can you help me Here.
Thanking you.
You will need to develop two web services with almost similar contract.
Hi Lokesh,
Yes, but at the SOAP Point of view we can See WSDL, But JAX-RS API , Resteasy Impl will not support the any WSDl and WADL, in this case one Contract is not usefull.
here i have some doubts, IF we develop the SOAP Web Service then the Web Service will not take the GET method , Bcoz the Complexity xml Data we cant send over the Get method String Query param, So that the SOAP failed Here as per my knowledge, is there any alternative tools are there in market to support the above business case, please tell me.
I am not aware of any such tool or methodology.
OK thanks for your answer,
is it possible to build one web Service and that could be work as SOAP and REST Web Service
Not really!! Both are too much different with very less in common.
Which algorithm is better for sorting Linked List and Searching the Element in Linked list
Perhaps MergeSort will give you best results in case of LinkedList. It has been established many times by many researchers e.g. here.
Hi,
This is a very good article which helped through the issue I have been struggling with a few days now.
How can I get rid of the unwanted tags , 1 and from the output xml and only retain the actual Employee related Tags.
Thanks,
Ganga
Sorry, looks like the tags that I was referring to in the Query I posted did not display quite well . The tags that I am referring to are
1. Entry
2. Key
3. Value
I found a solution for this..I used Arraylist instead of Map…I added all the map values into Arraylist before passing it to jaxb marshaller…
Thanks,
Ganga
Seems good to me.
I have one ParentItem.java class having common attributes and 2 child classes Merchandise.java and Offer.java. I have one Transaction.java class having list of ParentItem, so as to marshal list of 2 different object and want to get structure like this :
LINE_ITEM
ADD
1
REG2
7.00
7.42
0.42
5.00
#1 Combo Meal
1695155651
5.00
1
5.00
#1 Combo Meal
1695155652
5.00
1
OTHER_COUPON
1695155653
EmpDisc
2.00
1695155651
MERCHANT_COUPON
1695155654
1OffAnyPurch
1.00
1695155651
but doing all my stuff of coding I am getting following structure:
ADD
LINE_ITEM
TIE WAIST SHIRT DRESS
1
Offer
100
How i create a java client now to view all the employee and perform an simple query
Java client for what purpose??
to retrive employee information.
Ankush
I want output is like that as PFB
Employees e =
e.getFirstName() = “Ankush”
e.getAddress() = “>”
how can get this result from jaxb
Something missing in comment. I am not able to understand it properly.
Hi Lokesh,
Could you please help me with the below XML structure where the below block would be repeated many times depending upon the condition.
ABC
.
Many Thanks!
Hi Lokesh i am getting the following error while sending the @requestline(get test/search?userid={userId}deptid={deptid}
unable to marshal type “java.util.LinkedHashMap” as an element because it is missing an @XmlRootElement annotation
You can return an instance of LinkedHashMap from your method because it does not contain @XmlRootElement annotation. You must return an instance of class which has @XmlRootElement annotation and add LinkedHashMap as an attribute in this class (with setters and getters).
https://dzone.com/articles/jaxb-and-javautilmap has some good examples.
I need to send only couple of parameters but still facing the problem
Doesn’t matter the number of parameters. The class you return from method “MUST” have @XmlRootElement annotation.