Pracowania Programowania

Tagi

• element beginning tag:

<album>

• element end tag:

</album>

• empty tag:

<album />

Element

The element starts with the start tag, ends with the end tag, or is an empty tag.

Between the tags there is the content of the element, which can be either plain text or nested elements.

The start and empty tags can contain attributes, or key-value pairs.

We write the name of the key without quotes and values between quotes.

<track number="3" title="Time" length="3:57">
    Ticking away the moments that make up a dull day
    You fritter and waste the hours in an offhand way
    Kicking around on a piece of ground in your home town
    Waiting for someone or something to show you the way
</track>

Comments

Comments are placed between the "<! -" and "->" tags.

Jackson XML

Jackson has a module extending it to support XML serialization.

To use XML instead of JSON, just change the "ObjectMapper" to XmlMapper ":

ObjectMapper xmlMapper = new XmlMapper ();

More info:

http://www.baeldung.com/jackson-xml-serialization-and-deserialization

Task 5: XML

Using an existing JacksonSerialization class, modify it or create a new class to allow serialization / deserialization to / from XML format.

Add the xml files to the root/resources directory corresponding to existing json files.

Hint: You do not have to create the contents of xml files yourself, you can generate them using the appropriate methods.

Hint: Remember to add a library to pom.xml. The appropriate entry can be found in the XML module GitHub repository.

Task 6: Joda Time

Add a field

DateTime birthDate

to the Employee class containing the date of birth of the employee.

Add annotations on it

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm:ss.SSSZ")

Try to serialize and then deserialize the object of the modified class.

Hint: You may need the jackson-datatype-ioda module.

You need to register the Joda module in the mapper.

https://stackoverflow.com/questions/29523169/register-jodamodule-in-jax-rs-application

Task 7: Recursive references

Note that in JSON, entire objects with dependencies are printed. What would happen if employee X had a subordinate Y whose subordinate would be X again? We would get infinite recursion and error in serialization. To avoid this, we can use the annotation

Uncomment 61 line in ModeObjectCreator.java and add:

@JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class,
        property="refId", scope=Employee.class)
public class Employee { ... }

That will cause objects to be printed only once, and multiple references will use Id as a reference.

More on this topic:

http://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion

Classes from Json and XML with JAXB

Generate classes from Json / Json Schema :

http://www.jsonschema2pojo.org/

Generate classes form XML schema using Linux command

Uncomment classes ClassLoadinUtil,java and Unmarshaller.java

xjc

First create XSD schema file classes.xsd:

    <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
    <schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"
       xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="www.wmi.amu.edu.pl"
       xmlns:tns="www.wmi.amu.edu.pl" elementFormDefault="qualified">

<element name="employee" type="tns:employee"/>

<complexType name="employee">
    <sequence>
        <element name="name" type="string" minOccurs="0"/>
        <element name="salary" type="double"/>
        <element name="designation" type="string" minOccurs="0"/>
        <element name="address" type="tns:address" minOccurs="0"/>
    </sequence>
    <attribute name="id" type="int" use="required"/>
</complexType>

<complexType name="address">
    <sequence>
        <element name="city" type="string" minOccurs="0"/>
        <element name="line1" type="string" minOccurs="0"/>
        <element name="line2" type="string" minOccurs="0"/>
        <element name="state" type="string" minOccurs="0"/>
        <element name="zipcode" type="long"/>
    </sequence>
</complexType>
    </schema>

Go into the directory where schema is saved and run command

mkdir output
xjc -d output -p model2 classes.xsd

The clasess should be generated to directory output with package name model2.

Create xml file classes.xml :

<?xml version="1.0" encoding="UTF-8"?>
<tns:employee id="1" xmlns:tns="www.wmi.amu.edu.pl">
  <tns:name>Marcin Witkowski</tns:name>
  <tns:salary>100</tns:salary>
  <tns:designation>Poznan</tns:designation>
  <tns:address>
      <tns:city>Poznan</tns:city>
      <tns:line1>Uniwersytetu 78</tns:line1>
      <tns:zipcode>60606</tns:zipcode>
  </tns:address>
</tns:employee>

Check how Intellij helps you with giving hints on how to create the XML.

Validate your XML

public boolean validate(String xmlFile, StringBuilder error) {
     SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
     try {
         Resource resource = new ClassPathResource("classes.xsd");
         InputStream input = resource.getInputStream();
         File file = resource.getFile();
         Schema schema = schemaFactory.newSchema(file);
         Validator validator = schema.newValidator();
         validator.validate(new StreamSource(new StringReader(xmlFile)));
         return true;
     } catch (SAXException | IOException e) {
         error.append(e.getMessage());
         return false;
     }
 }

Serialize the XML with

                  File file = new File("classes.xml");

try (InputStream inputStream = new FileInputStream(file)) {
    model2.Employee a = new Unmarshaller().unmarshallConfiguration(inputStream);
    System.out.println(a.getName() + " " + a.getAddress().getCity());
}