Persist Data Within Your Java Applications

Evaluated skills

Persist data within your Java applications

Question 1
What does serializing mean?
- Storing things.
- Doing one thing after the other.
- Doing lots of things at once.
- Eating a corn-based breakfast with some milk and a cup of coffee.

Question 2

Have a look at the following code examples that persists data using the properties class:

public class Vehicle {
    public String registration;
    public String make;
    public String model;
    public int weightKg;
}

    public void serialiseVehicle(Vehicle v) throws IOException {
        Properties p = new Properties();

        p.setProperty("registration", v.registration);
        p.setProperty("make", v.make);
        p.setProperty("model", v.model);

        FileWriter fw = new FileWriter("Store.txt");
        p.store(fw, "Vehicle");
        fw.close();
    }

    public Vehicle deserialiseVehicle() throws IOException {
         Properties p = new Properties();
         FileReader fr = new FileReader("Store.txt"); 
         p.load(fr);
         fr.close();

         Vehicle v = new Vehicle();
         v.registration = p.getProperty("Registration");
         v.model = p.getProperty("model");
         v.make = p.getProperty("make");
         v.weightKg = p.getProperty("weight");

        return person;  
    }

Check the boxes for all the correct statements about this code.

Careful, there are several correct answers.

The deserialized Vehicle won't contain the same values as the serialized vehicle because property keys must be spelled the same - and use the same case - when writing and reading.
The deserialized vehicle will fail to load because the properties are read in the wrong order compared to the order they were written.
The code will fail because it tries to read a property that wasn't written.
The code will fail because the properties are stored as strings and not all the Vehicle fields are strings.

Question 3

Which one of the following annotations would be the best option to tell JAXB that you want to:

Store the class RobotPart.
Require the Robot Part to have a name?

@JaxbElement
public class RobotPart {

    @JaxbProperty(required=true)
    public String name;

    @JaxbProperty
    public Float price;
    
    @JaxbProperty
    public Float weight;
    
    @JaxbProperty
    public String description;
}

@XmlElement
public class RobotPart {

    @XmlElement(null=false)
    public String name;

    public Float price;
    
    public Float weight;
    
    public String description;
}

@XmlRootElement
public class RobotPart {

    @XmlElement(required=true)
    public String name;

    public Float price;
    public Float weight;
    public String description;
}

@XmlElement
public class RobotPart {

    @XmlProperty(required=true)
    public String name;

    @XmlProperty
    public Float price;
    
    @XmlProperty
    public Float weight;
    
    @XmlProperty
    public String description;
}

Persist Data Within Your Java Applications

Evaluated skills

Question 1

Question 2

Question 3