Deserializing JSON object using Xstream

Question

My task is to describe the classes Student and Academic group (with the field - an array of students). Create objects. Provide file creation and reading from files using three approaches:

serialization and deserialization in JSON (by means of XStream).

I serialize an Academic group that has students array list :

public class AcademicGroup  {

    private List<Student> students;

    public AcademicGroup() {
        this.students = new ArrayList<>();
    }

    public void addStudent(Student student) {
        students.add(student);
    }

    public Student[] getStudents() {
        return students.toArray(new Student[0]);
    }
}

and student:

public class Student {
    private String name;
    private String group;

    public Student(String name, String group) {
        this.name = name;
        this.group = group;
    }

    public String getName() {
        return name;
    }

    public String getGroup() {
        return group;
    }

    @Override
    public String toString() {
        return name + " " + group;
    }
}

serialize function

public static void studentJsonSerialization() {
        XStream xStream = new XStream(new JsonHierarchicalStreamDriver());
        List<Student> students = Arrays.asList(
                new Student("Student1", "KN-221A"),
                new Student("Student2", "KN-221A"),
                new Student("Student3", "KN-221A")
        );
        AcademicGroup academicGroup = new AcademicGroup();
        for (Student student : students) {
            academicGroup.addStudent(student);
        }
        xStream.alias("academicGroup", AcademicGroup.class);
        String xml = xStream.toXML(academicGroup);
        try (FileWriter fw = new FileWriter("AcademicGroup.json");
             PrintWriter out = new PrintWriter(fw)) {
            out.println(xml);
        }
        catch (IOException e) {
            e.printStackTrace();
        }
}

the file AcademicGroup.json that I get:

{"academicGroup": {
  "students": [
    {
      "name": "Student1",
      "group": "KN-221A"
    },
    {
      "name": "Student2",
      "group": "KN-221A"
    },
    {
      "name": "Student3",
      "group": "KN-221A"
    }
  ]
}}

deserialization function:

    public static void studentJsonDeserialization() {
        XStream xStream = new XStream(new JettisonMappedXmlDriver());
        xStream.addPermission(AnyTypePermission.ANY);
        xStream.alias("academicGroup", AcademicGroup.class);

        AcademicGroup newAcademicGroup = (AcademicGroup) xStream.fromXML(new File("AcademicGroup.json"));
        for (Student student : newAcademicGroup.getStudents()) {
            System.out.println(student.toString());
        }
    }

I need to print json objects in console, but I get an error message

Exception in thread "main" com.thoughtworks.xstream.converters.ConversionException: 
---- Debugging information ----
cause-exception     : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message       : name
class               : java.util.ArrayList
required-type       : java.util.ArrayList
converter-type      : com.thoughtworks.xstream.converters.collections.CollectionConverter
path                : /academicGroup/students/name
line number         : -1
class[1]            : org.example.AcademicGroup
required-type[1]    : org.example.AcademicGroup
converter-type[1]   : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
version             : 1.4.20

Answer 1

You try adding xStream.autodetectAnnotations(true). This should work.

public static void studentJsonDeserialization() {
    XStream xStream = new XStream(new JettisonMappedXmlDriver());
    xStream.autodetectAnnotations(true);
    xStream.addPermission(AnyTypePermission.ANY);
    xStream.alias("academicGroup", AcademicGroup.class);

    AcademicGroup newAcademicGroup = (AcademicGroup) xStream.fromXML(new File("AcademicGroup.json"));
    for (Student student : newAcademicGroup.getStudents()) {
        System.out.println(student.toString());
    }
}