使用Jackson的XML到Java对象的反序列化

Question

I have a XML file which i want to deserialize using Jackson.But i am getting the above Exception.

   <students>
     <student>
        <Name>Tapishnu2</Name>
        <Age>25</Age>
        <Department>Computer</Department>
     </student>
     <student>
        <Name>Tapishnu1</Name>
        <Age>25</Age>
        <Department>Computer</Department>
     </student>
      <student>
        <Name>Tapishnu2</Name>
        <Age>25</Age>
        <Department>Computer</Department>
     </student>
      <student>
        <Name>Tapishnu3</Name>
        <Age>25</Age>
        <Department>Computer</Department>
      </student>
   </students>

I have a POJO class like this

 @JacksonXmlRootElement(localName = "students")
    public class Students {

    @JacksonXmlProperty(localName = "student")  
    private Student[] student;

    /*public Students(){

    }*/

    public Students( Student[] student) {
        super();
        this.student = student;
    }

    public Student[] getStudent() {
        return student;
    }

    public void setStudent(Student[] student) {
        this.student = student;
    }

    @Override
    public String toString() {
        return "students [student=" + Arrays.toString(student) + "]";
      }
    }

     public class Student {
    @JacksonXmlProperty(localName = "Name")
    String Name;

    @JacksonXmlProperty(localName = "Age")  
    String Age;

    @JacksonXmlProperty(localName = "Department")
    String Department;

    public String getName() {
        return Name;
    } 

    public void setName(String Name) {
        this.Name = Name;
    }

    public String getAge() {
        return Age;
    }

    public void setAge(String Age) {
        this.Age = Age;
    }
    public String getDepartment() {
        return Department;
    }
    public void setDepartment(String department) {
        Department = department;
    }

    @Override
    public String toString() {
        return "Student [Name=" + Name + ", Age=" + Age + ", Department="
                + Department + "]";
       }
      }

       Main class 

        file = new File("C://Avatar//Students.xml");
        System.out.println(file.canRead());  
        XmlMapper mapper = new XmlMapper();
        Students openCredentials = mapper.readValue(file, Students.class);

I am getting the following Error com.fasterxml.jackson.databind.JsonMappingException: No suitable constructor found for type [simple type, class com.Team.Students]: can not instantiate from JSON object (missing default constructor or creator, or perhaps need to add/enable type information?) at [Source: C:\\Avatar\\Students.xml; line: 2, column: 3]

I guess there is a problem with the annotations.I am a newbie to Jackson.So a help will be appreciated.

Answer 1

You need a no-arg constructor for Jackson to deserialize JSON to Java objects. In the deserialization process Jackson uses the attributes/methods either directly rather than constructors.

Try adding

public Students() {
    super();
    this.student = new Student[]{};
}

or maybe

public Students() {
    this(new Student[]{});
}