无法在 Spring Boot 中反序列化嵌套对象“Role”

Question

I'm new to Spring boot. Trying to fetch all the documents from employee collections which has some roles associated with them.when tried fetching all employee documents using "findAll()" method from mongo repository, I'm getting empty roles as shown below in the output.

Note : Roles are associated with each employee in MongoDB. 

Output of REST call

[
    {
        "id": 0,
        "name": null,
        "organization": null,
        "email": null,
        "password": null,
        "roles": null,
        "enabled": false,
        "skills": null
    },
    {
        "id": 123,
        "name": "Harry",
        "organization": "Hollywood",
        "email": "harry@demo.com",
        "password": "HarryMovie",
        "roles": [],
        "enabled": true,
        "skills": [
            "Performer",
            "Entertainer",
            "Actor",
            "Producer"
        ]
    },
    {
        "id": 1902,
        "name": "Harry",
        "organization": "Hollywood",
        "email": "harry@demo.com",
        "password": "HarryMovie",
        "roles": [],
        "enabled": true,
        "skills": [
            "Performer",
            "Entertainer",
            "Actor",
            "Producer"
        ]
    }
]

Employee.class

package com.app.TestSecurityApp.Pojo;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.DBRef;
import org.springframework.data.mongodb.core.mapping.Document;

import java.io.Serializable;
import java.util.List;
import java.util.Set;

@Document(collection="employee")
public class Employee implements Serializable {

    @Id
    private int id;
    private String name;
    private String organization;
    private String email;
    private String password;
    @DBRef
    private List<Role> roles;
    private boolean enabled;
    private List <String> skills;



    public Employee() {
    }


    public List <Role> getRoles() {
        return roles;
    }

    public void setRoles(List <Role> roles) {
        this.roles = roles;
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }



    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getorganization() {
        return organization;
    }

    public void setorganization(String organization) {
        this.organization = organization;
    }

    public List <String> getSkills() {
        return skills;
    }

    public void setSkills(List <String> skills) {
        this.skills = skills;
    }



    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", organization='" + organization + '\'' +
                ", email='" + email + '\'' +
                ", password='" + password + '\'' +
                ", roles=" + roles +
                ", enabled=" + enabled +
                ", skills=" + skills +
                '}';
    }
}

Role.class

package com.app.TestSecurityApp.Pojo;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.index.IndexDirection;
import org.springframework.data.mongodb.core.index.Indexed;
import org.springframework.data.mongodb.core.mapping.Document;

import java.io.Serializable;


@Document(collection = "role")
public class Role{


    @Id
    private int id;

    @Indexed(unique = true, direction = IndexDirection.DESCENDING, dropDups = true)
    private String role;

    public Role(String role) {
        this.id = id;
        this.role = role;
    }

    public Role() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public Role(int id, String role) {
        this.id = id;
        this.role = role;
    }

    public String getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    }

    @Override
    public String toString() {
        return "Role{" +
                "id=" + id +
                ", role='" + role + '\'' +
                '}';
    }
}

Spring Controller:

package com.app.TestSecurityApp.controllers;


import com.app.TestSecurityApp.Pojo.Employee;
import com.app.TestSecurityApp.Pojo.Role;
import com.app.TestSecurityApp.repository.EmployeeRepsitory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import java.lang.invoke.MethodType;
import java.util.ArrayList;
import java.util.List;

@RestController
@RequestMapping(value = "/employee")
public class EmployeeAccessControllers {

    @Autowired
    EmployeeRepsitory employeeRepsitory;


    @RequestMapping(value = "/get", method = RequestMethod.GET,produces = MediaType.APPLICATION_JSON_VALUE)
    public List<Employee> getEmployeeList() {
        return employeeRepsitory.findAll();

    }

    @RequestMapping(value = "/set", method = RequestMethod.POST,produces = MediaType.APPLICATION_JSON_VALUE)
    public Employee setEmployee(@RequestBody Employee employee) {

        employeeRepsitory.save(employee);
        return employee;

    }


}

Answer 1

It's not serializing properly, because it does not implement the marking interface. Change public class Role to public class Role implements Serializable .

Also @DBRef is not needed, it's used to store parent with children as separate documents in db together with references. Adding serialization to all classes, makes the document embedded.