Develop Reference

#JsonMerge with list of objects and builder

I am trying to merge JSON objects with the new #JsonMerge annotation. I found a sample online that works when I run it in my IDE. Here's a snippet to run:
#Test
void mergeTest() throws IOException {
final Employee employee = new Employee("Serializon", new Address("Street 1", "City 1", "ZipCode1"));
final Employee newEmployee = new Employee("Serializon", new Address("Street 2", "City 2", "ZipCode2"));
assertThat(employee.getAddress().getCity()).isEqualTo("City 1");
final ObjectMapper objectMapper = new ObjectMapper();
final Employee mergedEmployee = objectMapper.readerForUpdating(employee).readValue(JSONUtil.toJSON(newEmployee));
System.out.println(objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(mergedEmployee));
assertThat(newEmployee.getAddress().getCity()).isEqualTo("City 2");
assertThat(mergedEmployee.getAddress().getCity()).isEqualTo("City 2");
}
public class Employee {
private String name;
#JsonMerge
private Address address;
public Employee(final String name, final Address address) {
this.name = name;
this.address = address;
}
public String getName() {
return name;
}
public Address getAddress() {
return address;
}
}
public class Address {
private String street;
private String city;
private String zipCode;
public Address(final String street, final String city, final String zipCode) {
this.street = street;
this.city = city;
this.zipCode = zipCode;
}
public String getStreet() {
return street;
}
public String getCity() {
return city;
}
public String getZipCode() {
return zipCode;
}
}
When I try to reproduce this with my own class, it fails with the following error:
Deserialization of [simple type, class package.State] by passing existing instance (of package.State) not supported
My class in question is a POJO with some lists and primitive properties, all with getters. It is constructed using a builder and is immutable. It looks like this:
#JsonDeserialize(builder = State.Builder.class)
public class State {
private final String id;
#JsonMerge
private final List<Module> modules;
protected State(final Builder builder) {
this.id = builder.id;
this.modules = builder.modules;
}
public static Builder builder() {
return new Builder();
}
public String getId() {
return id;
}
public List<Module> getModules() {
return modules;
}
#JsonIgnoreProperties(ignoreUnknown = true)
public static final class Builder {
private String id;
private List<Module> modules;
private Builder() {
}
public Builder withId(final String id) {
this.id = id;
return this;
}
public Builder withModules(final List<Module> modules) {
this.modules = modules;
return this;
}
public State build() {
return new State(this);
}
}
}
The merge annotation states the following:
Merging is only option if there is a way to introspect current state: if there is accessor (getter, field) to use. Merging can not be enabled if no accessor exists or if assignment occurs using a Creator setter (constructor or factory method), since there is no instance with state to introspect.
So I thought perhaps the builder might the problem, but retrofitting the Employee/Address sample with a builder still works:
#Test
void mergeTest() throws IOException {
final Employee employee = Employee.newBuilder()
.withName("Serializon")
.withAddress(Address.newBuilder()
.withStreet("Steet 1")
.withCity("City 1")
.withZipCode("ZipCode1")
.build())
.build();
assertThat(employee.getAddress().getCity()).isEqualTo("City 1");
final Employee newEmployee = Employee.newBuilder()
.withName("Serializon")
.withAddress(Address.newBuilder()
.withStreet("Steet 2")
.withCity("City 2")
.withZipCode("ZipCode2")
.build())
.build();
final ObjectMapper objectMapper = new ObjectMapper();
final Employee mergedEmployee = objectMapper.readerForUpdating(employee).readValue(JSONUtil.toJSON(newEmployee));
System.out.println(objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(mergedEmployee));
assertThat(newEmployee.getAddress().getCity()).isEqualTo("City 2");
assertThat(mergedEmployee.getAddress().getCity()).isEqualTo("City 2");
}
#JsonDeserialize(builder = Employee.Builder.class)
public class Employee {
private String name;
#JsonMerge
private Address address;
private Employee(final Builder builder) {
name = builder.name;
address = builder.address;
}
public static Builder newBuilder() {
return new Builder();
}
public String getName() {
return name;
}
public Address getAddress() {
return address;
}
public static final class Builder {
private String name;
private Address address;
private Builder() {
}
public Builder withName(final String name) {
this.name = name;
return this;
}
public Builder withAddress(final Address address) {
this.address = address;
return this;
}
public Employee build() {
return new Employee(this);
}
}
}
#JsonDeserialize(builder = Address.Builder.class)
public class Address {
private String street;
private String city;
private String zipCode;
private Address(final Builder builder) {
street = builder.street;
city = builder.city;
zipCode = builder.zipCode;
}
public static Builder newBuilder() {
return new Builder();
}
public String getStreet() {
return street;
}
public String getCity() {
return city;
}
public String getZipCode() {
return zipCode;
}
public static final class Builder {
private String street;
private String city;
private String zipCode;
private Builder() {
}
public Builder withStreet(final String street) {
this.street = street;
return this;
}
public Builder withCity(final String city) {
this.city = city;
return this;
}
public Builder withZipCode(final String zipCode) {
this.zipCode = zipCode;
return this;
}
public Address build() {
return new Address(this);
}
}
}
Finally I tried to have a list of addresses instead, and accepting the list in the builder as withAddresses instead. So, for brevity:
#JsonDeserialize(builder = Employee.Builder.class)
public class Employee {
#JsonMerge
private List<Address> addresses;
public static final class Builder {
public Builder withAddresses(final List<Address> addresses) {
this.addresses = addresses;
return this;
}
}
}
And when I run the testcase again, this fails with the same error as my own code:
Deserialization of [simple type, class se.itab.locker.core.util.Employee] by passing existing instance (of se.itab.locker.core.util.Employee) not supported
What is actually going on here, and can I resolve it somehow or is this an unsupported use case or bug?
Update
So I found that this works:
//#JsonDeserialize(builder = Employee.Builder.class)
public class Employee {
#JsonCreator
public Employee(final Employee employee) {
name = employee.name;
addresses = employee.addresses;
stringAddresses = employee.stringAddresses;
}
But then serializing causes an infinite loop instead.

Create a JSON structure from set of Java Pojo classes

I need to create a JSON object structure from set of java pojo classes. This will provide a better understand of how the objects are structured by just looking at the Json file. I tried both Gson and org.codehaus.jackson.map.ObjectMapper libraries. But couldn't generate all the Json tags relevant to all the fields in java pojo objects. The created json file is only having the values from the values stetted objects. I need to have all the fields of pojo objects in the Json file.
Gson
Hotel hotel = new Hotel(); //This hotel object includes multiple objects and those objects also include multiple objects, lists
Gson gson = new GsonBuilder().create();
String json = gson.toJson(hotel);
System.out.println(json);
ObjectMapper
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(new File("/home/Pojos.json");
This is the class and json response I got.
Hotel.java
package datatypes;
import java.util.ArrayList;
import java.util.List;
public class Hotel {
private String hotelCode;
private String chainCode;
private String hotelName;
private List<Room> rooms = new ArrayList<Room>();
private List<RoomRateRestriction> roomRateRestrictions
= new ArrayList<RoomRateRestriction>();
public String getHotelCode() {
return hotelCode;
}
public void setHotelCode(String hotelCode) {
this.hotelCode = hotelCode;
}
public String getChainCode() {
return chainCode;
}
public void setChainCode(String chainCode) {
this.chainCode = chainCode;
}
public String getHotelName() {
return hotelName;
}
public void setHotelName(String hotelName) {
this.hotelName = hotelName;
}
public List<Room> getRooms() {
return rooms;
}
public void setRooms(List<Room> rooms) {
this.rooms = rooms;
}
public void addRoom(Room room){
this.rooms.add(room);
}
public List<RoomRateRestriction> getRoomRateRestrictions() {
return roomRateRestrictions;
}
public void setRoomRateRestrictions(
List<RoomRateRestriction> roomRateRestrictions) {
this.roomRateRestrictions = roomRateRestrictions;
}
public void addRoomRateRestrictions(
RoomRateRestriction roomRateRestriction) {
this.roomRateRestrictions.add(roomRateRestriction);
}
}
JSON
{
"rooms":[],
"roomRateRestrictions":[]
}

Add serializeNulls() on GsonBuilder() to serialize null fields
Configure Gson to serialize null fields. By default, Gson omits all fields that are null
* during serialization.
class Hotel {
private String name;
private List<Guest> guests = new ArrayList<>(Collections.singleton(new Guest())); //you have to set a value in order to get the structure of the Guest class otherwise it will show an empty list []
//getter setter
}
class Guest {
private String name;
//getter setter
}
Gson
Hotel hotel = new Hotel();
Gson gson = new GsonBuilder().serializeNulls().create();
String json = gson.toJson(hotel);
System.out.println(json);
Output
{
"name":null,
"guests":[
{
"name":null
}
]
}

You can use jackson-databind library.
Maven dependency is :
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.10</version>
</dependency>
Also please find some of sample example below. Here I used Employee Object which is having nested Address object inside it.
Employee.java
public class Employee {
private int empId;
private String firstName;
private String lastName;
private double salary;
private Address address;
public Employee() {}
public Employee(int empId, String firstName, String lastName, double salary) {
this.empId = empId;
this.firstName = firstName;
this.lastName = lastName;
this.salary = salary;
}
public Employee(int empId, String firstName, String lastName, double salary, Address address) {
this.empId = empId;
this.firstName = firstName;
this.lastName = lastName;
this.salary = salary;
this.address = address;
}
public int getEmpId() {
return empId;
}
public void setEmpId(int empId) {
this.empId = empId;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
}
Address.java
public class Address {
private String street;
private String city;
private String state;
private String zip;
private String country;
public Address() {}
public Address(String street, String city, String state, String zip, String country) {
this.street = street;
this.city = city;
this.state = state;
this.zip = zip;
this.country = country;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public String getZip() {
return zip;
}
public void setZip(String zip) {
this.zip = zip;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
}
I converted a Sample java pojo class to Json and also JSON to pojo object back.
JacksonConvertion.java
public class JacksonConvertion {
public static void main(String[] args) {
pojoToJson();
jsonToPojo();
}
private static void pojoToJson() {
try {
System.out.println("Convert Object to json ");
ObjectMapper mapper = new ObjectMapper();
Address address = new Address("#103, 1st cross, manyta tech park", "Bengaluru", "Karnataka", "560010",
"India");
Address address1 = new Address();
address1.setCity("Bengaluru");
address1.setState("Karnataka");
address1.setCountry("India");
Employee emp = new Employee(1233, "Raju", "BG", 98734.23, address1);
mapper.writeValue(new File("staff.json"), emp);
String jsonString = mapper.writeValueAsString(emp);
System.out.println(jsonString);
} catch (JsonProcessingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
private static void jsonToPojo() {
try {
System.out.println("Convert Json to Object ");
ObjectMapper mapper = new ObjectMapper();
Employee employee = mapper.readValue(new File("staff.json"), Employee.class);
System.out.println(employee.getFirstName());
System.out.println(employee.getSalary());
System.out.println(employee.getAddress().getCity());
} catch (IOException e) {
e.printStackTrace();
}
}
}
Also included some of links for your reference.
Link1
Link2

I think this would work fine
Add http://www.java2s.com/Code/Jar/c/Downloadcomfasterxmljacksondatabindjar.htm and http://www.java2s.com/Code/Jar/j/Downloadjacksondatabind205sourcesjar.htm to your library.
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
public class javaPojo {
public static void main(String args[]){
Hotel hotel = new Hotel();
ObjectMapper mapper = new ObjectMapper();
try {
String json = mapper.writeValueAsString(hotel);
System.out.println("JSON = " + json);
} catch (JsonProcessingException e) {
e.printStackTrace();
}}
}
Hotel
import java.util.ArrayList;
import java.util.List;
public class Hotel {
private String hotelCode;
private String chainCode;
private String hotelName;
private List<Room> rooms = new ArrayList<Room>();
private List<RoomRateRestriction> roomRateRestrictions
= new ArrayList<RoomRateRestriction>();
public String getHotelCode() {
return hotelCode;
}
public void setHotelCode(String hotelCode) {
this.hotelCode = hotelCode;
}
public String getChainCode() {
return chainCode;
}
public void setChainCode(String chainCode) {
this.chainCode = chainCode;
}
public String getHotelName() {
return hotelName;
}
public void setHotelName(String hotelName) {
this.hotelName = hotelName;
}
public List<Room> getRooms() {
return rooms;
}
public void setRooms(List<Room> rooms) {
this.rooms = rooms;
}
public void addRoom(Room room){
this.rooms.add(room);
}
public List<RoomRateRestriction> getRoomRateRestrictions() {
return roomRateRestrictions;
}
public void setRoomRateRestrictions(
List<RoomRateRestriction> roomRateRestrictions) {
this.roomRateRestrictions = roomRateRestrictions;
}
public void addRoomRateRestrictions(
RoomRateRestriction roomRateRestriction) {
this.roomRateRestrictions.add(roomRateRestriction);
}
}
Room
public class Room {
}
RoomRateRestriction
public class RoomRateRestriction {
}
OUTPUT - JSON = {"hotelCode":null,"chainCode":null,"hotelName":null,"rooms":[],"roomRateRestrictions":[]}

Spring MVC form validation does't work for nested complex types

I am implementing a sample Spring MVC Form with Form Validation. I have a complex type Address as bean property for Student form bean. And I have added form validation #NotEmpty for Address bean properties. But the same is not reflecting in the UI. But form validation works for other primitive types of Student form bean.
So, Validation works perfectly for Student form bean but not for nested complex types like Address within Student form bean.
I am trying understand the reason and a fix.
Spring version 4.0+.
Hibernate Validator api:5.2.4
Student POJO:
package com.xyz.form.beans;
import java.util.Date;
import java.util.List;
import javax.validation.constraints.Past;
import javax.validation.constraints.Size;
import org.hibernate.validator.constraints.NotEmpty;
import com.xyz.validators.DateNotEmpty;
import com.xyz.validators.ListNotEmpty;
public class Student {
#Size(min = 2, max = 30)
private String firstName;
#Size(min = 2, max = 30)
private String lastName;
#NotEmpty
private String gender;
#DateNotEmpty
#Past
private Date DOB;
private String email;
private String mobileNumber;
#ListNotEmpty
private List<String> courses;
private Address address;
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public Date getDOB() {
return DOB;
}
public void setDOB(Date dOB) {
DOB = dOB;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getMobileNumber() {
return mobileNumber;
}
public void setMobileNumber(String mobileNumber) {
this.mobileNumber = mobileNumber;
}
public List<String> getCourses() {
return courses;
}
public void setCourses(List<String> courses) {
this.courses = courses;
}
}
Address POJO:
package com.xyz.form.beans;
import org.hibernate.validator.constraints.NotEmpty;
import com.xyz.validators.LongNotEmpty;
public class Address {
#NotEmpty
private String houseNo;
#NotEmpty
private String street;
#NotEmpty
private String area;
#NotEmpty
private String city;
#LongNotEmpty
private Long pin;
public String getHouseNo() {
return houseNo;
}
public void setHouseNo(String houseNo) {
this.houseNo = houseNo;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getArea() {
return area;
}
public void setArea(String area) {
this.area = area;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public Long getPin() {
return pin;
}
public void setPin(Long pin) {
this.pin = pin;
}
}
Student Controller:
#RequestMapping(value = "/newStudentDetails.do", method = RequestMethod.POST)
public ModelAndView newStudentDetails(
#Valid #ModelAttribute("student") com.xyz.form.beans.Student studentFormBean,
BindingResult bindingResult) {
if (bindingResult.hasErrors()) {
return new ModelAndView("newStudentPage");
}
Student studentDto = new Student();
studentDto.setFirstName(studentFormBean.getFirstName());
studentDto.setLastName(studentFormBean.getLastName());
studentDto.setGender(studentFormBean.getGender());
studentDto.setDOB(new Date(studentFormBean.getDOB().getTime()));
studentDto.setEmail(studentFormBean.getEmail());
studentDto.setMobileNumber(studentFormBean.getMobileNumber());
StringBuilder sb = new StringBuilder();
sb.append(studentFormBean.getAddress().getHouseNo() + ", ");
sb.append(studentFormBean.getAddress().getStreet() + ", ");
sb.append(studentFormBean.getAddress().getArea() + ", ");
sb.append(studentFormBean.getAddress().getCity() + "-");
sb.append(studentFormBean.getAddress().getPin());
studentDto.setAddress(sb.toString());
studentDto.setCourses(studentFormBean.getCourses());
studentDao.createStudent(studentDto);
ModelAndView mav = new ModelAndView("newStudentSuccess");
return mav;
}
Thanks,
Viswanath

You need to annotate your complex types with #Valid.
This is the reference (which references here)

Hi lets try #ModelAttribute("student") #Valid com.xyz.form.beans.Student studentFormBean in place of #Valid #ModelAttribute("student")

For nested complex types, you have to activate the direct field access. Just like below:
#org.springframework.web.bind.annotation.ControllerAdvice
public class ControllerAdvice {
#InitBinder
public void initBinder(WebDataBinder webDataBinder) {
webDataBinder.initDirectFieldAccess();
}

What's wrong with my builder pattern?

I have a problem in realisation of Builder pattern.
I have 2 classes:
package course_2;
import java.util.Date;
public class Student {
private static int idStart = 0;
private final int id = idStart++;
private String name;
private String surname;
private String secondName;
private Date birthDate;
private String address;
private String phone;
private int course;
private int group;
public static class Builder {
// Обязательные параметры
private final String name;
private final String surname;
private final Date birthDate;
// Необязательные параметры, инициализация по умолчанию
private String secondName = "";
private String address = "";
private String phone = "";
private int course = 1;
private int group = 1;
public Builder(String name, String surname, Date birthDate) {
this.name = name;
this.surname = surname;
this.birthDate = (Date) birthDate.clone();
}
public Builder SecondName(String secondName) {
this.secondName = secondName;
return this;
}
public Builder address(String address) {
this.address = address;
return this;
}
public Builder phone(String phone) {
this.phone = phone;
return this;
}
public Builder course(int course) {
this.course = course;
return this;
}
public Builder group(int group) {
this.group = group;
return this;
}
}
private Student(Builder builder) {
this.name = builder.name;
this.surname = builder.surname;
this.secondName = builder.secondName;
this.birthDate = builder.birthDate;
this.address = builder.address;
this.phone = builder.phone;
this.course = builder.course;
this.group = builder.group;
}
}
The problem is when I'm trying to call a Builder from my client code:
Student studentOne = new Student.Builder("Andrue", "Booble", /*Date variable here*/);
I'm getting a compiler problem :
Error:(24, 30) java: incompatible types: course_2.Student.Builder
cannot be converted to course_2.Student
Can somebody help me with understanding, why does this happen and how I can solve it? Thanks!

You need to add the following to your Builder:
public Student build(){
return new Student(this);
}
And call it like this:
Student studentOne = new Student.Builder("Andrue", "Booble", null).build();

new Student.Builder("Andrue", "Booble", /*Date variable here*/); returns you builder object not student.
Your factory is missing method create which invoke Student constructor
it should looks like this
public Student create(){
return new student (this);
}
and be implemented inside Builder class
now if you want to create Student, you call
Student studentOne = new Student.Builder("Andrue", "Booble", /*Date variable here*/).create();

Neo4J Spring relateTo function cannot be resolved

Given the following class:
package com.example.model;
import java.util.Collection;
import java.util.Set;
import org.neo4j.graphdb.Direction;
import org.neo4j.helpers.collection.IteratorUtil;
import org.springframework.data.neo4j.annotation.Indexed;
import org.springframework.data.neo4j.annotation.NodeEntity;
import org.springframework.data.neo4j.annotation.RelatedTo;
import org.springframework.data.neo4j.annotation.RelatedToVia;
import org.springframework.security.core.GrantedAuthority;
#NodeEntity
public class User {
private static final String SALT = "cewuiqwzie";
public static final String FRIEND = "FRIEND";
public static final String RATED = "RATED";
#Indexed
String login;
String name;
String password;
String info;
private Roles[] roles;
public User() {
}
public User(String login, String name, String password, Roles... roles) {
this.login = login;
this.name = name;
this.password = encode(password);
this.roles = roles;
}
private String encode(String password) {
return "";
// return new Md5PasswordEncoder().encodePassword(password, SALT);
}
#RelatedToVia(elementClass = Rating.class, type = RATED)
Iterable<Rating> ratings;
#RelatedTo(elementClass = Movie.class, type = RATED)
Set<Movie> favorites;
#RelatedTo(elementClass = User.class, type = FRIEND, direction = Direction.BOTH)
Set<User> friends;
public void addFriend(User friend) {
this.friends.add(friend);
}
public Rating rate(Movie movie, int stars, String comment) {
return relateTo(movie, Rating.class, RATED).rate(stars, comment);
}
public Collection<Rating> getRatings() {
return IteratorUtil.asCollection(ratings);
}
#Override
public String toString() {
return String.format("%s (%s)", name, login);
}
public String getName() {
return name;
}
public Set<User> getFriends() {
return friends;
}
public Roles[] getRole() {
return roles;
}
public String getLogin() {
return login;
}
public String getPassword() {
return password;
}
public String getInfo() {
return info;
}
public void setInfo(String info) {
this.info = info;
}
public void updatePassword(String old, String newPass1, String newPass2) {
if (!password.equals(encode(old)))
throw new IllegalArgumentException("Existing Password invalid");
if (!newPass1.equals(newPass2))
throw new IllegalArgumentException("New Passwords don't match");
this.password = encode(newPass1);
}
public void setName(String name) {
this.name = name;
}
public boolean isFriend(User other) {
return other != null && getFriends().contains(other);
}
public enum Roles implements GrantedAuthority {
ROLE_USER, ROLE_ADMIN;
#Override
public String getAuthority() {
return name();
}
}
}
I get a compilation exception here:
public Rating rate(Movie movie, int stars, String comment) {
return relateTo(movie, Rating.class, RATED).rate(stars, comment);
}
Following the tutorial here. Any insight as to where this function resides is appreciated.

You're trying to use the advanced mapping mode. See the reference manual for more information. You'll need to set up AspectJ support in your IDE. Methods are woven into your entity classes at compile time.