Deserialization converts a stream of bytes into a Java object that we can use in code.
We use Jackson’s ObjectMapper, as we did for serialization, using readValue() to process the input. Also, note our use of Jackson’s TypeReference, which we’ll use in all of our deserialization examples to describe the type of our destination Map.
The previous tutorial explains the Serializarion process that means converting Java Objects to JSON Payload. This is done using Jackson API. This tutorial explains the Deserialization, means converting JSON Payload to Java Objects.
Deserialization – It is the reverse of serializing. In this process, we will read the Serialized byte stream from the file and convert it back into the Class instance representation. Here, we are converting a JSON Object to an Employee class object.
We are using Jackson API for Serialization and Deserialization. So, add the Jackson dependency to the project.
Below is the sample code of the Employee table, which contains the data members needed for Employee JSON and their corresponding getter and setter methods.
public class Employee {
// private variables or data members of POJO class
private String firstName;
private String lastName;
private int age;
private double salary;
private String designation;
private String contactNumber;
private String emailId;
// Getter and setter methods
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public String getContactNumber() {
return contactNumber;
}
public void setContactNumber(String contactNumber) {
this.contactNumber = contactNumber;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
}
Now, let us create a Test Class to show Deserialization.
@Test
public void deserializationTest() {
Employee employee = new Employee();
employee.setFirstName("Tim");
employee.setLastName("Tran");
employee.setAge(49);
employee.setSalary(89000);
employee.setDesignation("Manager");
employee.setContactNumber("+3538944412341");
employee.setEmailId("ttran@test.com");
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
String employeeJson = null;
try {
employeeJson = mapper.writeValueAsString(employee);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
// Converting Employee json string to Employee class object
try {
Employee employee2 = mapper.readValue(employeeJson, Employee.class);
System.out.println("First Name of employee : " + employee2.getFirstName());
System.out.println("Last Name of employee : " + employee2.getLastName());
System.out.println("Age of employee : " + employee2.getAge());
System.out.println("Salary of employee : " + employee2.getSalary());
System.out.println("Designation of employee : " + employee2.getDesignation());
System.out.println("Contact Number of employee : " + employee2.getContactNumber());
System.out.println("EmailId of employee : " + employee2.getEmailId());
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
We can read JSON String and convert it back to Java Object as shown below. We will use readValue() to deserialize JSON content from the given file into a given Java type.
This is my JSON saved in a file placed at Desktop.
Below is the Test
@Test
public void readJson() {
ObjectMapper mapper = new ObjectMapper();
// Converting Employee JSON string to Employee class object
try {
Employee employee2 = mapper.readValue(new File(
"C:\\Users\\Vibha\\Desktop\\Employee.json"),
Employee.class);
System.out.println("First Name of employee : " + employee2.getFirstName());
System.out.println("Last Name of employee : " + employee2.getLastName());
System.out.println("Age of employee : " + employee2.getAge());
System.out.println("Salary of employee : " + employee2.getSalary());
System.out.println("Designation of employee : " + employee2.getDesignation());
System.out.println("Contact Number of employee : " + employee2.getContactNumber());
System.out.println("EmailId of employee : " + employee2.getEmailId());
} catch (StreamReadException e) {
e.printStackTrace();
} catch (DatabindException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
I hope this has helped to clear your doubts regarding how to create Java Objects from JSON using Jackson API.
We are done! Congratulations on making it through this tutorial and hope you found it useful! Happy Learning!!
This tutorial shows how to convert Java map to JSON string using Jackson’s data binding. In the previous tutorials, I have explained converting Java Objects/Arrays to JSON String using Jackson API. You can refer to the below tutorials.
This tutorial will show how to ignore certain fields when serializing an object to JSON or deserializing the JSON to object using Jackson 2.x.
This is very useful when the Jackson defaults aren’t enough and we need to control exactly what gets serialized to JSON – and there are several ways to ignore properties. One of the most common way is the use of @JsonIgnoreAnnotation, but it has some limitations. One of the major limitation is that if it is applied to getter method only, it will ignore setter method too. So, we cannot control if we want a property to be ignored for either Serialization or Deserialization.
Moreover, when there is a requirement to ignore multiple properties, it is tedious to mention @JsonIgnoreto all the properties which need to be ignored. Imagine there are 100 properties and we need to ignore 30 properties, it is tedious to mention @JsonIgnoreto each properties.
To start of, add Jackson databind dependency to the project. Always add the latest dependency to your project.
We need to create POJO for above JSON. So, let us create a class called Employee. Then create the private data members corresponding to the the nodes of the JSON and the getter and setter methods of these data members.
POJO Class
@JsonIgnoreProperties({"emailId","gender","maritalStatus"})
public class Employee {
// private variables or data members of pojo class
private String firstName;
private String lastName;
private int age;
private double salary;
private String designation;
private String contactNumber;
private String emailId;
private String gender;
private String maritalStatus;
// Getter and setter methods
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public String getContactNumber() {
return contactNumber;
}
public void setContactNumber(String contactNumber) {
this.contactNumber = contactNumber;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getMaritalStatus() {
return maritalStatus;
}
public void setMaritalStatus(String maritalStatus) {
this.maritalStatus = maritalStatus;
}
}
Here, we have added emailId, gender and maritalStatus to @JsonIgnoreProperties as shown above.
Let us create a test where we pass values to all the nodes present in the JSON and see what happens to properties – emailId, gender and maritalStatus which are tagged as @JsonIgnoreProperties.
SerializationTest
@Test
public void serializationTest() {
// Create an object of POJO class
Employee employee = new Employee();
employee.setFirstName("Vibha");
employee.setLastName("Singh");
employee.setAge(30);
employee.setSalary(75000);
employee.setDesignation("Manager");
employee.setContactNumber("+919999988822");
employee.setEmailId("abc@test.com");
employee.setMaritalStatus("married");
employee.setGender("female");
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
try {
String employeeJson = mapper.writeValueAsString(employee);
System.out.println(employeeJson);
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(employee);
System.out.println(employeePrettyJson);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
Output
You can see that emailId, gender and maritalStatus are not present in JSON Payload.
Let us see the impact of @JsonIgnoreProperties to the setter or deserialized properties.
Deserialization Test
@Test
public void deserializationTest() {
String employeeString = "{\r\n"
+ " \"firstName\" : \"Deserialization\",\r\n"
+ " \"lastName\" : \"Test\",\r\n"
+ " \"age\" : 30,\r\n"
+ " \"salary\" : 75000.0,\r\n"
+ " \"designation\" : \"Manager\",\r\n"
+ " \"contactNumber\" : \"+919999988822\",\r\n"
+ " \"emailId\" : \"abc@test.com\",\r\n"
+ " \"gender\" : \"female\",\r\n"
+ " \"maritalStatus\" : \"married\"\r\n"
+ " }";
// Converting a JSON Payload to a JAVA Object
ObjectMapper mapper = new ObjectMapper();
Employee employee2 = null;
try {
employee2 = mapper.readValue(employeeString, Employee.class);
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (JsonProcessingException e) {
e.printStackTrace();
}
System.out.println("First Name of employee : " + employee2.getFirstName());
System.out.println("Last Name of employee : " + employee2.getLastName());
System.out.println("Age of employee : " + employee2.getAge());
System.out.println("Salary of employee : " + employee2.getSalary());
System.out.println("Designation of employee : " + employee2.getDesignation());
System.out.println("Contact Number of employee : " + employee2.getContactNumber());
System.out.println("EmailId of employee : " + employee2.getEmailId());
System.out.println("Marital Status of employee : " + employee2.getMaritalStatus());
System.out.println("Gender of employee : " + employee2.getGender());
}
Output
You can see that emailId, gender and maritalStatus – the values present in JSON for all of them are ignored and default values are retrieved.
POJO with allowGetters
allowGetters are enabled to allow “getters” to be used. This is commonly set to support defining “read-only” properties; ones for which there is a getter, but no matching setter: in this case, properties should be ignored for deserialization but NOT serialization. Another way to think about this setting is that setting it to `true` will “disable” ignoring of getters.
Default value is `false`, which means that getters with matching names will be ignored.
In the below example, I have defined emailId, gender and maritalStatus as allowGetters as True.
public class EmployeeTest {
@Test
public void serializationTest() {
Employee employee = new Employee();
employee.setFirstName("Vibha");
employee.setLastName("Singh");
employee.setAge(30);
employee.setSalary(75000);
employee.setDesignation("Manager");
employee.setContactNumber("+919999988822");
employee.setEmailId("abc@test.com");
employee.setMaritalStatus("married");
employee.setGender("female");
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
try {
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(employee);
System.out.println(employeePrettyJson);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
@Test
public void deserializationTest() {
String employeeString = "{\r\n"
+ " \"firstName\" : \"Deserialization\",\r\n"
+ " \"lastName\" : \"Test\",\r\n"
+ " \"age\" : 30,\r\n"
+ " \"salary\" : 75000.0,\r\n"
+ " \"designation\" : \"Manager\",\r\n"
+ " \"contactNumber\" : \"+919999988822\",\r\n"
+ " \"emailId\" : \"abc@test.com\",\r\n"
+ " \"gender\" : \"female\",\r\n"
+ " \"maritalStatus\" : \"married\"\r\n"
+ " }";
// Converting a JSON Payload to a JAVA Object
ObjectMapper mapper = new ObjectMapper();
Employee employee2 = null;
try {
employee2 = mapper.readValue(employeeString, Employee.class);
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (JsonProcessingException e) {
e.printStackTrace();
}
System.out.println("First Name of employee : " + employee2.getFirstName());
System.out.println("Last Name of employee : " + employee2.getLastName());
System.out.println("Age of employee : " + employee2.getAge());
System.out.println("Salary of employee : " + employee2.getSalary());
System.out.println("Designation of employee : " + employee2.getDesignation());
System.out.println("Contact Number of employee : " + employee2.getContactNumber());
System.out.println("EmailId of employee : " + employee2.getEmailId());
System.out.println("Marital Status of employee : " + employee2.getMaritalStatus());
System.out.println("Gender of employee : " + employee2.getGender());
}
}
Output
In the below image, it shows that values of emailId, gender and maritalStatus are ignored and default value is passed.
POJO with allowSetters
allowSetters – Property that can be enabled to allow “setters” to be used. This could be used to specify “write-only” properties; ones that should not be serialized out, but that may be provided in for deserialization. Another way to think about this setting is that setting it to `true` will “disable” ignoring of setters.
Default value is `false`, which means that setters with matching names will be ignored.
public class EmployeeTest {
@Test
public void serializationTest() {
Employee employee = new Employee();
employee.setFirstName("Vibha");
employee.setLastName("Singh");
employee.setAge(30);
employee.setSalary(75000);
employee.setDesignation("Manager");
employee.setContactNumber("+919999988822");
employee.setEmailId("abc@test.com");
employee.setMaritalStatus("married");
employee.setGender("female");
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
try {
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(employee);
System.out.println(employeePrettyJson);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
System.out.println("########################################");
}
@Test
public void deserializationTest() {
String employeeString = "{\r\n"
+ " \"firstName\" : \"Deserialization\",\r\n"
+ " \"lastName\" : \"Test\",\r\n"
+ " \"age\" : 30,\r\n"
+ " \"salary\" : 75000.0,\r\n"
+ " \"designation\" : \"Manager\",\r\n"
+ " \"contactNumber\" : \"+919999988822\",\r\n"
+ " \"emailId\" : \"abc@test.com\",\r\n"
+ " \"gender\" : \"female\",\r\n"
+ " \"maritalStatus\" : \"married\"\r\n"
+ " }";
// Converting a JSON Payload to a JAVA Object
ObjectMapper mapper = new ObjectMapper();
Employee employee2 = null;
try {
employee2 = mapper.readValue(employeeString, Employee.class);
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (JsonProcessingException e) {
e.printStackTrace();
}
System.out.println("First Name of employee : " + employee2.getFirstName());
System.out.println("Last Name of employee : " + employee2.getLastName());
System.out.println("Age of employee : " + employee2.getAge());
System.out.println("Salary of employee : " + employee2.getSalary());
System.out.println("Designation of employee : " + employee2.getDesignation());
System.out.println("Contact Number of employee : " + employee2.getContactNumber());
System.out.println("EmailId of employee : " + employee2.getEmailId());
System.out.println("Marital Status of employee : " + employee2.getMaritalStatus());
System.out.println("Gender of employee : " + employee2.getGender());
System.out.println("########################################");
}
}
Output
We are done! Congratulations on making it through this tutorial and hope you found it useful! Happy Learning!!
This tutorial will show how to ignore certain fields when serializing an object to JSON using Jackson 2.x.
This is very useful when the Jackson defaults aren’t enough, and we need to control exactly what gets serialized to JSON – and there are several ways to ignore properties. One of the most common ways is the use of @JsonIgnore Annotation.
To start off, add Jackson’s databind dependency to the project. Always add the latest dependency to your project.
@JsonIgnore is used at field level to mark a property or list of properties to be ignored.
The Jackson’s @JsonIgnore annotation can be placed on fields, getters/setters and constructor parameters mark a property to be ignored during the serialization to JSON (or deserialization from JSON). If @JsonIgnore is the only annotation associated with a property, it will also cause the whole property to be ignored: that is, if setter has this annotation and getter has no annotations, the getter is also effectively ignored.
To learn about Serialization and Deserialization of a JSON Object using Jackson API, refer to this
To create a POJO of the above JSON, we need to create a class with the name Employee. Create private data members corresponding to these JSON nodes, and then create the corresponding getter and setter methods.
Here, I have assigned emailId and gender as @JsonIgnore.
public class Employee {
// private variables or data members of pojo class
private String firstName;
private String lastName;
private int age;
private double salary;
private String designation;
private String contactNumber;
@JsonIgnore
private String emailId;
@JsonIgnore
private String gender;
private String maritalStatus;
// Getter and setter methods
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public String getContactNumber() {
return contactNumber;
}
public void setContactNumber(String contactNumber) {
this.contactNumber = contactNumber;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getMaritalStatus() {
return maritalStatus;
}
public void setMaritalStatus(String maritalStatus) {
this.maritalStatus = maritalStatus;
}
}
Now, let us create a SerializationTest with the above-mentioned POJO.
@Test
public void serializationTest() {
Employee employee = new Employee();
employee.setFirstName("Vibha");
employee.setLastName("Singh");
employee.setAge(30);
employee.setSalary(75000);
employee.setDesignation("Manager");
employee.setContactNumber("+919999988822");
employee.setEmailId("abc@test.com");
employee.setMaritalStatus("married");
employee.setGender("female");
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
try {
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(employee);
System.out.println(employeePrettyJson);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
System.out.println("########################################");
}
Output
As you can see here that emailId and gender nodes are not present in this JSON payload.
Now, let us see an example of deserialization where nodes that are assigned as @JsonIgnore return null values.
@Test
public void deserializationTest() throws JsonMappingException, JsonProcessingException {
String employeeString = "{\r\n"
+ " \"firstName\" : \"Deserialization\",\r\n"
+ " \"lastName\" : \"Test\",\r\n"
+ " \"age\" : 30,\r\n"
+ " \"salary\" : 75000.0,\r\n"
+ " \"designation\" : \"Manager\",\r\n"
+ " \"contactNumber\" : \"+919999988822\",\r\n"
+ " \"emailId\" : \"abc@test.com\",\r\n"
+ " \"gender\" : \"female\",\r\n"
+ " \"maritalStatus\" : \"married\"\r\n"
+ " }";
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
Employee employee2 = mapper.readValue(employeeString, Employee.class);
System.out.println("First Name of employee : " + employee2.getFirstName());
System.out.println("Last Name of employee : " + employee2.getLastName());
System.out.println("Age of employee : " + employee2.getAge());
System.out.println("Salary of employee : " + employee2.getSalary());
System.out.println("Designation of employee : " + employee2.getDesignation());
System.out.println("Contact Number of employee : " + employee2.getContactNumber());
System.out.println("EmailId of employee : " + employee2.getEmailId());
System.out.println("Marital Status of employee : " + employee2.getMaritalStatus());
System.out.println("Gender of employee : " + employee2.getGender());
}
Output
We have values for fields emailId and gender in JSON, but it has not been deserialized as you can see it has default values, not from JSON.
I hope this has helped you to understand @JsonIgnore. Cheers!! Have happy learning!!
This dependency will also transitively add the following libraries to the classpath:
jackson-annotations
jackson-core
In the below example, let us assume that we need to create a new Employee (POST Request) .To start with, we need to create POJO class of the JSON payload (EmployeeDetails). This POJO class should contain the data members corresponding to the JSON nodes and their corresponding getter and setter methods.
public class EmployeeDetails {
// private variables or data members of pojo class
private String name;
private double salary;
private int age;
// Getter and Setters
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Now that we have our POJO class we can start writing some REST Assured Serialization tests!
Let’s start with REST Assured Serialization with JSON. I want to send a POST request to my EmployeeDetails API that will add a new Employee to the database. I will send a POJO of the employee in the request body. This is what the code looks like in the test class:
@Test
public void createEmployee() {
// Create an object of POJO class
EmployeeDetails emp = new EmployeeDetails();
emp.setName("Vibha");
emp.setSalary(75000);
emp.setAge(30);
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
String employeePrettyJson = null;
try {
employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(emp);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
System.out.println("Request");
System.out.println(employeePrettyJson);
System.out.println("=========================================");
System.out.println("Response");
// GIVEN
given().baseUri("http://dummy.restapiexample.com/api").contentType(ContentType.JSON).body(emp)
// WHEN
.when().post("/v1/create")
// THEN
.then().assertThat().statusCode(200).body("data.name", equalTo("Vibha"))
.body("message", equalTo("Successfully! Record has been added.")).log().body();
}
}
If you want to see the structure of Request, then add the below in the test code.
ObjectMapper mapper = new ObjectMapper();
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(emp);
System.out.println(employeePrettyJson);
REST Assured Serialization with Jackson handled all the serialization work for us. Great! See this has become so simple with the help of Jackson API.
We are done! Congratulations on making it through this tutorial and hope you found it useful! Happy Learning!!
In the previous tutorial, I have explained the creation of JSON Array using POJO. In this tutorial, I will explain the creation of a nested JSON Object (JSON with multiple nodes) using POJO.
It is recommended to go through these tutorials to understand about POJO, JSON Object and JSON Array.
It is very overwhelming to handle this type of nested JSON Object at a glance. So, we will split this into small parts or objects. So basically, we can split the above JSON into 4 parts – Employee, Contractors, CompanyPFDetails, and NestedPOJODemo.
companyName, companyEmailId, companyNumber, and companyAddress are 1:1 mapping in the payload. supportedSalaryBanks is an array of String values.
Employee has value as an array of employees. There is no ready-made data type to represent elements of this array as a whole. So here we need to create a POJO class that can contain all details of an employee.
To represent an array of Employees and Contractors
Here, I have used ObjectMapper for reading and writing JSON, either to and from basic POJOs (Plain Old Java Objects), or to and from a general-purpose JSON Tree Model (JsonNode), as well as related functionality for performing conversions.
We can save this JSON payload in a file in the project or any location of your choice. Here, I’m saving this Nested JSON Payload in a file within src/test/resources.
We need to create an Employee class that contains private data members and corresponding getter and setter methods of these data members.
Below is an Employee Class with private data members, as well as the corresponding getter and setter methods of these data members. Every IDE provides a shortcut to create these getter and setter methods.
public class Employee {
// private variables or data members of POJO class
private String firstName;
private String lastName;
private int age;
private double salary;
private String designation;
private String contactNumber;
private String emailId;
// Getter and setter methods
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public String getContactNumber() {
return contactNumber;
}
public void setContactNumber(String contactNumber) {
this.contactNumber = contactNumber;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
}
Serialization – Serialization is a process where you convert an Instance of a Class (Object of a class) into a Byte Stream. Here, we are converting Employee class object to JSON Array representation or Object.
Deserialization – It is the reverse of serializing. In this process, we will read the Serialized byte stream from the file and convert it back into the Class instance representation. Here, we are converting a JSON Array to an Employee class object.
We are using Jackson API for Serialization and Deserialization. So, add the Jackson dependency to the project.
In this tutorial, I will explain the creation of JSON Object Payload with the help of POJO (Plain Old Java Object).
What is POJO?
POJO stands for Plain Old Java Object. It is a very simple object and it has no bound or we can say that it has no restrictions other than the Java language specification. Also, it does not require any classpath.
A big advantage of POJO is it increases the readability and reusability of our project code and developers find it easy when understanding the code. Also, POJO is easy to write and anyone can understand them easily.
Now let’s deep dive into some technical terms about the POJO. Below are a few points about the POJO are:
A POJO should not have to extend prespecified classes.
Secondly, a POJO should not have implemented any prespecified interface.
Lastly, POJO should not contain prespecified annotations
A POJO class can follow some rules for better usability. These rules are:-
Each variable should be declared as private just to restrict direct access.
Each variable which needs to be accessed outside class may have a getter or a setter or both methods. If value of a field is stored after some calculations then we must not have any setter method for that.
It Should have a default public constructor.
Can override toString(), hashcode and equals() methods.
POJO classes are extensively used for creating JSON and XML payloads for API.
In the below example, let me create a simple JSON with some nodes which is actually a 1:1 mapping i.e. each key has a single value, and the type of values is mixed.
Let us create variables in the POJO class now for the above JSON. Now, a class name Employee will be created with the private data members as mentioned in the above JSON. Since we have created all variables as private, then there should be a way to manipulate or retrieve these data. So we create the corresponding getter and setter methods for these data members.
It is very tedious to create getter and setter methods for all the data members for big JSON strings. Every IDE gives you a shortcut to generate getter and setter methods. Here, I am using Eclipse and creating these getter and setter methods.
Select all the data members and Right-click on the page. Then select Source and then select Generate Getter and Setter methods.
This opens a new screen as shown below.
You can select the data member for which you want to create the getter and setter method. I want to create the getter and setter methods for all the data members, so click on Select All and then click on the Generate Button. This will generate the getter and setter methods for all the data members.
Below is the sample code of the Employee table, which contains the data members needed for Employee JSON and their corresponding getter and setter methods.
public class Employee {
// private variables or data members of POJO class
private String firstName;
private String lastName;
private int age;
private double salary;
private String designation;
private String contactNumber;
private String emailId;
// Getter and setter methods
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public String getContactNumber() {
return contactNumber;
}
public void setContactNumber(String contactNumber) {
this.contactNumber = contactNumber;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
}
Using the above POJO class, you can create any number of custom Employee objects and each object can be converted into a JSON Object and Each JSON object can be parsed into Employee POJO.
We will create a JSON object from POJO and vice versa now, which is generally called serialization and deserialization using Jackson APIs.
Serialization – Serialization is a process where you convert an Instance of a Class (Object of a class) into a Byte Stream. Here, we are converting Employee class object to JSON representation or Object
Deserialization – It is the reverse of serializing. In this process, we will read the Serialized byte stream from the file and convert it back into the Class instance representation. Here, we are converting a JSON Object to an Employee class object.
We are using Jackson API for Serialization and Deserialization. So, add the Jackson dependency to the project.
ObjectMapper provides functionality for reading and writing JSON, either to and from basic POJOs (Plain Old Java Objects), or to and from a general-purpose JSON Tree Model (JsonNode), as well as related functionality for performing conversions. It is also highly customizable to work both with different styles of JSON content and to support more advanced object concepts such as polymorphism and object identity.
Now, let us create a Test Class to show Serialization.
public class EmployeeTest {
@Test
public void serializationTest() {
Employee employee = new Employee();
employee.setFirstName("Vibha");
employee.setLastName("Singh");
employee.setAge(30);
employee.setSalary(75000);
employee.setDesignation("Manager");
// Converting a Java class object to a JSON payload as string
ObjectMapper mapper = new ObjectMapper();
String employeeJson = mapper.writeValueAsString(employee);
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(employee);
System.out.println(employeeJson);
System.out.println(employeePrettyJson);
}
}try {
String employeeJson = mapper.writeValueAsString(employee);
System.out.println(employeeJson);
String employeePrettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(employee);
System.out.println(employeePrettyJson);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
Here, ObjectMapper from fasterxml.jackson.databind is used for Serialization.
writeValueAsString() is a method that can be used to serialize any Java value as a String.
writerWithDefaultPrettyPrinter() is used to pretty-print the JSON output. It is a Factory method for constructing ObjectWriter that will serialize objects using the default pretty printer for indentation.
I hope this has helped to clear your doubts regarding POJO and how to create JSON Object using POJO.
We are done! Congratulations on making it through this tutorial and hope you found it useful! Happy Learning!!
Rest–Assured is a Java-based library that is used to test RESTful Web Services. REST-assured was designed to simplify the testing and validation of REST APIs and is highly influenced by testing techniques used in dynamic languages such as Ruby and Groovy.
QA Automation Expert 