The example in this section illustrates the usage of the JSR 353 object model APIs for building an object representation of the JSON data.

This example uses the JSON array of the employee objects stored in the emp-array.json file as an input source. The contents of this file are listed under the Sample JSON file representing employee objects section. Let's see how we can convert the JSON content present in the file into a Java object model by using the JSR 353 object model API.

As you may have guessed, the first step is to read the JSON content from the emp-array.json file and store it in an appropriate data structure. The following code snippet illustrates the APIs for reading the JSON content from the file to javax.json.JsonArray:

//Import statements for the core classes 
import java.io.InputStream; 
import javax.json.JsonArray; 
import javax.json.JsonReader;  
 
//Get input stream for reading the specified resource. 
InputStream inputStream = 
    getClass().getResourceAsStream("/emp-array.json"); 
// Create JsonReader to read JSON data from a stream  
Reader reader = new InputStreamReader(inputStream, "UTF-8"); 
JsonReader jsonReader = Json.createReader(reader); 
// Creates an object model in memory. 
JsonArray employeeArray = jsonReader.readArray(); 

Here is a brief description of the preceding code snippet. javax.json.Json is the factory class that we use for creating JSON processing objects. We will use this Json class to create the javax.json.JsonReader instance. The next step is to read the JSON content into an appropriate object model. As the JSON data that we use in this example holds an array of employee objects, we call readArray() on the JsonReader instance to retrieve javax.json.JsonArray. The JsonArray instance contains an ordered sequence of zero or more objects read from the input source.

Now, let's see how to convert the JsonArray elements into specific object types. In this example, we will convert each JsonObject object present in employeeArray into the Employee object. The Employee class used in this example is shown here for your reference:

//All import statements are removed for brevity 
public class Employee { 
    private String firstName; 
    private String lastName; 
    private String email; 
    private Integer employeeId; 
    private java.util.Date hireDate; 
    //Getters and Setter for the above properties are not  
    //shown in this code snippet to save space 
}     

In this example, we create the Employee instance for each JsonObject object present in employeeArray.

The following code snippet is a continuation of the previous example. This example converts the employeeArray array that we retrieved from the JSON input file into a list of Employee objects:

//import statements for the core APIs used in  
//the following code snippet 
import javax.json.JsonObject; 
import javax.json.JsonValue;  
import java.text.SimpleDateFormat; 
import java.util.Date; 
 
//Iterate over employeeArray(JsonArray)  
//and process each JsonObject 
List<Employee> employeeList = new ArrayList<Employee>(); 
for(JsonValue jsonValue : employeeArray) { 
  //Get JsonObject and read desired attributes  
  //and copy them to Employee object   
  if(JsonValue.ValueType.OBJECT == jsonValue.getValueType()){ 
      JsonObject jsonObject = (JsonObject) jsonValue; 
      Employee employee = new Employee(); 
      employee.setFirstName(jsonObject.getString("firstName")); 
      employee.setLastName(jsonObject.getString("lastName")); 
      employee.setEmployeeId(jsonObject.getInt("employeeId")); 
      //Converts date string (from JSON) to java.util.Date object 
      SimpleDateFormat dateFormat =  
        new SimpleDateFormat("yyyy-MM-dd"); 
      Date hireDate=  
        dateFormat.parse(jsonObject.getString("hireDate")) 
      employee.setHireDate(hireDate); 
      employeeList.add(employee); 
   } 
} 

The preceding code iterates over the JsonArray instance and builds the Employee instances. Let's take a closer look at the JsonArray object to understand how it stores JSON data.

A JsonArray instance contains one or more javax.json.JsonValue elements, each representing an item present in the input source. Let's take a closer look at the representation of different value types in JSON.