Deserializing JSON with Unknown Properties Jackson

In this section, we will cover the most important unmarshalling process by using Jackson’s “2.x” version. At present, the JSON has become popular for representing data. While we deal with the JSON data having unknown properties, and unmarshal such JSON, it will throw an Unknown Property exception.

Let’s understand how we can unmarshal JSON data with Additional/Unknown fields with an example.

Deserializing JSON with addition or unknown fields

At the time of unmarshalling the JSON, JSON data can be of any shape and size. When we map it to the predefined Java objects with a set number of fields, it may cause an exception. The exception may occur when it doesn’t find the matching field in the Java object. In order to handle this exception, we need to ignore the JSON properties that cannot be mapped to an existing Java field.

JSON Data

  {“proId”:”001″,”proName”:”MX Pro 20″,”price”:”25k”,”expire”:”10-11-2022″}  

Java Object

  class Product {    //Creating properties of Product class        private String proId;          private String proName;          private String price;  }  

When we deserialize the JSON to the Product object, it will lead to the com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.

DeserializeJSONWithUnknownFields1.java

  //import required classes and package     import java.io.IOException;      import com.fasterxml.jackson.databind.ObjectMapper;        //create class DeserializeJSONWithUnknownFields1   public class DeserializeJSONWithUnknownFields1 {       //main() method start     public static void main(String args[]){      //create instance of ObjectMapper class     ObjectMapper mapper = new ObjectMapper();      try{                 //deserialize JsonString     String jsonString = “{“proId”:”001″,”proName”:”MX Pro 20″,”price”:”25k”,”expire”:”10-11-2022″}”;                  System.out.println(jsonString);                                  Product pro = mapper.readerFor(Product.class).readValue(jsonString);                System.out.println(“Product Id: “+pro.getProId());                System.out.println(“Product Name: “+pro.getName());                System.out.println(“Product Price: “+pro.getPrice());                            } catch (IOException e) {                  e.printStackTrace();              }         }     }  class Product {      //Creating properties of Product class        private String proId;          private String proName;          private String price;            //Getter and Setters      public String getProId() {            return proId;        }        public void setProId(String proId) {            this.proId = proId;        }        public String getName() {            return proName;        }        public void setProName(String name) {            this.proName = name;        }        public String getPrice() {            return price;        }        public void setPrice(String price) {            this.price = price;        }      @Override          public String toString() {              // TODO Auto-generated method stub              return “”Product [ProductId “+ proId + “, ProductName = ” + proName + “, ProductPrice = ” + price + “]”;          }    }   

Output:

Deserializing JSON with Unknown Properties Jackson

Now, in order to deal with the unknown fields, we will configure the full ObjectMapper class for ignoring the unknown properties in the JSON. We configure the ObjectMapper class in the following way:

  new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)  

Now, we simply configure the ObjectMapper class and add it to the above code.

DeserializeJSONWithUnknownFields2.java

  //import required classes and package     import java.io.IOException;    import com.fasterxml.jackson.databind.DeserializationFeature;  import com.fasterxml.jackson.databind.ObjectMapper;        //create class DeserializeJSONWithUnknownFields2   public class DeserializeJSONWithUnknownFields2 {       //main() method start     public static void main(String args[]){      //create instance of ObjectMapper class     ObjectMapper mapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);    try{     //deserialize JsonString     String jsonString = “{“proId”:”001″,”proName”:”MX Pro 20″,”price”:”25k”,”expire”:”10-11-2022″}”;      System.out.println(jsonString);                    Product pro = mapper.readerFor(Product.class).readValue(jsonString);    System.out.println(“Product Id: “+pro.getProId());    System.out.println(“Product Name: “+pro.getName());    System.out.println(“Product Price: “+pro.getPrice());                    } catch (IOException e) {      e.printStackTrace();      }     }     }  class Product {      //Creating properties of Product class    private String proId;      private String proName;      private String price;      //Getter and Setters  public String getProId() {    return proId;    }    public void setProId(String proId) {    this.proId = proId;    }    public String getName() {    return proName;    }    public void setProName(String name) {    this.proName = name;    }    public String getPrice() {    return price;    }    public void setPrice(String price) {    this.price = price;    }  @Override      public String toString() {      // TODO Auto-generated method stub      return “”Product [ProductId “+ proId + “, ProductName = ” + proName + “, ProductPrice = ” + price + “]”;      }    }    

Output:

Deserializing JSON with Unknown Properties Jackson

There is one more way of dealing with unknown properties, i.e., by using @JsonIgnoreProperties(ignoreUnknown = true) annotation at the class level in the following way:

When we use annotation at the class level, there is no need to configure ObjectMapper class for ignoring JSON properties.

DeserializeJSONWithUnknownFields3.java

  //import required classes and package     import java.io.IOException;    import com.fasterxml.jackson.annotation.JsonIgnoreProperties;  import com.fasterxml.jackson.databind.ObjectMapper;        //create class DeserializeJSONWithUnknownFields3   public class DeserializeJSONWithUnknownFields3 {       //main() method start     public static void main(String args[]){      //create instance of ObjectMapper class     ObjectMapper mapper = new ObjectMapper();    try{     //deserialize JsonString     String jsonString = “{“proId”:”001″,”proName”:”MX Pro 20″,”price”:”25k”,”expire”:”10-11-2022″}”;      System.out.println(jsonString);                  Product pro = mapper.readerFor(Product.class).readValue(jsonString);    System.out.println(“Product Id: “+pro.getProId());    System.out.println(“Product Name: “+pro.getName());    System.out.println(“Product Price: “+pro.getPrice());                    } catch (IOException e) {      e.printStackTrace();      }     }     }    // create class Product by using @JsonIgnoreProperties annotation   @JsonIgnoreProperties(ignoreUnknown = true)  class Product {      //Creating properties of Product class    private String proId;      private String proName;      private String price;    //Getter and Setters  public String getProId() {    return proId;    }    public void setProId(String proId) {    this.proId = proId;    }    public String getName() {    return proName;    }    public void setProName(String name) {    this.proName = name;    }    public String getPrice() {    return price;    }    public void setPrice(String price) {    this.price = price;    }  @Override      public String toString() {      // TODO Auto-generated method stub      return “”Product [ProductId “+ proId + “, ProductName = ” + proName + “, ProductPrice = ” + price + “]”;      }    }    

Output:

Deserializing JSON with Unknown Properties Jackson

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