How To Ignore Unknown Properties Spell Parsing Json Inwards Coffee

One of the mutual occupation piece parsing JSON inwards Java using Jackson API is that it fails when your JSON contains unknown properties i.e. your Java shape doesn't convey all the land corresponding to all JSON properties. For example, if yous are consuming JSON from a REST Web Service as well as tomorrow they added a novel land into JSON as well as then your code volition suspension because Jackson volition throw UnrecognizedPropertyException as well as halt parsing JSON. This is troublesome as well as tin give notice motility problems in production if yous are non aware. I  convey faced this number when a developer shipped the code to swallow information from REST API without proper treatment unknown fields.

The code worked fine for months but it broke every bit shortly every bit source organization added a novel land is added to REST API. The developer chooses to ignore the update because nosotros weren't interested inwards that land but he failed to foresee that it volition touching on the JSON parsing.

Anyway, it was our fault that nosotros didn't review code properly as well as allowed him to unloose his code into production without treatment unknown files. The number could convey only been avoided if he was familiar amongst Jackson library inwards a picayune fighting to a greater extent than detail.

Jackson API provides 2 ways to ignore unknown fields, get-go at the shape grade using @JsonIgnoreProperties annotation as well as minute at the ObjectMapper grade using configure() method.

You volition regard both approaches inwards this article as well as larn how to purpose them as well as when to purpose @JsonIgnoreProperties as well as when to ignore unknown fields inwards JSON globally at the ObjectMapper level.

Ignoring unknown properties using @JsonIgnoreProperties

If yous are creating a Model shape to stand upwardly for the JSON inwards Java, as well as then yous tin give notice annotate the shape amongst @JsonIgnoreProperties(ignoreUnknown = true) to ignore whatever unknown field. Which way if at that topographic point is a novel land is added tomorrow on JSON which stand upwardly for your Model as well as then Jackson volition non throw UnrecognizedPropertyException piece parsing JSON inwards Java. 

You tin give notice purpose this approach if yous desire to ignore unknown properties alone for that Model class, but this is preferred approach because it provides yous to a greater extent than control.

Let's regard an instance of using @JsonIgnoreProperties inwards Java:

Suppose I convey next JSON, which represents my favorite book, Effective Java tertiary Edition, a must read books for every Java developer inwards 2019, as well as a Java model shape inwards my project:

If tomorrow, I add together a novel land called "edition" inwards the JSON as well as then parsing of this JSON volition neglect amongst the UnrecognizedPropertyException error. Something similar :

Exception inwards thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized land "edition" (class EBook), non marked every bit ignorable (3 known properties: , "title", "price", "author"])"

This way Jackson is non able to discovery whatever land inwards your EBook shape for "edition" belongings inwards JSON as well as therefore it's throwing the UnrecognizedPropertyException error.

You tin give notice solve this occupation as well as forestall this fault past times using @JsonIgnoreProperties annotation every bit shown below:

@JsonIgnoreProperties(ignoreUnknown = true) class EBook{   private String title;   private String author;   private int price;    ..  }

We convey exactly annotated a whole model shape every bit @JsonIgnoreProperties(ignoreUnknown = true), which hateful whatever unknown belongings inwards JSON String i.e. whatever belongings for which nosotros don't convey a corresponding land inwards the EBook shape volition survive ignored. If yous compile as well as run your programme over again it volition operate fine.

In Jackson 2.x, the @JsonIgnoreProperties reside inwards com.fasterxml.jackson.annotation package, therefore yous ask to import it every bit :

import com.fasterxml.jackson.annotation.JsonIgnoreProperties.

If yous are using an older version of Jackson API e.g. Jackson 1.x as well as then this annotation belongs to a dissimilar package, beware of that, peculiarly if yous convey both Jackson 1.x as well as Jackson 2.x inwards your classpath.

Ignoring Unknown Property inwards JSON Globally using Jackson

Another way to bargain amongst unknown properties inwards JSON yous are parsing is to configure ObjectMapper non to neglect when it encounters an unknown property. This volition also solve the occupation of UnrecognizedPropertyException. You tin give notice enable this setting past times calling configure() method every bit shown below:

import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.ObjectMapper;  ObjectMapper objectMapper = new ObjectMapper(); objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

This volition right away ignore unknown properties for whatever JSON it's going to parse, You should alone purpose this selection if yous can't annotate a shape amongst @JsonIgnoreProperties annotation.

Btw, if yous are non familiar amongst JSON parsing libraries inwards Java, then JSON amongst Java APIs, jQuery, as well as REST Web Services on Udemy is a skillful house to start with.

Java Program to Ignore Unknown Properties piece Parsing JSON using Jackson

Let's regard whatever nosotros convey learned so far inwards action. Btw, if yous are confused amongst my String JSON as well as a lot of "/r/n" string as well as then don't worry. I haven't done that manually. I used this Eclipse trick to re-create my JSON as well as it automatically included necessary escape characters. This is required because JSON string is enclosed amongst double quotes ("") which ask to survive escaped inwards Java.

Btw, if yous are novel to Eclipse IDE, as well as then I advise yous check Beginners Eclipse Java IDE Training Course on Udemy to larn it well. It's of import for Java developer to know their tools well, peculiarly IDE so that they effectively develop, test, debug, as well as run their Java application.

import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date;  import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.deser.std.StdDeserializer;  /*  * Java Program to iterate over JSONObject of json-simple  */ public class JacksonTest {    private static String json = "{\r\n" + "\"title\" : \"Effective Java\",\r\n"       + "\"author\" : \"Joshua Bloch\",\r\n" + "\"price\" : 37,\r\n"       + "\"edition\" : 37\r\n" + "}";    public static void main(String args[]) throws IOException {      // let's parse JSON amongst a appointment field     ObjectMapper mapper = new ObjectMapper();     // mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,     // false);      EBook effectiveJava = mapper.readValue(json, EBook.class);     System.out.println("Input json string");     System.out.println(json);     System.out.println("Generated coffee class: ");     System.out.println(effectiveJava);    }  }  class EBook {   private String title;   private String author;   private int price;    public EBook() {     // no declaration constructor required past times Jackson   }    public EBook(String title, String author, int price) {     this.title = title;     this.author = author;     this.price = price;   }    public String getTitle() {     return title;   }    public String getAuthor() {     return author;   }    public int getPrice() {     return price;   }    public void setTitle(String title) {     this.title = title;   }    public void setAuthor(String author) {     this.author = author;   }    public void setPrice(int price) {     this.price = price;   }    @Override   public String toString() {     return "EBook [title="How to Ignore Unknown Properties While Parsing JSON inwards Java "color: #006699; font-weight: 700;">+ title + ", author=" + writer + ", price=" + toll         + "]";   }  }  Output: Input json string { "title" : "Effective Java", "author" : "Joshua Bloch", "price" : 37, "version" : 37 } Generated coffee class:  EBook [title=Effective Java, author=Joshua Bloch, price=37]

In this program, I convey a JSON every bit discussed inwards a higher house which stand upwardly for the Effective Java tertiary edition book, a must-read for every Java developer.

I also convey a model shape called EBook, which is annotated amongst @JsonIgnoreProperties(ignoreUnknown = true) to ignore unknown properties.

If yous await closely, our JSON String contains an "edition" belongings which is non defined inwards the Java shape but the programme industrial plant because nosotros convey marked EBook with

@JsonIgnoreProperties(ignoreUnknown = true) annotation.

If yous desire to show this program, as well as then exactly take away that annotation as well as run the program, it volition throw the next error.

Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field  "edition" (class EBook), not marked every bit ignorable (3 known properties: , "title", "price", "author"]) at [Source: java.io.StringReader@19dfb72a; line: 5, column: 14] (through reference chain: EBook["edition"]) at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:79) at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty(DeserializationContext.java:555) at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:708) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1160) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:315) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:121) at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2888) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2034) at JacksonTest.main(JacksonTest.java:30)

This happened because of "edition" land which is alone acquaint inwards JSON as well as non inwards the Java class. If yous lay the annotation dorsum as well as then the code volition operate again.

You tin give notice similarly show how to ignore unknown land at the object mapper level, instead of putting the @JsonIgnoreProperties annotation back, yous exactly uncomment the mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) occupation inwards the code as well as run the program. This fourth dimension also it volition operate because Jackson is ignoring all unknown properties.


That's all most how to ignore unknown properties piece parsing JSON inwards Java using Jackson API. You tin give notice create this either past times using @JsonIgnoreProperties annotation or configuring ObjectMapper to non neglect when encountering unknown properties during deserialization past times disabling FAIL_ON_UNKNOWN_PROPERTIES.

Though, the preferred approach is to ignore unknown properties at shape grade using @JsonIgnoreProperties(ignoreUnknown = true) as well as alone create this on the ObjectMapper grade if yous can't annotate your shape amongst this annotation i.e. yous don't ain the class. It's also a best practise to annotated your model shape amongst @JsonIgnoreProperties to avoid the number I convey explained inwards the get-go paragraph.

Other Java and JSON resources yous may like
JSON inwards Action: Build JSON-Based Applications 
How to parse JSON using Gson?
5 JSON parsing libraries Java Developers Should Know
How to parse JSON array inwards Java?
How to convert JSON to HashMap inwards Java?
10 Things Java developer should larn inwards 2019
JSON amongst Java APIs, jQuery, as well as REST Web Services

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