How to fix Jackson Error: Java 8 date/type

In the realm of Java programming, efficiently handling data in JSON format is a common requirement. This is where the Jackson library steps in as a powerful tool for serialization and deserialization tasks. Jackson provides a comprehensive set of APIs for working with JSON data, making it a popular choice for Java developers.

After hours of coding, you’re still stuck at this error:

Exception in thread "main" java.lang.IllegalArgumentException: Java 8 date/time type `java.time.LocalDate` not supported by default: add Module "com.fasterxml.jackson.datatype:jackson-datatype-jsr310" to enable handling (through reference chain: xxx)
	at com.fasterxml.jackson.databind.ObjectMapper ._convert(ObjectMapper.java:4393)
	at com.fasterxml.jackson.databind.ObjectMapper .convertValue(ObjectMapper.java:4324)
	at com.howtodoinjava.core.objectToMap .ObjectToMapUsingJackson.main(ObjectToMapUsingJackson.java:25)

That’s not a good way to continue the rest of the day. Why Java 8 with LocaleDate is not happy with Jackson library? Let’s find out it!

Introduction

In the world of web development, communication between different systems is crucial. This is where JSON, or JavaScript Object Notation, steps in as a fundamental player. JSON serves as a standardized data format, offering a way to structure and transmit information between a server and a client, or between different parts of a program.

What is JSON?

At its core, JSON is a text-based data format designed to be both human-readable and machine-parseable. It provides a clear and organized way to represent complex data structures using a combination of key-value pairs, arrays, and nested objects. JSON’s simplicity and efficiency have made it a popular choice for data interchange on the web.

The Anatomy of JSON

JSON data is organized into two main structures: objects and arrays.

Objects

An object in JSON is enclosed within curly braces {} and consists of key-value pairs. Each key is a string that acts as a label for its corresponding value, which can be of any valid JSON data type (string, number, boolean, null, array, or another object). For example:

{
  "name": "John Doe",
  "age": 30,
  "isStudent": false,
  "languages": ["JavaScript", "Python", "Java"]
}

Arrays

An array is an ordered collection of values, enclosed within square brackets []. These values can be of any data type, including other arrays or objects. For instance:

[ "apple", "banana", "cherry", {"color": "red", "taste": "sweet"}, [1, 2, 3] ]

Why Use JSON?

1. Readability and Simplicity

One of JSON’s strengths is its human-readable format. Unlike binary formats, JSON can be easily inspected and understood by developers, which aids in debugging and troubleshooting.

2. Language Agnostic

JSON is not tied to any particular programming language or platform. This means that JSON data can be generated and consumed by a wide range of programming languages, making it an excellent choice for cross-platform communication.

3. Lightweight and Fast Parsing

JSON’s simplicity lends itself to efficient parsing, which is crucial for performance in web applications. This makes it an optimal choice for sending data over the internet.

4. Extensibility

JSON allows for nested structures, making it versatile for representing complex data. It can handle a wide range of data types and structures, making it suitable for various applications.

In summary, JSON serves as a universal language for data interchange on the web. Its simplicity, readability, and wide compatibility make it a powerful tool for developers across different domains. Whether you’re working on web applications, APIs, or even storing configuration settings, JSON is an essential part of the modern developer’s toolkit.

What is the Jackson Library?

The Jackson library is a high-performance JSON processing framework for Java. It offers a wide range of functionalities, including parsing JSON, generating JSON from Java objects, and vice versa. Jackson is widely recognized for its speed and efficiency, making it a top choice for processing JSON data in Java applications.

How to solve the Jackson error with Java LocaleDate?

Well after hours of search, this is the best way to solve the problem. The first step is to add to the pom.xml file this dependency:

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.datatype/jackson-datatype-jdk8 -->
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
            <version>2.15.2</version>
        </dependency>

JAX-RS or Spring Boot has an auto-detector component which detects all possible ObjectMapper , but the default is not able to map the LocalDate or LocaleDateTime element for Json. So it is necessary to add this class into your project:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;

@Provider
public class ObjectMapperContextResolver implements ContextResolver<ObjectMapper> {
    private final ObjectMapper MAPPER;

    public ObjectMapperContextResolver() {
        MAPPER = new ObjectMapper();
        // Now you should use JavaTimeModule instead
        MAPPER.registerModule(new JavaTimeModule());
        MAPPER.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
    }

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return MAPPER;
    }
}

Conclusion

If you face the Jackson error for Java 8 with LocaleDate or LocaleDateTime, this is a good workaround to fix it. Jackson is a very powerful library for your RESTFul API project, but of course you can still use other solutions!