Converting a List of Objects to JSON and Back in Java

Discover how to easily convert a list of objects to JSON and back using Java's Jackson library, ensuring each object's class name is included in the output.
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Converting a List of Objects to JSON and Back in Java

If you're a Java developer working with lists of complex objects, you may need to serialize these lists into JSON format for data interchange or storage. Additionally, deserialization—converting JSON back into Java objects—is essential for many applications. This guide will guide you through the process of converting a list of different objects to JSON and then back to a list while retaining each object's class name.

Problem Overview

You might find yourself with a List<Object> in Java that contains various types of objects, such as Worker, Teacher, and PoliceMan. The goal is to serialize this list into JSON format where each object is represented with its class name, along with its properties.

For example, given a list containing a Worker, the expected output should be:

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However, the challenge arises when your output JSON doesn't include the class name and appears as:

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Solution Steps

To achieve the desired output, we need to utilize the Jackson library effectively. We will break down the solution into two main functions: one for serialization (converting from list to JSON) and another for deserialization (converting from JSON back to a list of objects).

1. Setting Up the Classes

First, ensure you have a base abstract class Person with necessary subclasses for each type of object:

Abstract Class: Person

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Subclasses

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2. Serialize the List to JSON

Now, let’s create a function to convert the list of Person objects to JSON:

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3. Deserialize JSON Back to List

Next, we will create another function that converts the JSON back into a list of Person objects:

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4. Test the Conversion

Finally, let's put everything together in a test method:

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Conclusion

By following these steps, you can successfully convert a list of different objects into JSON format while retaining each object's class name, then deserialize it back into a list. This approach ensures your applications can handle complex data structures seamlessly using Java's Jackson library.

Now you can store lists of various objects as JSON, make API calls easily, or even save configurations in a human-readable format. Happy coding!