Скачать или смотреть How to Work with Wrapped Data using Moshi, Retrofit, and Java

Discover a simple method to handle wrapped data in APIs using Moshi and Retrofit in Java, without needing to create multiple parent classes for each model.
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Handling Wrapped Data with Moshi, Retrofit, and Java

When working with APIs, you sometimes encounter wrapped data structures that can complicate deserialization. If you’re using Moshi with Retrofit in Java, you might find yourself needing to extract data from a custom object wrap. This guide will help you navigate through this situation seamlessly.

The Problem

You have an API that responds with a specific JSON structure, encapsulating all data in a wrapper object. Here’s a simplified representation of the JSON structure you are working with:

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Since your model represents just part of this wrapped structure, using Moshi directly to convert the Retrofit body into your models won’t work as expected.

The Solution

To effectively manage the wrapped data without creating a parent class for every model, you can implement a generic class that handles the desired transformations.

Step 1: Change from Moshi to Gson

To facilitate the generic operations without altering your entire structure, a simple switch from Moshi to Gson is proposed. Gson is capable of handling such generic types easily.

Step 2: Create Your Model Class

Here’s an example of your model class, BookCollection, which represents each collection of books:

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Step 3: Define a Wrapper Class

Next, you’ll need to create a wrapper class that can encapsulate your API response:

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Step 4: Add an Error Class

An ApiError class will help you handle errors in the API response:

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Step 5: Integrate with Retrofit Call

You need to call an API method in your ViewModel that will utilize Retrofit to fetch the data. Here’s how you can define the interface and execute the network call:

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In your ViewModel, handle the response as follows:

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Benefits of Using the Wrapper Class

Reusability: The ApiWrapper class allows you to apply the same structure across different data models (e.g., Books, Users, etc.).

Clarity: By encapsulating the status and error information separately, your code becomes clearer and easier to maintain.

Simplicity: You'll avoid the overhead of creating multiple classes for every data type you wish to deserialize.

Conclusion

Working with wrapped data in APIs can often lead to unnecessary complexity. By utilizing a generic wrapper class and switching to Gson, you can streamline your data handling processes in Java while maintaining clean and organized code. Happy coding!