How to Fix UnrecognizedPropertyException When Using XmlMapper in Jackson

Discover how to resolve the `UnrecognizedPropertyException` error in Jackson's `XmlMapper` when working with XML data in Java. Follow our clear and concise guide to correctly map your XML structure to Java classes.
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Understanding the UnrecognizedPropertyException in Jackson's XmlMapper

When working with XML data in Java, many developers rely on Jackson's XmlMapper to parse their XML strings into Java objects. However, you may encounter an error known as UnrecognizedPropertyException, which can be quite frustrating. This guide will help you understand this error, its cause, and show you how to efficiently fix it.

The Problem Overview

The UnrecognizedPropertyException signifies that Jackson has come across an XML field that does not have a corresponding property in your Java class. In your particular scenario, you received the following error message:

[[See Video to Reveal this Text or Code Snippet]]

This indicates that the XML element maximumDownloadAttempts was not recognized in the Profile class.

Analyzing the XML Structure

To better understand the issue, let's break down the XML you are working with. The structure includes:

A profilesBatch, which contains:

A profilesList, that has one or more profile elements

Each profile contains a useRestrictions section with the following properties:

maximumDownloadAttempts

maximumConfirmationAttempts

maximumNumberEIDs

maximumDownloadsPerEID

allowDownloadForDownloaded

allowDownloadForInstalled

allowDownloadForError

Inspecting Java Classes

You have defined several Java classes to represent the XML structure:

ProfilesBatch

ProfilesList

Profile

UseRestrictions

Each of these classes includes necessary annotations from the Jackson library to map XML elements to Java properties.

The Critical Issue

The root cause of the error lies in the ProfilesList class. It is defined as follows:

[[See Video to Reveal this Text or Code Snippet]]

The default behavior of @ JacksonXmlElementWrapper requires that the list be wrapped in a <profile> tag again, leading to an incorrect XML mapping.

The Solution: Update the ProfilesList Class

To resolve the UnrecognizedPropertyException, you need to modify the ProfilesList class. Specifically, you should set the useWrapping parameter of @ JacksonXmlElementWrapper to false. Here’s the updated code:

[[See Video to Reveal this Text or Code Snippet]]

Why This Works

By setting useWrapping to false, you are instructing Jackson to directly map the XML list items without requiring an additional wrapper <profile> tag. This change aligns the XML structure with your Java class expectations and allows Jackson to successfully deserialize the XML into Java objects without encountering unrecognized fields.

Conclusion

The UnrecognizedPropertyException can be a common stumbling block when working with Jackson and XML data. By carefully analyzing your XML structure and ensuring your Java classes correctly represent that structure with appropriate annotations, you can easily avoid such errors. In this case, understanding the role of the @ JacksonXmlElementWrapper annotation was crucial in resolving the issue.

If you're facing similar issues or have other questions regarding Jackson or XML processing in Java, feel free to leave a comment below!