Failed to build ToXContent – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch fails to convert a Java object into a JSON string, which is a process known as ToXContent. This could be due to a variety of reasons such as incorrect data types, null values, or issues with the object’s structure. To resolve this issue, you can check the data types of your fields, ensure there are no null values, and verify the structure of your Java object. Additionally, you can also use a try-catch block to handle the exception and identify the problematic field or object.

This guide will help you check for common problems that cause the log ” Failed to build ToXContent ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, client.

Log Context

Log “Failed to build ToXContent” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 public final BytesReference buildAsBytes(XContentType contentType) {
 try {
 WatcherParams params = WatcherParams.builder().hideSecrets(false).build();
 return XContentHelper.toXContent(this; contentType; params; false);
 } catch (Exception e) {
 throw new ElasticsearchException("Failed to build ToXContent"; e);
 }  static class TransformedAction implements ToXContentObject {


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