Implementation:Datahub project Datahub ReadOnlyEntityException

Knowledge Sources	Datahub_project_Datahub
Domains	Java_SDK, Metadata_Management
Last Updated	2026-02-10 00:00 GMT

Overview

Description

ReadOnlyEntityException is an exception thrown when attempting to mutate a read-only entity. It extends UnsupportedOperationException and enforces immutability for entities fetched from the server. After fetching an entity via client.entities().get(), all mutation operations (set*(), add*(), remove*()) will throw this exception.

This immutability-by-default pattern:

• Makes mutations explicit and intentional
• Prevents accidental modification of fetched entities
• Enables safe passing of entities to functions without risk of mutation
• Provides a clear separation between read and write workflows

The exception generates a detailed error message with two resolution strategies and code examples specific to the entity type and operation.

Usage

This exception is thrown internally by the entity framework when a mutation method is called on a read-only entity. Users should call entity.mutable() to obtain a mutable copy before performing mutations, or use a builder to create new mutable entities.

Code Reference

Source Location

metadata-integration/java/datahub-client/src/main/java/datahub/client/v2/exceptions/ReadOnlyEntityException.java

Signature

public class ReadOnlyEntityException extends UnsupportedOperationException {

    public ReadOnlyEntityException(@Nonnull String entityType, @Nonnull String operation)

    @Nonnull
    public String getEntityType()

    @Nonnull
    public String getOperation()
}

Import

import datahub.client.v2.exceptions.ReadOnlyEntityException;

I/O Contract

Inputs

Parameter	Type	Description
entityType	String	The type of entity (e.g., "chart", "dataset")
operation	String	The mutation operation that was attempted (e.g., "set description", "add tag")

Outputs

Method	Return Type	Description
getEntityType	String	The entity type on which the mutation was attempted
getOperation	String	The mutation operation that was attempted
getMessage	String	Detailed error message with two resolution strategies and code examples

Usage Examples

// This exception is thrown automatically by the entity framework:
Dataset dataset = client.entities().get(urn);  // Read-only entity
dataset.setDescription("Updated");             // Throws ReadOnlyEntityException!

// Resolution 1: Create a mutable copy (recommended for fetched entities)
Dataset dataset = client.entities().get(urn);     // Read-only
String desc = dataset.getDescription();            // Reads work fine
Dataset mutable = dataset.mutable();               // Get mutable copy
mutable.setDescription("Updated");                 // Now mutations work
client.entities().upsert(mutable);

// Resolution 2: Use builder for new entities (already mutable)
Dataset dataset = Dataset.builder()
    .platform("snowflake")
    .name("table")
    .build();
dataset.setDescription("New description");         // Works - builder entities are mutable
client.entities().upsert(dataset);

// Catching the exception
try {
    fetchedEntity.setDescription("test");
} catch (ReadOnlyEntityException e) {
    System.err.println("Entity type: " + e.getEntityType());
    System.err.println("Operation: " + e.getOperation());
}

Related Pages

• Datahub_project_Datahub_PendingMutationsException - Complementary exception for reads on dirty entities
• Datahub_project_Datahub_DataHubClientException - Base exception class for the SDK
• Datahub_project_Datahub_HasDomains_Mixin - Example mixin using @RequiresMutable annotation