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https://issues.apache.org/jira/browse/SOLR-18196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18077226#comment-18077226
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Mikhail Khludnev commented on SOLR-18196:
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I haven't heard there are contract for Java's serialization for SolrJ and
others', just because Solr has own javabin serialization format. Maybe I miss
something. So, I suppose it was a de facto never guarantee behavior, which were
legally dropped in the next major release. It's sad, but that's it.
> Java serialization broken for QueryResponse - SimpleOrderedMap implements Map
> breaks ObjectOutputStream
> --------------------------------------------------------------------------------------------------------
>
> Key: SOLR-18196
> URL: https://issues.apache.org/jira/browse/SOLR-18196
> Project: Solr
> Issue Type: Bug
> Components: clients - java
> Affects Versions: 10.0
> Environment: Client using SolrJ on Mac OS using Java 21. Solr
> instances running in AWS on EC2 instances.
> Reporter: Geoffrey Slinker
> Priority: Major
>
> Bug Report: Java Serialization Broken for QueryResponse in SolrJ 10.0.0
> Summary
> -------
> org.apache.solr.client.solrj.response.QueryResponse declares "implements
> Serializable" (inherited from SolrResponse) but cannot be serialized using
> Java's ObjectOutputStream in SolrJ 10.0.0. This is a regression from SolrJ
> 9.x where Java serialization worked correctly.
> Affected Version
> ----------------
> SolrJ 10.0.0
> Steps to Reproduce
> ------------------
> 1. Obtain a QueryResponse from any SolrClient.query() call.
> 2. Attempt to serialize it with ObjectOutputStream:
> QueryResponse response = solrClient.query("collection", query,
> SolrRequest.METHOD.POST);
> ByteArrayOutputStream baos = new ByteArrayOutputStream();
> ObjectOutputStream oos = new ObjectOutputStream(baos);
> oos.writeObject(response); // FAILS
> Expected Behavior
> -----------------
> The QueryResponse object should serialize successfully, as it did in SolrJ
> 9.x. The class hierarchy declares Serializable:
> SolrResponse implements Serializable (with serialVersionUID)
> SolrResponseBase extends SolrResponse
> QueryResponse extends SolrResponseBase
> Actual Behavior
> ---------------
> Serialization fails with:
> java.lang.NoSuchFieldException: serialPersistentFields
> The exception is thrown during ObjectOutputStream.writeObject() when Java's
> serialization mechanism attempts to introspect the class hierarchy.
> Root Cause
> ----------
> In Solr 10.0.0, SimpleOrderedMap was changed to implement java.util.Map as
> part of SIP-22 (NamedList Reduction):
> SolrJ 9.x: public class SimpleOrderedMap<T> extends NamedList<T>
> SolrJ 10.0: public class SimpleOrderedMap<T> extends NamedList<T>
> implements Map<String, T>
> QueryResponse internally contains a NamedList (via
> SolrResponseBase.response), which at runtime is a SimpleOrderedMap. When
> Java's ObjectOutputStream walks the class hierarchy of SimpleOrderedMap to
> build serialization metadata, it encounters the Map interface and attempts to
> locate serialPersistentFields on the class. This introspection fails with
> NoSuchFieldException, which causes serialization to fail.
> Impact
> ------
> Any code that relies on Java serialization of QueryResponse (or any
> SolrResponse subclass containing SimpleOrderedMap instances) is broken. This
> includes:
> - Caching serialized Solr responses
> - Storing Solr responses for test fixtures
> - Any framework that serializes Serializable objects (session replication,
> distributed caches, etc.)
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