Geoffrey Slinker created SOLR-18196:
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Summary: 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
Bug Report: Java Serialization Broken for QueryResponse in SolrJ 10.0.0
Summary
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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
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SolrJ 10.0.0
Steps to Reproduce
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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
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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
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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.)
Suggested Fix
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Option 1: Fix SimpleOrderedMap serialization by adding proper
serialPersistentFields, writeObject, and readObject methods to handle the Map
interface correctly during Java serialization.
Option 2: Remove Serializable from SolrResponse if Java serialization is no
longer intended to be supported. Remove the serialVersionUID from SolrResponse
to make the contract explicit. Update the migration guide to document this
breaking change and recommend JavaBinCodec as the alternative.
Option 3: At minimum, add a note to the Solr 10 upgrade guide that Java
serialization of QueryResponse is no longer supported, and that JavaBinCodec
should be used instead. Note that JavaBinCodec only serializes the NamedList
response data and does not preserve client-side fields like elapsedTime.
Workaround
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Use JavaBinCodec to serialize the NamedList from QueryResponse.getResponse():
// Encode
JavaBinCodec codec = new JavaBinCodec();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
codec.marshal(response.getResponse(), baos);
byte[] bytes = baos.toByteArray();
// Decode
NamedList namedList = (NamedList) new JavaBinCodec().unmarshal(new
ByteArrayInputStream(bytes));
QueryResponse restored = new QueryResponse(namedList);
Note: elapsedTime (a client-side measurement set by SolrClient after the HTTP
round-trip) is NOT part of the NamedList and is lost during this process. QTime
(Solr's server-side query time) IS preserved as it is part of the
responseHeader in the NamedList.
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