`NoSuchMethodError` when querying sparse vectors on Java 8

[chocoboxxf]

Environment

• Runtime: Java 8 (observed from stack trace: java.lang.Thread.run(Thread.java:750))
• Milvus Java SDK: io.milvus:milvus-sdk-java:2.6.15 (also reproducible with 2.6.14 depending on the classpath, see below)
• API: Query (v2 client), requesting a sparse vector field in OutputFields

Problem
When performing a Query that returns sparse vector fields, the application crashes with a NoSuchMethodError:

java.lang.NoSuchMethodError: java.nio.ByteBuffer.rewind()Ljava/nio/ByteBuffer;
    at io.milvus.param.ParamUtils.decodeSparseFloatVector(ParamUtils.java:1332)
    at io.milvus.response.FieldDataWrapper.getVectorData(FieldDataWrapper.java:326)
    at io.milvus.response.FieldDataWrapper.getFieldDataInternal(FieldDataWrapper.java:244)
    at io.milvus.response.FieldDataWrapper.getFieldData(FieldDataWrapper.java:231)
    at io.milvus.response.FieldDataWrapper.valueByIdx(FieldDataWrapper.java:506)
    at io.milvus.response.basic.RowRecordWrapper.buildRowRecord(RowRecordWrapper.java:82)
    at io.milvus.response.QueryResultsWrapper.buildRowRecord(QueryResultsWrapper.java:94)
    at io.milvus.response.QueryResultsWrapper.getRowRecords(QueryResultsWrapper.java:78)
    at io.milvus.v2.utils.ConvertUtils.getEntities(ConvertUtils.java:86)
    at io.milvus.v2.service.vector.VectorService.query(VectorService.java:248)
    ...

How to reproduce

1. Run an application on Java 8 that uses milvus-sdk-java 2.6.15.
2. Query a collection and include a sparse vector field in OutputFields (or otherwise trigger decoding of sparse vectors).
3. The query fails with NoSuchMethodError shown above.

Expected behavior
Query should succeed and return entities (including sparse vectors) on Java 8.

Observed behavior
Query fails at runtime with NoSuchMethodError in ParamUtils.decodeSparseFloatVector while decoding sparse vectors.

Suspected root cause
This looks like a Java 8 compatibility issue caused by an incompatible method descriptor used by the SDK at runtime:

• On Java 8, java.nio.ByteBuffer.rewind() returns java.nio.Buffer (i.e., the method is rewind()Ljava/nio/Buffer;).
• The runtime error indicates the SDK is trying to call ByteBuffer.rewind() with the descriptor ()Ljava/nio/ByteBuffer;, which corresponds to the covariant return type introduced in later JDKs (Java 9+).
• Therefore, when running on Java 8, the JVM cannot resolve ByteBuffer.rewind(): ByteBuffer, causing NoSuchMethodError.

Workarounds

• Build milvus-sdk-java-2.6.x.jar using Java 8

[chocoboxxf]

reproduced as #877
@yhmo

[yhmo]

It is my mistake that some versions of 2.6 were built by JDK 11. I will use JDK 8 to build the future versions.
A fix is here: #1783
This fix ensures it is compatible with both Java 8 and Java 11, even though the SDK is built with JDK 11.

Version	Build JDK	Class Version	Language Level	rewind() signature	Java 8 compatible
2.6.0	JDK 8	52	Java 8	Buffer	Yes
2.6.1	JDK 8	52	Java 8	Buffer	Yes
2.6.2	JDK 8	52	Java 8	Buffer	Yes
2.6.3	JDK 8	52	Java 8	Buffer	Yes
2.6.4	JDK 8	52	Java 8	Buffer	Yes
2.6.5	JDK 8	52	Java 8	Buffer	Yes
2.6.6	JDK 8	52	Java 8	Buffer	Yes
2.6.7	JDK 11	52	Java 8	ByteBuffer	No
2.6.8	JDK 11	52	Java 8	ByteBuffer	No
2.6.9	JDK 11	52	Java 8	ByteBuffer	No
2.6.10	JDK 11	52	Java 8	ByteBuffer	No
2.6.11	JDK 11	52	Java 8	ByteBuffer	No
2.6.12	JDK 11	52	Java 8	ByteBuffer	No
2.6.13	JDK 11	52	Java 8	ByteBuffer	No
2.6.14	JDK 11	52	Java 8	ByteBuffer	No
2.6.15	JDK 11	52	Java 8	ByteBuffer	No

[yhmo]

@chocoboxxf
A new version v2.6.16 has been published. I verified the issue in my local environment with JDK 8 application, it has been fixed. You can try this new version.