Implementation:Microsoft Onnxruntime OnnxMap

Knowledge Sources	Description
Source File	java/src/main/java/ai/onnxruntime/OnnxMap.java
Repository	Microsoft/onnxruntime

Domains

• Machine Learning Runtime
• Map Value Container
• JNI Native Interop

Overview

OnnxMap is a container for map values returned by OrtSession.run(). It wraps a native ORT map value and provides access to the underlying key-value pairs. Supported key types are String and Long; supported value types are String, Long, Float, and Double. The class implements the OnnxValue interface and contains the OnnxMapValueType inner enum.

Description

The OnnxMap class provides:

• Value extraction: getValue() returns a Map<Object, Object> containing all entries. Keys and values are boxed as needed.
• Size: size() returns the number of entries from the MapInfo.
• Type info: getInfo() returns the MapInfo describing key and value types.
• Native key extraction: Private native methods getStringKeys and getLongKeys.
• Native value extraction: Private native methods getStringValues, getLongValues, getFloatValues, getDoubleValues.
• Lifecycle: close() releases native memory; isClosed() checks state.

The inner enum OnnxMapValueType defines INVALID, STRING, LONG, FLOAT, DOUBLE value types with mapping methods.

Code Reference

Source Location

// File: java/src/main/java/ai/onnxruntime/OnnxMap.java
// Package: ai.onnxruntime

Signature

public class OnnxMap implements OnnxValue {
    public int size();
    public OnnxValueType getType();
    public Map<? extends Object, ? extends Object> getValue() throws OrtException;
    public MapInfo getInfo();
    public synchronized boolean isClosed();
    public synchronized void close();

    public enum OnnxMapValueType {
        INVALID(0), STRING(1), LONG(2), FLOAT(3), DOUBLE(4);
        public static OnnxMapValueType mapFromInt(int value);
        public static OnnxMapValueType mapFromOnnxJavaType(OnnxJavaType type);
    }
}

Import

import ai.onnxruntime.OnnxMap;

I/O Contract

Inputs

Name	Type	Description
nativeHandle	long	Pointer to the native ORT map value (set internally)
allocatorHandle	long	Pointer to the allocator that created the map
info	MapInfo	Type information about keys and values

Outputs

Name	Type	Description
getValue()	Map<?, ?>	Java HashMap containing all key-value pairs
size()	int	Number of entries in the map
getInfo()	MapInfo	Map type metadata

Usage Examples

import ai.onnxruntime.*;
import java.util.*;

OrtEnvironment env = OrtEnvironment.getEnvironment();
try (OrtSession session = env.createSession("/path/to/model.onnx")) {
    Map<String, OnnxTensorLike> inputs = new HashMap<>();
    // ... prepare inputs ...

    try (OrtSession.Result results = session.run(inputs)) {
        // If output is a map
        OnnxValue output = results.get(0);
        if (output.getType() == OnnxValue.OnnxValueType.ONNX_TYPE_MAP) {
            OnnxMap map = (OnnxMap) output;
            Map<?, ?> javaMap = map.getValue();
            System.out.println("Map size: " + map.size());
            System.out.println("Key type: " + map.getInfo().keyType);
            System.out.println("Value type: " + map.getInfo().valueType);
            for (Map.Entry<?, ?> entry : javaMap.entrySet()) {
                System.out.println(entry.getKey() + " -> " + entry.getValue());
            }
        }
    }
}

Related Pages

• MapInfo.java - Type metadata for OnnxMap
• OnnxSequence.java - Sequence container that may contain maps
• OrtSession.java - Session that produces OnnxMap outputs
• OnnxJavaType.java - Type enum used for key/value types