Onnx4j是一个面向ONNX（开放式神经网络交换协议）的Java表达项目，其并不提供具体的运算实现。
ONNX官方提供了其规范的proto定义，我们可以通过Google ProtoBuffer生成用于Java的相关定义类。onnx4j在ONNX官方的proto定义基础上，通过使用OOP的相关手段，如：接口与实现、类与继承等，使其转换为一个更为结构化和更清晰的表达方式，为所有建基于ONNX规范的Java程序开发提供更友好的开发方式。
对于onnx4j的使用，我们可以参考基于onnx4j派生的，专注于神经网络forward操作的框架Forwarder：https://github.com/onnx4j/forwarder
| Operator | Opset1 | Opset2 | Opset3 | Opset4 | Opset5 | Opset6 | Opset7 | Opset8 | Opset9 | Opset10 | Opset11 | Opset12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Abs | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Add | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| ArgMax | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| AveragePool | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| BatchNormalization | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Cast | 1 | 1 | 1 | 1 | 1 | 6 | 6 | 6 | 9 | 9 | 9 | 9 |
| Concat | 1 | 1 | 1 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
| Constant | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Conv | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Div | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Dropout | 1 | 1 | 1 | 1 | 1 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| Gather | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Identity | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| ImageScaler | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| LeakyRelu | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| MatMul | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| MaxPool | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Mul | 1 | 1 | 1 | 1 | 1 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| Pad | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| ReduceMax | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 12 |
| Relu | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Reshape | 1 | 1 | 1 | 1 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
| Shape | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Sigmoid | 1 | 1 | 1 | 1 | 1 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| Softmax | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 11 |
| Squeeze | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 11 |
| Sub | 1 | 1 | 1 | 1 | 1 | 6 | 7 | 7 | 7 | 7 | 7 | 7 |
| Sum | 1 | 1 | 1 | 1 | 1 | 6 | 6 | 8 | 8 | 8 | 8 | 8 |
| Transpose | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Unsqueeze | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 11 |
暂不支持。