What is SPI in Java?

1. Concept

JDK’s built-in service discovery mechanism. SPI is a dynamic replacement and discovery mechanism. For example, there is an interface. If you want to add it dynamically at runtime, you just need to add an implementation. We often encounter the java.sql.Driver interface, and different vendors can implement different implementations of the same interface. mysql and postgresql provide different implementations for users, and Java's SPI mechanism can find services for a certain interface.

2. Example

public class KryoSerializer implements ObjectSerializer {
 
    @Override
    public byte[] serialize(Object obj) throws ObjectSerializerException {
        byte[] bytes;
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        try {
            //获取kryo对象
            Kryo kryo = new Kryo();
            Output output = new Output(outputStream);
            kryo.writeObject(output, obj);
            bytes = output.toBytes();
            output.flush();
        } catch (Exception ex) {
            throw new ObjectSerializerException("kryo serialize error" + ex.getMessage());
        } finally {
            try {
                outputStream.flush();
                outputStream.close();
            } catch (IOException e) {
 
            }
        }
        return bytes;
    }
 
    @Override
    public <T> T deSerialize(byte[] param, Class<T> clazz) throws ObjectSerializerException {
        T object;
        try (ByteArrayInputStream inputStream = new ByteArrayInputStream(param)) {
            Kryo kryo = new Kryo();
            Input input = new Input(inputStream);
            object = kryo.readObject(input, clazz);
            input.close();
        } catch (Exception e) {
            throw new ObjectSerializerException("kryo deSerialize error" + e.getMessage());
        }
        return object;
    }
 
    @Override
    public String getSchemeName() {
        return "kryoSerializer";
    }
 
}

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