Implementation:Apache Shardingsphere HintShadowAlgorithm SPI

Knowledge Sources	Apache_Shardingsphere Shadow Feature
Domains	Shadow_Testing, SPI, SQL_Routing
Last Updated	2026-02-10 00:00 GMT

Overview

SPI interface for hint-based shadow routing algorithms.

Description

HintShadowAlgorithm<T> is a generic interface extending ShadowAlgorithm that defines the contract for shadow algorithms based on SQL hints rather than column values. Implementors determine shadow routing by examining hint annotations attached to SQL statements.

Usage

Implement this interface when creating shadow algorithms that use SQL hint annotations (e.g., /* shadow:true */ comments) rather than column values for routing decisions.

Code Reference

Source Location

• Repository: Apache_Shardingsphere
• File: features/shadow/api/src/main/java/org/apache/shardingsphere/shadow/spi/hint/HintShadowAlgorithm.java
• Lines: 1-39

Signature

public interface HintShadowAlgorithm<T> extends ShadowAlgorithm {

    boolean isShadow(Collection<String> shadowTableNames, PreciseHintShadowValue<T> shadowValue);
}

Import

import org.apache.shardingsphere.shadow.spi.hint.HintShadowAlgorithm;

I/O Contract

Inputs

Name	Type	Required	Description
shadowTableNames	Collection<String>	Yes	Names of configured shadow tables
shadowValue	PreciseHintShadowValue<T>	Yes	Hint value context including table name, operation type, and hint value

Outputs

Name	Type	Description
isShadow() returns	boolean	True if the statement should route to shadow data source

Usage Examples

import org.apache.shardingsphere.shadow.spi.hint.HintShadowAlgorithm;
import org.apache.shardingsphere.shadow.spi.hint.PreciseHintShadowValue;

public final class SQLHintShadowAlgorithm implements HintShadowAlgorithm<String> {

    @Override
    public boolean isShadow(final Collection<String> shadowTableNames,
                            final PreciseHintShadowValue<String> shadowValue) {
        return "true".equalsIgnoreCase(shadowValue.getValue());
    }

    @Override
    public String getType() {
        return "SQL_HINT";
    }
}

Related Pages

• Principle:Apache_Shardingsphere_Hint_Based_Routing