apache/flink · error · RuntimeException

Please ensure that flink-datastream in your class path

Error message

Please ensure that flink-datastream in your class path

What it means

Error "Please ensure that flink-datastream in your class path" thrown in apache/flink.

Source

Thrown at flink-datastream-api/src/main/java/org/apache/flink/datastream/api/builtin/BuiltinFuncs.java:48

import org.apache.flink.datastream.api.function.TwoInputNonBroadcastStreamProcessFunction;
import org.apache.flink.datastream.api.function.TwoOutputStreamProcessFunction;
import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
import org.apache.flink.datastream.api.stream.NonKeyedPartitionStream;

/** Built-in functions for all extension of datastream v2. */
@Experimental
public class BuiltinFuncs {

    // =================== Join ===========================

    static final Class<?> JOIN_FUNCS_INSTANCE;

    static {
        try {
            JOIN_FUNCS_INSTANCE =
                    Class.forName("org.apache.flink.datastream.impl.builtin.BuiltinJoinFuncs");
        } catch (ClassNotFoundException e) {
            throw new RuntimeException("Please ensure that flink-datastream in your class path");
        }
    }

    /**
     * Wrap the JoinFunction and INNER JoinType within a ProcessFunction to perform the Join
     * operation. Note that the wrapped process function should only be used with KeyedStream.
     */
    public static <IN1, IN2, OUT> TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> join(
            JoinFunction<IN1, IN2, OUT> joinFunction) {
        return join(joinFunction, JoinType.INNER);
    }

    /**
     * Wrap the JoinFunction and JoinType within a ProcessFunction to perform the Join operation.
     * Note that the wrapped process function should only be used with KeyedStream.
     */
    public static <IN1, IN2, OUT> TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> join(
            JoinFunction<IN1, IN2, OUT> joinFunction, JoinType joinType) {

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Address the cause reported by the error message: Please ensure that flink-datastream in your class path
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("Please ensure that flink-datastream in your class path") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: Please ensure that flink-datastream in your class path.

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: Please ensure that flink-datastream in your class path.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/5eca2e24a13e5fd8. Report an issue: GitHub.