org.apache.flink.statefun.examples.greeter.GreetStatefulFunction Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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*/
package org.apache.flink.statefun.examples.greeter;
import org.apache.flink.statefun.examples.greeter.generated.GreetRequest;
import org.apache.flink.statefun.examples.greeter.generated.GreetResponse;
import org.apache.flink.statefun.sdk.Context;
import org.apache.flink.statefun.sdk.FunctionType;
import org.apache.flink.statefun.sdk.StatefulFunction;
import org.apache.flink.statefun.sdk.annotations.Persisted;
import org.apache.flink.statefun.sdk.state.PersistedValue;
/**
* A stateful function that generates a unique greeting for each user based on how many times that
* user has been seen by the system.
*/
final class GreetStatefulFunction implements StatefulFunction {
/**
* The function type is the unique identifier that identifies this type of function. The type, in
* conjunction with an identifier, is how routers and other functions can use to reference a
* particular instance of a greeter function.
*
* If this was a multi-module application, the function type could be in different package so
* functions in other modules could message the greeter without a direct dependency on this class.
*/
static final FunctionType TYPE = new FunctionType("apache", "greeter");
/**
* The persisted value for maintaining state about a particular user. The value returned by this
* field is always scoped to the current user. seenCount is the number of times the user has been
* greeted.
*/
@Persisted
private final PersistedValue seenCount = PersistedValue.of("seen-count", Integer.class);
@Override
public void invoke(Context context, Object input) {
GreetRequest greetMessage = (GreetRequest) input;
GreetResponse response = computePersonalizedGreeting(greetMessage);
context.send(GreetingIO.GREETING_EGRESS_ID, response);
}
private GreetResponse computePersonalizedGreeting(GreetRequest greetMessage) {
final String name = greetMessage.getWho();
final int seen = seenCount.getOrDefault(0);
seenCount.set(seen + 1);
String greeting = greetText(name, seen);
return GreetResponse.newBuilder().setWho(name).setGreeting(greeting).build();
}
private static String greetText(String name, int seen) {
switch (seen) {
case 0:
return String.format("Hello %s ! \uD83D\uDE0E", name);
case 1:
return String.format("Hello again %s ! \uD83E\uDD17", name);
case 2:
return String.format("Third time is a charm! %s! \uD83E\uDD73", name);
case 3:
return String.format("Happy to see you once again %s ! \uD83D\uDE32", name);
default:
return String.format("Hello at the %d-th time %s \uD83D\uDE4C", seen + 1, name);
}
}
}