Add examples for SE and MP to update counters of HTTP response status…

… ranges (1xx, 2xx, etc.) for 3.x (#4617)

examples/metrics/http-status-count-se/README.md

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+# http-status-count-se
+
+This Helidon SE project illustrates a service which updates a family of counters based on the HTTP status returned in each response.
+
+The main source in this example is identical to that in the Helidon SE QuickStart application except in these ways:
+* The `HttpStatusMetricService` class creates and updates the status metrics.
+* The `Main` class has a two small enhancements:
+   * The `createRouting` method instantiates `HttpStatusMetricService` and sets up routing for it.
+   * The `startServer` method has an additional variant to simplify a new unit test.
+
+## Incorporating status metrics into your own application
+Use this example for inspiration in writing your own service or just use the `HttpStatusMetricService` directly in your own application.
+
+1. Copy and paste the `HttpStatusMetricService` class into your application, adjusting the package declaration as needed.
+2. Register routing for an instance of `HttpStatusMetricService`, as shown here:
+   ```java
+   Routing.Builder builder = Routing.builder()
+                ...
+                .register(HttpStatusMetricService.create()
+                ...
+   ```
+
+## Build and run
+
+
+With JDK17+
+```bash
+mvn package
+java -jar target/http-status-count-se.jar
+```
+
+## Exercise the application
+```bash
+curl -X GET http://localhost:8080/simple-greet
+```
+```listing
+{"message":"Hello World!"}
+```
+
+```bash
+curl -X GET http://localhost:8080/greet
+```
+```listing
+{"message":"Hello World!"}
+```
+```bash
+curl -X GET http://localhost:8080/greet/Joe
+```
+```listing
+{"message":"Hello Joe!"}
+```
+```bash
+curl -X PUT -H "Content-Type: application/json" -d '{"greeting" : "Hola"}' http://localhost:8080/greet/greeting
+
+curl -X GET http://localhost:8080/greet/Jose
+```
+```listing
+{"message":"Hola Jose!"}
+```
+
+## Try metrics
+```bash
+# Prometheus Format
+curl -s -X GET http://localhost:8080/metrics/application
+```
+
+```listing
+...
+# TYPE application_httpStatus_total counter
+# HELP application_httpStatus_total Counts the number of HTTP responses in each status category (1xx, 2xx, etc.)
+application_httpStatus_total{range="1xx"} 0
+application_httpStatus_total{range="2xx"} 5
+application_httpStatus_total{range="3xx"} 0
+application_httpStatus_total{range="4xx"} 0
+application_httpStatus_total{range="5xx"} 0
+...
+```
+# JSON Format
+
+```bash
+curl -H "Accept: application/json" -X GET http://localhost:8080/metrics
+```
+```json
+{
+...
+    "httpStatus;range=1xx": 0,
+    "httpStatus;range=2xx": 5,
+    "httpStatus;range=3xx": 0,
+    "httpStatus;range=4xx": 0,
+    "httpStatus;range=5xx": 0,
+...
+```
+
+## Try health
+
+```bash
+curl -s -X GET http://localhost:8080/health
+```
+```listing
+{"outcome":"UP",...
+
+```

examples/metrics/http-status-count-se/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Copyright (c) 2017, 2022 Oracle and/or its affiliates.
+
+    Licensed 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,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
+
+-->
+
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>io.helidon.applications</groupId>
+        <artifactId>helidon-se</artifactId>
+        <version>3.0.0-SNAPSHOT</version>
+        <relativePath>../../../applications/se/pom.xml</relativePath>
+    </parent>
+    <groupId>io.helidon.examples</groupId>
+    <artifactId>http-status-count-se</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <name>Helidon Examples Metrics HTTP Status Counters</name>
+
+    <properties>
+        <mainClass>io.helidon.examples.se.httpstatuscount.Main</mainClass>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>io.helidon.webserver</groupId>
+            <artifactId>helidon-webserver</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.helidon.config</groupId>
+            <artifactId>helidon-config-yaml</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.helidon.metrics</groupId>
+            <artifactId>helidon-metrics</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.helidon.health</groupId>
+            <artifactId>helidon-health</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.helidon.health</groupId>
+            <artifactId>helidon-health-checks</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.helidon.media</groupId>
+            <artifactId>helidon-media-jsonp</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest-all</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.helidon.webclient</groupId>
+            <artifactId>helidon-webclient</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>copy-libs</id>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>io.helidon.build-tools</groupId>
+                <artifactId>helidon-maven-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>third-party-license-report</id>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

examples/metrics/http-status-count-se/src/main/java/io/helidon/examples/se/httpstatuscount/GreetService.java

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+/*
+ * Copyright (c) 2022 Oracle and/or its affiliates.
+ *
+ * Licensed 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,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.helidon.examples.se.httpstatuscount;
+
+import java.util.Collections;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import io.helidon.common.http.Http;
+import io.helidon.config.Config;
+import io.helidon.webserver.Routing;
+import io.helidon.webserver.ServerRequest;
+import io.helidon.webserver.ServerResponse;
+import io.helidon.webserver.Service;
+
+import jakarta.json.Json;
+import jakarta.json.JsonBuilderFactory;
+import jakarta.json.JsonException;
+import jakarta.json.JsonObject;
+
+
+/**
+ * A simple service to greet you. Examples:
+ *
+ * Get default greeting message:
+ * curl -X GET http://localhost:8080/greet
+ *
+ * Get greeting message for Joe:
+ * curl -X GET http://localhost:8080/greet/Joe
+ *
+ * Change greeting
+ * curl -X PUT -H "Content-Type: application/json" -d '{"greeting" : "Howdy"}' http://localhost:8080/greet/greeting
+ *
+ * The message is returned as a JSON object
+ */
+
+public class GreetService implements Service {
+
+    /**
+     * The config value for the key {@code greeting}.
+     */
+    private final AtomicReference<String> greeting = new AtomicReference<>();
+
+    private static final JsonBuilderFactory JSON = Json.createBuilderFactory(Collections.emptyMap());
+
+    private static final Logger LOGGER = Logger.getLogger(GreetService.class.getName());
+
+    GreetService(Config config) {
+        greeting.set(config.get("app.greeting").asString().orElse("Ciao"));
+    }
+
+    /**
+     * A service registers itself by updating the routing rules.
+     * @param rules the routing rules.
+     */
+    @Override
+    public void update(Routing.Rules rules) {
+        rules
+            .get("/", this::getDefaultMessageHandler)
+            .get("/{name}", this::getMessageHandler)
+            .put("/greeting", this::updateGreetingHandler);
+    }
+
+    /**
+     * Return a worldly greeting message.
+     * @param request the server request
+     * @param response the server response
+     */
+    private void getDefaultMessageHandler(ServerRequest request, ServerResponse response) {
+        sendResponse(response, "World");
+    }
+
+    /**
+     * Return a greeting message using the name that was provided.
+     * @param request the server request
+     * @param response the server response
+     */
+    private void getMessageHandler(ServerRequest request, ServerResponse response) {
+        String name = request.path().param("name");
+        sendResponse(response, name);
+    }
+
+    private void sendResponse(ServerResponse response, String name) {
+        String msg = String.format("%s %s!", greeting.get(), name);
+
+        JsonObject returnObject = JSON.createObjectBuilder()
+                .add("message", msg)
+                .build();
+        response.send(returnObject);
+    }
+
+    private static <T> T processErrors(Throwable ex, ServerRequest request, ServerResponse response) {
+
+         if (ex.getCause() instanceof JsonException) {
+            LOGGER.log(Level.FINE, "Invalid JSON", ex);
+            JsonObject jsonErrorObject = JSON.createObjectBuilder()
+                .add("error", "Invalid JSON")
+                .build();
+            response.status(Http.Status.BAD_REQUEST_400).send(jsonErrorObject);
+        }  else {
+            LOGGER.log(Level.FINE, "Internal error", ex);
+            JsonObject jsonErrorObject = JSON.createObjectBuilder()
+                .add("error", "Internal error")
+                .build();
+            response.status(Http.Status.INTERNAL_SERVER_ERROR_500).send(jsonErrorObject);
+        }
+
+        return null;
+    }
+
+    private void updateGreetingFromJson(JsonObject jo, ServerResponse response) {
+        if (!jo.containsKey("greeting")) {
+            JsonObject jsonErrorObject = JSON.createObjectBuilder()
+                    .add("error", "No greeting provided")
+                    .build();
+            response.status(Http.Status.BAD_REQUEST_400)
+                    .send(jsonErrorObject);
+            return;
+        }
+
+        greeting.set(jo.getString("greeting"));
+        response.status(Http.Status.NO_CONTENT_204).send();
+    }
+
+    /**
+     * Set the greeting to use in future messages.
+     * @param request the server request
+     * @param response the server response
+     */
+    private void updateGreetingHandler(ServerRequest request,
+                                       ServerResponse response) {
+        request.content().as(JsonObject.class)
+            .thenAccept(jo -> updateGreetingFromJson(jo, response))
+            .exceptionally(ex -> processErrors(ex, request, response));
+    }
+}