Add demo of job scheduling using quartz

The GreetingController is extended, so it now allows a POST which schedules a job to
run at a set frequency. The job just logs the Greeting to the console

Quartz is a framework which allows Jobs to be scheduled to run asynchronously, at a fixed
frequency or point in time. This is useful if you want to allow the API user to
schedule a task to be performed at a set point in the future

The job schedule is persisted in a postgres database, so they will live beyond the lifespan
of an application run. I.e. the application can be restarted, and the running jobs will
restart. The database schema is created using Flyway

Jira: n/a

build.gradle

@@ -2,7 +2,6 @@ plugins {
     id 'org.springframework.boot' version '2.2.2.RELEASE'
     id 'io.spring.dependency-management' version '1.0.8.RELEASE'
     id 'java'
-
     id "io.freefair.lombok" version "5.1.0"
 }
 
@@ -12,9 +11,13 @@ repositories {
 
 dependencies {
     implementation 'org.springframework.boot:spring-boot-starter-web'
+    implementation("org.springframework.boot:spring-boot-starter-quartz")
+    implementation("org.springframework.boot:spring-boot-starter-data-jpa")
+    implementation('org.flywaydb:flyway-core')
     testImplementation('org.springframework.boot:spring-boot-starter-test') {
         exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
     }
+    runtimeOnly('org.postgresql:postgresql')
 }
 
 test {

src/main/java/com/wilkins/showcase/controllers/Greeting.java

@@ -3,9 +3,13 @@
 import lombok.Value;
 import lombok.With;
 
+import java.io.Serializable;
+
 @Value(staticConstructor = "of")
 @With
-public class Greeting {
+public class Greeting implements Serializable {
+
+    private static final long serialVersionUID = -2464792326773658903L;
     // private and final modifiers added by @Value annotation
     String salutation;
     String name;

src/main/java/com/wilkins/showcase/controllers/GreetingController.java

@@ -1,33 +1,82 @@
 package com.wilkins.showcase.controllers;
 
+import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
-import org.springframework.web.bind.annotation.GetMapping;
-import org.springframework.web.bind.annotation.RequestParam;
-import org.springframework.web.bind.annotation.RestController;
+import org.quartz.*;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
 
-import static org.springframework.util.StringUtils.isEmpty;
+import java.sql.Timestamp;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.Date;
+import java.util.UUID;
+
+import static org.quartz.TriggerBuilder.newTrigger;
+import static org.springframework.http.MediaType.APPLICATION_JSON_VALUE;
+import static org.springframework.http.ResponseEntity.noContent;
+import static org.springframework.http.ResponseEntity.notFound;
 
 @Slf4j
 @RestController
+@RequestMapping(path = "/greeting", produces = APPLICATION_JSON_VALUE)
+@RequiredArgsConstructor
 public class GreetingController {
 
-    @GetMapping("/greeting")
-    public Greeting getGreeting(@RequestParam(name = "salutation", required = false) String salutationParam,
-                               @RequestParam(name = "name", required = false) String nameParam) {
+    private static final String JOB_GROUP = "greeting-jobs";
+    private final Scheduler scheduler;
 
-        log.info("A greeting was requested");
+    @GetMapping
+    public Greeting getGreeting(@RequestParam(name = "salutation", required = false, defaultValue = "hello") String salutationParam,
+                                @RequestParam(name = "name", required = false, defaultValue = "world") String nameParam) {
 
-        Greeting greeting = Greeting.of("hello", "world");
+        log.info("A greeting was requested");
 
-        if (!isEmpty(salutationParam)) {
-            greeting = greeting.withSalutation(salutationParam);
-        }
-        if (!isEmpty(nameParam)) {
-            greeting = greeting.withName(nameParam);
-        }
+        var greeting = Greeting.of(salutationParam, nameParam);
 
         log.info("Greeting returned: {}", greeting);
 
         return greeting;
     }
+
+    @PostMapping
+    public String postGreeting(@RequestParam(name = "salutation", required = false, defaultValue = "hello") String salutationParam,
+                         @RequestParam(name = "name", required = false, defaultValue = "world") String nameParam,
+                       @RequestParam(name = "durationMins", required = false, defaultValue = "2") String durationMins) throws SchedulerException {
+        var jobDataMap = new JobDataMap();
+        jobDataMap.put("salutation", salutationParam);
+        jobDataMap.put("name", nameParam);
+        jobDataMap.put("greeting", Greeting.of(salutationParam, nameParam));
+        var id = UUID.randomUUID().toString();
+        var jobDetail = JobBuilder.newJob()
+                .ofType(GreetingJob.class)
+                .withIdentity(id, JOB_GROUP)
+                .withDescription("Send Greeting Job")
+                .usingJobData(jobDataMap)
+                .requestRecovery()
+//                .storeDurably()
+                .build();
+        Date now = new Date();
+        Date startAt = Timestamp.valueOf(LocalDateTime.from(
+                now.toInstant()
+                        .atZone(ZoneId.systemDefault())
+                        .toLocalDateTime())
+                .plusMinutes(1));
+        var trigger = newTrigger()
+                .forJob(jobDetail)
+                .withIdentity(jobDetail.getKey().getName(), "greeting-triggers")
+                .withDescription("Send Greeting Trigger")
+                .startAt(startAt)
+                .withSchedule(SimpleScheduleBuilder.simpleSchedule().withRepeatCount(0))
+                .build();
+        log.info("scheduling job");
+        scheduler.scheduleJob(jobDetail, trigger);
+        return id;
+    }
+
+    @DeleteMapping("/{id}")
+    public ResponseEntity<?> deleteGreeting(@PathVariable String id) throws SchedulerException {
+        log.info("deleting job: {}", id);
+        return scheduler.deleteJob(new JobKey(id, JOB_GROUP)) ? noContent().build() : notFound().build();
+    }
 }

src/main/java/com/wilkins/showcase/controllers/GreetingJob.java

@@ -0,0 +1,22 @@
+package com.wilkins.showcase.controllers;
+
+import com.wilkins.showcase.services.Greeter;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.quartz.Job;
+import org.quartz.JobDataMap;
+import org.quartz.JobExecutionContext;
+
+@Slf4j
+@RequiredArgsConstructor
+public class GreetingJob implements Job {
+
+    private final Greeter greeter;
+
+    @Override
+    public void execute(JobExecutionContext context) {
+        JobDataMap jobDataMap = context.getMergedJobDataMap();
+        log.info("******** {}, {} *************", context.getJobDetail().getKey().getName(),
+                 greeter.greet((Greeting) jobDataMap.get("greeting")));
+    }
+}

src/main/java/com/wilkins/showcase/services/Greeter.java

@@ -0,0 +1,12 @@
+package com.wilkins.showcase.services;
+
+import com.wilkins.showcase.controllers.Greeting;
+import org.springframework.stereotype.Component;
+
+@Component
+public class Greeter {
+
+    public String greet(Greeting greeting) {
+        return greeting.getSalutation() + " " + greeting.getName();
+    }
+}

src/main/resources/application.yaml

@@ -0,0 +1,17 @@
+spring:
+  quartz:
+    job-store-type: jdbc
+    properties.org.quartz.threadPool.threadCount: 5
+    properties:
+      org:
+        quartz:
+          jobStore:
+            driverDelegateClass: "org.quartz.impl.jdbcjobstore.PostgreSQLDelegate"
+    wait-for-jobs-to-complete-on-shutdown: true
+    jdbc:
+      initialize-schema: never
+
+  datasource:
+    url: "jdbc:postgresql://localhost:5432/postgres?currentSchema=showcase"
+    username: "postgres"
+    password: "Passw0rd"