Comprehensive Spring Boot examples (#349)

* Start spring-examples

* Fixing TODOs for TaskDescriptor

* LongRunning task example

* MultiInstance recurring task example

* StateTracking recurring task example

* Correct copyright for google code

* Restructuring

* Cleaning up. Examples in README

* Cleaning

README.md

@@ -146,6 +146,8 @@ scheduler.schedule(myAdhocTask.instance("1045", new MyTaskData(1001L)), Instant.
 
 ### More examples
 
+#### Plain Java
+
 * [EnableImmediateExecutionMain.java](./examples/features/src/main/java/com/github/kagkarlsson/examples/EnableImmediateExecutionMain.java)
 * [MaxRetriesMain.java](./examples/features/src/main/java/com/github/kagkarlsson/examples/MaxRetriesMain.java)
 * [ExponentialBackoffMain.java](./examples/features/src/main/java/com/github/kagkarlsson/examples/ExponentialBackoffMain.java)
@@ -159,6 +161,21 @@ scheduler.schedule(myAdhocTask.instance("1045", new MyTaskData(1001L)), Instant.
 * [JobChainingUsingTaskDataMain.java](./examples/features/src/main/java/com/github/kagkarlsson/examples/JobChainingUsingTaskDataMain.java)
 * [JobChainingUsingSeparateTasksMain.java](./examples/features/src/main/java/com/github/kagkarlsson/examples/JobChainingUsingSeparateTasksMain.java)
 
+#### Spring Boot
+
+
+
+| Example                                                                                                                                                         | Description                                                                                                                                                                                                                                |
+|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| [BasicExamples](./examples/spring-boot-example/src/main/java/com/github/kagkarlsson/examples/boot/config/BasicExamplesConfiguration.java)                       | A basic one-time task and recurring task                                                                                                                                                                                                   |
+| [TransactionallyStagedJob](./examples/spring-boot-example/src/main/java/com/github/kagkarlsson/examples/boot/config/TransactionallyStagedJobConfiguration.java) | Example of [transactionally staging a job](https://brandur.org/job-drain), i.e. making sure the background job runs **iff** the transaction commits (along with other db-modifications).                                                   |
+| [LongRunningJob](./examples/spring-boot-example/src/main/java/com/github/kagkarlsson/examples/boot/config/LongRunningJobConfiguration.java)                     | Long-running jobs need to **survive application restarts** and avoid restarting from the beginning. This example demonstrates how to **persisting progress** on shutdown and additionally  a technique for limiting the job to run nightly. |
+| [RecurringStateTracking](./examples/spring-boot-example/src/main/java/com/github/kagkarlsson/examples/boot/config/RecurringStateTrackingConfiguration.java)     | A recurring task with state that can be modified after each run.                                                                                                                                                                           |
+| [ParallellJobSpawner](./examples/spring-boot-example/src/main/java/com/github/kagkarlsson/examples/boot/config/ParallellJobConfiguration.java)                  | Demonstrates how to use a recurring job to spawn one-time jobs, e.g. for parallelization.                                                                                                                                                  |
+| [JobChaining](./examples/spring-boot-example/src/main/java/com/github/kagkarlsson/examples/boot/config/JobChainingConfiguration.java)                           | A one-time job with **multiple steps**. The next step is scheduled after the previous one completes.                                                                                                                                       |
+| [MultiInstanceRecurring](./examples/spring-boot-example/src/main/java/com/github/kagkarlsson/examples/boot/config/MultiInstanceRecurringConfiguration.java)     | Demonstrates how to achieve **multiple recurring jobs** of the same type, but potentially differing schedules and data.                                                                                                                    |
+
+
 
 ## Configuration
 

db-scheduler/pom.xml

@@ -76,6 +76,11 @@
             <artifactId>jackson-annotations</artifactId>
             <optional>true</optional>
         </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jsr310</artifactId>
+            <optional>true</optional>
+        </dependency>
 
 
         <!-- Test -->

db-scheduler/src/main/java/com/github/kagkarlsson/scheduler/ScheduledExecution.java

@@ -37,10 +37,13 @@ public Instant getExecutionTime() {
 
     @SuppressWarnings("unchecked")
     public DATA_TYPE getData() {
-        if (dataClass.isInstance(this.execution.taskInstance.getData())) {
-            return (DATA_TYPE) this.execution.taskInstance.getData();
+        Object data = this.execution.taskInstance.getData();
+        if (data == null) {
+            return null;
+        } else if (dataClass.isInstance(data)) {
+            return (DATA_TYPE) data;
         }
-        throw new DataClassMismatchException(dataClass, this.execution.taskInstance.getData().getClass());
+        throw new DataClassMismatchException(dataClass, data.getClass());
     }
 
     public Instant getLastSuccess() {

db-scheduler/src/main/java/com/github/kagkarlsson/scheduler/serializer/GsonSerializer.java

@@ -15,23 +15,40 @@
  */
 package com.github.kagkarlsson.scheduler.serializer;
 
-import com.github.kagkarlsson.scheduler.serializer.gson.InstantAdapter;
+import com.github.kagkarlsson.scheduler.serializer.gson.*;
+import com.github.kagkarlsson.scheduler.task.schedule.CronSchedule;
+import com.github.kagkarlsson.scheduler.task.schedule.Daily;
+import com.github.kagkarlsson.scheduler.task.schedule.FixedDelay;
+import com.github.kagkarlsson.scheduler.task.schedule.Schedule;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.time.Duration;
 import java.time.Instant;
+import java.time.LocalTime;
+import java.time.ZoneId;
 import java.util.function.Consumer;
 
 public class GsonSerializer implements Serializer {
     public static final Charset CHARSET = StandardCharsets.UTF_8;
     private final Gson gson;
 
     public static GsonBuilder getDefaultGson() {
+        RuntimeTypeAdapterFactory<Schedule> runtimeTypeAdapterFactory = RuntimeTypeAdapterFactory
+            .of(Schedule.class, "type")
+            .registerSubtype(CronSchedule.class, "cron")
+            .registerSubtype(FixedDelay.class, "fixedDelay")
+            .registerSubtype(Daily.class, "daily");
+
         return new GsonBuilder()
             .serializeNulls()
-            .registerTypeAdapter(Instant.class, new InstantAdapter());
+            .registerTypeAdapter(Instant.class, new InstantAdapter())
+            .registerTypeAdapter(Duration.class, new DurationAdapter())
+            .registerTypeAdapter(LocalTime.class, new LocalTimeAdapter())
+            .registerTypeHierarchyAdapter(ZoneId.class, new ZoneIdAdapter())
+            .registerTypeAdapterFactory(runtimeTypeAdapterFactory);
     }
 
     public GsonSerializer() {

db-scheduler/src/main/java/com/github/kagkarlsson/scheduler/serializer/JacksonSerializer.java

@@ -19,19 +19,17 @@
 import com.fasterxml.jackson.annotation.PropertyAccessor;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
-import com.fasterxml.jackson.databind.MapperFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import com.github.kagkarlsson.scheduler.exceptions.SerializationException;
-import com.github.kagkarlsson.scheduler.serializer.gson.InstantAdapter;
+import com.github.kagkarlsson.scheduler.serializer.jackson.ScheduleMixin;
 import com.github.kagkarlsson.scheduler.serializer.jackson.InstantDeserializer;
 import com.github.kagkarlsson.scheduler.serializer.jackson.InstantSerializer;
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
+import com.github.kagkarlsson.scheduler.task.helper.ScheduleAndData;
+import com.github.kagkarlsson.scheduler.task.schedule.Schedule;
 
 import java.io.IOException;
-import java.sql.Time;
 import java.time.Instant;
 import java.util.function.Consumer;
 
@@ -46,7 +44,9 @@ public static ObjectMapper getDefaultObjectMapper() {
         return new ObjectMapper()
             .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
             .setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY)
-            .registerModule(module);
+            .addMixIn(Schedule.class, ScheduleMixin.class)
+            .registerModule(module)
+            .registerModule(new JavaTimeModule());
     }
 
     public JacksonSerializer() {

db-scheduler/src/main/java/com/github/kagkarlsson/scheduler/serializer/gson/DurationAdapter.java

@@ -0,0 +1,38 @@
+/**
+ * Copyright (C) Gustav Karlsson
+ *
+ * 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 com.github.kagkarlsson.scheduler.serializer.gson;
+
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+
+import java.io.IOException;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.format.DateTimeFormatter;
+
+public class DurationAdapter extends TypeAdapter<Duration> {
+
+    @Override
+    public void write(JsonWriter jsonWriter, Duration duration) throws IOException {
+        jsonWriter.value(duration.toMillis());
+    }
+
+    @Override
+    public Duration read(JsonReader jsonReader) throws IOException {
+        return Duration.ofMillis(Long.parseLong(jsonReader.nextString()));
+    }
+}

db-scheduler/src/main/java/com/github/kagkarlsson/scheduler/serializer/gson/LocalTimeAdapter.java

@@ -0,0 +1,40 @@
+/**
+ * Copyright (C) Gustav Karlsson
+ *
+ * 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 com.github.kagkarlsson.scheduler.serializer.gson;
+
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+
+import java.io.IOException;
+import java.time.LocalTime;
+import java.time.format.DateTimeFormatter;
+import java.time.format.FormatStyle;
+
+public class LocalTimeAdapter extends TypeAdapter<LocalTime> {
+
+    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofLocalizedTime(FormatStyle.SHORT);
+
+    @Override
+    public void write(JsonWriter jsonWriter, LocalTime localTime) throws IOException {
+        jsonWriter.value(localTime.format(FORMATTER));
+    }
+
+    @Override
+    public LocalTime read(JsonReader jsonReader) throws IOException {
+        return FORMATTER.parse(jsonReader.nextString(), LocalTime::from);
+    }
+}