support for generator/sequence

core/src/main/java/io/github/mmm/entity/id/IdGenerator.java → core/src/main/java/io/github/mmm/entity/id/generator/IdGenerator.java

@@ -1,6 +1,8 @@
 /* Copyright (c) The m-m-m Team, Licensed under the Apache License, Version 2.0
  * http://www.apache.org/licenses/LICENSE-2.0 */
-package io.github.mmm.entity.id;
+package io.github.mmm.entity.id.generator;
+
+import io.github.mmm.entity.id.Id;
 
 /**
  * Interface for a generator of {@link Id}s that are unique (for a type of {@link io.github.mmm.entity.Entity}).
@@ -9,7 +11,8 @@ public interface IdGenerator {
 
   /**
    * @param <E> type of the {@link io.github.mmm.entity.Entity}.
-   * @param template the {@link Id#isTransient() transient} {@link Id} that may be used as template.
+   * @param template the {@link Id#isTransient() transient} {@link Id} of the {@link io.github.mmm.entity.Entity entity}
+   *        to insert.
    * @return the new unique {@link Id}.
    */
   <E> Id<E> generate(Id<E> template);

core/src/main/java/io/github/mmm/entity/id/LongIdGenerator.java → core/src/main/java/io/github/mmm/entity/id/generator/LongIdGenerator.java

@@ -1,23 +1,29 @@
 /* Copyright (c) The m-m-m Team, Licensed under the Apache License, Version 2.0
  * http://www.apache.org/licenses/LICENSE-2.0 */
-package io.github.mmm.entity.id;
+package io.github.mmm.entity.id.generator;
 
 import java.time.Instant;
-import java.util.function.Function;
+
+import io.github.mmm.entity.id.AbstractVersionId;
+import io.github.mmm.entity.id.Id;
+import io.github.mmm.entity.id.LongId;
+import io.github.mmm.entity.id.LongInstantId;
+import io.github.mmm.entity.id.LongVersionId;
+import io.github.mmm.entity.id.sequence.IdSequence;
 
 /**
  * {@link IdGenerator} for {@link LongId}.
  */
 public class LongIdGenerator implements IdGenerator {
 
-  private final Function<Id<?>, Long> sequence;
+  private final IdSequence sequence;
 
   /**
    * The constructor.
    *
-   * @param sequence the {@link Function} doing the actual job. Typically via a sequence.
+   * @param sequence the {@link IdSequence}.
    */
-  public LongIdGenerator(Function<Id<?>, Long> sequence) {
+  public LongIdGenerator(IdSequence sequence) {
 
     super();
     this.sequence = sequence;
@@ -27,7 +33,7 @@ public LongIdGenerator(Function<Id<?>, Long> sequence) {
   public <E> LongId<E, ?> generate(Id<E> template) {
 
     Class<E> entityType = template.getEntityClass();
-    Long pk = this.sequence.apply(template);
+    Long pk = Long.valueOf(this.sequence.next(template));
     Class<? extends Comparable<?>> revisionType = template.getRevisionType();
     if (revisionType == Long.class) {
       return new LongVersionId<>(entityType, pk, AbstractVersionId.INSERT_REVISION);

core/src/main/java/io/github/mmm/entity/id/UuidIdGenerator.java → core/src/main/java/io/github/mmm/entity/id/generator/UuidIdGenerator.java

@@ -1,10 +1,16 @@
 /* Copyright (c) The m-m-m Team, Licensed under the Apache License, Version 2.0
  * http://www.apache.org/licenses/LICENSE-2.0 */
-package io.github.mmm.entity.id;
+package io.github.mmm.entity.id.generator;
 
 import java.time.Instant;
 import java.util.UUID;
 
+import io.github.mmm.entity.id.AbstractVersionId;
+import io.github.mmm.entity.id.Id;
+import io.github.mmm.entity.id.UuidId;
+import io.github.mmm.entity.id.UuidInstantId;
+import io.github.mmm.entity.id.UuidVersionId;
+
 /**
  * {@link IdGenerator} for {@link UuidId}.
  */

core/src/main/java/io/github/mmm/entity/id/sequence/IdSequence.java

@@ -0,0 +1,25 @@
+/* Copyright (c) The m-m-m Team, Licensed under the Apache License, Version 2.0
+ * http://www.apache.org/licenses/LICENSE-2.0 */
+package io.github.mmm.entity.id.sequence;
+
+import io.github.mmm.entity.id.Id;
+import io.github.mmm.entity.id.LongId;
+import io.github.mmm.entity.id.generator.IdGenerator;
+
+/**
+ * Interface for a sequence that can generate the next unique {@link Id#get() primary key} of type {@link Long} for a
+ * new {@link LongId}.
+ *
+ * @see IdGenerator#generate(Id)
+ */
+public interface IdSequence {
+
+  /**
+   * @param template the {@link Id#isTransient() transient} {@link Id} of the {@link io.github.mmm.entity.Entity entity}
+   *        to insert.
+   * @return the next long value guaranteed to be unique for this sequence. Proper implementations delegate to a
+   *         database sequence.
+   */
+  long next(Id<?> template);
+
+}

core/src/main/java/io/github/mmm/entity/id/sequence/IdSequenceMemory.java

@@ -0,0 +1,57 @@
+/* Copyright (c) The m-m-m Team, Licensed under the Apache License, Version 2.0
+ * http://www.apache.org/licenses/LICENSE-2.0 */
+package io.github.mmm.entity.id.sequence;
+
+import io.github.mmm.entity.id.Id;
+
+/**
+ * {@link IdSequence} implementation using an in-memory counter that is NOT persistent. By design this implementation
+ * can not guarantee correctness. Only use this for pragmatic scenarios e.g. for tests or if you are not using a
+ * database at all (e.g. also all data is hold in memory for simple apps that persist all data to JSON or the like).
+ */
+public final class IdSequenceMemory implements IdSequence {
+
+  private volatile long sequence;
+
+  /**
+   * The constructor.
+   */
+  public IdSequenceMemory() {
+
+    this(10_000_000L); // enough room for your own master data
+  }
+
+  /**
+   * The constructor.
+   *
+   * @param sequenceStart the start value of the sequence.
+   */
+  public IdSequenceMemory(long sequenceStart) {
+
+    super();
+    this.sequence = sequenceStart;
+  }
+
+  /**
+   * @return the current sequence value.
+   */
+  public long getSequence() {
+
+    return this.sequence;
+  }
+
+  /**
+   * @param sequence new value of {@link #getSequence()}.
+   */
+  public void setSequence(long sequence) {
+
+    this.sequence = sequence;
+  }
+
+  @Override
+  public long next(Id<?> template) {
+
+    return this.sequence++;
+  }
+
+}

core/src/main/java/module-info.java

@@ -17,6 +17,10 @@
 
   exports io.github.mmm.entity.id;
 
+  exports io.github.mmm.entity.id.generator;
+
+  exports io.github.mmm.entity.id.sequence;
+
   exports io.github.mmm.entity.link;
 
 }