functional interface cmd pattern

Author: zachauten

src/main/java/app/work/CommandExecutor.java

@@ -0,0 +1,33 @@
+package app.work;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.List;
+
+public class CommandExecutor {
+    List<ICommand> commands = new ArrayList<>();
+    Deque<Runnable> undos = new ArrayDeque<>();
+
+    public void add(ICommand cmd) {
+        this.commands.add(cmd);
+    }
+
+    public boolean execute() {
+        for (var cmd : commands) {
+            try {
+                var undo = cmd.execute();
+                undos.push(undo);
+            } catch(Exception e) {
+                for (var undo : undos) {
+                    undo.run();
+                }
+            }
+        }
+        return true;
+    }
+
+    interface ICommand {
+        Runnable execute() throws Exception;
+    }
+}

src/main/java/app/work/ICommand.java

@@ -0,0 +1,5 @@
+package app.work;
+
+// public interface ICommand {
+//     void execute();
+// }

src/main/java/app/work/Person.java

@@ -0,0 +1,12 @@
+package app.work;
+
+import java.util.Optional;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+
+@JsonInclude(JsonInclude.Include.NON_EMPTY)
+public record Person(String name, int age, Optional<String> job) {
+    public Person(String name, int age) {
+        this(name, age, Optional.empty());
+    }
+}

src/main/java/app/work/WorkController.java

@@ -81,6 +81,28 @@ public String hello() {
     return "bar";
   }
 
+  @GetMapping("zach")
+  public Person zach() {
+    return new Person("zach", 31);
+  }
+
+  @PostMapping("commands")
+  public Person commands(@RequestBody Person person) {
+    var executor = new CommandExecutor();
+    var n = new Object() { int value = person.age(); };
+    executor.add(() -> {
+      var rand = ThreadLocalRandom.current().nextInt(5);
+      if (rand < 3) {
+        throw new Exception("Oops!");
+      }
+      n.value += rand;
+      return () -> {
+      };
+    });
+    executor.execute();
+    return new Person(person.name(), n.value);
+  }
+
   @WithSpan
   private void doSomeWork(int time) throws InterruptedException {
     log.info("doing work for " + time + "ms");