merge into spring-boot module

spring-boot/src/main/java/org/baeldung/controller/GenericEntityController.java

@@ -0,0 +1,38 @@
+package org.baeldung.controller;
+
+import org.baeldung.domain.GenericEntity;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@RestController
+public class GenericEntityController {
+    private List<GenericEntity> entityList = new ArrayList<>();
+
+    {
+        entityList.add(new GenericEntity(1l, "entity_1"));
+        entityList.add(new GenericEntity(2l, "entity_2"));
+        entityList.add(new GenericEntity(3l, "entity_3"));
+        entityList.add(new GenericEntity(4l, "entity_4"));
+    }
+
+    @RequestMapping("/entity/all")
+    public List<GenericEntity> findAll() {
+        return entityList;
+    }
+
+    @RequestMapping(value = "/entity", method = RequestMethod.POST)
+    public GenericEntity addEntity(GenericEntity entity) {
+        entityList.add(entity);
+        return entity;
+    }
+
+    @RequestMapping("/entity/findby/{id}")
+    public GenericEntity findById(@PathVariable Long id) {
+        return entityList.stream().filter(entity -> entity.getId().equals(id)).findFirst().get();
+    }
+}