Bael 4781: Introduction to ZeroCode (#10482)

* small example of hexagonal architecture in java

* Bael-4781: Introduction to ZeroCode

* add readme

* Revert "small example of hexagonal architecture in java"

This reverts commit c0f96441

* refactoring

* refactoring

testing-modules/zerocode/src/main/java/com/baeldung/zerocode/User.java

@@ -0,0 +1,31 @@
+package com.baeldung.zerocode;
+
+public class User {
+    private String id;
+    private String firstName;
+    private String lastName;
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+}

testing-modules/zerocode/src/main/java/com/baeldung/zerocode/ZerocodeApplication.java

@@ -0,0 +1,38 @@
+package com.baeldung.zerocode;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.util.StringUtils;
+import org.springframework.web.bind.annotation.*;
+
+@SpringBootApplication
+@RestController
+@RequestMapping("/api/users")
+public class ZerocodeApplication {
+    private List<User> users = new ArrayList<>();
+
+    public static void main(String[] args) {
+        SpringApplication.run(ZerocodeApplication.class, args);
+    }
+
+    @PostMapping
+    public ResponseEntity create(@RequestBody User user) {
+        if (!StringUtils.hasText(user.getFirstName())) {
+            return new ResponseEntity("firstName can't be empty!", HttpStatus.BAD_REQUEST);
+        }
+        if (!StringUtils.hasText(user.getLastName())) {
+            return new ResponseEntity("lastName can't be empty!", HttpStatus.BAD_REQUEST);
+        }
+        user.setId(UUID.randomUUID()
+            .toString());
+        users.add(user);
+        return new ResponseEntity(user, HttpStatus.CREATED);
+    }
+
+}