From 4e3b5cd357003eb6235b14e65cfbf1fca3424c17 Mon Sep 17 00:00:00 2001
From: Kai Moritz <kai@juplo.de>
Date: Sun, 25 Oct 2020 15:24:39 +0100
Subject: [PATCH] Wiredly enforcing uniqe-users with an exception

---
 src/main/java/de/juplo/boot/data/jdbc/User.java |  6 ++++++
 .../de/juplo/boot/data/jdbc/UserController.java | 17 +++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/src/main/java/de/juplo/boot/data/jdbc/User.java b/src/main/java/de/juplo/boot/data/jdbc/User.java
index 16587c1..2cc62bd 100644
--- a/src/main/java/de/juplo/boot/data/jdbc/User.java
+++ b/src/main/java/de/juplo/boot/data/jdbc/User.java
@@ -25,4 +25,10 @@ public class User {
         this.created = created;
         this.loggedIn = loggedIn;
     }
+
+
+    @Override
+    public String toString() {
+        return username;
+    }
 }
diff --git a/src/main/java/de/juplo/boot/data/jdbc/UserController.java b/src/main/java/de/juplo/boot/data/jdbc/UserController.java
index 177b120..ac5ddbc 100644
--- a/src/main/java/de/juplo/boot/data/jdbc/UserController.java
+++ b/src/main/java/de/juplo/boot/data/jdbc/UserController.java
@@ -3,6 +3,7 @@ package de.juplo.boot.data.jdbc;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.dao.IncorrectResultSizeDataAccessException;
 import org.springframework.http.ResponseEntity;
 import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.bind.annotation.*;
@@ -46,6 +47,9 @@ public class UserController {
             @RequestBody String username) {
         String sanitizedUsername = UserController.sanitize(username);
         User user = new User(sanitizedUsername, LocalDateTime.now(), false);
+
+        LOG.info("Request to create user: {}", user);
+
         repository.save(user);
         publisher.publishEvent(
             new UserEvent(
@@ -53,6 +57,10 @@ public class UserController {
                 sanitizedUsername,
                 CREATED,
                 ZonedDateTime.now(clock)));
+
+        // Triggers an IncorrectResultSizeDataAccessException, if the user already existed!
+        user = repository.findByUsername(sanitizedUsername);
+
         UriComponents uri =
             builder
                 .fromCurrentRequest()
@@ -101,4 +109,13 @@ public class UserController {
 
         return string.trim().toLowerCase();
     }
+
+    @ExceptionHandler
+    public ResponseEntity<?> incorrectResultSizeDataAccessException(
+        IncorrectResultSizeDataAccessException e
+        )
+    {
+      LOG.info("User already exists!");
+      return ResponseEntity.badRequest().build();
+    }
 }
-- 
2.20.1