Changes not persisted in database in a Spring Boot application using Spring JPA - spring-boot

Question

I have a Spring Boot application that needs adds a post to a feed list. A post is written by a user and consists of a content and several attachments. The database has 3 tables: post, attachment and user.
The main class of the application is:
#SpringBootApplication
public class SocialMediaApplication {
public static void main(String[] args) {
SpringApplication.run(SocialMediaApplication.class, args);
}
}
The entities are the following:
Post.java
#Entity
public class Post implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(nullable = false)
private String content;
#ManyToOne
#JoinColumn(name = "user_id")
private User user;
#Column(nullable = false)
private Timestamp createdAt;
#Column
private String location;
#OneToMany(mappedBy = "post", cascade = CascadeType.ALL)
private List<Attachment> attachmentList;
#OneToMany(mappedBy = "post", cascade = CascadeType.ALL)
private List<Rating> ratingList;
public Post() {
}
public Post(String content, User user, Timestamp createdAt, String location, List<Attachment> attachmentList, List<Rating> ratingList) {
super();
this.content = content;
this.user = user;
this.createdAt = createdAt;
this.location = location;
this.attachmentList = attachmentList;
this.ratingList = ratingList;
}
// ...
}
Attachment.java
#Entity
public class Attachment implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Lob
#Column(length = 100_000, nullable = false)
private byte[] content;
#ManyToOne
#JoinColumn(name = "post_id")
private Post post;
public Attachment() {
}
public Attachment(byte[] content, Post post) {
super();
this.content = content;
this.post = post;
}
// ...
}
User.java
#Entity
public class User implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue
private Long id;
#Column(nullable = false)
private String firstName;
#Column(nullable = false)
private String lastName;
#Column(nullable = false)
private Date dateOfBirth;
#Column(nullable = false)
private String credential;
#Column(nullable = false)
private String password;
#Column
private String location;
#Lob
#Column(length = 100_000)
private byte[] photo;
#Column
private String motto;
public User() {
}
public User(String firstName, String lastName, Date dateOfBirth, String credential, String password,
String location, byte[] photo, String motto) {
super();
this.firstName = firstName;
this.lastName = lastName;
this.dateOfBirth = dateOfBirth;
this.credential = credential;
this.password = password;
this.location = location;
this.photo = photo;
this.motto = motto;
}
// ...
}
All repositories extend CrudRepository and are annotated with #Transactional:
PostRepository.java
#Transactional
public interface PostRepository extends CrudRepository<Post, Long> {
}
AttachmentRepository.java
#Transactional
public interface AttachmentRepository extends CrudRepository<Attachment, Long> {
}
UserRepository.java
#Transactional
public interface UserRepository extends CrudRepository<User, Long> {
}
The controller that should add a post to the feed is the following:
#Controller
#RequestMapping("/post")
public class PostController {
#Autowired
PostRepository postRepository;
#GetMapping("/add")
public String greetingForm(Model model) {
model.addAttribute("post", new Post());
return "addPost";
}
#PostMapping("/add")
public String addPost(#ModelAttribute Post post, #RequestParam("attachment") MultipartFile uploadingFile) throws IOException {
User user = new User();
user.setId(1L);
post.setUser(user);
post.setCreatedAt(Timestamp.valueOf(LocalDateTime.now()));
List<Attachment> attachmentList = new ArrayList<>();
Attachment attachment = new Attachment();
attachment.setContent(uploadingFile.getBytes());
attachment.setPost(post);
attachmentList.add(attachment);
post.setAttachmentList(attachmentList);
List<Rating> ratingList = new ArrayList<>();
post.setRatingList(ratingList);
postRepository.save(post);
return "allPosts";
}
}
The addPost.html page has the following content:
<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<title>Add Post</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
<h1>Add Post</h1>
<form action="#" th:action="#{/post/add}" th:object="${post}" method="post" enctype="multipart/form-data">
<table border="0">
<tr>
<td>Content</td>
<td><textarea id="content" th:field="*{content}" rows="5" cols="50"></textarea></td>
</tr>
<tr>
<td>Location</td>
<td><input type="text" id="location" th:field="*{location}"/></td>
</tr>
<tr>
<td>Attachment</td>
<td><input type="file" id="attachment" name="attachment"/></td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="Submit" />
<input type="reset" value="Reset" />
</td>
</tr>
</table>
</form>
</body>
</html>
The application.properties file has the following content:
spring.datasource.url=jdbc:mysql://localhost:3306/****?useSSL=false
spring.datasource.username=root
spring.datasource.password=****
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.jpa.properties.hibernate.id.new_generator_mappings=false
spring.jpa.show-sql=true
spring.thymeleaf.cache=false
spring.thymeleaf.enabled=true
spring.thymeleaf.prefix=classpath:/templates/
spring.thymeleaf.suffix=.html
However, when I press the submit button, nothing is persisted into the database, although the queries are being displayed in the console:
Hibernate: insert into post (content, created_at, location, user_id) values (?, ?, ?, ?)
Hibernate: insert into attachment (content, post_id) values (?, ?)
What could be the cause?