Problem with passing changed subobject in SPRING application via Thymeleaf template - spring

Question

I am new in SPING and web developing.
I am developing the test task - quote book (without authorizing). I have two entities: Quote and Author. There is the code:
#Entity
#Table(name="authors")
public class Author {
#Id
#SequenceGenerator(name="author_id_seq", sequenceName="author_id_seq", allocationSize=1)
#GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "author_id_seq")
#Column(name = "id")
private long id;
#Column(name = "nick_name")
private String nickName;
public Author() {
}
public Author(long id, String nickName) {
this.id = id;
nickName = nickName;
}
/*
Getters and Setters
*/
}
Quote:
#Entity
#Table(name = "quotes")
public class Quote {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "quotes_id_seq")
#SequenceGenerator(name="quotes_id_seq", sequenceName="quotes_id_seq", allocationSize=1)
#Column(name = "id")
private long id;
#Column(name = "content")
private String content;
// #Temporal(TemporalType.DATE)
#Column(name = "date")
private LocalDate date;
#ManyToOne
#JoinColumn(name = "author")
private Author author;
public Quote() {
}
public Quote(long id, String content, LocalDate date, Author author) {
this.id = id;
this.content = content;
this.date = date;
this.author = author;
}
/*
Getters and Setters
*/
}
My Thymeleaf template contains form with two input fields(for quote.content and for quote.author.nickName) and select with existing authors. I want to see the behavior, when i fill input for author, content and if author is not existing in authors table, my application add the row in this table with specified by value from input nickName and generated id. But the problem is in getting unexpected result for me from Thymeleaf template. Template pass to controller the Quote object with author, which nickname is null instead of value from my input. There is thymeleaf template code of my form:
<form action="#" th:action="#{/newQuote}" th:object="${quote}" method="post">
<div class="form-row">
<div class="form-group col-md-3">
<label class="sr-only" for="inputNick">Nick Name</label>
<!--/*#thymesVar id="author" type="hello.entity.Author"*/-->
<input type="text" class="form-control" id="inputNick" th:field="*{author.nickName}"
placeholder="enter Nick Name">
</div>
<div class="form-group col-md-6">
<select id="nickNames">
<th:block th:each="author : ${allAuthors}">
<option th:text="${author.nickName}">Nick Name</option>
</th:block>
</select>
</div>
<div class="form-group col-md-12">
<label for="postContent">Your Quote:</label>
<input type="text" class="form-control" id="postContent" th:field="*{content}"
placeholder="quote text">
</div>
</div>
<div class="form-group col-md-2">
<input type="submit" value="Add Quote"/>
</div>
<div class="form-group col-md-2">
<input type="reset" value="Reset"/>
</div>
</form>
Controller methods:
#GetMapping("/newQuote")
public String showAuthors(Model model){
model.addAttribute("allAuthors",authorService.findAll());
model.addAttribute("quote", new Quote());
return "newQuote";
}
#PostMapping("/newQuote")
public String addQuote (#ModelAttribute Quote quote) {
quote.setDate(LocalDate.now());
quoteRepository.save(quote);
return "redirect:/";
I've tried:
to add Author object in GetMapping, pass it in newQuote template,
pass from it to PostMapping - no effect. Null in nickname.
to create and insert author object in quote object, pass to
template, pass to postmapping. no effect
I know that i can create DTO class with field nickname insteadof author field and convert it into my entity class in postmapping method of controller. But i think that it is "bad practice" way. I think, that i made wrong steps,may be, when tried to change author object and pass it from thymeleaf to controller. And also i suppose, that there is no way to realize this logic in this situation. i dont know where is the truth. Please, help me in finding it.
P.S: sorry for my bad english

Answer 1

So, the answer is asking how to add a quote and it's author at the same time. With a select approach is impossible, since our author doesn't exists. And simple way to achieve this, is changing your quote entity and adding #Cascade(CascadeType.PERSIST) to the author field in quote. This will automatically persist the author with your quote.
These would be the changes to your code that you would required to accomplish this.
Update
Since, the last solution didn't work, we will try sending an additional parameter to our controller, to avoid receiving a null, instead of the author's nickname.
Controller
#PostMapping("/newQuote")
public String addQuote (#ModelAttribute Quote quote,
#RequestParam("nickName") String nickName) {
// This will automatically persist your quote and it's author.
quote.setDate(LocalDate.now());
Author author = new Author();
author.setNickName(nickName);
quoteRepository.save(quote);
}
Quote Entity
#Entity
#Table(name = "quotes")
public class Quote {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "quotes_id_seq")
#SequenceGenerator(name="quotes_id_seq", sequenceName="quotes_id_seq", allocationSize=1)
#Column(name = "id")
private long id;
#Column(name = "content")
private String content;
#Column(name = "date")
private LocalDate date;
#ManyToOne
#Cascade(CascadeType.PERSIST)
#JoinColumn(name = "author")
private Author author;
// Getters and Setters
}
Important, make sure to notice that we are adding a new annotation #Cascade(CascadeType.PERSIST) to our author field.
HTML
Here we will simply remove the unnecessary select.
<form action="#" th:action="#{/newQuote}" th:object="${quote}" method="post">
<div class="form-row">
<div class="form-group col-md-3">
<label class="sr-only" for="inputNick">Nick Name</label>
<!--/*#thymesVar id="author" type="hello.entity.Author"*/-->
<input type="text" name="nickName" class="form-control" id="inputNick" placeholder="enter Nick Name"/>
</div>
<div class="form-group col-md-12">
<label for="postContent">Your Quote:</label>
<input type="text" class="form-control" id="postContent" th:field="*{content}" placeholder="quote text"/>
</div>
</div>
<div class="form-group col-md-2">
<input type="submit" value="Add Quote"/>
</div>
<div class="form-group col-md-2">
<input type="reset" value="Reset"/>
</div>
</form>