[JAVA] Create a simple CRUD with SpringBoot + JPA + Thymeleaf ③ ～ Add Validation ～

-Continued from Last time --Create a simple CRUD app with Spring Boot --This time, validate the input area --Make name and age required --Age should be in the range 0-150 --Team name can be up to 20 characters

procedure

Add validation settings to entity
Add error control to controller
Add an error message to the template

1. Add validation settings to entity

--Validation setting annotates variables of entity class --Edit Player.java

`src/main/java/com/example/baseball/domain/Player.java`


    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @NotEmpty // ①
    private String name;
    @NotNull // ②
    @Min(value = 0) // ③
    @Max(value = 150)
    private Integer age;
    @Size(max = 20) // ④
    private String team;
    private String position;

-①: If @NotEmpty is added, null and empty string will not be allowed. -②: If @NotNull is added, null will not be allowed. --③: Set the minimum value with @ Min and the maximum value with @ Max -④: Add @Size to limit the number of characters

2. Add error control to controller

--Add a process to return to the original screen if there is an error --Modify PlayerController.java

`src/main/java/com/example/baseball/controller/PlayerController.java`


    @GetMapping("new")
    public String newPlayer(Model model) {
        // ①
        Player player = new Player();
        model.addAttribute("player", player);
        return "players/new";
    }

    @PostMapping
    public String create(@Valid @ModelAttribute Player player, BindingResult bindingResult) { // ②
        if(bindingResult.hasErrors()) return "players/new"; // ③
        playerService.save(player);
        return "redirect:/players";
    }

    @PutMapping("{id}")
    public String update(@PathVariable Long id, @Valid @ModelAttribute Player player, BindingResult bindingResult) {
        if(bindingResult.hasErrors()) return "players/edit";
        player.setId(id);
        playerService.save(player);
        return "redirect:/players";
    }

-①: Pass the Player instance to the new creation screen --Without this, the contents entered at the time of the input error cannot be retained. -②: By adding @Valid to player, it becomes a validation check target. --Annotations are arranged side by side, but @Valid depends on player

@Valid @ModelAttribute Player player
//↑ and ↓ are the same
@Valid
@ModelAttribute
Player player

-②: If there is an error, the error information is set in BindingResult bindingResult. --③: If there is an error, bindingResult.hasErrors () returns true, so in that case it is returned to the original screen.

3. Add error message to template

new.html

--Display an error message when there is an error and it is thrown back to the controller

`src/main/resources/templates/players/new.html`


      <!-- ① -->
      <form th:action="@{/players}" th:method="post" th:object="${player}">
        <!-- ② -->
        <div class="form-group" th:classappend="${#fields.hasErrors('name')}? has-error">
          <label class="control-label">name</label>
          <input class="form-control" type="text" th:field="*{name}" />
          <!-- ③ -->
          <span class="text-danger" th:if="${#fields.hasErrors('name')}" th:errors="*{name}"></span>
        </div>
        <div class="form-group" th:classappend="${#fields.hasErrors('age')}? has-error">
          <label class="control-label">age</label>
          <input class="form-control" type="number" th:field="*{age}" />
          <span class="text-danger" th:if="${#fields.hasErrors('age')}" th:errors="*{age}"></span>
        </div>
        <div class="form-group" th:classappend="${#fields.hasErrors('team')}? has-error">
          <label class="control-label">Team name</label>
          <input class="form-control" type="text" th:field="*{team}" />
          <span class="text-danger" th:if="${#fields.hasErrors('team')}" th:errors="*{team}"></span>
        </div>
        <div class="form-group" th:classappend="${#fields.hasErrors('position')}? has-error">
          <label class="control-label">Defensive position</label>
          <input class="form-control" type="text" th:field="*{position}" />
          <span class="text-danger" th:if="${#fields.hasErrors('position')}" th:errors="*{position}"></span>
        </div>
        <button class="btn btn-default" type="submit">Create</button>
      </form>

--①: Since the player is now received from the controller, set it to th: object. --Modified so that each input field also uses th: field (see ③ of here) ――The reason why I made this change is because I want to reset the input contents to value when an error occurs and it is thrown back. --②: th: classappend =" $ {# fields.hasErrors ('name')}? has-error " means has in the class attribute when # fields.hasErrors ('name') is true. -Add error --Error information is contained in # fields --If you add has-error to the class attribute, the label and frame will turn red according to the Bootstrap definition. --③: Area for displaying error messages --Elements with th: if set are displayed only when the value of th: if is true (in this case, when there is an error). -- th: errors =" * {name} " displays all error messages set for * {name} --Although it does not occur in this example, if there are multiple errors, all will be displayed with line breaks.

edit.html

--Added the same processing as new.html

`src/main/resources/templates/players/edit.html`


      <form th:action="@{/players/{id}(id=*{id})}" th:method="put" th:object="${player}">
        <div class="form-group" th:classappend="${#fields.hasErrors('name')}? has-error">
          <label class="control-label">name</label>
          <input class="form-control" type="text" th:field="*{name}" />
          <span class="text-danger" th:if="${#fields.hasErrors('name')}" th:errors="*{name}"></span>
        </div>
        <div class="form-group" th:classappend="${#fields.hasErrors('age')}? has-error">
          <label class="control-label">age</label>
          <input class="form-control" type="number" th:field="*{age}" />
          <span class="text-danger" th:if="${#fields.hasErrors('age')}" th:errors="*{age}"></span>
        </div>
        <div class="form-group" th:classappend="${#fields.hasErrors('team')}? has-error">
          <label class="control-label">Team name</label>
          <input class="form-control" type="text" th:field="*{team}" />
          <span class="text-danger" th:if="${#fields.hasErrors('team')}" th:errors="*{team}"></span>
        </div>
        <div class="form-group" th:classappend="${#fields.hasErrors('position')}? has-error">
          <label class="control-label">Defensive position</label>
          <input class="form-control" type="text" th:field="*{position}" />
          <span class="text-danger" th:if="${#fields.hasErrors('position')}" th:errors="*{position}"></span>
        </div>
        <button class="btn btn-default" type="submit">update</button>
      </form>

Operation check

--With the modifications made so far, when you access http: // localhost: 8080 / players, the behavior is as follows.

next time

--Next is here

[JAVA] Create a simple CRUD with SpringBoot + JPA + Thymeleaf ③ ～ Add Validation ～

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