Organize the differences in behavior of @NotBlank, @NotEmpty, @NotNull with Spring Boot + Thymeleaf

Thing you want to do

I don't understand the behavior of JSR-303 Bean Validation well, which caused confusion in the field, so I will try to organize it. Specifically, it is the following annotation. · Javax.validation.constraints.NotBlank (@NotBlank) · Javax.validation.constraints.NotEmpty (@NotEmpty) · Javax.validation.constraints.NotNull (@NotNull)

Conclusion

I have not verified escape sequences other than tabs, but I think that they will probably behave the same as tabs (probably).

Please note that if all spaces are full-width spaces, the check will not be caught.

Verification

I tried to verify it on the following simple screen.

`HelloController.java`


package com.example.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;

import com.example.demo.form.HelloForm;

@Controller
@RequestMapping(value = "/")
public class HelloController {
	
	private static final String SAMPLE_URL = "sample/Hello";

	@GetMapping
	public String index(@ModelAttribute HelloForm helloForm) {
		return SAMPLE_URL;
	}

	@PostMapping
	public String register(@Validated HelloForm helloForm, BindingResult result) {
		return SAMPLE_URL;
	}
}

`HelloForm.java`


package com.example.demo.form;

import javax.validation.constraints.NotBlank;
import javax.validation.constraints.NotEmpty;
import javax.validation.constraints.NotNull;

public class HelloForm {
	
	@NotBlank
	String notBlankField;
	
	@NotEmpty
	String notEmptyField;
	
	@NotNull
	String notNullField;
	
	public String getNotBlankField() {
		return notBlankField;
	}

	public void setNotBlankField(String notBlankField) {
		this.notBlankField = notBlankField;
	}

	public String getNotEmptyField() {
		return notEmptyField;
	}

	public void setNotEmptyField(String notEmptyField) {
		this.notEmptyField = notEmptyField;
	}

	public String getNotNullField() {
		return notNullField;
	}

	public void setNotNullField(String notNullField) {
		this.notNullField = notNullField;
	}
}

`Hello.html`


<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<title>Hello</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
	<form method="post" action="/" th:object="${helloForm}">
		<span th:if="${#fields.hasErrors('notBlankField')}" th:errors="*{notBlankField}" style="color: red"></span><br /> 
		NotBlankField：<input type="text" name="notBlankField" th:field="*{notBlankField}" /><br /> 
		<span th:if="${#fields.hasErrors('notEmptyField')}" th:errors="*{notEmptyField}" style="color: red"></span><br /> 
		NotEmptyField：<input type="text" name="notEmptyField" th:field="*{notEmptyField}" /><br /> 
		<span th:if="${#fields.hasErrors('notNullField')}" th:errors="*{notNullField}" style="color: red"></span><br /> 
		NotNullField：<input type="text" name="notNullField" th:field="*{notNullField}" /><br /><br />
		<input type="submit" value="Submit" />
	</form>
</body>
</html>

Empty string

Only NotBlank and NotEmpty get stuck in the check 空文字.PNG

All half-width spaces

Only Not Blank is checked

All full-width space

Not Blank, Not Empty, Not Null are all not checked. The source is below. https://github.com/kenichi-nagaoka/spring-boot-form-validation-sample

that's all.