Spring Boot + LocalDate：“无主构造函数或默认构造函数”

Question

我<input type="date" ...>为 Spring Boot 应用程序创建了一个简单的表单。我想把它变成LocalDate控制器中的一个。我收到错误：Fri Aug 17 15:32:01 CEST 2018There was an unexpected error (type=Internal Server Error, status=500).No primary or default constructor found for class java.time.LocalDate这当然是正确的，但是 - 据我所知 - 应该无关紧要，因为根据文档：“[...]@DateTimeFormat注释应该适用java.time于 Java 8 和 Spring 4。”控制器方法：@PostMapping("/users")public String register(String user, String pw, @DateTimeFormat(iso=DateTimeFormat.ISO.DATE) LocalDate beginning){    MyUser myUser = MyUser.create(user,pw);    MyUser.setEnabled(beginning);    repo.register(myUser);    return "redirect:/users/"+user;}HTML/百里香叶：<form method="POST"><div><label> Benutzername : <input type="text" name="user"/> </label></div><div><label> Passwort: <input type="password" name="password"/> </label></div><div><label> Freigeschaltet ab (optional): <input type="date" name="beginning"/> </label></div><div><input type="submit" value="Registrieren"/></div></form>pom（摘录） <dependencyManagement>    <dependencies>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-dependencies</artifactId>            <version>2.0.4.RELEASE</version>            <type>pom</type>            <scope>import</scope>        </dependency>    </dependencies></dependencyManagement><dependencies>    <dependency>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-thymeleaf</artifactId>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-web</artifactId>    </dependency>...</dependencies>   <properties>    <java.version>1.8</java.version></properties>