使用 Thymeleaf 在 Spring Boot 中的表单出错

Question

我最近开始使用 spring boot，我正在尝试创建一个表单来将学生添加到我创建的 API 中。

它告诉我这个错误：

There was an unexpected error (type=Internal Server Error, status=500).
An error happened during template parsing (template: "class path resource [templates/add.html]")
org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/add.html]")
    at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:241)
    at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parseStandalone(AbstractMarkupTemplateParser.java:100)
    at org.thymeleaf.engine.TemplateManager.parseAndProcess(TemplateManager.java:666)
    at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1098)
    at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1072)
    at org.thymeleaf.spring5.view.ThymeleafView.renderFragment(ThymeleafView.java:366)
    at org.thymeleaf.spring5.view.ThymeleafView.render(ThymeleafView.java:190)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1401)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1145)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1084)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:655)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:890)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1743)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: org.attoparser.ParseException: Error during execution of processor 'org.thymeleaf.spring5.processor.SpringInputGeneralFieldTagProcessor' (template: "add" - line 15, col 25)
    at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:393)
    at org.attoparser.MarkupParser.parse(MarkupParser.java:257)
    at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:230)
    ... 48 more
Caused by: org.thymeleaf.exceptions.TemplateProcessingException: Error during execution of processor 'org.thymeleaf.spring5.processor.SpringInputGeneralFieldTagProcessor' (template: "add" - line 15, col 25)
    at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:117)
    at org.thymeleaf.processor.element.AbstractElementTagProcessor.process(AbstractElementTagProcessor.java:95)
    at org.thymeleaf.util.ProcessorConfigurationUtils$ElementTagProcessorWrapper.process(ProcessorConfigurationUtils.java:633)
    at org.thymeleaf.engine.ProcessorTemplateHandler.handleStandaloneElement(ProcessorTemplateHandler.java:918)
    at org.thymeleaf.engine.TemplateHandlerAdapterMarkupHandler.handleStandaloneElementEnd(TemplateHandlerAdapterMarkupHandler.java:260)
    at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler$InlineMarkupAdapterPreProcessorHandler.handleStandaloneElementEnd(InlinedOutputExpressionMarkupHandler.java:256)
    at org.thymeleaf.standard.inline.OutputExpressionInlinePreProcessorHandler.handleStandaloneElementEnd(OutputExpressionInlinePreProcessorHandler.java:169)
    at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler.handleStandaloneElementEnd(InlinedOutputExpressionMarkupHandler.java:104)
    at org.attoparser.HtmlElement.handleStandaloneElementEnd(HtmlElement.java:79)
    at org.attoparser.HtmlMarkupHandler.handleStandaloneElementEnd(HtmlMarkupHandler.java:241)
    at org.attoparser.MarkupEventProcessorHandler.handleStandaloneElementEnd(MarkupEventProcessorHandler.java:327)
    at org.attoparser.ParsingElementMarkupUtil.parseStandaloneElement(ParsingElementMarkupUtil.java:96)
    at org.attoparser.MarkupParser.parseBuffer(MarkupParser.java:706)
    at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:301)
    ... 50 more
Caused by: org.springframework.beans.InvalidPropertyException: Invalid property 'age' of bean class [com.example.demo.model.Student]: Getter for property 'age' threw exception; nested exception is java.lang.reflect.InvocationTargetException
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:708)
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:617)
    at org.springframework.validation.AbstractPropertyBindingResult.getActualFieldValue(AbstractPropertyBindingResult.java:104)
    at org.springframework.validation.AbstractBindingResult.getFieldValue(AbstractBindingResult.java:228)
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:129)
    at org.springframework.web.servlet.support.RequestContext.getBindStatus(RequestContext.java:903)
    at org.thymeleaf.spring5.context.webmvc.SpringWebMvcThymeleafRequestContext.getBindStatus(SpringWebMvcThymeleafRequestContext.java:227)
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatusFromParsedExpression(FieldUtils.java:306)
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatus(FieldUtils.java:253)
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatus(FieldUtils.java:227)
    at org.thymeleaf.spring5.processor.AbstractSpringFieldTagProcessor.doProcess(AbstractSpringFieldTagProcessor.java:174)
    at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:74)
    ... 63 more
Caused by: java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.springframework.beans.BeanWrapperImpl$BeanPropertyHandler.getValue(BeanWrapperImpl.java:308)
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:630)
    ... 74 more
Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because "this.age" is null
    at com.example.demo.model.Student.getAge(Student.java:43) \

这是我的文件：

我的控制器：

@GetMapping(value="/add")
public  String addStudentForm (Model model)
{
    model.addAttribute("student",new Student());

    return "add"; 
}
@PostMapping(value = "/add")
public String addStudentSubmit(@ModelAttribute("student") Student student) {
    System.out.println(student.getLastname());
    return "addStudent";
}   

我的实体学生：

@Entity
@Table(name = "students")
public class Student {

public Student(long id, int age, String lastname, String surname, String mail, String course) {
    this.age=age;
    this.id=id;
    this.course=course;
    this.lastName= lastname;
    this.surname=surname;
    this.mail=mail;
    
}
public Student() {
    
}
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@Column(name="lastname")
private String lastName;

@Column(name="surname")
private String surname;

private Integer age;
private String course;
private String mail;  

public long getId() {
    return this.id;
}

public String getSurname() {
    return this.surname;
}
public void setSurname(String surname) {
    this.surname=surname;
}
public String getLastname() {
    return this.lastName;
}
public void setLastname(String lastname) {
    this.lastName=lastname;
}

public int getAge() {
    return this.age;
}
public void setAge(int age) {
    this.age=age;
}
public String getCourse() {
    return this.course;
}
public void setCourse(String course) {
    this.course=course;
}
public String getMail() {
    return this.mail;
}
public void setMail(String mail) {
    this.mail=mail;
}    

}

学生服务：

   @Data
   @Service
   public class StudentService {

    @Autowired
    private StudentRepository studentRepository;

    public Optional<Student> getStudentID(final Long id) {
        return studentRepository.findById(id);
    }

    public Iterable<Student> getStudents() {
        return studentRepository.findAll();
    }

    public void deleteStudent(final Long id) {
        studentRepository.deleteById(id);
    }

    public Student saveStudent(Student student) {
        Student savedStudent = studentRepository.save(student);
        return savedStudent;
    }

  }

添加.html

<!DOCTYPE HTML>
<html xmlns:th="https://www.thymeleaf.org">
<head>
  <title>Add a new student</title>
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
<h1>Add a student</h1>
  <form action="#" th:object="${student}" th:action="@{/add}" method="post">
  <label>Last name:</label>
  <input type="text" th:field="*{lastname}" name="lastname"/>
  <label>First name:</label>
  <input type="text" th:field="*{surname}" name="surname" />
  <label>Age:</label>
  <input type="number" th:field="*{age}" name="age" />
  <label>Email:</label>
  <input type="email" th:field="*{mail}" name="mail" />
  <label>Course:</label>
  <input type="text" th:field="*{course}"  name="course"/>

  <input type="submit" value="Submit" /> 
  <input type="reset" value="Reset" />
</form>

AddStudent.html

<!DOCTYPE HTML>
<html xmlns:th="https://www.thymeleaf.org">
<head>
   <title>Add a new student</title>
   <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
   <p "'${student.lastname} + ${student.surname}" />
   <a href="/add">Add another student</a>
   <a href="/"> Return to home page </a>

自上周以来，我一直在寻找原因，但找不到解决方案。
任何帮助，将不胜感激 ：）

Answer 1

发生错误是因为“年龄”属性包含“空”值。 当您输入“数字”类型时，它需要一个值，因此百里香试图在“学生”对象的“年龄”属性中获取该值。

尝试在输入中插入“最小”和“最大”属性..

<input type="number" th:field="*{age}" min="1" max="100" />