Spring boot 使用Thymeleaf的Spring Boot应用程序中的表单提交问题

我用Spring Boot编写了这个基本的应用程序，带有一个Web控制器。我包括了一个HTML表单来添加一些输入，这些输入将使用JpaRepository保存方法保存输入

我使用Thymeleaf作为模板引擎，MySql作为数据库。当我运行应用程序时，它运行得很好。但是，当我点击localhost:8080/addExpense页面时，它给出了一个带有以下错误的白标签错误页面：

出现意外错误（类型=内部服务器错误， 状态=500）。 执行处理器“org.thymeleaf.spring5.processor.SpringInputGeneralFieldTagProcessor”时出错 （模板：“addExpense”-第19行，第49列）

我认为问题在于这个代码

th:field=“*{expense}”

我的IDE控制台打印以下错误：

org.thymeleaf.exceptions.TemplateProcessingException:运行期间出错 处理器的执行 'org.thymeleaf.spring5.processor.SpringInputGeneralFieldTagProcessor' （模板：“addExpense”-第19行，第49列）位于 org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess（AbstractAttributeTagProcessor.java:117） ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.processor.element.AbstractElementTagProcessor.process（AbstractElementTagProcessor.java:95） ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.util.ProcessorConfiguration Utils$ElementTagProcessorWrapper.process（ProcessorConfiguration Utils.java:633） ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.engine.ProcessorTemplateHandler.handleStandaloneElement（ProcessorTemplateHandler.java:918） ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.engine.StandaloneElementTag.beHandled（StandaloneElementTag.java:228） ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.engine.TemplateModel.process（TemplateModel.java:136） ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.engine.TemplateManager.parseAndProcess（TemplateManager.java:661） ~[thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.TemplateEngine.process（TemplateEngine.java:1098） [thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.TemplateEngine.process（TemplateEngine.java:1072） [thymeleaf-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.spring5.view.ThymeleafView.renderFragment（ThymeleafView.java:354） [thymeleaf-spring5-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.thymeleaf.spring5.view.ThymeleafView.render（ThymeleafView.java:187） [thymeleaf-spring5-3.0.9.RELEASE.jar:3.0.9.RELEASE]at org.springframework.web.servlet.DispatcherServlet.render（DispatcherServlet.java:1325） [spring-webmvc-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.servlet.DispatcherServlet.processDispatchResult（DispatcherServlet.java:1069） [spring-webmvc-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.servlet.DispatcherServlet.doDispatch（DispatcherServlet.java:1008） [spring-webmvc-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.servlet.DispatcherServlet.doService（DispatcherServlet.java:925） [spring-webmvc-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.servlet.FrameworkServlet.processRequest（FrameworkServlet.java:974） [spring-webmvc-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.servlet.FrameworkServlet.doGet（FrameworkServlet.java:866） [spring-webmvc-5.0.6.RELEASE.jar:5.0.6.RELEASE] javaservlet.http.HttpServlet.service（HttpServlet.java:635） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.springframework.web.servlet.FrameworkServlet.service（FrameworkServlet.java:851） [spring-webmvc-5.0.6.RELEASE.jar:5.0.6.RELEASE] javaservlet.http.HttpServlet.service（HttpServlet.java:742） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:231） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:166） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52） [tomcat-embed-websocket-8.5.31.jar:8.5.31]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:193） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:166） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.springframework.web.filter.RequestContextFilter.doFilterInternal（RequestContextFilter.java:99） [spring-web-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.filter.OncePerRequestFilter.doFilter（OncePerRequestFilter.java:107） [spring-web-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:193） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:166） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal（HttpPutFormContentFilter.java:109） [spring-web-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.filter.OncePerRequestFilter.doFilter（OncePerRequestFilter.java:107） [spring-web-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:193） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:166） [tomcat-embed-core-8.5.31.jar:8.5.31]at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal（HiddenHttpMethodFilter.java:81） [spring-web-5.0.6.RELEASE.jar:5.0.6.RELEASE] org.springframework.web.filter.OncePerRequestFilter.doFilter（OncePerRequestFilter.java:107） [spring-web-5.0.6.0版本]

Here's my codes:

Model File: Expense.java

package com.ksk.expenseapp.model;


import javax.persistence.*;
import java.time.LocalDate;

@Entity
public class Expense {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

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

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

    @Column(name = "amount")
    private int amount;

    //No Arg Construction required by JPA
    public Expense() {
    }

    public Expense(String expense, int amount) {
        this.date = LocalDate.now().toString();
        this.expense = expense;
        this.amount = amount;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getExpense() {
        return expense;
    }

    public void setExpense(String expense) {
        this.expense = expense;
    }

    public int getAmount() {
        return amount;
    }

    public void setAmount(int amount) {
        this.amount = amount;
    }
}

package com.ksk.expenseapp.controller;

import com.ksk.expenseapp.model.Expense;
import com.ksk.expenseapp.repo.ExpenseRepo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
public class WebController {

    ExpenseRepo expenseRepo;

    @Autowired
    public WebController(ExpenseRepo expenseRepo) {
        this.expenseRepo = expenseRepo;
    }

    @RequestMapping("/addExpense")
    public String addExpense(){
        return "addExpense";
    }

    @RequestMapping(value = "/save", method = RequestMethod.POST)
    public String addNewExpense(@ModelAttribute Expense expense){
        expenseRepo.save(expense);
        return "addExpense";
    }
}

<!doctype html>
<html xmlns:th="http://www.thymeleaf.org" lang="en">
<head>
    <!-- Required meta tags -->
    <meta charset="utf-8"/>
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"/>

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css"/>

    <title>Hello, world!</title>
</head>
<body>
<h1>Add Expense</h1>

<form th:action="@{/save}" th:object="${expense}" method="post">
    <div class="form-group">
        <label>Expense</label>
        <input type="text" class="form-control" th:field="*{expense}"/>

        <label>Amount</label>
        <input type="text" class="form-control"  th:field="*{amount}"/>
        <button class="btn btn-success" type="submit">Submit</button>
    </div>

</form>


<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>