java - 在 com.spring.schoolmanagement.model.Subject 类型上找不到属性 'id'

Question

我试图将两个对象放入 JSP View 中，但是通过 getter 获取值时工作正常，而通过对象的属性引用值时会引发错误。

JSP 代码片段是:

<div class="row">
     <div class="box">
		<div class="col-lg-12">
            <hr><h2 class="intro-text text-center">Manage Subject</h2><hr>
        </div>
        <div class="col-md-12">
			<c:url var="addAction" value="/data-entry/subject/add" ></c:url>
			
			<form:form action="${addAction}" commandName="subject">
			<table>
				<c:if test="${!empty subject.name}">
				<tr>
					<td>
						<form:label path="id">
							<spring:message text="ID"/>
						</form:label>
					</td>
					<td>
						<form:input path="id" readonly="true" size="8"  disabled="true" />
						<form:hidden path="id" />
					</td> 
				</tr>
				</c:if>
				<tr>
					<td>
						<form:label path="name">
							<spring:message text="Name"/>
						</form:label>
					</td>
					<td>
						<form:input path="name" />
					</td> 
				</tr>
				<tr>
					<td>
						<form:label path="description">
							<spring:message text="Description"/>
						</form:label>
					</td>
					<td>
						<form:input path="description" />
					</td>
				</tr>
				<tr>
					<td colspan="2">
						<c:if test="${!empty subject.name}">
							<input type="submit"
								value="<spring:message text="Edit Subject"/>" />
						</c:if>
						<c:if test="${empty subject.name}">
							<input type="submit"
								value="<spring:message text="Add Subject"/>" />
						</c:if>
					</td>
				</tr>
			</table>	
			</form:form>
			<br>
			<h3>Subject List</h3>
			<c:if test="${!empty subjectlist}">
				<table class="tg">
				<tr>
					<th>ID</th>
					<th>Name</th>
					<th>Description</th>
					<th>Edit</th>
					<th>Delete</th>
				</tr>
				<c:forEach items="${subjectlist}" var="subject">
					<tr>
						<td>${subject.getID()}</td>
						<td>${subject.getName()}</td>
						<td>${subject.getDescription()}</td>
						<td><a href="<c:url value='/admin/subject/edit/${subject.getID()}' />" >Edit</a></td>
						<td><a href="<c:url value='/admin/subject/remove/${subject.getID()}' />" >Delete</a></td>
					</tr>
				</c:forEach>
				</table>
			</c:if>
		</div>
     </div>
</div>

模型类:

package com.spring.schoolmanagement.model;

public class Subject {
	private int id;
	private String name;
	private String description;

	public void setID(int id) {
		this.id = id;
	}

	public int getID() {
		return this.id;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getName() {
		return this.name;
	}

	public void setDescription( String description ) {
		this.description = description;
	}
	
	public String getDescription() {
		return this.description;
	}

	@Override
    public String toString(){
        return "{ID=" + id + ",Name=" + name + ",Description=" + description + "}";
    }
}

Controller 类:

package com.spring.schoolmangement;

import java.util.Locale;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.spring.schoolmanagement.dao.SubjectDAOImpl;
import com.spring.schoolmanagement.model.Subject;

/**
 * Handles requests for admin specific pages.
 */
@Controller
public class AdminController {

	private static final Logger logger = LoggerFactory.getLogger(HomeController.class);

	
	
	@Autowired
	private SubjectDAOImpl subjectService;
	
	
	/**
	 * Simply selects the home view to render by returning its name.
	 */
	@RequestMapping(value = {"/admin/", "/admin"}, method = RequestMethod.GET)
	public String home(Locale locale, Model model) {
		return "admin-dash-board";
	}

	
	@RequestMapping(value = "/admin/student")
	public String student(Model model) {
		return "admin-student";
	}
	
	@RequestMapping(value = "/admin/subject")
	public String displaySubjects(Model model) {
		model.addAttribute("subject", new Subject());
		model.addAttribute("subjectlist", this.subjectService.getAll());
		return "manage-subject";
	}
	
	@RequestMapping(value = "/admin/subject/edit/{id}")
	public String course(@PathVariable("id") int id, Model model) {
		model.addAttribute("subject", this.subjectService.getById(id));
		model.addAttribute("subjectlist", this.subjectService.getAll());
		return "manage-subject";
	}
}

请指出我在哪里犯了错误。

Answer 1

更改 getter/setter 方法:

public void setID(int id) {
    this.id = id;
}

public int getID() {
    return this.id;
}

至

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

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

您的 Bean 缺少命名约定，应遵循 JavaBean (read pdf section 8.8)命名约定。