我通读了the similar question，不幸的是没有找到解决方案。
我将学生实体作为@ModelAttribute发送到JSP，允许用户编辑它。当学生被POST回控制器（StudentController）时，字段rates和id为空。rates的空值是可以的，我将学生的费率作为单独的@RequestParam传递。其他字段也可以。但是id意外地为空。
我使用的是Java 8，Spring 4.1，Tomcat 7.0.55，JSTL 1.2。
下面是我的StudentController的相关部分：
@Controller
@RequestMapping(value = "/student")
public class StudentController {
@Autowired
private StudentService studentService;
@Autowired
private FacultyService facultyService;
@RequestMapping(value = "/edit/{id:.+}", method = RequestMethod.GET)
public ModelAndView editStudentPage(@PathVariable Long id) {
ModelAndView mav = new ModelAndView("student-edit");
Student student = (id > 0)? studentService.findById(id) : new Student();
mav.addObject("student", student);
// or
//mav.getModelMap().addAttribute(student);
/* other objects omitted */
return mav;
}
@RequestMapping(value = "/edit/{id:.+}", method = RequestMethod.POST)
public ModelAndView editStudent(
@ModelAttribute Student student,
@RequestParam(value="rates", required = false) String ratesString,
@PathVariable Long id,
final RedirectAttributes redirectAttributes) throws StudentNotFoundException {
ModelAndView mav = new ModelAndView("redirect:/student/list");
student = studentService.update(student);
student.updateRates(ratesString);
String msg = "Student was successfully updated";
redirectAttributes.addFlashAttribute("message", msg);
return mav;
}
/* ... */
}下面是一个学生编辑的JSP文件：
<jsp:useBean id="student" scope="request" class="by.naxa.demo.model.Student" />
<!-- I've tried to comment out the above line in order to avoid collision with `modelAttribute` (in hope that this was a culprit) -->
<%@page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<c:url var="formAction" value="/student/edit/${student.id}" /> <!-- simplified -->
<!-- <head> omitted -->
<body>
<form:form action="${formAction}" method="POST" modelAttribute="student" >
<form:hidden path="id" /> <!-- I've tried to specify `value="${student.id}"` here -->
<div>
<form:label path="name">Student's name:</form:label>
<form:input path="name" required="true"/><br />
<!-- other fields omitted -->
<input type="submit" value="Save" />
<!-- `Cancel` omitted -->
</div>
</form:form>
</body>我看到生成的页面上的输入填充了正确的值：
<input id="id" name="id" value="1" type="hidden" />
<input id="name" name="name" required="true" type="text" value="John Snow"/>web.xml:
<!-- Creates the Spring Container shared by all Servlets and Filters -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!-- Processes application requests -->
<servlet>
<servlet-name>appServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/app/servlet-context.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>jsp</servlet-name>
<servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
<load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>appServlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>jsp</servlet-name>
<url-pattern>/WEB-INF/views/*</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file />
</welcome-file-list>Spring servlet-context.xml中的视图解析器：
<!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
<property name="prefix" value="/WEB-INF/views/" />
<property name="suffix" value=".jsp" />
</bean>类学生扩展了AbstractNamedPersistable。它们如下所示（使用Lombok和JPA进行注解）：
@Entity
@NoArgsConstructor
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true, includeFieldNames = false)
@NamedQuery(name = "Student.findByTheStudentsName", query = "select s from Student s where s.name = ?1")
public @Data class Student extends AbstractNamedPersistable<Long> {
/* all fields and `updateRates(String)` omitted */
}
@MappedSuperclass
@EqualsAndHashCode(callSuper = false)
@NoArgsConstructor
@AllArgsConstructor
public abstract @Data class AbstractNamedPersistable<PK extends Serializable> extends AbstractPersistable<PK> {
@Column(name = "Name", nullable = false, unique = true)
private String name;
@Override
public String toString() {
return getName();
}
}有什么问题吗？
1条答案
按热度按时间xtupzzrd1#
我猜这是Lombok的一个问题（bug），当我们使用@NoArgsConstructor处理一个属性为@ModelAttribute的请求时，它会用一个默认的构造函数覆盖请求参数，因为它是用@ModelAttribute而不是@RequestBody来属性化的，所以JSON主体会覆盖查询字符串中传递的字段。避免这种情况的方法是删除@NoArgsConstructor对@ModelAttribute注解的请求pojo的注解。