spring 3.2 mvc如何接收复杂对象?
在下面的简单示例中,我有两个模型类,具有多对一关系。添加新的 Employee 对象时,我想使用 html 选择来选择它的部门。
当我发帖添加新员工时,出现以下错误:
Failed to convert property value of type java.lang.String to required type hu.pikk.model.Department for property department; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [hu.pikk.model.Department] for property department: no matching editors or conversion strategy found
我应该如何实现编辑器或转换策略?是否存在应注意的最佳实践或陷阱?
我已经阅读了 spring mvc 文档、一些文章和 stackoverflow 问题,但老实说,我发现它们有点令人困惑,而且很多时候太短、太草率了。
模型:
@Entity
public class Employee {
@Id
@GeneratedValue
private int employeeId;
@NotEmpty
private String name;
@ManyToOne
@JoinColumn(name="department_id")
private Department department;
//getters,setters
}
@Entity
public class Department {
@Id
@GeneratedValue
private int departmentId;
@Column
private String departmentName;
@OneToMany
@JoinColumn(name = "department_id")
private List<Employee> employees;
//getters,setters
}
在我的 Controller 类中:
@RequestMapping(value = "/add", method = RequestMethod.GET)
private String addNew(ModelMap model) {
Employee newEmployee = new Employee();
model.addAttribute("employee", newEmployee);
model.addAttribute("departments", departmentDao.getAllDepartments());
return "employee/add";
}
@RequestMapping(value = "/add", method = RequestMethod.POST)
private String addNewHandle(@Valid Employee employee, BindingResult bindingResult, ModelMap model, RedirectAttributes redirectAttributes) {
if (bindingResult.hasErrors()) {
model.addAttribute("departments", departmentDao.getAllDepartments());
return "employee/add";
}
employeeDao.persist(employee);
redirectAttributes.addFlashAttribute("added_employee", employee.getName());
redirectAttributes.addFlashAttribute("message", "employee added...");
return "redirect:list";
}
在 add.jsp 中:
<f:form commandName="employee" action="${pageContext.request.contextPath}/employee/add" method="POST">
<table>
<tr>
<td><f:label path="name">Name:</f:label></td>
<td><f:input path="name" /></td>
<td><f:errors path="name" class="error" /></td>
</tr>
<tr>
<td><f:label path="department">Department:</f:label></td>
<td><f:select path="department">
<f:option value="${null}" label="NO DEPARTMENT" />
<f:options items="${departments}" itemLabel="departmentName" itemValue="departmentId" />
</f:select></td>
<td><f:errors path="department" class="error" /></td>
</tr>
</table>
<input type="submit" value="Add Employee">
</f:form>
最佳答案
问题是,当 Controller 收到 POST 时,它不知道如何将 id 字符串转换为 Department 对象。 我发现基本上有三种方法可以解决这个问题:
- 不使用 spring form jSTL,而是使用自定义名称的简单 html 选择,并在 Controller 中使用 @RequestParam 读取它,访问数据库并填充它。
- 实现 Converter 接口(interface),并将其注册为 bean。
- 实现 PropertyEditor 接口(interface)。通过扩展 PropertyEditorSupport 类可以更轻松地做到这一点。
我选择了第三个选项。 (稍后当我有时间时,我将使用探索的前两个选项编辑此答案。)
2。实现 Converter 接口(interface)
@Component
public class DepartmentConverter implements Converter<String,Department>{
@Autowired
private DepartmentDao departmentDao;
@Override
public Department convert(String id){
Department department = null;
try {
Integer id = Integer.parseInt(text);
department = departmentDao.getById(id);
System.out.println("Department name:" + department.getDepartmentName());
} catch (NumberFormatException ex) {
System.out.println("Department will be null");
}
return department;
}
}
在spring beans配置文件中:
<mvc:annotation-driven conversion-service="conversionService"/>
<bean id="conversionService"
class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
<list>
<bean class="package.DepartmentConverter"/>
</list>
</property>
</bean>
3。扩展 PropertyEditorSupport 类
public class SimpleDepartmentEditor extends PropertyEditorSupport {
private DepartmentDao departmentDao;
public SimpleDepartmentEditor(DepartmentDao departmentDao){
this.departmentDao = departmentDao;
}
@Override
public void setAsText(String text) throws IllegalArgumentException {
Department department = null;
try {
Integer id = Integer.parseInt(text);
department = departmentDao.getById(id);
System.out.println("Department name:" + department.getDepartmentName());
} catch (NumberFormatException ex) {
System.out.println("Department will be null");
}
setValue(department);
}
}
在 Controller 内部,我需要添加一个@InitBinder:
@InitBinder
protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) {
binder.registerCustomEditor(Department.class, new SimpleDepartmentEditor(departmentDao));
}
关于java - 如何在 spring 3.2 mvc 中接收复杂对象?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19957760/