Этот момент все еще довольно запутан и неясен в Интернете, поэтому я решил мою проблему.Это решение, вероятно, не самое оптимизированное, но оно работает, когда создает и обновляет мастер-сущность.
Теория
Использование List вместо Set для ваших отношений «один ко многим», которые должны динамически управляться.
Инициализируйте ваш List как AutoPopulatingList.Это ленивый список, который позволяет динамически добавлять элементов.
Добавить атрибут remove из int к вашему дочернему объекту.Это будет играть роль логического флага и будет полезно, когда динамически удаляет элемент.
При публикации формы сохраняются только те элементы, которые имеют флагremove на 0 (т. Е. false).
Практика
Полный рабочий пример: у работодателя много работников, у работника есть один работодатель.
Объекты:
Employer.java
@Entity
@Table(name = "employer")
public class Employer
private Integer id;
private String firstname;
private String lastname;
private String company;
private List<Employee> employees; // one-to-many
/* getters & setters */
}
Employee.java
@Entity
@Table(name = "employee")
public class Employee {
private Integer id;
@Transient // means "not a DB field"
private Integer remove; // boolean flag
private String firstname;
private String lastname;
private Employer employer; // many-to-one
/* getters & setters */
}
Контроллер:
EmployerController.java
@Controller
@RequestMapping("employer")
public class EmployerController {
// Manage dynamically added or removed employees
private List<Employee> manageEmployees(Employer employer) {
// Store the employees which shouldn't be persisted
List<Employee> employees2remove = new ArrayList<Employee>();
if (employer.getEmployees() != null) {
for (Iterator<Employee> i = employer.getEmployees().iterator(); i.hasNext();) {
Employee employee = i.next();
// If the remove flag is true, remove the employee from the list
if (employee.getRemove() == 1) {
employees2remove.add(employee);
i.remove();
// Otherwise, perform the links
} else {
employee.setEmployer(employer);
}
}
}
return employees2remove;
}
// -- Creating a new employer ----------
@RequestMapping(value = "create", method = RequestMethod.GET)
public String create(@ModelAttribute Employer employer, Model model) {
// Should init the AutoPopulatingList
return create(employer, model, true);
}
private String create(Employer employer, Model model, boolean init) {
if (init) {
// Init the AutoPopulatingList
employer.setEmployees(new AutoPopulatingList<Employee>(Employee.class));
}
model.addAttribute("type", "create");
return "employer/edit";
}
@RequestMapping(value = "create", method = RequestMethod.POST)
public String create(@Valid @ModelAttribute Employer employer, BindingResult bindingResult, Model model) {
if (bindingResult.hasErrors()) {
// Should not re-init the AutoPopulatingList
return create(employer, model, false);
}
// Call the private method
manageEmployees(employer);
// Persist the employer
employerService.save(employer);
return "redirect:employer/show/" + employer.getId();
}
// -- Updating an existing employer ----------
@RequestMapping(value = "update/{pk}", method = RequestMethod.GET)
public String update(@PathVariable Integer pk, @ModelAttribute Employer employer, Model model) {
// Add your own getEmployerById(pk)
model.addAttribute("type", "update");
return "employer/edit";
}
@RequestMapping(value = "update/{pk}", method = RequestMethod.POST)
public String update(@PathVariable Integer pk, @Valid @ModelAttribute Employer employer, BindingResult bindingResult, Model model) {
// Add your own getEmployerById(pk)
if (bindingResult.hasErrors()) {
return update(pk, employer, model);
}
List<Employee> employees2remove = manageEmployees(employer);
// First, save the employer
employerService.update(employer);
// Then, delete the previously linked employees which should be now removed
for (Employee employee : employees2remove) {
if (employee.getId() != null) {
employeeService.delete(employee);
}
}
return "redirect:employer/show/" + employer.getId();
}
// -- Show an existing employer ----------
@RequestMapping(value = "show/{pk}", method = RequestMethod.GET)
public String show(@PathVariable Integer pk, @ModelAttribute Employer employer) {
// Add your own getEmployerById(pk)
return "employer/show";
}
}
Просмотр:
employer/edit.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"
%><%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"
%><%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"
%><%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"
%><!DOCTYPE HTML>
<html>
<head>
<title>Edit</title>
<style type="text/css">.hidden {display: none;}</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>
<script type="text/javascript">
$(function() {
// Start indexing at the size of the current list
var index = ${fn:length(employer.employees)};
// Add a new Employee
$("#add").off("click").on("click", function() {
$(this).before(function() {
var html = '<div id="employees' + index + '.wrapper" class="hidden">';
html += '<input type="text" id="employees' + index + '.firstname" name="employees[' + index + '].firstname" />';
html += '<input type="text" id="employees' + index + '.lastname" name="employees[' + index + '].lastname" />';
html += '<input type="hidden" id="employees' + index + '.remove" name="employees[' + index + '].remove" value="0" />';
html += '<a href="#" class="employees.remove" data-index="' + index + '">remove</a>';
html += "</div>";
return html;
});
$("#employees" + index + "\\.wrapper").show();
index++;
return false;
});
// Remove an Employee
$("a.employees\\.remove").off("click").on("click", function() {
var index2remove = $(this).data("index");
$("#employees" + index2remove + "\\.wrapper").hide();
$("#employees" + index2remove + "\\.remove").val("1");
return false;
});
});
</script>
</head>
<body>
<c:choose>
<c:when test="${type eq 'create'}"><c:set var="actionUrl" value="employer/create" /></c:when>
<c:otherwise><c:set var="actionUrl" value="employer/update/${employer.id}" /></c:otherwise>
</c:choose>
<form:form action="${actionUrl}" modelAttribute="employer" method="POST" name="employer">
<form:hidden path="id" />
<table>
<tr>
<td><form:label path="firstname">Firstname</form:label></td>
<td><form:input path="firstname" /><form:errors path="firstname" /></td>
</tr>
<tr>
<td><form:label path="lastname">Lastname</form:label></td>
<td><form:input path="lastname" /><form:errors path="lastname" /></td>
</tr>
<tr>
<td><form:label path="company">company</form:label></td>
<td><form:input path="company" /><form:errors path="company" /></td>
</tr>
<tr>
<td>Employees</td>
<td>
<c:forEach items="${employer.employees}" varStatus="loop">
<!-- Add a wrapping div -->
<c:choose>
<c:when test="${employer.employees[loop.index].remove eq 1}">
<div id="employees${loop.index}.wrapper" class="hidden">
</c:when>
<c:otherwise>
<div id="employees${loop.index}.wrapper">
</c:otherwise>
</c:choose>
<!-- Generate the fields -->
<form:input path="employees[${loop.index}].firstname" />
<form:input path="employees[${loop.index}].lastname" />
<!-- Add the remove flag -->
<c:choose>
<c:when test="${employees[loop.index].remove eq 1}"><c:set var="hiddenValue" value="1" /></c:when>
<c:otherwise><c:set var="hiddenValue" value="0" /></c:otherwise>
</c:choose>
<form:hidden path="employees[${loop.index}].remove" value="${hiddenValue}" />
<!-- Add a link to remove the Employee -->
<a href="#" class="employees.remove" data-index="${loop.index}">remove</a>
</div>
</c:forEach>
<button id="add" type="button">add</button>
</td>
</tr>
</table>
<button type="submit">OK</button>
</form:form>
</body>
</html>
Надеюсь, что может помочь :)