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我最近开始使用Spring Boot（我主要来自python/flask和节点背景）与JPA和thymeleaf，我试图在我的数据库中创建一个项目。一切进展顺利，我能够添加，删除等。项目。无法保存实体使用百里香和弹簧启动
我添加了一个变量设置用户到我的项目实体，看起来像这样：
@Entity
@Table(name = "project")
public class Project {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name = "project_id")
private int id;
@Column(name = "title")
@NotEmpty(message = "*Please provide a title")
private String title;
@Column(name = "description")
private String description;
@OneToOne(cascade = CascadeType.ALL)
@JoinTable(name = "project_lead", joinColumns = @JoinColumn(name = "project_id"), inverseJoinColumns = @JoinColumn(name = "user_id"))
private User projectLead;
@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "project_user", joinColumns = @JoinColumn(name = "project_id"), inverseJoinColumns = @JoinColumn(name = "user_id"))
private Set<User> users;
...
}
用户类看起来是这样的：
@Entity
@Table(name = "user")
public class User {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name = "user_id")
private int id;
@Column(name = "email")
@Email(message = "*Please provide a valid Email")
@NotEmpty(message = "*Please provide an email")
private String email;
@Column(name = "username")
@NotEmpty(message = "*Please provide a username")
private String username;
@Column(name = "password")
@Length(min = 5, message = "*Your password must have at least 5 characters")
@NotEmpty(message = "*Please provide your password")
@Transient
private String password;
@Column(name = "enabled")
private int enabled;
@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
private Set<Role> roles;
...
}
我能当我创建新项目不要指定项目的用户。但是当我使用多重选择指定用户时，我无法创建项目。在我的表单中我有：
<form th:action="@{/secure/projects}" th:object="${project}" method="POST">
<div class="form-group">
<label th:if="${#fields.hasErrors('title')}" th:errors="*{title}" class="validation-message"></label>
<input type="text" class="form-control" th:field="*{title}" id="title" th:placeholder="Title" />
</div>
<div class="form-group">
<input type="text" class="form-control" th:field="*{description}" id="description" th:placeholder="Description" />
</div>
<div class="form-group">
<select th:field="*{users}" class="users-select form-control" multiple="multiple">
<option th:each="user : ${allUsers}" th:value="${user}" th:text="${user.username}"></option>
</select>
</div>
<button name="Submit" value="Submit" type="Submit" th:text="Create"></button>
</form>
我不断收到“未能类型的属性值转换‘java.lang.String中’所需类型‘为java.util.Set’财产‘用户’”为次：字段= “* {用户}”。我不明白为什么th：value =“$ {user}”被认为是一个String，当它被认为是User类的时候。有没有办法让我简单地得到select的结果，循环遍历它，然后手动将它添加到控制器中，以便将其添加到我的对象项目中？
我的控制器看起来是这样的：
@RequestMapping(value = "/projects", method=RequestMethod.GET)
public ModelAndView showProjectForm() {
ModelAndView modelAndView = new ModelAndView();
// Get authenticated user
Authentication auth = SecurityContextHolder.getContext().getAuthentication();
User user = userService.findByEmail(auth.getName());
modelAndView.addObject("userName", "Welcome " + user.getUsername() + " (" + user.getEmail() + ")");
modelAndView.addObject("project", new Project());
modelAndView.addObject("allUsers", userService.findAll());
modelAndView.setViewName("project_creation");
return modelAndView;
}
@RequestMapping(value = "/projects", method=RequestMethod.POST)
public ModelAndView processProjectForm(@Valid Project project, BindingResult bindingResult) {
ModelAndView modelAndView = new ModelAndView();
// Get authenticated user
Authentication auth = SecurityContextHolder.getContext().getAuthentication();
User user = userService.findByEmail(auth.getName());
// Get all projects
List<Project> allProjects = projectService.findAll();
// Check if project already exists
Project projectExist = projectService.findByTitle(project.getTitle());
if(projectExist != null) {
bindingResult
.rejectValue("title", "error.project",
"There is already a project with this title");
}
// Get all users
List<User> allUsers = userService.findAll();
if(bindingResult.hasErrors()) {
modelAndView.addObject("userName", "Welcome " + user.getUsername() + " (" + user.getEmail() + ")");
modelAndView.addObject("project", new Project());
modelAndView.addObject("allUsers", allUsers);
modelAndView.setViewName("project_creation");
} else {
// Create project
project.setProjectLead(user);
projectService.saveProject(project);
modelAndView.addObject("userName", "Welcome " + user.getUsername() + " (" + user.getEmail() + ")");
modelAndView.addObject("success", "Project successfully created!");
modelAndView.addObject("project", new Project());
modelAndView.addObject("projects", allProjects);
modelAndView.setViewName("redirect:/secure/dashboard");
}
return modelAndView;
}