Spring MVC - 使用转换器将ID绑定到对象（ConversionServiceFactoryBean）

Question

我有两个班级（Team，Coach）：

Team.java：

@Entity
@Table(name="TEAM")
public class Team {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ID_TEAM")
    private Long idTeam;

    @Column(name = "NAME_TEAM")
    private String nameTeam;

    @OneToOne
    @JoinColumn(name = "ID_COACH")
    private Coach coach;

    //Getters & Setters...
}

Coach.java：

@Entity
@Table(name="COACH")
public class Coach {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ID_COACH")
    private Long idCoach;

    @Column(name = "NAME_COACH")
    private String nameCoach;

    @OneToOne
    private Team team;

    //Getters & Setters...
}

如您所见，它们之间存在OneToOne关系。

在我的表格中，我从数据库中检索（成功）所有教练。

<form action="add" method="post">
    <label for="nameTeam">Team <span style="color: red;">*</span></label>
    <input type="text" name="nameTeam" id="nameTeam"/>

    <label for="coach">Coach <span style="color: red;">*</span></label>
    <select name="coach" id="coach">
        <option value="" disabled selected>- Select a coach -</option>
        <c:forEach var="coach" items="${coachs}">
            <option value="${coach.idCoach}">${coach.nameCoach}</option>
        </c:forEach>
    </select>

    <button type="submit">Add</button>
</form>

所以我从select元素中选择了一个教练。当我提交表单时，团队会添加到数据库中，但我会在null字段中获得ID_COACH。

这是我的Controller：

@RequestMapping(value = "/team/add", method = RequestMethod.POST)
public String addTeam(Team team) {
    this.teamService.add(team);
    return "new_team";
}

ConversionService：

<!-- Conversion Service -->
<mvc:annotation-driven conversion-service="conversionService"/>

<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
    <property name="converters">
        <list>
            <bean class="converters.ToCoach"/>
        </list>
    </property> 
</bean>

这是我的Converter：

public class ToCoach implements Converter<Long, Coach> {    
    @Autowired
    CoachRepository coachRepo;

    public Coach convert(Long idCoach) {
        return this.coachRepo.findOne(idCoach);
    }
}