java - Spring 3.0 MVC 绑定(bind)嵌套对象

Question

为什么 spring 不绑定(bind)嵌套对象上的值？

RegistrationBean 上的 SecurityQuestion 对象分别将问题和答案设置为 null、null，尽管在 View 中使用 bean 表示法在表单中设置 then。

bean 类:

public class SecurityQuestion {
  SecurityQuestionType type;
  String answer;
}

public class RegistrationBean {
  @Valid
  SecurityQuestion securityQuestion;
  String name;


  public SecurityQuestionType[] getSecurityQuestionOptions() {
    return SecurityQuestionType.values();
  }
}

查看:

<form:form modelAttribute="registrationBean" method="POST">
  <form:select id="securityQuestion" path="securityQuestion.question">
    <c:forEach var="securityQuestionOption" items="${securityQuestionOptions}">
      <form:option value="${securityQuestionOption}">${securityQuestionOption</form:option>
    </c:forEach>
  </form:select>

  <form:input id="securityAnswer" path="securityQuestion.answer" />
  <form:input id="name" path="name" />
</form:form>

Controller :

@RequestMapping(value = URL_PATTERN, method = RequestMethod.POST)
public ModelAndView submit(@Valid final RegistrationBean registrationBean) {
  // registrationBean.getSecurityQuestion().getQuestion() == null
  // registrationBean.getSecurityQuestion().getAnswer() == null
}

解决方案

所有 bean 的所有字段都必须有 getters/setters。 Spring 使用默认构造函数，然后使用 setter 来改变 View 中的对象。

Answer 1

您能否尝试为 RegistrationBean 提供适当的 getter/setter。

public class RegistrationBean {
  @Valid
  SecurityQuestion securityQuestion;
  String name;

  public SecurityQuestion getSecurityQuestion(){
        return securityQuestion;
  }
  public void setSecurityQuestion(SecurityQuestion q){
      this.securityQuestion = q;
  }    
  public SecurityQuestionType[] getSecurityQuestionOptions() {
    return SecurityQuestionType.values();
  }
}