java - spring mvc 表单 :select tag

Question

我有一个包含国家列表(列表)的模型和一个包含国家对象的用户对象。我认为用户可以选择他的国家。
这是我的jsp页面的片段:

<form:select path="user.country">
    <form:option value="-1">Select your country</form:option>
    <form:options items="${account.countries}" itemLabel="name" itemValue="id" />
</form:select>

这是我的帐户模型:

public class Account {

    private User user;
    private List<Country> countries;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public List<Country> getCountries() {
        return countries;
    }

    public void setCountries(List<Country> countries) {
        this.countries = countries;
    }
}

当 jsp 加载 (GET) 表单时:select 显示当前用户国家的选定项。问题是，当我发布表单时，我得到了这个异常:

Field error in object 'account' on field 'user.country': rejected value [90];
  codes [typeMismatch.account.user.country,typeMismatch.user.country,typeMismatch.country,typeMismatch.org.MyCompany.entities.Country,typeMismatch];
  arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [account.user.country,user.country];
  arguments []; default message [user.country]];
  default message [Failed to convert property value of type 'java.lang.String' to required type 'org.MyCompany.entities.Country' for property 'user.country';
  nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [org.MyCompany.entities.Country] for property 'country': no matching editors or conversion strategy found]

知道如何克服这个问题吗？

Answer 1

您需要以某种方式告诉 Spring 将 String 转换为 Country。这是一个例子:

@Component
public class CountryEditor extends PropertyEditorSupport {

    private @Autowired CountryService countryService;

    // Converts a String to a Country (when submitting form)
    @Override
    public void setAsText(String text) {
        Country c = this.countryService.findById(Long.valueOf(text));

        this.setValue(c);
    }

}

和

...
public class MyController {

    private @Autowired CountryEditor countryEditor;

    @InitBinder
    public void initBinder(WebDataBinder binder) {
        binder.registerCustomEditor(Country.class, this.countryEditor);
    }

    ...

}