Spring MultipartFile验证和转换 [英] Spring MultipartFile validation and conversion

问题描述

我目前有一个采用MultipartFile的Spring MVC控制器

I currently have a Spring MVC controller that takes a MultipartFile

@RequestMapping(method = RequestMethod.POST)
public String doUpload(@RequestParam("file") final MultipartFile file) {
    /* ... */
}

该文件包含csv数据，每行将使用该数据创建域对象列表.工作正常.

The file contains csv data which will be used, one per row, to create a list of domain objects. This is working.

我已经为行数据编写了一个转换器:

I have written a converter for the line data:

class MyObjectConverter implements org.springframework...Converter<String[], MyObject> {
    /* ... */
}

以及文件的验证器

class UploadFileValidator implements org.springframework.validation.Validator { 
    /* ... */
}

我有一个表格可以上传:

And I have a form to do the uploading:

<form method="post" 
    action="<@spring.url '/upload'/>" 
    enctype="multipart/form-data">
        <input id="upload" type="file" name="file"/>
        <input type="submit" id="uploadButton"/>
    </form

但是我真正想做的是将它们绑在一起，以便我的控制器可以使用类似的方法

But what I really want to do is tie it all together so that my controller can have a method something like

@RequestMapping(method = RequestMethod.POST)
public String doUpload(
    @Valid final List<MyObject> objList, 
    final BindingResult result) { ...}

我知道Spring MVC框架支持转换器和验证器，但我不了解如何使它们协同工作.

I know that the Spring MVC framework supports converters and validators, but I am failing to understand how to get them to work together.

推荐答案

首先，我将MultipartFile包装在一个表单支持对象中:

First I wrapped the MultipartFile in a form backing object:

public class UploadBackingForm {
    private MultipartFile multipartFile;
    /* ... getter/setter */
}

然后绑定到我的表单:

<form method="post" enctype="multipart/form-data">
<@spring.bind "backingform.*"/>
<tr>
    <td><@spring.formInput 'backingform.multipartFile' '' 'file' /></td>
    <td> <button type="submit">Upload</button> </td>
</tr>
</form>

在控制器中，我分配了一个验证器:

In the controller I assign a validator:

@InitBinder
public void initBinder(final DataBinder binder) {
    binder.setValidator(new UploadValidator());
}

这是验证者:

public class UploadValidator implements Validator {
    private final Converter<String[], MyObject> converter 
        = new MyObjectConverter();

    @Override
    public boolean supports(final Class<?> clazz) {
        return UploadBackingForm.class.equals(clazz);
    }

    @Override
    public void validate(final Object target, final Errors errors) {
        final UploadBackingForm backingForm = (UploadBackingForm) target;
        final MultipartFile multipartFile = backingForm.getMultipartFile();
        final List<String[]> uploadData = /* parse file */
        for (final String[] uploadDataRow : uploadData){
            try {
                converter.convert(uploadDataRow);
            } catch (IllegalArgumentException e) {
                errors.rejectValue("multipartFile", "line.invalid", ...);
            }
        }
    }
}

验证器使用Converter将行项目转换为MyObj.

The validator uses a Converter for the line-item conversion to MyObj.

doPost方法现在看起来像这样:

The doPost method now looks like this:

@RequestMapping(method = RequestMethod.POST)
public String doUpload(
    @Valid @ModelAttribute("backingform") UploadBackingForm backingForm, 
    final BindingResult result, 
    final HttpSession session) throws IOException {

    final UploadConverter converter = new UploadConverter();
    final List<MyObj> imports = 
        converter.convert(backingForm.getMultipartFile().getInputStream());
 }

UploadConverter与UploadValidator大致相同:

The UploadConverter is much the same as the UploadValidator:

public class UploadConverter implements Converter<InputStream, List<MyObject>> {
    private final Converter<String[], MyObject> converter = new MyObjectConverter();

    @Override
    public List<MyObject> convert(final InputStream source) {
        final List<String[]> detailLines = /* ... getDetailLines */
        final List<MyObject> importList = 
            new ArrayList<MyObject>(detailLines.size());

        for (final String[] row : detailLines) {
            importList.add(converter.convert(row));
        }
        return importList;
    }
}

唯一的问题是验证和转换过程几乎是同一回事.幸运的是，上传文件不会很大，因此重复工作不会成为大问题.

The only problem is that the validation and conversion processes are much the same thing. Luckily the upload files will not be very large so the duplication of effort is not a big problem.

这篇关于Spring MultipartFile验证和转换的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！