3

我有一个带有文件上传表单的Spring MVC应用程序。

如果上传的内容无效（例如内容不是图像等），我希望能够向用户显示验证错误

但是，根据定义，发布的内容是类型：（MultipartFilemultipart /form-data），因此我的表单中不能有 a @ModelAttribute，为了使用 a BindingResult，似乎我确实需要@ModelAttribute在BindingResult.

那么我的问题是，当我只有一个时，向用户显示验证错误的最合适的方式是MultipartFile什么？我当然可以手动将模型属性添加到模型中，但我确信有更好的方法。

4

2 回答 2

6

如果您使用的是 Java Bean Validation (JSR 303)，则可以制作验证内容类型的注释。请参阅下面的代码。

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
/**
 * The annotated element must have specified content type.
 *
 * Supported types are:
 * <ul>
 * <li><code>MultipartFile</code></li>
 * </ul>
 *
 * @author Michal Kreuzman
 */
@Documented
@Retention(RUNTIME)
@Constraint(validatedBy = {ContentTypeMultipartFileValidator.class})
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
public @interface ContentType {

    String message() default "{com.kreuzman.ContentType.message}";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

/**
 * Specify accepted content types.
 *
 * Content type example :
 * <ul>
 * <li>application/pdf - accepts PDF documents only</li>
 * <li>application/msword - accepts MS Word documents only</li>
 * <li>images/png - accepts PNG images only</li>
 * </ul>
 *
 * @return accepted content types
 */
     String[] value();
}

/**
  * Validator of content type. This is simple and not complete implementation
  * of content type validating. It's based just on <code>String</code> equalsIgnoreCase
  * method.
  *
  * @author Michal Kreuzman
  */
 public class ContentTypeMultipartFileValidator implements ConstraintValidator<ContentType, MultipartFile> {

private String[] acceptedContentTypes;

@Override
public void initialize(ContentType constraintAnnotation) {
    this.acceptedContentTypes = constraintAnnotation.value();
}

@Override
public boolean isValid(MultipartFile value, ConstraintValidatorContext context) {
    if (value == null || value.isEmpty())
        return true;

    return ContentTypeMultipartFileValidator.acceptContentType(value.getContentType(), acceptedContentTypes);
}

private static boolean acceptContentType(String contentType, String[] acceptedContentTypes) {
    for (String accept : acceptedContentTypes) {
            // TODO this should be done more clever to accept all possible content types
        if (contentType.equalsIgnoreCase(accept)) {
            return true;
        }
    }

    return false;
}
}

public class MyModelAttribute {

@ContentType("application/pdf")
private MultipartFile file;

public MultipartFile getFile() {
    return file;
}

public void setFile(MultipartFile file) {
    this.file = file;
}
}
@RequestMapping(method = RequestMethod.POST)
public String processUploadWithModelAttribute(@ModelAttribute("myModelAttribute") @Validated final MyModelAttribute myModelAttribute, final BindingResult result, final Model model) throws IOException {
 if (result.hasErrors()) {
     // Error handling
     return "fileupload";
 }

 return "fileupload";
}
于 2013-02-06T13:14:51.263 回答
2

我得到了 Spring 社区论坛问题的答案：

这是控制器方法：

@RequestMapping(method = RequestMethod.POST)
    public String processUploadWithModelAttribute(@ModelAttribute("myModelAttribute") final MyModelAttribute myModelAttribute, final BindingResult result, final Model model) throws IOException {
        String mimeType = determineMimeType(myModelAttribute.getFile().getBytes());
        if (mimeType.equalsIgnoreCase("application/pdf")){
            result.addError(new ObjectError("file", "pdf not accepted"));
        }
            return "fileupload";
    }

和模型属性类：

public class MyModelAttribute {

    private MultipartFile file;

    public MultipartFile getFile() {
        return file;
    }

    public void setFile(MultipartFile file) {
        this.file = file;
    }
}

想法是将 MultipartFile 作为属性放入 ModelAttribute 中。

于 2012-10-26T11:21:38.400 回答