Action File Upload Interceptor

• Parameters
  • Dynamic Parameter Evaluation
• Extending the Interceptor
• Examples

Available since Struts 6.4.0 as replacement for File Upload Interceptor

See this page for more examples and advanced configuration.

Interceptor that is based off of MultiPartRequestWrapper, which is automatically applied for any request that includes a file. If an action implements org.apache.struts2.action.UploadedFilesAware interface, the interceptor will pass information and content of uploaded files using the callback method withUploadedFiles(List<UploadedFile>).

See the example code section.

This interceptor will add several field errors, assuming that the action implements ValidationAware. These error messages are based on several i18n values stored in struts-messages.properties, a default i18n file processed for all i18n requests. You can override the text of these messages by providing text for the following keys:

• struts.messages.error.uploading - a general error that occurs when the file could not be uploaded
• struts.messages.error.file.too.large - occurs when the uploaded file is too large
• struts.messages.error.content.type.not.allowed - occurs when the uploaded file does not match the expected content types specified
• struts.messages.error.file.extension.not.allowed - occurs when the uploaded file does not match the expected file extensions specified

Parameters

• maximumSize (optional) - the maximum size (in bytes) that the interceptor will allow a file reference to be set on the action. Note, this is not related to the various properties found in struts.properties. Default to approximately 2MB.
• allowedTypes (optional) - a comma separated list of content types (ie: text/html) that the interceptor will allow a file reference to be set on the action. If none is specified allow all types to be uploaded.
• allowedExtensions (optional) - a comma separated list of file extensions (ie: .html) that the interceptor will allow a file reference to be set on the action. If none is specified allow all extensions to be uploaded.

Dynamic Parameter Evaluation

Since Struts 7.2.0

The allowedTypes, allowedExtensions, and maximumSize parameters support ${...} expression evaluation, enabling per-request dynamic validation. This is available when used with WithLazyParams.

<interceptor-ref name="actionFileUpload">
  <param name="allowedTypes">${allowedContentTypes}</param>
  <param name="maximumSize">${maxFileSize}</param>
</interceptor-ref>

The expressions are evaluated against the ValueStack at the time of the upload, allowing your action to provide dynamic values based on the current request context.

Extending the Interceptor

You can extend this interceptor and override the acceptFile method to provide more control over which files are supported and which are not.

Examples

See this page for more examples and advanced configuration.

Example action mapping:

 <action name="doUpload" class="com.example.UploadAction">
     <interceptor-ref name="actionFileUpload"/>
     <interceptor-ref name="basicStack"/>
     <result name="success">good_result.jsp</result>
 </action>

Notice the interceptor configuration in the preceding example.

Example JSP form tags:

   <s:form action="doUpload" method="post" enctype="multipart/form-data">
       <s:file name="upload" label="File"/>
       <s:submit/>
   </s:form>

You must set the encoding to multipart/form-data in the form where the user selects the file to upload.

Example Action class:

public class UploadAction extends ActionSupport implements UploadedFilesAware {
   private UploadedFile uploadedFile;
   private String contentType;
   private String fileName;
   private String originalName;

   @Override
   public void withUploadedFiles(List<UploadedFile> uploadedFiles) {
      if (!uploadedFiles.isEmpty()) {
         this.uploadedFile = uploadedFiles.get(0);
         this.fileName = uploadedFile.getName();
         this.contentType = uploadedFile.getContentType();
         this.originalName = uploadedFile.getOriginalName();
      }
   }

   public String execute() {
      //do something with the file
      return SUCCESS;
   }
}

Setting parameters example:

<interceptor-ref name="actionFileUpload">
  <param name="allowedTypes">
     image/png,image/gif,image/jpeg
  </param>
</interceptor-ref>

This part is optional and would be done in place of the <interceptor-ref name="actionFileUpload"/> line in the action mapping example above.