Package org.apache.struts2.interceptor

Class ActionFileUploadInterceptor

java.lang.Object
org.apache.struts2.interceptor.AbstractInterceptor
org.apache.struts2.interceptor.AbstractFileUploadInterceptor
org.apache.struts2.interceptor.ActionFileUploadInterceptor
All Implemented Interfaces:
Serializable, ConditionalInterceptor, Interceptor, WithLazyParams
public class ActionFileUploadInterceptor extends AbstractFileUploadInterceptor implements WithLazyParams

Interceptor that is based off of MultiPartRequestWrapper, which is automatically applied for any request that includes a file when the support for multi-part request is enabled, see Disabling file upload.

You can get access to these files by implementing UploadedFilesAware interface. The interceptor will then call UploadedFilesAware.withUploadedFiles(List) when there are files which were accepted during the upload process.

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

Interceptor 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

This interceptor implements WithLazyParams, which enables dynamic parameter evaluation at runtime. Parameters can use ${...} expressions that will be evaluated against the ValueStack for each request, allowing file upload validation rules to be determined dynamically based on action properties, session data, or other runtime values.

Static configuration example:

 <action name="upload" class="com.example.UploadAction">
     <interceptor-ref name="actionFileUpload">
         <param name="allowedTypes">image/jpeg,image/png,application/pdf</param>
         <param name="allowedExtensions">.jpg,.png,.pdf</param>
         <param name="maximumSize">5242880</param>
     </interceptor-ref>
     <interceptor-ref name="basicStack"/>
 </action>

Dynamic configuration example:

 <action name="dynamicUpload" class="com.example.DynamicUploadAction">
     <interceptor-ref name="actionFileUpload">
         <param name="allowedTypes">${uploadConfig.allowedMimeTypes}</param>
         <param name="allowedExtensions">${uploadConfig.allowedExtensions}</param>
         <param name="maximumSize">${uploadConfig.maxFileSize}</param>
     </interceptor-ref>
     <interceptor-ref name="basicStack"/>
 </action>

Action class with dynamic configuration:

  package com.example;

  import org.apache.struts2.ActionSupport;
  import org.apache.struts2.action.UploadedFilesAware;

  public class DynamicUploadAction extends ActionSupport implements UploadedFilesAware {
    private UploadedFile uploadedFile;
    private UploadConfig uploadConfig;

    public void prepare() {
        // Load configuration dynamically (from database, properties, etc.)
        uploadConfig = new UploadConfig();
        uploadConfig.setAllowedMimeTypes("image/jpeg,image/png");
        uploadConfig.setAllowedExtensions(".jpg,.png");
        uploadConfig.setMaxFileSize(5242880L);
    }

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

    public UploadConfig getUploadConfig() {
        return uploadConfig;
    }

    public String execute() {
       //...
       return SUCCESS;
    }
  }

Performance Note: When using dynamic parameters with ${...} expressions, parameters are evaluated for each request. For static validation rules, use literal values for better performance.

Example code:

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

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

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

And then in your action code you'll have access to the File object if you provide setters according to the naming convention documented in the start. 

  package com.example;

  import java.io.File;
  import org.apache.struts2.ActionSupport;
  import org.apache.struts2.action.UploadedFilesAware;

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

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

    public String execute() {
       //...
       return SUCCESS;
    }
  }
See Also: