Struts实现任意文件的快速上传和下载
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Struts框架是Java Web开发中常用的一个开源框架,它基于MVC(Model-View-Controller)设计模式,用于简化Web应用程序的开发。在本案例中,我们关注的是如何使用Struts来实现文件的快速上传与下载功能。 1. **文件上传** 文件上传功能在Web应用中很常见,例如用户提交表单时附带附件。Struts通过`Commons FileUpload`库实现了文件上传。你需要在项目中引入`commons-fileupload`和`commons-io`这两个依赖库。然后,在Struts的Action类中创建一个`File`类型的属性,对应于用户上传的文件。在表单中,使用`<input type="file">`元素让用户选择文件。在Action的执行方法中,可以调用`ServletFileUpload`类的解析方法来获取上传的文件。 2. **配置Struts** 在`struts.xml`配置文件中,需要为文件上传的Action添加特定的配置,包括接收文件的参数名、允许的文件类型和大小限制等。例如: ```xml <action name="upload" class="com.example.UploadAction"> <interceptor-ref name="fileUpload"> <param name="maximumSize">1048576</param> <!-- 1MB --> <param name="allowedTypes">image/jpeg,image/png,application/pdf</param> </interceptor-ref> <result name="success">/success.jsp</result> </action> ``` 这里,`fileUpload`拦截器用于处理文件上传,配置了最大文件大小和允许的文件类型。 3. **处理上传** 在Action的执行方法中,可以使用`ServletFileUpload`解析上传请求,获取到`FileItem`对象,然后将其保存到服务器的指定目录。例如: ```java public String execute() { List<FileItem> items = upload.parseRequest(request); for (FileItem item : items) { if (!item.isFormField()) { String fileName = item.getName(); item.write(new File("/path/to/save/files/" + fileName)); } } return "success"; } ``` 4. **文件下载** 文件下载通常通过HTTP的`Content-Disposition`和`Content-Type`响应头来实现。在Struts Action中,可以创建一个流Result类型,读取服务器上的文件并返回给客户端。例如: ```java public InputStream getDownload() throws IOException { File file = new File("/path/to/file"); return new FileInputStream(file); } ``` 在`struts.xml`中配置下载Action的Result: ```xml <action name="download" class="com.example.DownloadAction"> <result type="stream"> <param name="contentType">application/octet-stream</param> <param name="inputName">download</param> <param name="contentDisposition">attachment; filename="yourfile.ext"</param> </result> </action> ``` 这里的`contentDisposition`参数告诉浏览器将文件作为附件下载。 5. **安全注意事项** 在实现文件上传下载时,一定要注意安全性。例如,防止文件覆盖、路径遍历攻击、非法文件类型的上传以及大文件可能导致的服务器资源耗尽等问题。应确保上传的文件保存在安全的目录下,并且只允许用户下载他们自己的文件。 Struts通过集成`Commons FileUpload`库,提供了方便的文件上传和下载功能。通过合理的配置和编程,可以实现高效、安全的文件操作。这个示例项目中的`Struts_Upload`可能包含了实现这些功能的完整代码,供学习和参考。
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