使用commons file upload上传本地文件

你可以使用Apache Commons FileUpload库来上传本地文件。以下是一个简单的示例代码：

1. 首先，你需要在项目中添加commons-fileupload和commons-io库的依赖，可以在Maven或Gradle中添加以下依赖：

Maven:

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.8.0</version>
</dependency>

Gradle:

implementation 'commons-fileupload:commons-fileupload:1.4'
implementation 'commons-io:commons-io:2.8.0'

2. 在你的Servlet或Controller中，编写以下代码：

import java.io.File;
import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

@WebServlet("/upload")
public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        if (ServletFileUpload.isMultipartContent(request)) {
            FileItemFactory factory = new DiskFileItemFactory();
            ServletFileUpload upload = new ServletFileUpload(factory);
            try {
                List<FileItem> items = upload.parseRequest(request);
                for (FileItem item : items) {
                    if (!item.isFormField()) { // 判断是否是文件类型
                        String fileName = item.getName();
                        String filePath = "/path/to/upload/folder/" + fileName;
                        File uploadedFile = new File(filePath);
                        item.write(uploadedFile);
                    }
                }
                response.getWriter().println("File uploaded successfully!");
            } catch (Exception e) {
                response.getWriter().println("File upload failed!");
                e.printStackTrace();
            }
        }
    }
}

这个示例代码将上传的文件保存在`/path/to/upload/folder/`路径下。你可以根据你的实际情况修改保存路径。

3. 在前端，你可以使用HTML表单来上传文件：

<form action="upload" method="post" enctype="multipart/form-data">
    <input type="file" name="file">
    <input type="submit" value="Upload">
</form>

当用户单击“上传”按钮时，表单将提交到`/upload`URL，然后Servlet将处理上传的文件。