java上传图片到linux

基础概念

Java上传图片到Linux涉及多个基础概念，包括文件上传、网络通信、文件系统操作等。具体来说：

文件上传：客户端将文件通过HTTP请求发送到服务器。
网络通信：使用HTTP或HTTPS协议进行数据传输。
文件系统操作：在服务器端接收文件并保存到指定目录。

类型

单文件上传：一次只上传一个文件。
多文件上传：一次上传多个文件。

应用场景

用户头像上传：用户在注册或修改个人信息时上传头像。
图片分享平台：用户上传图片并分享到平台上。
电子商务网站：用户上传商品图片。

示例代码

以下是一个简单的Java示例，展示如何使用Apache Commons FileUpload库上传图片到Linux服务器。

前端HTML表单

<!DOCTYPE html>
<html>
<head>
    <title>Upload Image</title>
</head>
<body>
    <h1>Upload Image</h1>
    <form action="upload" method="post" enctype="multipart/form-data">
        <input type="file" name="file" />
        <input type="submit" value="Upload" />
    </form>
</body>
</html>

后端Java代码

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

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

@WebServlet("/upload")
public class FileUploadServlet extends HttpServlet {
    private static final String UPLOAD_DIRECTORY = "uploads";
    private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3;  // 3MB
    private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB
    private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        if (!ServletFileUpload.isMultipartContent(request)) {
            response.getWriter().println("Error: Form must have enctype=multipart/form-data.");
            response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
            return;
        }

        DiskFileItemFactory factory = new DiskFileItemFactory();
        factory.setSizeThreshold(MEMORY_THRESHOLD);
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

        ServletFileUpload upload = new ServletFileUpload(factory);
        upload.setFileSizeMax(MAX_FILE_SIZE);
        upload.setSizeMax(MAX_REQUEST_SIZE);

        String uploadPath = getServletContext().getRealPath("") + File.separator + UPLOAD_DIRECTORY;
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }

        try {
            List<FileItem> formItems = upload.parseRequest(request);
            if (formItems != null && formItems.size() > 0) {
                for (FileItem item : formItems) {
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        String filePath = uploadPath + File.separator + fileName;
                        File storeFile = new File(filePath);
                        item.write(storeFile);
                        response.getWriter().println("File " + fileName + " has uploaded successfully!");
                    }
                }
            }
        } catch (Exception ex) {
            response.getWriter().println("There was an error: " + ex.getMessage());
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        }
    }
}