如何在Java中解析多部分表单请求 Java Multipart表单处理技巧

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.5</version>
</dependency>
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.15.1</version>
</dependency>

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.util.List;

public class MultipartParser {

    public void parse(HttpServletRequest request, String uploadPath) {
        // 检查是否为Multipart请求
        if (!ServletFileUpload.isMultipartContent(request)) {
            System.err.println("Not a multipart request");
            return;
        }

        // 创建DiskFileItemFactory，用于配置如何存储文件
        DiskFileItemFactory factory = new DiskFileItemFactory();
        // 设置临时文件目录
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

        // 创建ServletFileUpload处理器
        ServletFileUpload upload = new ServletFileUpload(factory);

        try {
            // 解析请求
            List<FileItem> items = upload.parseRequest(request);

            for (FileItem item : items) {
                if (item.isFormField()) {
                    // 处理普通表单字段
                    String name = item.getFieldName();
                    String value = item.getString("UTF-8"); // 确保指定编码
                    System.out.println("Field: " + name + ", Value: " + value);
                } else {
                    // 处理文件上传
                    String fileName = item.getName();
                    if (fileName != null && !fileName.isEmpty()) {
                        String filePath = uploadPath + File.separator + fileName;
                        File uploadedFile = new File(filePath);
                        item.write(uploadedFile);
                        System.out.println("File saved to: " + filePath);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class UploadController {

    @PostMapping("/upload")
    public String handleFileUpload(@RequestParam("file") MultipartFile file) {

        if (!file.isEmpty()) {
            try {
                byte[] bytes = file.getBytes();
                Path path = Paths.get("./uploads/" + file.getOriginalFilename()); // 存储路径
                Files.write(path, bytes);
                return "上传成功: " + file.getOriginalFilename();
            } catch (IOException e) {
                e.printStackTrace();
                return "上传失败: " + e.getMessage();
            }
        } else {
            return "上传文件为空";
        }
    }
}

import org.springframework.boot.web.servlet.MultipartConfigFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import javax.servlet.MultipartConfigElement;

@Configuration
public class MultipartConfig {

    @Bean
    public MultipartConfigElement multipartConfigElement() {
        MultipartConfigFactory factory = new MultipartConfigFactory();
        factory.setMaxFileSize("10MB"); // 设置最大文件大小
        factory.setMaxRequestSize("10MB"); // 设置最大请求大小
        return factory.createMultipartConfig();
    }
}

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;

public class LargeFileUploader {

    public void upload(HttpServletRequest request, String uploadDir) throws Exception {
        if (!ServletFileUpload.isMultipartContent(request)) {
            throw new IllegalArgumentException("Request is not multipart, please 'multipart/form-data' enctype.");
        }

        DiskFileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload upload = new ServletFileUpload(factory);

        List<FileItem> items = upload.parseRequest(request);
        for (FileItem item : items) {
            if (!item.isFormField()) {
                String fileName = item.getName();
                if (fileName != null && !fileName.isEmpty()) {
                    Path filePath = Paths.get(uploadDir, fileName);
                    try (InputStream inputStream = item.getInputStream()) {
                        Files.copy(inputStream, filePath); // 直接从输入流写入文件
                    }
                    System.out.println("File uploaded to: " + filePath);
                }
            }
        }
    }
}

// 使用commons-fileupload读取字段时指定编码
String value = item.getString("UTF-8");

// 在Servlet中设置请求编码
request.setCharacterEncoding("UTF-8");