SpringBoot入门建站全系列（九）文件上传功能与下载方式

品茗IT

发布于 2019-09-12 10:33:02

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文章被收录于专栏：品茗IT品茗IT

SpringBoot入门建站全系列（九）文件上传功能与下载方式

Spring对文件上传做了简单的封装，就是用MultipartFile这个对象去接收文件，当然有很多种写法，下面会一一介绍。

文件的下载很简单，给一个链接就行，而这个链接怎么生成，也有很多方式，下面也会讲解下常用的方式。

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一、配置

本文假设你已经引入spring-boot-starter-web。已经是个SpringBoot项目了,如果不会搭建，可以打开这篇文章看一看《SpringBoot入门建站全系列（一）项目建立》。因为文件上传和下载不需要引入额外的jar包了。但是需要做如下配置：

application.properties 中需要添加下面的配置：

spring.servlet.multipart.enabled=true
spring.servlet.multipart.max-file-size=20MB
spring.servlet.multipart.max-request-size=50MB

这里，

spring.servlet.multipart.max-file-size是对单个文件大小的限制。
spring.servlet.multipart.max-request-size是对单次请求的大小进行限制

至此，已经可以正常的进行上传下载了，就剩下写代码了。

二、文件上传的几种方式

2.1 单个文件上传

在Controller的RequestMapping注解的方法参数中，直接将MultipartFile作为参数传递进来。

package com.cff.springbootwork.web.file;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

import com.cff.springbootwork.dto.ResultModel;
import com.cff.springbootwork.service.UploadService;

@RestController
@RequestMapping("/file")
public class FileRest {
	private Logger log = LoggerFactory.getLogger(this.getClass());

	@Value("${upload.static.url}")
	private String uploadStaticUrl;

	@Autowired
	UploadService uploadService;

	@RequestMapping("/upload")
	public ResultModel upload(@RequestParam("files") MultipartFile file) {
		try {
			if (file.isEmpty()) {
				return ResultModel.error("文件不能为空！");
			}
			String fileName = uploadService.saveUploadFile(file);
			return ResultModel.ok(uploadStaticUrl + fileName);
		} catch (Exception e) {
			e.printStackTrace();
			log.error("文件上传失败！", e);
			return ResultModel.error("文件上传失败！");
		}
	}
}

测试的时候，使用postman可以这样传参：

在这里插入图片描述

2.2 多个文件上传

在Controller的RequestMapping注解的方法参数中，直接将MultipartFile作为list传递进来。在FileRest中增加uploadList方法。

package com.cff.springbootwork.web.file;

import java.util.ArrayList;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

import com.cff.springbootwork.dto.ResultModel;
import com.cff.springbootwork.service.UploadService;

@RestController
@RequestMapping("/file")
public class FileRest {
	private Logger log = LoggerFactory.getLogger(this.getClass());

	@Value("${upload.static.url}")
	private String uploadStaticUrl;

	@Autowired
	UploadService uploadService;

	@RequestMapping("/upload")
	public ResultModel upload(@RequestParam("files") MultipartFile file) {
		try {
			if (file.isEmpty()) {
				return ResultModel.error("文件不能为空！");
			}
			String fileName = uploadService.saveUploadFile(file);
			return ResultModel.ok(uploadStaticUrl + fileName);
		} catch (Exception e) {
			e.printStackTrace();
			log.error("文件上传失败！", e);
			return ResultModel.error("文件上传失败！");
		}
	}

	@RequestMapping("/uploadList")
	public ResultModel uploadList(@RequestParam("files") List<MultipartFile> fileList) {
		try {
			List<String> list = new ArrayList<>();
			for (MultipartFile file : fileList) {
				String fileName = uploadService.saveUploadFile(file);
				list.add(uploadStaticUrl + fileName);
			}
			return ResultModel.ok(list);
		} catch (Exception e) {
			e.printStackTrace();
			log.error("文件上传失败！", e);
			return ResultModel.error("文件上传失败！");
		}
	}
}

测试的时候，使用postman可以这样传参：

在这里插入图片描述

2.3 从HttpServletRequest中取文件

新建uploadByRequest方法，将HttpServletRequest作为参数，Spring自动传入。

Spring对Request做了一层封装，如果有文件，它就是MultipartHttpServletRequest。

然后我们可以从MultipartHttpServletRequest获取到MultipartFile。后面的处理方式一样了。

package com.cff.springbootwork.web.file;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartHttpServletRequest;

import com.cff.springbootwork.dto.ResultModel;
import com.cff.springbootwork.service.UploadService;

@RestController
@RequestMapping("/file")
public class FileRest {
	private Logger log = LoggerFactory.getLogger(this.getClass());

	@Value("${upload.static.url}")
	private String uploadStaticUrl;

	@Autowired
	UploadService uploadService;

	@RequestMapping("/upload")
	public ResultModel upload(@RequestParam("files") MultipartFile file) {
		try {
			if (file.isEmpty()) {
				return ResultModel.error("文件不能为空！");
			}
			String fileName = uploadService.saveUploadFile(file);
			return ResultModel.ok(uploadStaticUrl + fileName);
		} catch (Exception e) {
			e.printStackTrace();
			log.error("文件上传失败！", e);
			return ResultModel.error("文件上传失败！");
		}
	}

	@RequestMapping("/uploadList")
	public ResultModel uploadList(@RequestParam("files") List<MultipartFile> fileList) {
		try {
			List<String> list = new ArrayList<>();
			for (MultipartFile file : fileList) {
				String fileName = uploadService.saveUploadFile(file);
				list.add(uploadStaticUrl + fileName);
			}
			return ResultModel.ok(list);
		} catch (Exception e) {
			e.printStackTrace();
			log.error("文件上传失败！", e);
			return ResultModel.error("文件上传失败！");
		}
	}

	@RequestMapping("/uploadByRequest")
	public ResultModel uploadByRequest(HttpServletRequest request) {
		try {
			Map<String, MultipartFile> files = new HashMap<>();

			if (request instanceof MultipartHttpServletRequest) {
				MultipartHttpServletRequest req = (MultipartHttpServletRequest) request;
				MultiValueMap<String, MultipartFile> multiValueMap = req.getMultiFileMap();
				if (multiValueMap != null && !multiValueMap.isEmpty()) {
					for (String key : multiValueMap.keySet()) {
						files.put(key, multiValueMap.getFirst(key));
					}
				}
			}
			if (files.isEmpty())
				return ResultModel.error("文件木有？");

			List<String> list = new ArrayList<>();
			for (MultipartFile file : files.values()) {
				String fileName = uploadService.saveUploadFile(file);
				list.add(uploadStaticUrl + fileName);
			}
			return ResultModel.ok(list);
		} catch (Exception e) {
			e.printStackTrace();
			log.error("文件上传失败！", e);
			return ResultModel.error("文件上传失败！");
		}
	}
}

测试的时候，传参方式使用上面两种都可以了。

三、文件下载方式

文件上传成功后，我们同时会提供下载功能。下载功能很简单，有以下几种方式：

3.1 Spring配置映射

新建一个WebStaticConfig配置类，实现WebMvcConfigurer接口即可：

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebStaticConfig implements WebMvcConfigurer {
	@Value("${upload.static.local}")
	private String uploadStaticLocal;

	@Override
	public void addResourceHandlers(ResourceHandlerRegistry registry) {
		registry.addResourceHandler("/static/**").addResourceLocations("file:" + uploadStaticLocal);
	}

	public String getUploadStaticLocal() {
		return uploadStaticLocal;
	}

	public void setUploadStaticLocal(String uploadStaticLocal) {
		this.uploadStaticLocal = uploadStaticLocal;
	}

}

这句话将当前服务器（比如是http://127.0.0.1:8080 ）的/static路径（http://127.0.0.1:8080/static/ ）下的资源，映射到uploadStaticLocal指定的本地路径下的文件。

然后我们就可以直接访问文件了。

3.2 代理(nginx)映射

代理首选nginx了。高性能快捷的代理转发工具。

比如要将http://127.0.0.1:8081/static/ 下的资源，映射到/static/指定的本地路径下的文件，可以这样配置：

server {
    listen       8081;
    server_name  localhost;

	location /static {
		alias /static/;
		index index.html;
	}
}

这里为什么用8081而不是上面的8080了呢？因为上面的8080端口已经被SpringBoot应用占用了。nginx要在另一个端口监听了，如果非要将SpringBoot应用和静态资源在一个端口，可以对SpringBoot应用也做代理，例如：

server {
    listen       8081;
    server_name  localhost;

    location ^~ /api/ {
		proxy_pass   http://127.0.0.1:8080/;
    }
	
	location /static {
		alias /static/;
		index index.html;
	}
}

3.3 ResponseEntity读取文件并返回

比如我们在FileRest的Controller中建立个downloadFile方法，传入文件名，将文件读取为byte，包装成ResponseEntity返回。

	@RequestMapping(value = "/downloadFile", method = { RequestMethod.GET })
	public ResponseEntity<byte[]> downloadFile(@RequestParam("fileName") String fileName) {
		try {
			File file = new File(fileName);
			byte[] body = null;
			InputStream is = new FileInputStream(file);
			body = new byte[is.available()];
			is.read(body);
			is.close();
			HttpHeaders headers = new HttpHeaders();
			headers.add("Content-Disposition", "attchement;filename=" + file.getName());
			HttpStatus statusCode = HttpStatus.OK;
			ResponseEntity<byte[]> entity = new ResponseEntity<byte[]>(body, headers, statusCode);
			return entity;
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}

	}

四、过程中用到的实体及Service

UploadService：

package com.cff.springbootwork.service;

import java.io.File;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

@Service
public class UploadService {
	@Value("${upload.static.local}")
	private String uploadStaticLocal;

	public String saveUploadFile(MultipartFile file) throws Exception {
		String fileName = file.getOriginalFilename();

		String localPath = uploadStaticLocal + fileName;
		file.transferTo(new File(localPath));

		return fileName;
	}

}

ResultCode：

package com.cff.springbootwork.dto;

/**
 * 响应码及其描述 Created by txl on 15/7/9.
 */
public enum ResultCode {

	/**
	 * 通用
	 */
	CODE_00000("00000", "操作成功"), CODE_00001("00001", "请求失败"), CODE_00002("00002", "错误的请求方法"), CODE_00003("00003", "非法的参数字段"), CODE_00004("00004", "异常抛出"), CODE_00005("00005", "权限不足"), CODE_00006("00006", "分页limit参数错误"), CODE_00007("00007", "分页offset参数错误"), CODE_00009("00009", "请求过于频繁"), CODE_00010("00010", "数据已存在"), CODE_00011("00011", "数据不存在"), CODE_00012("00012", "参数缺失"), CODE_00013("00013", "系统维护中"), CODE_00014("00014", "token缺失"), CODE_00015("00015", "token失效"), CODE_00016("00016", "签名错误"),

	CODE_10000("10000", "操作部分成功"),
	/**
	 * 系统
	 */
	CODE_30000("30000", "系统ID错误"),

	/**
	 * 授权
	 */
	CODE_40001("40001", "用户未找到"), CODE_40002("40002", "该用户状态异常"), CODE_40003("40003", "该用户已被删除"), CODE_40004("40004", "授权异常"),

	CODE_99999("99999", "签名无效");

	private String code;
	private String desc;

	ResultCode(String code, String desc) {
		this.code = code;
		this.desc = desc;
	}

	public String getCode() {
		return code;
	}

	public String getDesc() {
		return desc;
	}

	/**
	 * 根据code匹配枚举
	 * 
	 * @param code
	 * @return
	 */
	public static ResultCode getResultCodeByCode(String code) {
		for (ResultCode resultCode : ResultCode.values()) {
			if (code.equals(resultCode.getCode())) {
				return resultCode;
			}
		}
		return null;
	}

	public static ResultCode getResultCodeByDesc(String desc) {
		for (ResultCode resultCode : ResultCode.values()) {
			if (desc.equals(resultCode.getDesc())) {
				return resultCode;
			}
		}
		return null;
	}
}

ResultModel ：

package com.cff.springbootwork.dto;

/**
 */
public class ResultModel {

	private String errorCode;
	private String message;
	private Object remark;
	private Object data;

	public ResultModel(String errorCode, String message) {
		this.errorCode = errorCode;
		this.message = message;
	}

	public ResultModel() {
	}

	public ResultModel(String errorCode, String message, Object data) {
		this.errorCode = errorCode;
		this.message = message;
		this.data = data;
	}

	public ResultModel(ResultCode resultCodeEnum, Object data) {
		this.errorCode = resultCodeEnum.getCode();
		this.message = resultCodeEnum.getDesc();
		this.data = data;
	}

	public ResultModel(ResultCode resultCodeEnum, Object data, Object remark) {
		this.errorCode = resultCodeEnum.getCode();
		this.message = resultCodeEnum.getDesc();
		this.data = data;
		this.remark = remark;
	}

	public ResultModel(ResultCode resultCodeEnum) {
		this.errorCode = resultCodeEnum.getCode();
		this.message = resultCodeEnum.getDesc();
	}

	public String getErrorCode() {
		return errorCode;
	}

	public void setErrorCode(String errorCode) {
		this.errorCode = errorCode;
	}

	public String getMessage() {
		return message;
	}

	public void setMessage(String message) {
		this.message = message;
	}

	public Object getData() {
		return data;
	}

	public void setData(Object data) {
		this.data = data;
	}

	public static ResultModel ok() {
		return new ResultModel(ResultCode.CODE_00000);
	}

	public static ResultModel ok(Object data) {
		return new ResultModel(ResultCode.CODE_00000, data);
	}

	public static ResultModel unAuth() {
		return new ResultModel(ResultCode.CODE_00002);
	}

	public static ResultModel unAuth(Object data) {
		return new ResultModel(ResultCode.CODE_00002, data);
	}

	public static ResultModel error(String message) {
		return new ResultModel(ResultCode.CODE_00001.getCode(), message);
	}

	public Object getRemark() {
		return remark;
	}

	public void setRemark(Object remark) {
		this.remark = remark;
	}

}

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原始发表：2019/06/18 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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