导入包
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.2</version>
</dependency>
后端成功代码
package com.example.weixin.controller;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.sf.json.JSONObject;
import org.apache.commons.fileupload.disk.DiskFileItem;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
@RestController
@RequestMapping("/upload")
public class uploadController {
//小程序上传照片到后台并返回路径
@PostMapping("/img")
public JSONObject uploadFile(HttpServletResponse response, HttpServletRequest request,@RequestParam MultipartFile file) throws IOException {
Map map = new HashMap();//temp
map.put("msg","error occur.");
map.put("status",-1);
// String realPath = request.getSession().getServletContext().getRealPath("/images");
//获取文件需要上传到的路径
File directory = new File("./webapps/biyeji");
String realPath = directory.getCanonicalPath() + "/images";
// 判断存放上传文件的目录是否存在（不存在则创建）
File dir = new File(realPath);
if (!dir.exists()) {
dir.mkdir();
}
try {
if(file == null){
map.put("msg","图片文件不能为空");
map.put("status",-2);
}
else{
// CommonsMultipartFile cf = (CommonsMultipartFile) file;
// DiskFileItem fi = (DiskFileItem) cf.getFileItem();
// File f1 = fi.getStoreLocation();
MultipartFile f = file;
File f1 = null;
try {
File dfile = File.createTempFile("prefix", "_" + f.getOriginalFilename());
f.transferTo(dfile);
f1 = dfile;
} catch (IOException e) {
e.printStackTrace();
}
InputStream ips = new FileInputStream(f1);
String id = "test";
String path = realPath + "/" + id+ ".jpg";
OutputStream ops = new FileOutputStream(path);
byte[] b = new byte[1024];
int len;
try {
while ((len = ips.read(b)) != -1) {
ops.write(b, 0, len);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
// 完毕，关闭所有链接
try {
ops.close();
ips.close();
} catch (IOException e) {
e.printStackTrace();
}
}
map.put("path","images/"+id+".jpg");
map.put("msg","图片上传成功");
map.put("status",0);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
JSONObject json = JSONObject.fromObject(map);
return json;
}
}
遇到的坑
MultipartFile不能强转CommonsMultipartFile
目的：
使用MultipartFile接收http post传进来的图片，Controller中把接收到的图像转换为File对象给后续程序使用。
报错：
java.lang.ClassCastException: org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile cannot be cast to org.springframework.web.multipart.commons.CommonsMultipartFile
原代码：
CommonsMultipartFile cf = (CommonsMultipartFile) file;
DiskFileItem fi = (DiskFileItem) cf.getFileItem();
File f1 = fi.getStoreLocation();
修改后的代码：
MultipartFile f = file;
File f1 = null;
try {
File dfile = File.createTempFile("prefix", "_" + f.getOriginalFilename());
f.transferTo(dfile);
f1 = dfile;
} catch (IOException e) {
e.printStackTrace();
}
总结解决方案：
先创建一个新的临时文件dfile对象，然后调用MultipartFile.transferTo(File dfile)方法把MultipartFile转换为File对象
MultipartFile传值text报错400
application.yml配置事例
servlet:
multipart:
max-file-size: 100MB
max-request-size: 100MB
enabled: true
服务器照片调取实现
把图片置入tomcat文件夹的webapps中相应的项目即可，值得注意的是在linux服务器上跑tomcat获取的路径是/usr/local/tomcat，因此相应创建图片目录的路径应该为./webapps/项目名/文件名，上传图片之后直接在网址中输入相应的路径就能看到图片啦！
https://blog.csdn.net/qq__1358521215/article/details/78884334
https://blog.csdn.net/ramesha/article/details/84925390
过滤上传图片格式
String IMG_TYPE_PNG = "PNG";
String IMG_TYPE_JPG = "JPG";
String IMG_TYPE_JPEG = "JPEG";
String suffix = file.getOriginalFilename().substring(file.getOriginalFilename().lastIndexOf(".") + 1);
if(!(IMG_TYPE_JPEG.equals(suffix.toUpperCase()) || IMG_TYPE_JPG.equals(suffix.toUpperCase()) || IMG_TYPE_PNG.equals(suffix.toUpperCase()))){
map.put("msg","图片文件格式不匹配");
map.put("status",-3);
}