项目地址：https://github.com/snjl/springboot.upload.git

上传多个文件项目地址：https://github.com/snjl/springboot.uploads.git

使用Spring Boot最新版本1.5.9、jdk使用1.8、tomcat8.0。

pom包配置

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.9.RELEASE</version>
</parent>

<properties>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

引入了spring-boot-starter-thymeleaf做页面模板引擎，写一些简单的上传示例。

启动类设置

@SpringBootApplication
public class FileUploadWebApplication {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(FileUploadWebApplication.class, args);
    }

    //Tomcat large file upload connection reset
    @Bean
    public TomcatEmbeddedServletContainerFactory tomcatEmbedded() {
        TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory();
        tomcat.addConnectorCustomizers((TomcatConnectorCustomizer) connector -> {
            if ((connector.getProtocolHandler() instanceof AbstractHttp11Protocol<?>)) {
                //-1 means unlimited
                ((AbstractHttp11Protocol<?>) connector.getProtocolHandler()).setMaxSwallowSize(-1);
            }
        });
        return tomcat;
    }

}

tomcatEmbedded这段代码是为了解决，上传文件大于10M出现连接重置的问题。此异常内容GlobalException也捕获不到。

编写前端页面

上传页面

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<body>
<h1>Spring Boot file upload example</h1>
<form method="POST" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file" /><br/><br/>
    <input type="submit" value="Submit" />
</form>
</body>
</html>

非常简单的一个Post请求，一个选择框选择文件，一个提交按钮。

上传结果展示页面：

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<body>
<h1>Spring Boot - Upload Status</h1>
<div th:if="${message}">
    <h2 th:text="${message}"/>
</div>
</body>
</html>

编写上传控制类

@GetMapping("/")
public String index() {
    return "upload";
}
//上传业务处理
@PostMapping("/upload") 
public String singleFileUpload(@RequestParam("file") MultipartFile file,
                               RedirectAttributes redirectAttributes) {
    if (file.isEmpty()) {
        redirectAttributes.addFlashAttribute("message", "Please select a file to upload");
        return "redirect:uploadStatus";
    }

    try {
        // Get the file and save it somewhere
        byte[] bytes = file.getBytes();
        Path path = Paths.get(UPLOADED_FOLDER + file.getOriginalFilename());
        Files.write(path, bytes);

        redirectAttributes.addFlashAttribute("message",
                "You successfully uploaded '" + file.getOriginalFilename() + "'");

    } catch (IOException e) {
        e.printStackTrace();
    }

    return "redirect:/uploadStatus";
}

上面代码的意思就是，通过MultipartFile读取文件信息，如果文件为空跳转到结果页并给出提示；如果不为空读取文件流并写入到指定目录，最后将结果展示到页面。

MultipartFile是Spring上传文件的封装类，包含了文件的二进制流和文件属性等信息，在配置文件中也可对相关属性进行配置，基本的配置信息如下：

spring.http.multipart.enabled=true #默认支持文件上传.
spring.http.multipart.file-size-threshold=0 #支持文件写入磁盘.
spring.http.multipart.location= # 上传文件的临时目录
spring.http.multipart.max-file-size=1Mb # 最大支持文件大小
spring.http.multipart.max-request-size=10Mb # 最大支持请求大小

最常用的是最后两个配置内容，限制文件上传大小，上传时超过大小会抛出异常。

异常处理

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(MultipartException.class)
    public String handleError1(MultipartException e, RedirectAttributes redirectAttributes) {
        redirectAttributes.addFlashAttribute("message", e.getCause().getMessage());
        return "redirect:/uploadStatus";
    }
}

设置一个@ControllerAdvice用来监控Multipart上传的文件大小是否受限，当出现此异常时在前端页面给出提示。利用@ControllerAdvice可以做很多东西，比如全局的统一异常处理等，感兴趣的同学可以下来了解。

使用ajax上传文件

加入函数

@ResponseBody
@PostMapping("/ajax/upload") // //new annotation since 4.3
public String uploadByAjax(@RequestParam("file") MultipartFile file) {
    if (file.isEmpty()) {
        return "error,the file is empty!";
    }

    try {
        // Get the file and save it somewhere
        byte[] bytes = file.getBytes();
        Path path = Paths.get(UPLOADED_FOLDER + file.getOriginalFilename());
        Files.write(path, bytes);

        return "You successfully uploaded '" + file.getOriginalFilename() + "'";

    } catch (IOException e) {
        return "upload error!";
    }
}

可以使用postman测试，使用form-data，key为file和enctype，其中enctype为multipart/form-data（也可以不设置）。

多文件上传

先将文件上传抽离出一个类，Upload：

package com.neo.tools;

import org.springframework.stereotype.Component;
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;
/**
 * @author 34924
 */
@Component
public class Upload {
    private static String UPLOADED_FOLDER = "D:\\test\\";

    public static String uploadFile( MultipartFile file) {
        if (file.isEmpty()) {
            return "error,the file is empty!";
        }

        try {
            // Get the file and save it somewhere
            byte[] bytes = file.getBytes();
            Path path = Paths.get(UPLOADED_FOLDER + file.getOriginalFilename());
            Files.write(path, bytes);

            return "You successfully uploaded '" + file.getOriginalFilename() + "'";

        } catch (IOException e) {
            return "upload error!";
        }
    }
    
    ...
}

加上多文件上传：

public static String uploadFiles( MultipartFile [] files) {
    String message = "success uploaded ";
    for (MultipartFile file : files) {
        try {
            uploadFile(file);
        } catch (Exception e) {
            return "upload error!";
        }
        message = message + file.getOriginalFilename() + " ";
    }
    return message;

}

或

public static String uploadFiles( List<MultipartFile> files) {
    String message = "success uploaded ";
    for (MultipartFile file : files) {
        try {
            uploadFile(file);
        } catch (Exception e) {
            return "upload error!";
        }
        message = message + file.getOriginalFilename() + " ";
    }
    return message;

}

controller中改为：

@ResponseBody
@PostMapping("/ajax/uploads") // //new annotation since 4.3
public String uploadsByAjax(@RequestParam("file") MultipartFile []files) {
    System.out.println("uploads");

    return Upload.uploadFiles(files);
}

或

@ResponseBody
@PostMapping("/ajax/uploads") // //new annotation since 4.3
public String uploadsByAjax(HttpServletRequest request) {
    List<MultipartFile> files = ((MultipartHttpServletRequest)request).getFiles("file");
    System.out.println("uploads");

    return Upload.uploadFiles(files);
}

均可实现多文件上传。

前端在input标签中添加属性multiple=”multiple”。

1	<input multiple="multiple" type="file" name="file" />

springboot：文件上传路径的几种设置方式

在配置文件中配置如下：

1	xcloud.uploadPath=D:\\test\\

编写上传路径配置类：


@Component
@ConfigurationProperties(prefix="xcloud")
public class UploadConfig {
   //上传路径
   @Value("${xcloud.uploadPath}")
   private String uploadPath;
 
   public String getUploadPath() {
      return uploadPath;
   }
 
   public void setUploadPath(String uploadPath) {
      this.uploadPath = uploadPath;
   }
}

上传文件方法注入：

@Autowired
UploadConfig uploadConfig;
@Value("${media.save.urlprefix}")
private String urlprefix;

controller：

@ResponseBody
@PostMapping("/{savePath}/upload") // //new annotation since 4.3
public String uploadByAjax(@RequestParam("file") MultipartFile file, @PathVariable String savePath) {

    if (file.isEmpty()) {
        return "error,the file is empty!";
    }

    try {
        // Get the file and save it somewhere
        byte[] bytes = file.getBytes();
        Path path = Paths.get(uploadConfig.getUploadPath() + savePath +"//" + file.getOriginalFilename());
        System.out.println(path);
        Files.write(path, bytes);

        return "You successfully uploaded '" + file.getOriginalFilename() + "'";

    } catch (IOException e) {
        return "upload error!";
    }
}

综上可以看出，可以使用固定的static String path来设置path，也可以在配置文件中配置，使用UploadConfig这样的配置类来取出配置路径，也可以综合上一种方式或者独立使用@PathVariable来获取需要的文件夹名，来进行路径生成。