Spring Boot 教程：文件处理

【注】本文译自： https://www.tutorialspoint.com/spring_boot/spring_boot_file_handling.htm

本文学习如何使用 web 服务进行文件上传和下载。

文件上传

上传一个文件，能够使用 MultipartFile 做为请求参数，而且这个 API 应当消费 Multi-Part 表单数据值。示例代码以下：

@RequestMapping(value = "/upload", method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)

  

public String fileUpload(@RequestParam("file") MultipartFile file) {

 return null;

}

完整代码以下：

package com.tutorialspoint.demo.controller;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

  

@RestController
public class FileUploadController {
 @RequestMapping(value = "/upload", method = RequestMethod.POST, 

 consumes = MediaType.MULTIPART_FORM_DATA_VALUE)

 public String fileUpload(@RequestParam("file") MultipartFile file) throws IOException {

 File convertFile = new File("/var/tmp/"+file.getOriginalFilename());

 convertFile.createNewFile();

 FileOutputStream fout = new FileOutputStream(convertFile);

 fout.write(file.getBytes());

 fout.close();

 return "File is upload successfully";

 }

}

文件下载

文件下载应当使用 InputStreamResource。咱们要在响应中设置 HttpHeader Content-Disposition，而且要指定应用的响应媒体类型（Media Type）。

注意： 如下面的例子中，在应用运行时指定路径上的文件应当是可用的。

@RequestMapping(value = "/download", method = RequestMethod.GET) 

public ResponseEntity<Object> downloadFile() throws IOException  {

 String filename = "/var/tmp/mysql.png";

 File file = new File(filename);

 InputStreamResource resource = new InputStreamResource(new FileInputStream(file));

 HttpHeaders headers = new HttpHeaders();

 headers.add("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));

 headers.add("Cache-Control", "no-cache, no-store, must-revalidate");

 headers.add("Pragma", "no-cache");

 headers.add("Expires", "0");

 ResponseEntity<Object> 

 responseEntity = ResponseEntity.ok().headers(headers).contentLength(file.length()).contentType(

 MediaType.parseMediaType("application/txt")).body(resource);

 return responseEntity;

}

完整代码以下：

package com.tutorialspoint.demo.controller;


import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

  
import org.springframework.core.io.InputStreamResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;


@RestController

public class FileDownloadController {

 @RequestMapping(value = "/download", method = RequestMethod.GET) 

 public ResponseEntity<Object> downloadFile() throws IOException {

 String filename = "/var/tmp/mysql.png";

 File file = new File(filename);

 InputStreamResource resource = new InputStreamResource(new FileInputStream(file));

 HttpHeaders headers = new HttpHeaders();

 headers.add("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));

 headers.add("Cache-Control", "no-cache, no-store, must-revalidate");

 headers.add("Pragma", "no-cache");

 headers.add("Expires", "0");

 ResponseEntity<Object> 

 responseEntity = ResponseEntity.ok().headers(headers).contentLength(

 file.length()).contentType(MediaType.parseMediaType("application/txt")).body(resource);

 return responseEntity;

 }

}

主 Spring Boot 应用类以下：

package com.tutorialspoint.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;


@SpringBootApplication

public class DemoApplication {

 public static void main(String[] args) {

 SpringApplication.run(DemoApplication.class, args);

 }

}

Maven build – pom.xml 代码以下：

<?xml version = "1.0" encoding = "UTF-8"?>

<project xmlns = "[http://maven.apache.org/POM/4.0.0](http://maven.apache.org/POM/4.0.0)" 

 xmlns:xsi = "[http://www.w3.org/2001/XMLSchema-instance](http://www.w3.org/2001/XMLSchema-instance)"

 xsi:schemaLocation = "[http://maven.apache.org/POM/4.0.0](http://maven.apache.org/POM/4.0.0) 

 [http://maven.apache.org/xsd/maven-4.0.0.xsd](http://maven.apache.org/xsd/maven-4.0.0.xsd)"> 

 <modelVersion>4.0.0</modelVersion>

 <groupId>com.tutorialspoint</groupId>

 <artifactId>demo</artifactId>

 <version>0.0.1-SNAPSHOT</version>

 <packaging>jar</packaging>

 <name>demo</name>

 <description>Demo project for Spring Boot</description>

  

 <parent>

 <groupId>org.springframework.boot</groupId>

 <artifactId>spring-boot-starter-parent</artifactId>

 <version>1.5.8.RELEASE</version>

 <relativePath> 

 </parent>

  

 <properties>

 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

 <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

 <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-test</artifactId>

 <scope>test</scope>

 </dependency>

 </dependencies>

  

 <build>

 <plugins>

 <plugin>

 <groupId>org.springframework.boot</groupId>

 <artifactId>spring-boot-maven-plugin</artifactId>

 </plugin>

 </plugins>

 </build>

</project>

Gradle Build – build.gradle 代码以下：

buildscript {

 ext {

 springBootVersion = '1.5.8.RELEASE'

 }

 repositories {

 mavenCentral()

 }

 dependencies {

 classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")

 }

}

  

apply plugin: 'java'

apply plugin: 'eclipse'

apply plugin: 'org.springframework.boot'

  

group = 'com.tutorialspoint'

version = '0.0.1-SNAPSHOT'

sourceCompatibility = 1.8

  

repositories {

 mavenCentral()

}

dependencies {

 compile('org.springframework.boot:spring-boot-starter-web')

 testCompile('org.springframework.boot:spring-boot-starter-test')

}

如今你能够使用 Maven 或 Gradle 命令建立可执行 executable JAR 文件并运行 Spring Boot 应用了：

Maven 命令以下：

mvn clean install

在 “BUILD SUCCESS” 以后，你能够在 target 目录下找到 JAR 文件。

Gradle 能够使用如下命令：

gradle clean build

在 “BUILD SUCCESSFUL” 以后，你能够在 build/libs 目录下找到 JAR 文件。

如今，使用如下命令运行 JAR 文件：

java –jar <JARFILE>

应用将在 Tomcat 8080 端口启动，以下 所示：

如今在 POSTMAN 应用中输入如下 URL’s in POSTMAN，能够看到下图所示的输出：

文件上传： http://localhost:8080/upload

文件下载： http://localhost:8080/download