【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，可以使用 MultipartFile 作为请求参数，并且这个 API 应当消费 Multi-Part 表单数据值。示例代码如下：
@RequestMapping(value = "/upload", method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public String fileUpload(@RequestParam("file") MultipartFile file) {
return null;
}
完整代码如下：
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。我们要在响应中设置 HttpHeader Content-Disposition，并且要指定应用的响应媒体类型（Media Type）。
注意： 以下面的例子中，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;
}
完整代码如下：
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 应用类如下：
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 代码如下：
<?xml version = "1.0" encoding = "UTF-8"?>
<project xmlns = "http://maven.apache.org/POM/4.0.0"
xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0
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 代码如下：
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')
}
现在你可以使用 Maven 或 Gradle 命令创建可执行 executable JAR 文件并运行 Spring Boot 应用了：
Maven 命令如下：
mvn clean install
在 “BUILD SUCCESS” 之后，你可以在 target 目录下找到 JAR 文件。
Gradle 可以使用以下命令：
gradle clean build
在 “BUILD SUCCESSFUL” 之后，你可以在 build/libs 目录下找到 JAR 文件。
现在，使用以下命令运行 JAR 文件：
java –jar <JARFILE>
应用将在 Tomcat 8080 端口启动，如下 所示：
现在在 POSTMAN 应用中输入以下 URL’s in POSTMAN，可以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
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