无涯教程-Spring Boot - 文件处理在本章中，您将学习如何使用Web服务上传和下载文件。上传文件要上传文

在本章中，您将学习如何使用Web服务上传和下载文件。

上传文件

要上传文件，可以使用 MultipartFile 作为请求参数，并且此API应该使用"Multi-Part form "数据值。遵守下面给出的代码-

@RequestMapping(value="/upload", method=RequestMethod.POST, consumes=MediaType.MULTIPART_FORM_DATA_VALUE)
public String fileUpload(@RequestParam("file") MultipartFile file) {
return null;
}

相同的完整代码如下-

package com.learnfk.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

对于文件下载，应使用InputStreamResource下载文件。需要在Response中设置HttpHeader Content-Disposition 并需要指定应用程序的响应媒体类型。

注意-在以下示例中，文件应在运行应用程序的指定路径上可用。

@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;
}

相同的完整代码如下-

package com.learnfk.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</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"Content-Disposition"</span><span class="pun">,</span><span class="pln"> </span><span class="typ">String</span><span class="pun">.</span><span class="pln">format</span><span class="pun">(</span><span class="str">"attachment; filename=\"%s\""</span><span class="pun">,</span><span class="pln"> file</span><span class="pun">.</span><span class="pln">getName</span><span class="pun">()));</span><span class="pln">
  headers</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"Cache-Control"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"no-cache, no-store, must-revalidate"</span><span class="pun">);</span><span class="pln">
  headers</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"Pragma"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"no-cache"</span><span class="pun">);</span><span class="pln">
  headers</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"Expires"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"0"</span><span class="pun">);</span><span class="pln">
  
  </span><span class="typ">ResponseEntity</span><span class="pun">&lt;</span><span class="typ">Object</span><span class="pun">&gt;</span><span class="pln"> 
  responseEntity</span><span class="pun">=</span><span class="typ">ResponseEntity</span><span class="pun">.</span><span class="pln">ok</span><span class="pun">().</span><span class="pln">headers</span><span class="pun">(</span><span class="pln">headers</span><span class="pun">).</span><span class="pln">contentLength</span><span class="pun">(</span><span class="pln">
     file</span><span class="pun">.</span><span class="pln">length</span><span class="pun">()).</span><span class="pln">contentType</span><span class="pun">(</span><span class="typ">MediaType</span><span class="pun">.</span><span class="pln">parseMediaType</span><span class="pun">(</span><span class="str">"application/txt"</span><span class="pun">)).</span><span class="pln">body</span><span class="pun">(</span><span class="pln">resource</span><span class="pun">);</span><span class="pln">
  
  </span><span class="kwd">return</span><span class="pln"> responseEntity</span><span class="pun">;</span><span class="pln">

}
}

下面给出了主要的Spring Boot应用程序-

package com.learnfk.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);
}
}

下面给出了Maven构建的代码– pom.xml-

<?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.learnfk</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>
  </span><span class="tag">&lt;dependency&gt;</span><span class="pln">
     </span><span class="tag">&lt;groupId&gt;</span><span class="pln">org.springframework.boot</span><span class="tag">&lt;/groupId&gt;</span><span class="pln">
     </span><span class="tag">&lt;artifactId&gt;</span><span class="pln">spring-boot-starter-test</span><span class="tag">&lt;/artifactId&gt;</span><span class="pln">
     </span><span class="tag">&lt;scope&gt;</span><span class="pln">test</span><span class="tag">&lt;/scope&gt;</span><span class="pln">
  </span><span class="tag">&lt;/dependency&gt;</span><span class="pln">

</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

下面给出了Gradle Build – build.gradle的代码-

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.learnfk
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)
}

现在您可以创建一个可执行的JAR文件，并使用下面给出的Maven或Gradle命令运行Spring Boot应用程序-

对于Maven，请使用以下命令-

mvn clean install

在" BUILD SUCCESS"之后，您可以在目标目录下找到JAR文件。

对于Gradle，您可以使用下面显示的命令-

sgradle clean build

在" BUILD SUCCESSFUL"之后，您可以在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>

这将在Tomcat端口8080上启动应用程序，如下所示-

现在在POSTMAN应用程序中单击下面的URL，您可以看到如下所示的输出-

文件上传- http:// localhost:8080/upload

文件下载- http:// localhost:8080/upload

无涯教程-Spring Boot - 文件处理

上传文件

文件下载

参考链接