Spring Boot 教程：文件处理

    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：
1 @RequestMapping(value = "/upload", method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
2  
3 public String fileUpload(@RequestParam("file") MultipartFile file) {
4    return null;
5 }

   完整代码如下：

 1 package com.tutorialspoint.demo.controller;
 2  
 3 import java.io.File;
 4 import java.io.FileOutputStream;
 5 import java.io.IOException;
 6  
 7 import org.springframework.http.MediaType;
 8 import org.springframework.web.bind.annotation.RequestMapping;
 9 import org.springframework.web.bind.annotation.RequestMethod;
10 import org.springframework.web.bind.annotation.RequestParam;
11 import org.springframework.web.bind.annotation.RestController;
12 import org.springframework.web.multipart.MultipartFile;
13  
14 @RestController
15 public class FileUploadController {
16    @RequestMapping(value = "/upload", method = RequestMethod.POST, 
17       consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
18    
19    public String fileUpload(@RequestParam("file") MultipartFile file) throws IOException {
20       File convertFile = new File("/var/tmp/"+file.getOriginalFilename());
21       convertFile.createNewFile();
22       FileOutputStream fout = new FileOutputStream(convertFile);
23       fout.write(file.getBytes());
24       fout.close();
25       return "File is upload successfully";
26    }
27 }

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。 
 1 @RequestMapping(value = "/download", method = RequestMethod.GET) 
 2 public ResponseEntity<Object> downloadFile() throws IOException  {
 3    String filename = "/var/tmp/mysql.png";
 4    File file = new File(filename);
 5    InputStreamResource resource = new InputStreamResource(new FileInputStream(file));
 6    HttpHeaders headers = new HttpHeaders();
 7       
 8    headers.add("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));
 9    headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
10    headers.add("Pragma", "no-cache");
11    headers.add("Expires", "0");
12       
13    ResponseEntity<Object> 
14    responseEntity = ResponseEntity.ok().headers(headers).contentLength(file.length()).contentType(
15       MediaType.parseMediaType("application/txt")).body(resource);
16       
17    return responseEntity;
18 }
   完整代码如下：
 1 package com.tutorialspoint.demo.controller;
 2  
 3 import java.io.File;
 4 import java.io.FileInputStream;
 5 import java.io.IOException;
 6  
 7 import org.springframework.core.io.InputStreamResource;
 8 import org.springframework.http.HttpHeaders;
 9 import org.springframework.http.MediaType;
10 import org.springframework.http.ResponseEntity;
11 import org.springframework.web.bind.annotation.RequestMapping;
12 import org.springframework.web.bind.annotation.RequestMethod;
13 import org.springframework.web.bind.annotation.RestController;
14  
15 @RestController
16 public class FileDownloadController {
17    @RequestMapping(value = "/download", method = RequestMethod.GET) 
18    public ResponseEntity<Object> downloadFile() throws IOException  {
19       String filename = "/var/tmp/mysql.png";
20       File file = new File(filename);
21       InputStreamResource resource = new InputStreamResource(new FileInputStream(file));
22       HttpHeaders headers = new HttpHeaders();
23       
24       headers.add("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));
25       headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
26       headers.add("Pragma", "no-cache");
27       headers.add("Expires", "0");
28       
29       ResponseEntity<Object> 
30       responseEntity = ResponseEntity.ok().headers(headers).contentLength(
31          file.length()).contentType(MediaType.parseMediaType("application/txt")).body(resource);
32       
33       return responseEntity;
34    }
35 }
   主 Spring Boot 应用类如下：
 1 package com.tutorialspoint.demo;
 2  
 3 import org.springframework.boot.SpringApplication;
 4 import org.springframework.boot.autoconfigure.SpringBootApplication;
 5  
 6 @SpringBootApplication
 7 public class DemoApplication {
 8    public static void main(String[] args) {
 9       SpringApplication.run(DemoApplication.class, args);
10    }
11 }
   Maven build – pom.xml 代码如下：
 1 <?xml version = "1.0" encoding = "UTF-8"?>
 2 <project xmlns = "http://maven.apache.org/POM/4.0.0" 
 3    xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
 4    xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 
 5    http://maven.apache.org/xsd/maven-4.0.0.xsd"> 
 6    
 7    <modelVersion>4.0.0</modelVersion>
 8    <groupId>com.tutorialspoint</groupId>
 9    <artifactId>demo</artifactId>
10    <version>0.0.1-SNAPSHOT</version>
11    <packaging>jar</packaging>
12    <name>demo</name>
13    <description>Demo project for Spring Boot</description>
14  
15    <parent>
16       <groupId>org.springframework.boot</groupId>
17       <artifactId>spring-boot-starter-parent</artifactId>
18       <version>1.5.8.RELEASE</version>
19       <relativePath/> 
20    </parent>
21  
22    <properties>
23       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
24       <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
25       <java.version>1.8</java.version>
26    </properties>
27  
28    <dependencies>
29       <dependency>
30          <groupId>org.springframework.boot</groupId>
31          <artifactId>spring-boot-starter-web</artifactId>
32       </dependency>
33  
34       <dependency>
35          <groupId>org.springframework.boot</groupId>
36          <artifactId>spring-boot-starter-test</artifactId>
37          <scope>test</scope>
38       </dependency>
39    </dependencies>
40  
41    <build>
42       <plugins>
43          <plugin>
44             <groupId>org.springframework.boot</groupId>
45             <artifactId>spring-boot-maven-plugin</artifactId>
46          </plugin>
47       </plugins>
48    </build>
49 </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
 
 
posted @ 2020-09-03 13:34  码者无疆  阅读(418)  评论(0)    收藏  举报