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Spring implements file upload function

  • 2020-06-01 09:56:24
  • OfStack

In this article, we will do a file upload function of Spring:

1. Create an Maven web project and then configure the pom.xml file to add dependencies: 


<dependency>

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

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

  <version>1.0.2.RELEASE</version>

</dependency>

2. Enter 1 form in the index.jsp file in the webapp directory: 


<html>

<body>

<form method="POST" enctype="multipart/form-data"

   action="/upload">

  File to upload: <input type="file" name="file"><br /> Name: <input

    type="text" name="name"><br /> <br /> <input type="submit"

                           value="Upload"> Press here to upload the file!

</form>

</body>

</html>

This form is our simulated upload page.

3. Write Controller to handle this form: 


import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileOutputStream;

 

import org.springframework.stereotype.Controller;

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.ResponseBody;

import org.springframework.web.multipart.MultipartFile;

 

@Controller

public class FileUploadController {

 

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

  public @ResponseBody String provideUploadInfo() {

    return "You can upload a file by posting to this same URL.";

  }

 

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

  public @ResponseBody String handleFileUpload(@RequestParam("name") String name,

      @RequestParam("file") MultipartFile file){

    if (!file.isEmpty()) {

      try {

        byte[] bytes = file.getBytes();

        BufferedOutputStream stream =

            new BufferedOutputStream(new FileOutputStream(new File(name + "-uploaded")));

        stream.write(bytes);

        stream.close();

        return "You successfully uploaded " + name + " into " + name + "-uploaded !";

      } catch (Exception e) {

        return "You failed to upload " + name + " => " + e.getMessage();

      }

    } else {

      return "You failed to upload " + name + " because the file was empty.";

    }

  }

 

}

4. Then we put some restrictions on the uploaded files and wrote the main method to launch the web: 


import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

import org.springframework.boot.context.embedded.MultiPartConfigFactory;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

 

import javax.servlet.MultipartConfigElement;

 

@Configuration

@ComponentScan

@EnableAutoConfiguration

public class Application {

 

  @Bean

  public MultipartConfigElement multipartConfigElement() {

    MultiPartConfigFactory factory = new MultiPartConfigFactory();

    factory.setMaxFileSize("128KB");

    factory.setMaxRequestSize("128KB");

    return factory.createMultipartConfig();

  }

 

  public static void main(String[] args) {

    SpringApplication.run(Application.class, args);

  }

}

5. Then visit http: / / localhost: 8080 / upload can see the page.

The above example is to achieve a single file upload function, assuming that we now want to achieve the file batch upload function, we only need to modify the above code 1 line, considering the length of the problem, the following is only posted and the above different code, no instructions and the above 1. :

1. Add batchUpload.jsp file 


<html>

<body>

<form method="POST" enctype="multipart/form-data"

   action="/batch/upload">

  File to upload: <input type="file" name="file"><br />

  File to upload: <input type="file" name="file"><br />

  <input type="submit" value="Upload"> Press here to upload the file!

</form>

</body>

</html>

2. New BatchFileUploadController.java file: 


import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.ResponseBody;

import org.springframework.web.multipart.MultipartFile;

import org.springframework.web.multipart.MultipartHttpServletRequest;

 

import javax.servlet.http.HttpServletRequest;

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileOutputStream;

import java.util.List;

 

/**

 * Created by wenchao.ren on 2014/4/26.

 */

 

@Controller

public class BatchFileUploadController {

 

  @RequestMapping(value="/batch/upload", method= RequestMethod.POST)

  public @ResponseBody

  String handleFileUpload(HttpServletRequest request){

    List<MultipartFile> files = ((MultipartHttpServletRequest)request).getFiles("file");

    for (int i =0; i< files.size(); ++i) {

      MultipartFile file = files.get(i);

      String name = file.getName();

      if (!file.isEmpty()) {

        try {

          byte[] bytes = file.getBytes();

          BufferedOutputStream stream =

              new BufferedOutputStream(new FileOutputStream(new File(name + i)));

          stream.write(bytes);

          stream.close();

        } catch (Exception e) {

          return "You failed to upload " + name + " => " + e.getMessage();

        }

      } else {

        return "You failed to upload " + name + " because the file was empty.";

      }

    }

    return "upload successful";

  }

}

So a simple batch file upload function ok, is not very simple ah.

Note: the above code is for demonstration purposes only, so the coding style is arbitrary and is not recommended.

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