There is the concept of flying in the sky, there must be the realization of landing

  • Concept + code implementation is the feature of this article, the tutorial will cover complete graphic tutorials, code cases
  • The end of the article supporting self-test interview questions, learn more solid technology self-test
  • The concept ten times is not as good as the code once, my friend, I hope you can type all the code cases in the article once

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SpringBoot graphic series tutorials technical outline

Teacher Deer’s Java notes

SpringBoot illustrated tutorial series article directory

  1. SpringBoot图文教程1 “concept + case mind mapping” “basics”
  2. Use “logback” and “log4j” to log.
  3. SpringBoot graphic tutorial 3 – “‘ first love ‘complex” integrated Jsp

preface

From the previous three tutorials, you can already implement a Web project, but the functionality of the project is still a little simple, and the following articles will gradually improve and add new features.

Everything in this article will be done in the previous demo. If you don’t have a written demo, go to the Git repository and download it: gitee.com/bingqilinpe…

File upload

1. Prepare the upload page 

<form action="Path..." method="post" enctype="multipart/form-data">

        <input type="file" name="aa">

        <input type="submit" value="Upload">

</form>

<! --

1. The form submission mode must be POST

2. The encType attribute of the form must be multipart/form-data

3. The name of the background variable must be the same as the name attribute of the file selection

4. Action Specifies the path to write Controller methods

-->

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2. Write the controller 

@Controller

@RequestMapping("/file")

public class FileController {

  @RequestMapping("/upload")

  public String upload(MultipartFile aa, HttpServletRequest request) throws IOException {

// Get the path to the upload folder

        String realPath = request.getRealPath("/upload");

// Write the uploaded file to the upload folder

        aa.transferTo(new File(realPath,aa.getOriginalFilename()));// File upload

        return "index";

  }

}

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3. Change the file upload size 

The size of the uploaded file exceeds the default value of 10M

nested exception is java.lang.IllegalStateException: org.apache.tomcat.util.http.fileupload.FileUploadBase$SizeLimitExceededException: the request was rejected because its size (38443713) exceeds the configured maximum (10485760)

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In the application.properties configuration file

File download

1. Provide the link to download the file 

<a href=".. /file/download? fileName=corejava.txt">corejava.txt</a>

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2. Develop controllers 

@RequestMapping("/download")

public void download(String fileName, HttpServletRequest request, HttpServletResponse response) throws Exception {

// Get the path to the upload folder

        String realPath = request.getRealPath("/upload");

// Read files by stream

        FileInputStream is = new FileInputStream(new File(realPath, fileName));

// Get the response flow

        ServletOutputStream os = response.getOutputStream();

// Set the response header information

        response.setHeader("content-disposition"."attachment; fileName="+ URLEncoder.encode(fileName,"UTF-8"));

// Write out the file read by the file input stream through the response stream

        IOUtils.copy(is,os);

/ / close the flow

        IOUtils.closeQuietly(is);

        IOUtils.closeQuietly(os);

    }

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conclusion

Congratulations on completing this chapter. A round of applause! If this article is helpful to you, please help to like, comment, retweet, this is very important to the author, thank you.

Let’s review the learning objectives of this article again

  • Master the use of file upload and file download in SpringBoot

To learn more about SpringBoot, stay tuned for this series of tutorials.

Below, I have prepared some self-test interview questions and project cases for my friend Meng. I hope you can become a hot iron and consolidate your knowledge.

Test your answers to the previous interview questions

Meet exam highlights gitee.com/bingqilinpe…

Self-test interview questions (see next section for answers)

  • SpringMvc file upload steps
  • Steps to download the SpringMvc file

The last self-test project to achieve small case answers

See code cloud warehouse gitee.com/bingqilinpe…

Self-test implementation project short case (see next issue for answers)

This demand:

Practice article demo

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