check internet connection. Spring MVC Download file

I have a project with which I learn to upload and download files, I implemented such a system, the file name, the path to it, its id and UUID are stored in the database (this is necessary so that there are no such problems when several files with the same name are uploaded) , everything works almost perfectly, but when I try to download a file, it says in my downloads: "check internet connection." screenshot:

FileEntity.class:

package instagram.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.SequenceGenerator;
import jakarta.persistence.Table;

@Entity
@Table(name = "files")
public class FileEntity {

@Id
@SequenceGenerator(name = "file_seq", sequenceName = "file_seq", allocationSize = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "file_seq")
private long id;

private String name;

private String path;

private String uuid;

public FileEntity() {}

public FileEntity(long id, String name, String path, String uuid) {
this.id = id;
this.name = name;
this.path = path;
this.uuid = uuid;
}

public FileEntity(String name, String path, String uuid) {
this.name = name;
this.path = path;
this.uuid = uuid;
}

public long getId() {
return id;
}

public void setId(long id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getPath() {
return path;
}

public void setPath(String path) {
this.path = path;
}

public String getUuid() {
return uuid;
}

public void setUuid(String uuid) {
this.uuid = uuid;
}

}

FileController.class:

package instagram.controller;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.UUID;
import java.util.logging.Logger;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

import instagram.entity.FileEntity;
import instagram.service.FileService;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

@Controller
public class FileController {

private FileService fileService;

private static Logger log = Logger.getGlobal();
private static String UPLOAD_FOLDER = "C://Users//SystemX//eclipse-workspace//instagram//lib//src//main//resources//images//";
private static String DOWNLOAD_FOLDER = "C://Users//SystemX//Downloads//";

public FileController(FileService fileService) {
this.fileService = fileService;
}

@GetMapping("/")
public String templateView(Model model) {
model.addAttribute("files", fileService.getAllFiles());
	
model.addAttribute("file", new FileEntity());
	
return "home";
}

@PostMapping("/")
public String addNewFile(@RequestParam(value = "file", required = false) MultipartFile multipart, Model model) {
if (multipart.isEmpty()) {
		
}
	
try {
String uuid = UUID.randomUUID().toString();
String newName = uuid + "." + multipart.getOriginalFilename();
		
byte[] bytes = multipart.getBytes();
Path path = Paths.get(UPLOAD_FOLDER + newName);
Files.write(path, bytes);
		
String[] newFile = newName.split("[.\\s]+");
		
fileService.saveNewFile(newFile);
		
} catch (IOException exception) {
exception.printStackTrace();
}
	
return "home";
}

@GetMapping("/download/{fileId}")
public String downloadFile(@PathVariable(value = "fileId") long fileId, Model model, HttpServletRequest request, HttpServletResponse response) {
	
FileEntity fileEntity = fileService.findById(fileId);
	
log.info(UPLOAD_FOLDER + fileEntity.getUuid() + "." + fileEntity.getName());
	
Path file = Paths.get(UPLOAD_FOLDER, fileEntity.getUuid() + "." + fileEntity.getName());
if (Files.exists(file)) {
response.setContentType("application/pdf");
response.addHeader("Content-Disposition", "attachment; filename=" + fileEntity.getName());
try {
Files.copy(file, response.getOutputStream());
response.getOutputStream().flush();
} catch (IOException ex) {
ex.printStackTrace();
}
}
	
return "home";
}

}

FileService.class:

package instagram.service;

import java.util.List;
import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import instagram.entity.FileEntity;
import instagram.repository.FileRepository;

@Service
public class FileService {

private FileRepository fileRepository;

@Autowired
public FileService(FileRepository fileRepository) {
this.fileRepository = fileRepository;
}

public List<FileEntity> getAllFiles() {
return fileRepository.findAll();
}

public FileEntity saveNewFile(String[] newFile) {
FileEntity file = new FileEntity();
	
file.setName(newFile[1] + "." + newFile[2]);
file.setPath("C://Users//SystemX//eclipse-workspace//instagram//lib//src//main//resources//images//");
file.setUuid(newFile[0]);
	
return fileRepository.save(file);
}

public FileEntity findById(long id) {
return fileRepository.findById(id);
}

}

FileRepository.interface:

package instagram.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import instagram.entity.FileEntity;

@Repository
public interface FileRepository extends JpaRepository<FileEntity, Long> {

FileEntity findById(long id);

}

home.html:

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

<form th:method="POST" th:action="@{/}" enctype="multipart/form-data">
<input type="file" name="file"/>
<button type="submit">Send file</button>
</form>

<div th:each="newfiles: ${files}">
<a th:href="@{'/download/' + ${newfiles.id}}">
<span th:text="${newfiles.name}"></span>
</a>
</div>

</body>
</html>

application.properties:

spring.datasource.url=jdbc:postgresql://localhost:5432/instagram
spring.datasource.username=postgres
spring.datasource.password=

spring.thymeleaf.prefix=classpath:/templates/
spring.thymeleaf.suffix=.html

spring.servlet.multipart.enabled=true
spring.servlet.multipart.max-file-size=50MB
spring.servlet.multipart.max-request-size=50MB

spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.properties.hibernate.format_sql=true
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect

build.gradle:

dependencies {

testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'

api 'org.apache.commons:commons-math3:3.6.1'

implementation 'com.google.guava:guava:30.1.1-jre'

implementation 'org.springframework.boot:spring-boot-starter-web:3.1.0'

implementation 'org.springframework.boot:spring-boot-starter-data-jpa:3.1.0'

implementation 'org.postgresql:postgresql:42.6.0'

implementation 'org.springframework.boot:spring-boot-starter-thymeleaf:3.1.0'

implementation 'commons-io:commons-io:2.13.0'

}

what mistakes did I make in the implementation of the project and what exactly is the problem with connecting to the Internet?

After line:

response.getOutputStream().flush();

I added this:

response.getOutputStream().close();

Due to the fact that I didn’t close the stream, he couldn’t download the file, apparently that’s why when I googled yesterday and a little today and didn’t find a solution, good and happiness to everyone!

UDP:

By the way, on the topic of downloading a file from a folder, this code works well, the book was downloaded successfully!

UDP 2:

To avoid unnecessary problems in the console, I recommend changing the type of the method in which the file jump occurs to

void

and after

close();

write

return;

Download Method:

@GetMapping("/download/{fileId}")
public void downloadFile(@PathVariable(value = "fileId") long fileId, Model model, HttpServletRequest request, HttpServletResponse response) {
	
FileEntity fileEntity = fileService.findById(fileId);
	
log.info(UPLOAD_FOLDER + fileEntity.getUuid() + "." + fileEntity.getName());
	
Path file = Paths.get(UPLOAD_FOLDER, fileEntity.getUuid() + "." + fileEntity.getName());
if (Files.exists(file)) {
response.setContentType("application/pdf");
response.addHeader("Content-Disposition", "attachment; filename=" + fileEntity.getName());
try {
Files.copy(file, response.getOutputStream());
response.getOutputStream().flush();
response.getOutputStream().close();
return;
} catch (IOException ex) {
ex.printStackTrace();
}
}
	
return;
}