环境：jdk1.8，springboot2.5.3,项目端口号：9100

1.待转换的文件

一、路径

二、文件内容

2.controller中代码

package com.example.pdf.controller;

import com.example.pdf.service.GetFileStreamService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletResponse;

/**
 * @author 
 * @date 2024/3/29 16:28
 * @describe
 */
@RestController
@RequestMapping(value = "test")
public class GetFileStreamController {

    @Resource
    private GetFileStreamService getFileStreamService;
	
	/**
     * 获取文件流
     */
    @GetMapping("getFileStream")
    public void getFileStream(HttpServletResponse response) {
        getFileStreamService.getFileStream(response);

    }

}

3.service中代码

package com.example.pdf.service;

import javax.servlet.http.HttpServletResponse;

/**
 * @author 
 * @date 2024/3/29 16:30
 * @describe
 */
public interface GetFileStreamService {

    /**
     * 获取文件流
     * @param response
     */
    void getFileStream(HttpServletResponse response);
}

4.实现类代码

package com.example.pdf.service.impl;

import com.example.pdf.service.GetFileStreamService;
import org.springframework.stereotype.Service;

import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.OutputStream;

/**
 * @author
 * @date 2024/3/29 16:31
 * @describe
 */
@Service
public class GetFileStreamServiceImpl implements GetFileStreamService {
    /**
     * 获取文件流
     */
    @Override
    public void getFileStream(HttpServletResponse response) {
        // 指定文件路径，获取file文件
        File file = new File("E:\\Desktop\\temps\\test.pdf");
        try {
            // 将文件转为文件输入流
            FileInputStream fileInputStream = new FileInputStream(file);
            // 获取响应的输出流
            OutputStream outputStream = response.getOutputStream();
            // 将文件转成字节数组，再将数组写入响应的输出流
            byte[] buffer = new byte[1024];
            int bytesRead = -1;
            while ((bytesRead = fileInputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
            // 刷新输出流
            outputStream.flush();
            // 关闭流
            fileInputStream.close();
            outputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

5.postman中访问结果示例

6.浏览器中访问结果示例