Java实现文件图片的预览和下载功能

    @apioperation("访问文件")
    @getmapping("/download/{name}")
    public void getimage(httpservletresponse response, @pathvariable("name") string name) throws ioexception {
        //动态获取图片存放位置
        //        string path = getuploadpath();//获取当前系统路径
        string path = upload;
        string imagepath = path + file.separator + name;
        if (!new file(imagepath).exists()) {
            return;
        }
        if (name.endswith("jpg") || name.endswith("png") || name.endswith("gif") || name.endswith("jpeg")) {
            //预览时不需设置content-disposition
            response.setcontenttype("image/jpeg;charset=utf-8");//图片
        }else {
            //下载
        response.setcontenttype("application/octet-stream");//文件
        response.setheader("content-disposition", "inline; filename=" + urlencoder.encode(name, "utf-8"));
        }
        servletoutputstream outputstream = response.getoutputstream();
        outputstream.write(files.readallbytes(paths.get(path).resolve(name)));
        outputstream.flush();
        outputstream.close();
    }

package com.example.controller;

import org.springframework.core.io.classpathresource;
import org.springframework.core.io.resource;
import org.springframework.http.httpheaders;
import org.springframework.http.httpstatus;
import org.springframework.http.responseentity;
import org.springframework.web.bind.annotation.getmapping;
import org.springframework.web.bind.annotation.requestmapping;
import org.springframework.web.bind.annotation.restcontroller;

import java.io.ioexception;
import java.nio.file.files;

@restcontroller
@requestmapping("/api/files")
public class filedownloadcontroller {

    @getmapping("/download")
    public responseentity<resource> downloadfile() {
        string filename = "example.txt"; // 要下载的文件名
        
        try {
            // 从 resources 目录加载文件
            classpathresource resource = new classpathresource(filename);
            
            if (!resource.exists()) {
                return responseentity.notfound().build();
            }

            // 设置响应头
            httpheaders headers = new httpheaders();
            headers.add(httpheaders.content_disposition, "attachment; filename=" + resource.getfilename());

            // 返回文件作为响应
            return responseentity.ok()
                    .headers(headers)
                    .contenttype(org.springframework.http.mediatype.application_octet_stream)
                    .body(resource);
        } catch (ioexception e) {
            return responseentity.status(httpstatus.internal_server_error).build();
        }
    }
}

package com.example.demo.controller;

import org.springframework.web.bind.annotation.getmapping;
import org.springframework.web.bind.annotation.requestmapping;
import org.springframework.web.bind.annotation.restcontroller;

import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.file;
import java.io.fileinputstream;
import java.io.outputstream;

/**
 * @author long
 * @version 1.0.0
 * @classname filecontroller
 * @description todo
 * @createtime 2022.03.18 18:47
 */
@restcontroller
@requestmapping("/demo")
public class filecontroller {


    @getmapping("/file")
    public void filepreviewordownload(httpservletrequest request, httpservletresponse response) throws exception {
        string filename = request.getparameter("filename");
        //type. p预览，d下载
        string type = request.getparameter("type");
        response.reset();
        response.setcharacterencoding("utf-8");

        file file = new file("c:\\users\\long\\desktop\\" + filename);
        fileinputstream fis = new fileinputstream(file);

        if ("d".equalsignorecase(type)) {
            //下载
            response.setcontenttype("application/octet-stream");
            response.setheader("content-disposition", "attachment;filename*=utf-8''" + system.currenttimemillis() + filename.substring(filename.lastindexof(".")));

        } else {
            //预览时不需设置content-disposition
//            response.setcontenttype("application/octet-stream");
//            response.setcontenttype("text/html;charset=utf-8");
//            response.setheader("content-disposition","inline;filename=" + system.currenttimemillis() + filename.substring(filename.lastindexof(".")));
        }
        outputstream os = response.getoutputstream();
        byte[] bytes = new byte[1024];
        int length = 0;
        while ((length = fis.read(bytes)) != -1) {
            os.write(bytes, 0, length);
        }
        os.close();
        fis.close();
    }


}

@getmapping("/downfile")
    public void downfile(httpservletresponse response, httpservletrequest request) {
        try {
//            file file = new file("c:\\users\\hnsh\\pictures\\铁山靠.png");
            file file = new file("f:\\baidunetdiskdownload\\activiti教程 (1).pdf");
            string filename = file.getname();
            string filetype = filename.substring(filename.indexof(".") + 1);

            // 以流的形式下载文件。
            fileinputstream fileinputstream = new fileinputstream(file);
            inputstream fis = new bufferedinputstream(fileinputstream);
            byte[] buffer = new byte[1024];
            int len = 0;
            // 清空response
            response.reset();
            // 设置response的header
            // 解决跨域
            response.addheader("access-control-allow-origin", "*");
            boolean b = "jpg".equalsignorecase(filetype) || "png".equalsignorecase(filetype) || "gif".equalsignorecase(filetype);
            // 图片预览
            if (b) {
                response.setcontenttype("image/" + filetype);
            } else if ("pdf".equalsignorecase(filetype)) {
                // pdf 预览
                response.setcontenttype("application/pdf");
            } else {
                // 直接下载
                response.setcontenttype("application/text;chartset=utf-8");
                response.addheader("content-disposition", "attachment;filename=" + urlencoder.encode(filename, "utf-8"));
                response.addheader("content-length", "" + file.length());
            }
            outputstream toclient = new bufferedoutputstream(response.getoutputstream());
            int a = 0;
            while ((len = fis.read(buffer)) != -1) {
                a = len + a;
                toclient.write(buffer, 0, len);
            }
            toclient.flush();
            toclient.close();
        } catch (ioexception ex) {
            ex.printstacktrace();
        }
    }