基于SpringBoot实现图片上传并生成缩略图功能_Java

在实际开发中，上传图片并生成缩略图是一项常见需求，例如在电商平台、社交应用等场景中，缩略图可以有效提高页面加载速度，优化用户体验。本文将介绍如何在 spring boot 项目中实现上传图片并生成缩略图的功能。

1. 依赖配置

在 pom.xml 文件中添加以下依赖：

<!-- spring boot web -->
<dependency>
    <groupid>org.springframework.boot</groupid>
    <artifactid>spring-boot-starter-web</artifactid>
</dependency>
 
<!-- 文件上传 -->
<dependency>
    <groupid>org.springframework.boot</groupid>
    <artifactid>spring-boot-starter-tomcat</artifactid>
</dependency>
 
<!-- 图片处理依赖 -->
<dependency>
    <groupid>com.twelvemonkeys.imageio</groupid>
    <artifactid>imageio-core</artifactid>
    <version>3.8.1</version>
</dependency>
 
<!-- apache commons io -->
<dependency>
    <groupid>commons-io</groupid>
    <artifactid>commons-io</artifactid>
    <version>2.8.0</version>
</dependency>

2. 核心代码实现

以下方法将实现图片上传并生成缩略图的功能：

import org.springframework.web.multipart.multipartfile;
import javax.imageio.imageio;
import java.awt.*;
import java.awt.image.bufferedimage;
import java.io.*;
import java.nio.file.files;
import java.nio.file.path;
import java.nio.file.paths;
import java.util.*;
 
public string uploadpicturethumbnail(string bucketname, multipartfile multipartfile, long associd, string originalstoragename, integer scale, integer width, integer height) {
    string directorypath = "";
    if (osutils.islinux()) {
        directorypath = "/tempdir";
    } else if (osutils.iswindows()) {
        directorypath = "c:/tempdir";
    }
 
    file directory = new file(directorypath);
    if (!directory.exists()) {
        directory.mkdir();
    }
 
    string originalname = multipartfile.getoriginalfilename();
    string suffixname = getsuffixname(originalname, ".", 0);
    string suffix = getsuffixname(originalname, ".", 1);
    string storagename = uuid.randomuuid().tostring() + suffixname;
    string storagefilename = null;
 
    list<string> thumbnailsuffixname = arrays.aslist(".png", ".jpg", ".jpeg", ".gif");
    if (thumbnailsuffixname.contains(suffixname.tolowercase())) {
        try {
            // 保存原始图片
            string originalimagepath = directorypath + "/" + storagename;
            path filepath = paths.get(originalimagepath);
            files.write(filepath, multipartfile.getbytes());
 
            // 读取原始图片并生成缩略图
            bufferedimage originalimage = imageio.read(new file(originalimagepath));
            int originalwidth = originalimage.getwidth();
            int originalheight = originalimage.getheight();
 
            // 计算缩略图尺寸
            int[] data = computesize(originalwidth, originalheight, scale, width, height);
            int thumbnailwidth = data[0];
            int thumbnailheight = data[1];
 
            image scaledimage = originalimage.getscaledinstance(thumbnailwidth, thumbnailheight, image.scale_smooth);
            bufferedimage thumbnailimage = new bufferedimage(thumbnailwidth, thumbnailheight, bufferedimage.type_int_rgb);
            graphics2d g2d = thumbnailimage.creategraphics();
            g2d.drawimage(scaledimage, 0, 0, null);
            g2d.dispose();
 
            // 保存缩略图
            string thumbnailpath = directorypath + "/" + uuid.randomuuid().tostring() + suffixname;
            file thumbnailfile = new file(thumbnailpath);
            imageio.write(thumbnailimage, suffix.replace(".", ""), thumbnailfile);
 
            // 上传缩略图（这里用自定义 uploadfile 方法上传到对象存储）
            try (fileinputstream in = new fileinputstream(thumbnailfile)) {
                string name = getsuffixname(originalstoragename, "/", 1);
                storagefilename = uploadfile(bucketname, in, multipartfile.getcontenttype(), associd, thumbnailfile.length(), name, "thumbnail");
            }
 
            // 清理临时文件
            new file(originalimagepath).delete();
            thumbnailfile.delete();
        } catch (ioexception e) {
            e.printstacktrace();
        }
    }
    return storagefilename;
}

3. 计算缩略图尺寸方法

根据原始尺寸、比例、指定宽高生成合适的缩略图尺寸：

private int[] computesize(int originalwidth, int originalheight, integer scale, integer width, integer height) {
    if (scale != null && scale > 0) {
        return new int[]{originalwidth * scale / 100, originalheight * scale / 100};
    } else if (width != null && height != null) {
        return new int[]{width, height};
    } else {
        // 默认缩小为原始尺寸的 50%
        return new int[]{originalwidth / 2, originalheight / 2};
    }
}