一、背景

最近在做一个项目，里面有一个一次性下载多张证书的接口，我需要将多张证书返回给前端，然后我就想到是否可以把证书文件压缩到一个zip文件，讨论之后就采用了我的想法。之后就想着怎么才能方便的写入呢？实现如下：

二、代码实现

import java.io.*;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

public class ZipUtil {

    private static ReentrantReadWriteLock reentrantReadWriteLock = new ReentrantReadWriteLock();

    /**
     * 获取指定路径下的文件，如果没有就直接创建一个
     * @param path 文件夹名称，可空
     * @param fileName 文件名，非空
     * @return 返回指定w文件
     * @throws IOException 读取异常
     */
    public static File getFile(String path, String fileName) throws IOException {
        File file;
        if (path != null && !path.equals("")) {
            file = new File(path, fileName);
        } else {
            file = new File(fileName);
        }
        if (!file.exists()) {
            file.createNewFile();
        }
        return file;
    }

    /**
     * 获取文件输出流
     * @param file 文件
     * @return 文件输出流
     * @throws FileNotFoundException 文件未找到异常
     */
    public static FileOutputStream getFileStream(File file) throws FileNotFoundException {
        return new FileOutputStream(file);
    }

    /**
     * 将文件夹中的文件打包到zip文件中
     * @param folder 待压缩文件夹
     * @param zipPath zip存放路径
     * @param zipName zip文件名
     * @return zip文件
     * @throws IOException 输出异常
     */
    public static File getZipFile(String folder,String zipPath,String zipName) throws IOException {
        File file = new File(folder);
        if(!file.exists()){
            return null;
        }
        File[] files = file.listFiles();
        List<File> fileList = Arrays.asList(files);
        return getZipFile(fileList,zipPath,zipName);
    }

    /**
     * 将批量文件加入到zip文件中
     * @param fileList 文件列
     * @param zipFilePath zip文件存放路径
     * @param zipFileName zip文件名
     * @return zip文件
     * @throws IOException 输入输出异常
     */
    public static File getZipFile(List<File> fileList, String zipFilePath, String zipFileName) throws IOException {
        reentrantReadWriteLock.writeLock().lock();
        File zipFile = getFile(zipFilePath, zipFileName);
        try (
                FileOutputStream outputStream = getFileStream(zipFile);
                ZipOutputStream zipOutputStream = new ZipOutputStream(outputStream);
                ){

            int size = fileList.size();

            fileList.forEach(file->{
                try {
                    zipFile(file,zipOutputStream);
                    file.delete();
                } catch (IOException e) {
                    System.out.println("文件处理异常");
                }
            });

            zipOutputStream.flush();
            outputStream.flush();
            return zipFile;
        } catch (Exception e) {
            throw new IOException(e);
        } finally {
            reentrantReadWriteLock.writeLock().unlock();
        }
    }


    /**
     * 将文件写入zip
     * @param file 需要写入到zip文件的
     * @param zipOutputStream
     * @throws IOException
     */
    private static void zipFile(File file, ZipOutputStream zipOutputStream) throws IOException {
        if (file.exists() && file.isFile()) {

            try (
                    FileInputStream fis = new FileInputStream(file);
                    BufferedInputStream bis = new BufferedInputStream(fis);
                    ){
                ZipEntry entry = new ZipEntry(file.getName());
                zipOutputStream.putNextEntry(entry);
                long streamTotal = 0L;
                streamTotal = (long)bis.available();
                int streamNum = (int)Math.floor((double)(streamTotal / 10485760L));
                int leaveByte = (int)(streamTotal % 10485760L);
                byte[] buffer;
                if (streamNum > 0) {
                    for(int i = 0; i < streamNum; ++i) {
                        buffer = new byte[10485760];
                        bis.read(buffer, 0, 10485760);
                        zipOutputStream.write(buffer, 0, 10485760);
                    }
                }
                buffer = new byte[leaveByte];
                bis.read(buffer, 0, leaveByte);
                zipOutputStream.write(buffer, 0, leaveByte);
                zipOutputStream.closeEntry();
            }catch (Exception e){
                throw new IOException(e);
            }


        }

    }

    public static void main(String[] args) throws IOException {
        File file = new File("F:\\2345Downloads\\综述\\Desktop\\颈动脉");
        File[] files = file.listFiles();
        List<File> files1 = Arrays.asList(files);
        getZipFile(files1,"F:\\2345Downloads\\综述\\Desktop\\颈动脉","test.zip");
    }
}