java.io.IOException: Stream closed的问题排查

最近开发“导出数据生成文件”功能时使用到多处OutputStream流操作。

如导出excel文件：

//创建outputStream
response.setContentType("APPLICATION/OCTET-STREAM");
response.setHeader("Content-Disposition",
                "attachment;filename=" + URLEncoder.encode(zipName.concat(".zip"), "UTF-8"));
outputStream = response.getOutputStream();
                                                           
//写入                                                           
wb.write(outputStream);
outputStream.flush();

如导出zip文件：

//创建zipOutputStream
public static void setZipOutputStream(HttpServletResponse response, String zipName) throws IOException {
        response.setContentType("APPLICATION/OCTET-STREAM");
        response.setHeader("Content-Disposition",
                "attachment;filename=" + URLEncoder.encode(zipName.concat(".zip"), "UTF-8"));

        outputStream = new ZipOutputStream(response.getOutputStream());
    }
//excel压缩到zip                                           
public static void excelToZipEntry(SXSSFWorkbook workbook, String excelName) throws IOException {
        File tmpFile = TempFile.createTempFile("poi-sxssf-template", ".xlsx");
        boolean deleted;

        try (FileOutputStream os = new FileOutputStream(tmpFile);
                FileInputStream fileInputStream = new FileInputStream(tmpFile);
                BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream)) {

            workbook.write(os);

            ZipEntry entry = new ZipEntry(excelName + ".xlsx");
            outputStream.putNextEntry(entry);

            byte[] buffer = new byte[1024];
            int len;
            while ((len = bufferedInputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, len);
            }
        } finally {
            outputStream.closeEntry();
            deleted = tmpFile.delete();
            if (!deleted) {
                throw new IOException("Could not delete temporary file after processing: " + tmpFile);
            }
        }
 }
 //压缩pdf到zip
public static void pdfToZipEntry(String pdfFileName, byte[] bytes) throws IOException {
        try (ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes)) {
            ZipEntry entry = new ZipEntry(pdfFileName + ".pdf");
            outputStream.putNextEntry(entry);

            byte[] buffer = new byte[1024];
            int len;
            while ((len = byteArrayInputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, len);
            }

        } finally {
            outputStream.closeEntry();
        }
    }                                          

经常会遇到的异常就是：

java.io.IOException: Stream closed

原因在于：
每次往流里写数据的源代码里，都会检查一下流是否关闭，关闭就抛 java.io.IOException: Stream closed

虽然知道这个异常的意思，但是在找关闭outputstream的原因的时候，还是花费了一些时间。

例如：
在ZipFileUtil是一个生成zip文件的工具类。
ZipFileUtil.class里创建了一个全局唯一的OutputStream，但是在创建的时候，却使用了如下方式创建：

public class ZipFileUtil {
    private static ZipOutputStream outputStream;
    private static File file;

    public static void setZipOutputStream(String filePath) {
        file = new File(filePath);
        
        try (FileOutputStream fileOutputStream = new FileOutputStream(file)) {
            outputStream = new ZipOutputStream(fileOutputStream);
        } catch (Exception e) {
            log.error("创建ZipOutputStream失败,filePath={}", filePath, e);
        }
                                                                      
        outputStream = new ZipOutputStream(fileOutputStream);
    }
} 

try-catch的方式创建流，在try-catch代码结束的时候会自动关闭OutputStream，

所以在后续插入数据的时候，直接抛出了java.io.IOException: Stream closed

修改方案：

public static void setZipOutputStream(String filePath) {
        file = new File(filePath);
        try {
            fileOutputStream = new FileOutputStream(file);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        outputStream = new ZipOutputStream(fileOutputStream);
}