findbugs报OBL_UNSATISFIED_OBLIGATION_EXCEPTION_EDGE的修改实例

先看出问题的一段代码

    public void encode(String xxxPath, String thumbTmpPath, String imageType)
    {
        LOGGER.info("encode image, xxxPath={}, thumbTmpPath={}, imageType={}",
            safeVideoPath,
            thumbTmpPath,
            imageType);
        safeVideoPath = XxxUtils.trimPrefixDir(xxxPath);
        InputStream srcInputStream = null;
        FileOutputStream thumbOutStream = null;
        BufferedImage srcBufImg;
        BufferedImage result;
        try
        {
            srcInputStream = getByteArrayInpuStreamByXxx(xxxPath);
            thumbOutStream = new FileOutputStream(thumbTmpPath);
            if (srcInputStream != null && thumbOutStream != null)
            {
                srcBufImg = ImageIO.read(srcInputStream);
                result = new BufferedImage(srcBufImg.getWidth(), srcBufImg.getHeight(), BufferedImage.TYPE_INT_RGB);
                Graphics2D graphics2D = result.createGraphics();
                graphics2D.drawImage(srcBufImg, 0, 0, null);
                ImageIO.write(result, imageType, thumbOutStream);
            }
        }
        catch (IOException e)
        {
            LOGGER.info("IO Error, {}", ExceptionUtils.getStackTrace(e));
        }
        finally
        {
            try
            {
                IOUtils.closeQuietly(srcInputStream);
            }
            catch (Exception e)
            {
                LOGGER.error("fail to close srcInputStream, {}", ExceptionUtils.getStackTrace(e));
            }
            try
            {
                IOUtils.closeQuietly(thumbOutStream);
            }
            catch (Exception e)
            {
                LOGGER.error("fail to close thumbOutStream, {}", ExceptionUtils.getStackTrace(e));
            }
        }
    }

findbugs报出问题

XXXOOO.java:992, OBL_UNSATISFIED_OBLIGATION_EXCEPTION_EDGE, Priority: Normal
OBL: com.xxx1.xxx2.xxx3.XXXOOO.encode(String, String, String) may fail to clean up java.io.OutputStream on checked exception

This method may fail to clean up (close, dispose of) a stream, database object, or other resource requiring an explicit cleanup operation.

In general, if a method opens a stream or other resource, the method should use a try/finally block to ensure that the stream or resource is cleaned up before the method returns.

This bug pattern is essentially the same as the OS_OPEN_STREAM and ODR_OPEN_DATABASE_RESOURCE bug patterns, but is based on a different (and hopefully better) static analysis technique. We are interested is getting feedback about the usefulness of this bug pattern. To send feedback, either:

send email to findbugs@cs.umd.edu
file a bug report: http://findbugs.sourceforge.net/reportingBugs.html
In particular, the false-positive suppression heuristics for this bug pattern have not been extensively tuned, so reports about false positives are helpful to us.

See Weimer and Necula, Finding and Preventing Run-Time Error Handling Mistakes, for a description of the analysis technique.

报错代码：thumbOutStream = new FileOutputStream(thumbTmpPath);

原因分析：由于thumbOutStream依赖于流srcInputStream，如果srcInputStream关闭失败，就会导致thumbOutStream也关闭失败，所以恰当的做法是先关闭依赖流，再关闭被依赖的流。

修改后的代码如下，将关闭流的顺序反过来即可

    public void encode(String safeVideoPath, String thumbTmpPath, String imageType)
    {
        LOGGER.info("encode image, xxxPath={}, thumbTmpPath={}, imageType={}",
            xxxPath,
            thumbTmpPath,
            imageType);
        safeVideoPath = XxxUtil.trimPrefixDir(xxxPath);
        InputStream srcInputStream = null;
        FileOutputStream thumbOutStream = null;
        BufferedImage srcBufImg;
        BufferedImage result;
        try
        {
            srcInputStream = getByteArrayInpuStreamByXxx(xxxPath);
            thumbOutStream = new FileOutputStream(thumbTmpPath);
            if (srcInputStream != null && thumbOutStream != null)
            {
                srcBufImg = ImageIO.read(srcInputStream);
                result = new BufferedImage(srcBufImg.getWidth(), srcBufImg.getHeight(), BufferedImage.TYPE_INT_RGB);
                Graphics2D graphics2D = result.createGraphics();
                graphics2D.drawImage(srcBufImg, 0, 0, null);
                ImageIO.write(result, imageType, thumbOutStream);
            }
        }
        catch (IOException e)
        {
            LOGGER.info("IO Error, {}", ExceptionUtils.getStackTrace(e));
        }finally
        {
            try
            {
                IOUtils.closeQuietly(thumbOutStream);
            }
            catch (Exception e)
            {
                LOGGER.error("fail to close thumbOutStream, {}", ExceptionUtils.getStackTrace(e));
            }
            try
            {
                IOUtils.closeQuietly(srcInputStream);
            }
            catch (Exception e)
            {
                LOGGER.error("fail to close srcInputStream, {}", ExceptionUtils.getStackTrace(e));
            }
        }
    }

一般性总结：一般资源的打开顺序和关闭顺序相反