I have a method generateXmlAndImages with input xmlDataMap size of 400. Each of these map entries will cause four images to be created and written to storage.

In a single thread it is taking long time to process, about 15 minutes. So I thought concurrent execution might improve performance. But when I switch to parallel streams rather than single-thread, the data is never generated.

The buildIt method is printing first log message “generatingXmlAndImages” for few xml-ids bun never printing the end log message “generatedXmlAndImages”.

It never printed below lines when I ran the method.

log.info("1:collect.size() = " + collect.size());
log.info("2:input map.size() = " + xmlDataMap.values().size());

Please help me with this, or any ideas, how I can solve this issue.

private void generateXmlAndImages() {
    List<XmlData> collect = xmlDataMap.keySet().stream()
            .parallel()
            .map(xmlId -> xmlDataMap.get(xmlId))
            .map(data -> buildIt(data))
            .collect(Collectors.toList());
    log.info("1:collect.size() = " + collect.size());
    log.info("2:input map.size() = " + xmlDataMap.values().size());
}

private XmlData buildIt(XmlData xmlData) {
    log.info("generatingXmlAndImages: xmlId=" + xmlData.getId());
    try {
        if (!xmlData.isValid()) {
            return null;
        }
        Map<String, String> imagesPaths = generateSignatureAndLogoImages(xmlData);
        XML xml = XmlGenerator.generateXML(imagesPaths, xmlData);
        xmlData.setXml(xml);
        xmlData.setValid(true);
        log.info("generatedXmlAndImages: xmlId=" + xmlData.getId());
    } catch (Exception e) {
        String errorMessage = "Unable to generate Images or XML for xml Id:" + xmlData.getId();
        log.error("FAILED" + errorMessage, e);
        xmlData.setValid(false);
        xmlData.addError(e.toString());
    }
    return xmlData;
}

private Map<String, String> generateSignatureAndLogoImages(XmlData xmlData) {
    SignatureDataImpl signatureData = xmlData.getSignatureData();
    Map<String, String> paths = new HashMap<>();
    String sig1 = createImage("SIG1", xmlData.getId(), signatureData.getSignature1Data(), signatureData.getSignature1Format());
    String sig2 = createImage("SIG2", xmlData.getId(), signatureData.getSignature2Data(), signatureData.getSignature2Format());
    String blogo1 = createImage("LOGO1", xmlData.getId(), signatureData.getLogo1Data(), signatureData.getLogo1Format());
    String blogo2 = createImage("LOGO2", xmlData.getId(), signatureData.getLogo1Data(), signatureData.getLogo1Format());

    if (StringUtils.isEmpty(sig1) && StringUtils.isEmpty(sig2)) {
        String error = "Failed to generate signature images for xmlId " + xmlData.getId();
        log.error(error);
        throw new RuntimeException(error);
    }
        paths.put(Properties.SIGNATURE_1, sig1);
        paths.put(Properties.SIGNATURE_2, sig2);
        paths.put(Properties.LOGO1, blogo1);
        paths.put(Properties.LOGO1, blogo2);
    
    return paths;
}

private String createImage(String suffix, String name, String imageData, String format) {
    if (imageData == null || imageData.isEmpty()) {
        return "";
    }
    String imageFileName = (name+"_"+ suffix+"."+ format);
    String decodedBase64 = FileUtils.decodeBase64(imageData);
    FileUtils.writeToFile( TMP_IMAGE_STORE_DIR, imageFileName, decodedBase64);
    Files.write(Path.of(TMP_IMAGE_STORE_DIR + "/" + imageFileName),data.getBytes());
    StringBuilder pathBuilder = new StringBuilder();
    pathBuilder.append(TMP_IMAGE_STORE_DIR).append("/");
    pathBuilder.append(imageFileName);
    return pathBuilder.toString();
}

public static XML generateXML(Map<String, String> imagePaths, XmlData xmlData) {
    XML xml = new XML();
    Element customerRootElement = createRoot(xml, "customer");

    Element stubElement = createTag(xml, customerRootElement, "stub");
    Element bodyElement = createTag(xml, customerRootElement, "body");
    Element mailFaceElement = createTag(xml, customerRootElement, "mailface");

    addStubXml(xmlData, xml, stubElement);
    addBodyXML(xmlData, imagePaths, xml, bodyElement);
    addMailFaceXML(xmlData, xml, mailFaceElement);

    return xml;
}