java - Sax 解析器 - 无法将 XML 文件分割为指定大小

Question

我在如何读取 xml 并使用 SAX 解析器将其拆分为多个文件方面遇到了一些困难。考虑一下我们的输入遵循生成的 xml:

<?xml version="1.0" encoding="utf-8"?>
<record-table>
  <record>
    <record_id>12345</record_id>
    <record_rows>
      <record_row>str1234</record_row>
    </record_rows>
  </record>
  <footer>
    <record_count>12345</record_count>
    <record_row_count>12345</record_row_count>
  </footer>
</record-table>

为了使它干净和甜蜜，我制作了“TODO”列表:

XML splitting:
 * Splits file generated by XML generation functionality in multiple files of configurable size.
 * Asks the user XML file location.
 * Asks the user maximum single file size in bytes.
 * Each split file must conform to schema.
 * Elements record_count and record_row_count should contain actual numbers for each file.
 * Files should be split as close to specified limit as possible.

截至目前，我多次尝试读取它，程序执行但没有执行任何操作。

代码草案:

    public static void splitXML(File fileToSplit, int splitFileSize) {
    try {
        SAXParserFactory factory = SAXParserFactory.newInstance();
        SAXParser parser = factory.newSAXParser();
        XMLReader reader = parser.getXMLReader();

        reader.parse(new InputSource(new FileInputStream(fileToSplit)));
        reader.setContentHandler(new DefaultHandler() {

            public static final String DIRECTORY = "target/results";

            private int fileSize = 0;

            private File fileLocation;

            // counts number of files created
            private int fileCount = 0;

            // counts characters to decide where to split file
            private long charCount = 0;
            // data line buffer (is reset when the file is split)
            private StringBuilder recordRowDataLines = new StringBuilder();

            // temporary variables used for the parser events
            private String currentElement = null;
            private String currentRecordId = null;
            private String currentRecordRowData = null;

            public final long TAG_CHAR_SIZE = 5;

            @Override
            public void startDocument() throws SAXException {
                File directory = new File(DIRECTORY);
                if(!directory.exists())
                    directory.mkdir();
            }

            @Override
            public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
                currentElement = qName;
            }

            @Override
            public void endElement(String uri, String localName, String qName) throws SAXException {
                if(qName.equals("record_rows")) {
                    try {
                        savePatch();
                    } catch (IOException e) {
                        throw new SAXException(e);
                    }
                }
                if (qName.equals("record_row")) { // one record finished - save in buffer & calculate size so far
                    charCount += tagSize("record_row");
                    recordRowDataLines.append("<record_row>")
                            .append(currentRecordRowData)
                            .append("</record_row>");
                    if (charCount >= fileSize) { // if max size was reached, save what was read so far in a new file
                        try {
                            savePatch();
                        } catch (IOException ex) {
                            throw new SAXException(ex);
                        }
                    }
                }
                currentElement = null;
            }

            @Override
            public void characters(char[] ch, int start, int length) throws SAXException {
                System.out.println(new String(ch, start, length));
                if (currentElement == null) {
                    return;
                }
                if (currentElement.equals("record_id")) {
                    currentRecordId = new String(ch, start, length);
                }
                if (currentElement.equals("record_row")) {
                    currentRecordRowData = new String(ch, start, length);
                    charCount += currentRecordRowData.length(); // storing size so far
                }
            }

            public long tagSize(String tagName) {
                return TAG_CHAR_SIZE + tagName.length() * 2; // size of text + tags
            }

            public void savePatch() throws IOException {
                ++fileCount;
                StringBuilder stringBuilder = new StringBuilder();
                stringBuilder.append("<record part='")
                        .append(fileCount)
                        .append("'><record_id>")
                        .append(currentRecordId)
                        .append("</record_id>")
                        .append("<record_rows>")
                        .append(recordRowDataLines)
                        .append("</record_rows></record>");
                File fragment = new File(DIRECTORY, "data_part_" + fileCount + ".xml");
                System.out.println("File " + fragment.getAbsolutePath() + "has been saved!");

                try(FileWriter out = new FileWriter(fragment)){
                    out.write(stringBuilder.toString());
                } catch (Exception e) {
                    e.printStackTrace();
                }

                //flush current information that was saved.
                recordRowDataLines = new StringBuilder();
                charCount = 0;
            }
        });

    } catch (ParserConfigurationException | SAXException | IOException e) {
        e.printStackTrace();
    }
}

主类看起来如何:

public class Main {

    public static void main(String[] args) {
        System.out.println("Welcome!");

        <omitted>
        File f = CommonUtils.requestFilePath();
        int fileSize = CommonUtils.requestUserValueInt("Enter file split size : ");
        XMLSplitter.splitXML(f, fileSize);
    }
}

愿你看到，我看不到的东西。请帮忙。

Answer 1

您应该在解析之前调用setContentHandler。