使用java解析xml中的元素数组

Question

Here, I'm using SAX method for parsing array. I'm facing an issue where I'm not able to write a generic code to parse an array type of xml. I couldn't find a solution for generic way methodology to identify it as an array and iterate over it and store it in List

<bookstore>
  <book category="children">
    <title>Harry Potter</title>
    <author>J K. Rowling</author>
    <year>2005</year>
    <price>29.99</price>
  </book>
  <book category="web">
    <title>Learning XML</title>
    <author>Erik T. Ray</author>
    <year>2003</year>
    <price>39.95</price>
  </book>
</bookstore>

Any solution will help. Thanks in advance

Answer 1

I use code below. I got it from: https://github.com/niteshapte/generic-xml-parser

public class GenericXMLParserSAX extends DefaultHandler {

    private ListMultimap<String, String> listMultimap = ArrayListMultimap.create();
    String tempCharacter;   
    private String[] startElements;
    private String[] endElements;

    public void setStartElements(String[] startElements) {
            this.startElements = startElements;
    }

    public String[] getStartElements() {
            return startElements;
    }

    public void setEndElements(String[] endElements) {
            this.endElements = endElements;
    }

    public String[] getEndElements() {
            return endElements;
    }

    public void parseDocument(String xml, String[] startElements, String[] endElements) {
            setStartElements(startElements);
            setEndElements(endElements);

            SAXParserFactory spf = SAXParserFactory.newInstance();
            try {
                    SAXParser sp = spf.newSAXParser();                      
                    InputStream inputStream = new ByteArrayInputStream(xml.getBytes());                     
                    sp.parse(inputStream, this);
            } catch(SAXException se) {
                    se.printStackTrace();
            } catch(ParserConfigurationException pce) {
                    pce.printStackTrace();
            } catch (IOException ie) {
                    ie.printStackTrace();
            }
    }

    public void parseDocument(String xml, String[] endElements) {           
            setEndElements(endElements);

            SAXParserFactory spf = SAXParserFactory.newInstance();
            try {
                    SAXParser sp = spf.newSAXParser();                      
                    InputStream inputStream = new ByteArrayInputStream(xml.getBytes());                     
                    sp.parse(inputStream, this);
            } catch(SAXException se) {
                    se.printStackTrace();
            } catch(ParserConfigurationException pce) {
                    pce.printStackTrace();
            } catch (IOException ie) {
                    ie.printStackTrace();
            }
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
            String[] startElements = getStartElements();

            if(startElements!= null){
                    for(int i = 0; i < startElements.length; i++) {
                            if(qName.startsWith(startElements[i])) {                                
                                    listMultimap.put(startElements[i], qName);
                            }
                    }       
            }
    }

    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
            tempCharacter = new String(ch, start, length);
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {                
            String[] endElements = getEndElements();

            for(int i = 0; i < endElements.length; i++) {
                    if (qName.equalsIgnoreCase(endElements[i])) {
                            listMultimap.put(endElements[i], tempCharacter);                
                    }
            }
    }

    public ListMultimap<String, String> multiSetResult() {            
            return listMultimap;
    }
}

Answer 2

You can create a custom Handler that extends DefaultHandler and use it to parse your XML and generate the List<Book> for you.

The Handler will maintain a List<Book> and:

• every time it will encounter the book start tag, it will create a new Book
• every time it will encounter the book end tag, it will add this Book to the List.

In the end it will be holding the complete list of Books and you can access it via its getBooks() method

Assuming this Book class:

class Book {
    private String category;
    private String title;
    private String author;
    private String year;
    private String price;
    // GETTERS/SETTERS
}

You can create a custom Handler like this:

class MyHandler extends DefaultHandler {

    private boolean title = false;
    private boolean author = false;
    private boolean year = false;
    private boolean price = false;

    // Holds the list of Books
    private List<Book> books = new ArrayList<>();
    // Holds the Book we are currently parsing
    private Book book;

    public void startElement(String uri, String localName,String qName, Attributes attributes) {

        switch (qName) {
            // Create a new Book when finding the start book tag
            case "book": {
                book = new Book();
                book.setCategory(attributes.getValue("category"));
            }
            case "title": title = true;
            case "author": author = true;
            case "year": year = true;
            case "price": price = true;
        }
    }

    public void endElement(String uri, String localName, String qName) {
        // Add the current Book to the list when finding the end book tag
        if("book".equals(qName)) {
            books.add(book);
        }
    }

    public void characters(char[] ch, int start, int length) {
        String value = new String(ch, start, length);

        if (title) {
            book.setTitle(value);
            title = false;
        } else if (author) {
            book.setAuthor(value);
            author = false;
        } else if (year) {
            book.setYear(value);
            year = false;
        } else if (price) {
            book.setPrice(value);
            price = false;
        }
    }

    public List<Book> getBooks() {
        return books;
    }
}

Then you parse using this custom Handler and retrieve the list of Books

SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();

MyHandler myHandler = new MyHandler();
saxParser.parse("/path/to/file.xml", myHandler);
List<Book> books = myHandler.getBooks();