在Java中使用SAX解析器同时读取父级和子级

我有一个非常小的xml文件，我只想用Java阅读。参考之后，我决定使用SAX解析器。我的xml文件如下所示-

<?xml version="1.0" encoding="UTF-8"?>
<catalog>
    <library name="Central Library">
        <read>
            <book id="001" lang="ENG" title="Operating System Concepts" author="Silberschatz" />
            <book id="002" lang="ENG" title="Design Patterns: Elements of Reusable Object-Oriented Software" author="Gangs of Four" />
        </read>
        <unread>
            <book id="003" lang="ENG" title="Introduction to Algorithms" author="Cormen" />
            <book id="004" lang="ENG" title="Computer networks" author="Tanenbaum" />
        </unread>
    </library>
</catalog>

图书馆和图书课如下-

Library.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public final class Library {
    private final String name;
    private final List<Book> readBooks;
    private final List<Book> unreadBooks;

    public Library(String name) {
        this.name = name;
        readBooks = new ArrayList<Book>();
        unreadBooks = new ArrayList<Book>();
    }

    public void addIntoReadBooks(Book book) {
        getReadBooks().add(book);
    }

    public void addIntoUnreadBooks(Book book) {
        getUnreadBooks().add(book);
    }
    //Getters
}

如何决定该书应添加到哪个列表

我的回答 不知怎的，我设法接受了下面的代码，它使用两个标志来跟踪访问的节点-

import java.io.IOException;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class ParseXML extends DefaultHandler {

    private Library lib;
    private boolean read;
    private boolean unread;

    public ParseXML(String file) throws ParserConfigurationException, SAXException, IOException {
        parse(file);
    }

    private void parse(String file) throws ParserConfigurationException, SAXException, IOException {
        final SAXParserFactory factory = SAXParserFactory.newInstance();
        final SAXParser parser = factory.newSAXParser();
        parser.parse(file, this);
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (qName.equals("read")) {
            read = false;
        }
        if (qName.equals("unread")) {
            unread = false;
        }
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if (qName.equals("library")) {
            String name = attributes.getValue("name");
            lib = new Library(name);
        }
        if (qName.equals("read")) {
            read = true;
        }
        if (qName.equals("unread")) {
            unread = true;
        }
        if (qName.equals("book")) {
            String id = attributes.getValue("id");
            String lang = attributes.getValue("lang");
            String title = attributes.getValue("title");
            String author = attributes.getValue("author");

            Book book = new Book(id, lang, title, author);

            // How to decide here, to which list this book should be added
            if (read && !unread) {
                lib.addIntoReadBooks(book);
                } else if (!read && unread) {
                lib.addIntoUnreadBooks(book);
            }
        }
    }

    /**
    * @return the lib
    */
    public Library getLibrary() {
        return lib;
    }
}

---

是否有更好的解决方案？

我不清楚这是否一定更好，但您可以在

ParseXML

类中维护一个

currentList

字段，以便当前列表进行操作：

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class ParseXML extends DefaultHandler {

    private Library lib;
    private List<Book> extraBooks = new ArrayList<Book>();
    private List<Book> currentList = extraBooks;

    public ParseXML(String file) throws ParserConfigurationException, SAXException, IOException {
        parse(file);
    }

    private void parse(String file) throws ParserConfigurationException, SAXException, IOException {
        final SAXParserFactory factory = SAXParserFactory.newInstance();
        final SAXParser parser = factory.newSAXParser();
        parser.parse(file, this);
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (qName.equals("read") || qName.equals("unread"))
            currentList = extraBooks;
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if (qName.equals("library")) {
            String name = attributes.getValue("name");
            lib = new Library(name);
        }
        else if (qName.equals("read")) {
            currentList = lib.getReadBooks();
        }
        else if (qName.equals("unread")) {
            currentList = lib.getUnreadBooks();
        }
        else if (qName.equals("book")) {
            String id = attributes.getValue("id");
            String lang = attributes.getValue("lang");
            String title = attributes.getValue("title");
            String author = attributes.getValue("author");

            currentList.add(new Book(id, lang, title, author));
        }
    }

    /**
     * @return the lib
     */
    public Library getLibrary() {
        return lib;
    }

}

以及

endElement

方法

@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
    if (qName.equals("read") || qName.equals("unread"))
        currentList = new ArrayList<Book>();
}

@覆盖
public void endElement（字符串uri、字符串localName、字符串qName）引发SAXException{
if（qName.equals（“读取”）| | qName.equals（“未读”））
currentList=新的ArrayList（）；
}

为什么投票关闭？我已经在很多地方提到过，但没有发现这种情况。为什么你没有正确地缩进代码？读起来很痛苦：）@Pavelholl:我道歉。我只是从Eclipse复制并粘贴。这个问题似乎离题了，因为它不是关于解决问题的。非常感谢。我在SAX中使用

XMLReader

又找到了一种方法。它具有设置

ContentHandler

的功能。非常感谢你。

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class ParseXML extends DefaultHandler {

    private Library lib;
    private List<Book> extraBooks = new ArrayList<Book>();
    private List<Book> currentList = extraBooks;

    public ParseXML(String file) throws ParserConfigurationException, SAXException, IOException {
        parse(file);
    }

    private void parse(String file) throws ParserConfigurationException, SAXException, IOException {
        final SAXParserFactory factory = SAXParserFactory.newInstance();
        final SAXParser parser = factory.newSAXParser();
        parser.parse(file, this);
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (qName.equals("read") || qName.equals("unread"))
            currentList = extraBooks;
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if (qName.equals("library")) {
            String name = attributes.getValue("name");
            lib = new Library(name);
        }
        else if (qName.equals("read")) {
            currentList = lib.getReadBooks();
        }
        else if (qName.equals("unread")) {
            currentList = lib.getUnreadBooks();
        }
        else if (qName.equals("book")) {
            String id = attributes.getValue("id");
            String lang = attributes.getValue("lang");
            String title = attributes.getValue("title");
            String author = attributes.getValue("author");

            currentList.add(new Book(id, lang, title, author));
        }
    }

    /**
     * @return the lib
     */
    public Library getLibrary() {
        return lib;
    }

}

private List<Book> currentList = new ArrayList<Book>();

@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
    if (qName.equals("read") || qName.equals("unread"))
        currentList = new ArrayList<Book>();
}