SAX 解析到文件，缓存到内存

目的
    通过一个小的SAX例子，我们更清晰的理解SAX的工作原理。

    本文例子主要实现：
    1. 将每个Employee信息输出到自己的文件中，文件名是以Employee ID和Employee Name来命名的，注意，观察代码中是如何得到Employee ID和Employee Name；
    2. 将每个Employee信息存入到Map中，其中，Map中的每个Value对应一个Employee的Collection，Map中的每个Key对应该Employee的ID。

    package shuai.study.sax.demo;  

    import java.io.File;
    import java.io.IOException;
    import java.util.Collection;
    import java.util.HashMap;
    import java.util.LinkedList;
    import java.util.Map;  

    import javax.xml.parsers.ParserConfigurationException;
    import javax.xml.parsers.SAXParser;
    import javax.xml.parsers.SAXParserFactory;  

    import org.apache.commons.io.FileUtils;
    import org.apache.commons.lang3.StringUtils;
    import org.xml.sax.Attributes;
    import org.xml.sax.SAXException;
    import org.xml.sax.helpers.DefaultHandler;  

    /**
     * @author shengshu
     *
     */
    public class SaxHandler extends DefaultHandler {
        private final static String leafNodeText = "|firstname|;|lastname|;|sex|;|country|;|province|;|city|;|village|;|mobile|;|mail|;|qq|;|postcode|;|profession|";  

        private Map<String, Collection<String>> companyMap = null;
        private Collection<String> employeeCollection = null;  

        private String currentValue = null;
        private String currentCharacters = null;  

        private StringBuffer idAndNameStringBuffer = null;  

        public SaxHandler(File inputFile) {
            this.parseDocument(inputFile);
        }  

        private void parseDocument(File inputFile) {
            SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();  

            try {
                SAXParser saxParser = saxParserFactory.newSAXParser();
                saxParser.parse(inputFile, this);
            } catch (ParserConfigurationException pce) {
                pce.printStackTrace();
            } catch (SAXException saxe) {
                saxe.printStackTrace();
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
        }  

        @Override
        public void startDocument() throws SAXException {
            super.startDocument();
            this.companyMap = new HashMap<String, Collection<String>>();
        }  

        @Override
        public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
            if (qName.equalsIgnoreCase("Employee")) {
                this.employeeCollection = new LinkedList<String>();
                this.idAndNameStringBuffer = new StringBuffer();  

                this.currentValue = attributes.getValue("ID");
            }
        }  

        @Override
        public void characters(char[] buffer, int start, int length) {
            this.currentCharacters = new String(buffer, start, length);
        }  

        @Override
        public void endElement(String uri, String localName, String qName) throws SAXException {
            if (StringUtils.containsIgnoreCase(leafNodeText, "|" + qName + "|")) {
                this.employeeCollection.add(qName + ": " + this.currentCharacters);  

                if (qName.equalsIgnoreCase("FirstName")) {
                    this.idAndNameStringBuffer.append(this.currentCharacters);
                }  

                if (qName.equalsIgnoreCase("LastName")) {
                    this.idAndNameStringBuffer.append(this.currentCharacters);
                }
            }  

            if (qName.equalsIgnoreCase("Employee")) {
                this.companyMap.put(this.currentValue, this.employeeCollection);  

                this.idAndNameStringBuffer.append("-").append(this.currentValue);  

                this.writeEmployee(employeeCollection, idAndNameStringBuffer.toString());
            }
        }  

        private void writeEmployee(Collection<String> employeeCollection, String fileName) {
            String outputFileDirectory = SaxHandler.class.getResource("/file/output/").getPath();
            String outputFilePath = outputFileDirectory + fileName + ".xml";
            File outputFile = new File(outputFilePath);  

            try {
                FileUtils.writeLines(outputFile, employeeCollection, false);
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
        }  

        @Override
        public void endDocument() throws SAXException {
            super.endDocument();
        }  

        public Map<String, Collection<String>> getCompanyMap() {
            return this.companyMap;
        }  

    }  

    package shuai.study.sax.demo;  

    import java.io.File;
    import java.util.Collection;
    import java.util.Iterator;
    import java.util.Map;
    import java.util.Map.Entry;  

    /**
     * @author shengshu
     *
     */
    public class SaxDemo {
        public static void displayCompany(Map<String, Collection<String>> companyMap) {
            Iterator<Entry<String, Collection<String>>> companyIterator = companyMap.entrySet().iterator();  

            while (companyIterator.hasNext()) {
                Entry<String, Collection<String>> companyEntry = companyIterator.next();  

                String id = companyEntry.getKey();
                System.out.println("============== Employee ID " + id + " Start ==============");  

                Collection<String> employeeCollection = companyEntry.getValue();
                Iterator<String> employeeIterator = employeeCollection.iterator();  

                while (employeeIterator.hasNext()) {
                    String leafNodeAndValue = employeeIterator.next();
                    System.out.println(leafNodeAndValue);
                }  

                System.out.println("============== Employee ID " + id + " End ==============");
            }
        }  

        public static void main(String[] args) {
            String inputFilePath = SaxDemo.class.getResource("/file/input/company.xml").getPath();
            File inputFile = new File(inputFilePath);  

            SaxHandler saxHandler = new SaxHandler(inputFile);  

            Map<String, Collection<String>> companyMap = saxHandler.getCompanyMap();  

            SaxDemo.displayCompany(companyMap);
        }
    }  

    <?xml version = "1.0" encoding="UTF-8"?>  

    <Company>
        <Employee ID="37">
            <Name>
                <FirstName>Zhou</FirstName>
                <LastName>Shengshuai</LastName>
            </Name>  

            <Sex>Male</Sex>  

            <Address>
                <Country>China</Country>
                <Province>ShanDong</Province>
                <City>LinYi</City>
                <Village>FengHuangYu</Village>  

                <Contact>
                    <Mobile>18108***778</Mobile>
                    <Mail>zhoushengshuai2007@163.com</Mail>
                    <QQ>254392398</QQ>
                    <Postcode>276422</Postcode>
                </Contact>
            </Address>  

            <Profession>Software</Profession>
        </Employee>  

        <Employee ID="66">
            <Name>
                <FirstName>Wang</FirstName>
                <LastName>Eric</LastName>
            </Name>  

            <Sex>Male</Sex>  

            <Address>
                <Country>China</Country>
                <Province>HeBei</Province>
                <City>QinHuangDao</City>
                <Village>hhh</Village>  

                <Contact>
                    <Mobile>150*****955</Mobile>
                    <Mail>eric@163.com</Mail>
                    <QQ>666666666</QQ>
                    <Postcode>111666</Postcode>
                </Contact>
            </Address>  

            <Profession>Software</Profession>
        </Employee>  

        <Employee ID="99">
            <Name>
                <FirstName>Shi</FirstName>
                <LastName>Stone</LastName>
            </Name>  

            <Sex>Male</Sex>  

            <Address>
                <Country>China</Country>
                <Province>HeNan</Province>
                <City>PingDingShan</City>
                <Village>nnn</Village>  

                <Contact>
                    <Mobile>186*****015</Mobile>
                    <Mail>stone@163.com</Mail>
                    <QQ>999999999</QQ>
                    <Postcode>111999</Postcode>
                </Contact>
            </Address>  

            <Profession>Software</Profession>
        </Employee>
    </Company>