JAVA原生API读取XML大文件的DOM方式和SAX方式比较
一直都在使用dom的方式读取xml文件，但如果稍大点的xml文件那么dom方式就有点不太适合。
研究了下jdk的api，用dom和sax方式的解析结果做了个对比
要解析的xml内容格式如下
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xml文件大小16.5M
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首先是dom方式读取，代码如下
package test.xml;import java.io.FileInputStream;import java.io.InputStream;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Set;import javax.xml.parsers.SAXParser;import javax.xml.parsers.SAXParserFactory;import org.apache.commons.lang.StringUtils;import org.xml.sax.Attributes;import org.xml.sax.SAXException;import org.xml.sax.helpers.DefaultHandler;public class JDKBigXmlSaxParse extends DefaultHandler {private int statmentSize = 6;private List<Map<String, Object>> dataList = new ArrayList<Map<String, Object>>(statmentSize);private Map<String, Object> dataMap;private String currentTag = "";public void test() throws Exception {SAXParser sax = SAXParserFactory.newInstance().newSAXParser();InputStream in = new FileInputStream("f:\\test.xml");sax.parse(in, this);in.close();}@Overridepublic void characters(char[] ch, int start, int length)throws SAXException {String value = new String(ch, start, length);if(!StringUtils.isBlank(value)){dataMap.put(currentTag, value.trim());}}@Overridepublic void endElement(String uri, String localName, String qName)throws SAXException {if("url".equals(qName)){dataList.add(dataMap);//dataMap.clear();}if(dataList.size() == statmentSize){doSomeThing();dataList.clear();}if("urlset".equals(qName) && dataList.size() != 0){doSomeThing();dataList.clear();}}@Overridepublic void startElement(String uri, String localName, String qName,Attributes attributes) throws SAXException {if ("url".equals(qName)) {dataMap = new HashMap<String, Object>();return;}currentTag = qName;}public static void main(String[] args) throws Exception {long start = System.nanoTime();new JDKBigXmlSaxParse().test();long end = System.nanoTime();System.out.println("耗时:"+(end-start)/1000000000.0+"秒");}public void doSomeThing(){//printMapList(dataList);}private void printMapList(List<Map<String,Object>> dataList){boolean first = true;for(Map<String,Object> map:dataList){System.out.println();System.out.print("{");Set<Map.Entry<String, Object>> entries = map.entrySet();for(Map.Entry<String, Object> entry:entries){if(!first){System.out.print(",");}System.out.print("""+entry.getKey()+"":");System.out.print("""+entry.getValue()+""");first = false;}first = true;System.out.print("}");}System.out.println();}}?运行结果：
耗时:0.639864769秒
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可以看到dom消耗的时间是sax方式的5倍。结论：如果只是读取xml文件，还是sax方式强。。。
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而且在eclipse里面用dom方式运行的时候可能会出现eclipse java.lang.OutOfMemoryError: Java heap space这个问题
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