java解析XML的方式有使用DOM解析通過DOM對(duì)象以樹狀結(jié)構(gòu)連接在一起;使用SAX 解析它是遇到不同元素時(shí)會(huì)逐行解析;使用StAX解析會(huì)從XML中提取所需的數(shù)據(jù)
XML是一種通用的數(shù)據(jù)交換格式,它的平臺(tái)無關(guān)性、語言無關(guān)性、系統(tǒng)無關(guān)性、給數(shù)據(jù)集成與交互帶來了極大的方便。接下來將要在文章中為大家具體介紹在Java中解析XML的方式,具有一定的參考作用,希望對(duì)大家有所幫助
【推薦課程:XML教程】
立即學(xué)習(xí)“Java免費(fèi)學(xué)習(xí)筆記(深入)”;
使用DOM解析
DOM解析器主要用于在內(nèi)存中使用XML作為對(duì)象圖(樹狀結(jié)構(gòu)) 也就是文檔對(duì)象模型(DOM)。首先解析器遍歷輸入XML文件并創(chuàng)建與XML文件中的節(jié)點(diǎn)相對(duì)應(yīng)的DOM對(duì)象。這些DOM對(duì)象以樹狀結(jié)構(gòu)鏈接在一起。一旦解析器完成了解析過程,就會(huì)從中獲得這個(gè)類似樹的DOM對(duì)象結(jié)構(gòu)。
例:在所有代碼示例中解析xml內(nèi)容
public class DOMParserDemo { public static void main(String[] args) throws Exception { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); Document document = builder.parse( ClassLoader.getSystemResourceAsStream("xml/employee.xml")); List<Employee> empList = new ArrayList<>(); NodeList nodeList = document.getDocumentElement().getChildNodes(); for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (node instanceof Element) { Employee emp = new Employee(); emp.id = node.getAttributes(). getNamedItem("id").getNodeValue(); NodeList childNodes = node.getChildNodes(); for (int j = 0; j < childNodes.getLength(); j++) { Node cNode = childNodes.item(j); if (cNode instanceof Element) { String content = cNode.getLastChild(). getTextContent().trim(); switch (cNode.getNodeName()) { case "firstName": emp.firstName = content; break; case "lastName": emp.lastName = content; break; case "location": emp.location = content; break; } } } empList.add(emp); } } for (Employee emp : empList) { System.out.println(emp); } } } class Employee{ String id; String firstName; String lastName; String location; @Override public String toString() { return firstName+" "+lastName+"("+id+")"+location; } }
輸出結(jié)果為:
Rakesh Mishra(111)Bangalore John Davis(112)Chennai Rajesh Sharma(113)Pune
使用SAX 解析
SAX Parser與DOM解析器的不同之處在于SAX解析器不會(huì)將完整的XML加載到內(nèi)存中,而是在遇到不同的元素時(shí),它逐行解析XML,c觸發(fā)不同的事件,例如:打開標(biāo)記,結(jié)束標(biāo)記,字符數(shù)據(jù),評(píng)論等。
使用SAX Parser解析XML的代碼如下:
import java.util.ArrayList; import java.util.List; 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 SAXParserDemo { public static void main(String[] args) throws Exception { SAXParserFactory parserFactor = SAXParserFactory.newInstance(); SAXParser parser = parserFactor.newSAXParser(); SAXHandler handler = new SAXHandler(); parser.parse(ClassLoader.getSystemResourceAsStream("xml/employee.xml"), handler); for ( Employee emp : handler.empList){ System.out.println(emp); } } } class SAXHandler extends DefaultHandler { List<Employee> empList = new ArrayList<>(); Employee emp = null; String content = null; @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { switch(qName){ case "employee": emp = new Employee(); emp.id = attributes.getValue("id"); break; } } @Override public void endElement(String uri, String localName, String qName) throws SAXException { switch(qName){ case "employee": empList.add(emp); break; case "firstName": emp.firstName = content; break; case "lastName": emp.lastName = content; break; case "location": emp.location = content; break; } } @Override public void characters(char[] ch, int start, int length) throws SAXException { content = String.copyValueOf(ch, start, length).trim(); } } class Employee { String id; String firstName; String lastName; String location; @Override public String toString() { return firstName + " " + lastName + "(" + id + ")" + location; } }
輸出結(jié)果為:
Rakesh Mishra(111)Bangalore John Davis(112)Chennai Rajesh Sharma(113)Pune
使用StAX Parser
StAX用于XML的Streaming API,而StAX Parser與SA的不同之處在于SAX Parser。StAX解析器也是一種與SAX解析器也是有所不同的
SAX Parser會(huì)推送數(shù)據(jù),但StAX解析器會(huì)從XML中提取所需的數(shù)據(jù)。StAX解析器將光標(biāo)維持在文檔中的當(dāng)前位置,允許提取光標(biāo)處可用的內(nèi)容,而SAX解析器在遇到某些數(shù)據(jù)時(shí)發(fā)出事件。
XMLInputFactory和XMLStreamReader是可用于加載XML文件的兩個(gè)類。當(dāng)我們使用XMLStreamReader讀取XML文件時(shí),事件以整數(shù)值的形式生成,然后將這些事件與XMLStreamConstants中的常量進(jìn)行比較。以下代碼顯示了如何使用StAX解析器解析XML:
import java.util.ArrayList; import java.util.List; import javax.xml.stream.XMLInputFactory; import javax.xml.stream.XMLStreamConstants; import javax.xml.stream.XMLStreamException; import javax.xml.stream.XMLStreamReader; public class StaxParserDemo { public static void main(String[] args) throws XMLStreamException { List<Employee> empList = null; Employee currEmp = null; String tagContent = null; XMLInputFactory factory = XMLInputFactory.newInstance(); XMLStreamReader reader = factory.createXMLStreamReader( ClassLoader.getSystemResourceAsStream("xml/employee.xml")); while(reader.hasNext()){ int event = reader.next(); switch(event){ case XMLStreamConstants.START_ELEMENT: if ("employee".equals(reader.getLocalName())){ currEmp = new Employee(); currEmp.id = reader.getAttributeValue(0); } if("employees".equals(reader.getLocalName())){ empList = new ArrayList<>(); } break; case XMLStreamConstants.CHARACTERS: tagContent = reader.getText().trim(); break; case XMLStreamConstants.END_ELEMENT: switch(reader.getLocalName()){ case "employee": empList.add(currEmp); break; case "firstName": currEmp.firstName = tagContent; break; case "lastName": currEmp.lastName = tagContent; break; case "location": currEmp.location = tagContent; break; } break; case XMLStreamConstants.START_DOCUMENT: empList = new ArrayList<>(); break; } } for ( Employee emp : empList){ System.out.println(emp); } } } class Employee{ String id; String firstName; String lastName; String location; @Override public String toString(){ return firstName+" "+lastName+"("+id+") "+location; } }
輸出結(jié)果為:
Rakesh Mishra(111) Bangalore John Davis(112) Chennai Rajesh Sharma(113) Pune
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