使用SAX解析器，如何解析具有相同名称标签但在不同元素中的xml文件？

是否可以在SAX解析器中提供路径表达式？ 我有一个XML文件，它有几个相同的名称标签，但它们在不同的元素中。 有没有办法区分它们。 这是XML：

  335823 Fairfax High School  4195653 Will Turner   4195654 Bruce Paltrow   4195655 Santosh Gowswami    335824 FallsChurch High School  4153 John Singer   4154 Shane Warne   4155 Eddie Diaz    

我想根据学校的名称和ID来区分学生的姓名和身份certificate。

谢谢你的回复：

我创建了一个学生pojo，其中包含以下字段：school_id，school_name，student_id和student_name以及getter和setter方法。 这是我的临时解析器实现。 当我解析xml时，我需要将学校名称，id，学生姓名，id的值放在pojo中并返回它。 你能告诉我如何实现堆栈以区分。 这是我的解析器框架::

 import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; public class HandleXML extends DefaultHandler { private student info; private boolean school_id = false; private boolean school_name = false; private boolean student_id = false; private boolean student_name = false; private boolean student = false; private boolean school = false; public HandleXML(student record) { super(); this.info = record; school_id = false; school_name = false; student_id = false; student_name = false; student = false; school = false; } @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { if (qName.equalsIgnoreCase("student")) { student = true; } if (qName.equalsIgnoreCase("school")) { school_id = true; } if (qName.equalsIgnoreCase("school_id")) { school_id = true; } if (qName.equalsIgnoreCase("student_id")) { student_id = true; } if (qName.equalsIgnoreCase("school_name")) { school_name = true; } if (qName.equalsIgnoreCase("student_name")) { student_name = true; } } @Override public void endElement(String uri, String localName, String qName) throws SAXException { } @Override public void characters(char ch[], int start, int length) throws SAXException { String data = new String(ch, start, length); } } 

Answer 1

好吧，我在Java中没有使用过多年的SAX，所以这是我对它的看法：

 package play.xml.sax; import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.Stack; public class Test1 { public static void main(String[] args) { SAXParserFactory spf = SAXParserFactory.newInstance(); SchoolsHandler handler = new SchoolsHandler(); try { SAXParser sp = spf.newSAXParser(); sp.parse("schools.xml", handler); System.out.println("Number of read schools: " + handler.getSchools().size()); } catch (SAXException se) { se.printStackTrace(); } catch (ParserConfigurationException pce) { pce.printStackTrace(); } catch (IOException ie) { ie.printStackTrace(); } } } class SchoolsHandler extends DefaultHandler { private static final String TAG_SCHOOLS = "Schools"; private static final String TAG_SCHOOL = "School"; private static final String TAG_STUDENT = "Student"; private static final String TAG_ID = "ID"; private static final String TAG_NAME = "Name"; private final Stack tagsStack = new Stack(); private final StringBuilder tempVal = new StringBuilder(); private List schools; private School school; private Student student; public void startElement(String uri, String localName, String qName, Attributes attributes) { pushTag(qName); tempVal.setLength(0); if (TAG_SCHOOLS.equalsIgnoreCase(qName)) { schools = new ArrayList(); } else if (TAG_SCHOOL.equalsIgnoreCase(qName)) { school = new School(); } else if (TAG_STUDENT.equalsIgnoreCase(qName)) { student = new Student(); } } public void characters(char ch[], int start, int length) { tempVal.append(ch, start, length); } public void endElement(String uri, String localName, String qName) { String tag = peekTag(); if (!qName.equals(tag)) { throw new InternalError(); } popTag(); String parentTag = peekTag(); if (TAG_ID.equalsIgnoreCase(tag)) { int id = Integer.valueOf(tempVal.toString().trim()); if (TAG_STUDENT.equalsIgnoreCase(parentTag)) { student.setId(id); } else if (TAG_SCHOOL.equalsIgnoreCase(parentTag)) { school.setId(id); } } else if (TAG_NAME.equalsIgnoreCase(tag)) { String name = tempVal.toString().trim(); if (TAG_STUDENT.equalsIgnoreCase(parentTag)) { student.setName(name); } else if (TAG_SCHOOL.equalsIgnoreCase(parentTag)) { school.setName(name); } } else if (TAG_STUDENT.equalsIgnoreCase(tag)) { school.addStudent(student); } else if (TAG_SCHOOL.equalsIgnoreCase(tag)) { schools.add(school); } } public void startDocument() { pushTag(""); } public List getSchools() { return schools; } private void pushTag(String tag) { tagsStack.push(tag); } private String popTag() { return tagsStack.pop(); } private String peekTag() { return tagsStack.peek(); } } class School { private int id; private String name; private List students = new ArrayList(); public String getName() { return name; } public void setName(String name) { this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } public void addStudent(Student student) { students.add(student); } public List getStudents() { return students; } } class Student { private int id; private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } } 

schools.xml包含您的示例XML。 请注意，我把所有内容都塞进了一个文件中，但这只是因为我只是在玩耍。

Answer 2

在SAX解析器中，按文档顺序给出每个元素。 您必须维护堆栈以跟踪嵌套（在处理startElement时推入堆栈，并为endElement弹出）。 您可以通过堆栈中当前的内容区分不同的元素。

或者，只需保留一个变量，告诉您是否遇到标记或标记，以告诉您所看到的类型。

Answer 3

是的，使用SAX解析器理解xml通常比使用DOM更复杂。 基本上，您需要在SAX解析器中维护状态/上下文，以便区分这些情况。

请注意，实现SAX处理程序的另一个关键是理解可以跨多个字符事件拆分值。

Answer 4

Sax是基于事件的，通过回调，您可以连续读取XML文档。 Sax非常适合读取大型XML文档，因为整个文档没有加载到内存中。 你可能想看看Xpath ，例如

 XPathFactory xPathFactory = XPathFactory.newInstance(); XPath xPath = xPathFactory.newXPath(); String expression = "/Schools/school/ ..."; XPathExpression xPathExpression = xPath.compile(expression); // Compile the expression to get a XPathExpression object. Object result = xPathExpression.evaluate(xmlDocument); 

Answer 5

 private boolean isInStudentNode; ................................................... public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { // enter node Student if(qName.equalEgnoreCase("Student"){ isInStudentNode = true; } ... } public void endElement(String uri, String localName, String qName) throws SAXException { // end node Student if(qName.equalEgnoreCase("Student"){ isInStudentNode = false; ........... } // end node Name (school|student) if(qName.equalEgnoreCase("Name"){ if(isInStudentNode) student.setName(...); else school.setName(...); } } 

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