java 使用 SAX 解析器，您如何解析具有相同名称标签但具有不同元素的 xml 文件？
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using SAX parser, how do you parse an xml file which has same name tags but in different elements?
提问by Srinivas
Is it possible to give path expressions in SAX parser? I have an XML file which has a few same name tags, but they are in different element. Is there any way to differentiate between them. Here is the XML:
是否可以在 SAX 解析器中给出路径表达式？我有一个 XML 文件，它有几个相同的名称标签，但它们位于不同的元素中。有什么办法可以区分它们。这是 XML：
<Schools>
<School>
<ID>335823</ID>
<Name>Fairfax High School</Name>
<Student>
<ID>4195653</ID>
<Name>Will Turner</Name>
</Student>
<Student>
<ID>4195654</ID>
<Name>Bruce Paltrow</Name>
</Student>
<Student>
<ID>4195655</ID>
<Name>Santosh Gowswami</Name>
</Student>
</School>
<School>
<ID>335824</ID>
<Name>FallsChurch High School</Name>
<Student>
<ID>4153</ID>
<Name>John Singer</Name>
</Student>
<Student>
<ID>4154</ID>
<Name>Shane Warne</Name>
</Student>
<Student>
<ID>4155</ID>
<Name>Eddie Diaz</Name>
</Student>
</School>
</Schools>
I want to differentiate between the Name and Id of a student from the name and ID of a school.
我想将学生的姓名和身与学校的姓名和身区分开来。
Thanks for the response:
感谢您的回复：
I have created a student pojo which has the following fields- school_id,school_name, student_id and student_name and getter and setter methods for them. This is my temporary parser implementation. When i parse the xml, I need to put the values of school name, id , student name, id in the pojo and return it. Can you tell me on how I should implement the stack for the differentiation. This is my parser framework::
我创建了一个学生 pojo，它具有以下字段 - school_id、school_name、student_id 和 student_name 以及它们的 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、学生名称、id 的值放入 pojo 并返回它。你能告诉我我应该如何实现差异化的堆栈。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);
}
}
回答by Jim Garrison
In a SAX parser you are given each element in document order. You have to maintain a stack to track nesting (push onto the stack when handling startElement, and pop for endElement). You can differentiate the different <Name>elements by what is currently on the stack.
在 SAX 解析器中，您会按文档顺序获得每个元素。您必须维护一个堆栈来跟踪嵌套（处理 startElement 时压入堆栈，并为 endElement 弹出）。您可以<Name>通过当前堆栈中的内容来区分不同的元素。
Alternatively, just keep a variable that tells you if you've encountered a <School>tag or <Student>tag to tell you which type of <Name>you are seeing.
或者，只需保留一个变量，告诉您是否遇到了<School>标签或<Student>标签，以告诉您<Name>看到的是哪种类型。
回答by Marius Burz
Well, I haven't played in years with SAX in Java, so here's my take on it:
好吧，我已经好几年没有在 Java 中使用 SAX，所以这是我的看法：
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<String> tagsStack = new Stack<String>();
private final StringBuilder tempVal = new StringBuilder();
private List<School> 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<School>();
} 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<School> 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<Student> students = new ArrayList<Student>();
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<Student> 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.xmlcontains your example XML. Please note that I crammed everything in a single file, but this is only for I was just playing around.
schools.xml包含您的示例 XML。请注意，我把所有东西都塞进了一个文件中，但这只是因为我只是在玩。
回答by jtahlborn
Yes, understanding xml using a SAX parser is generally a bit more complicated than working with DOM. basically, you need to maintain state/context in your SAX parser so that you can differentiate between those situations.
是的，使用 SAX 解析器理解 xml 通常比使用 DOM 复杂一些。基本上，您需要在 SAX 解析器中维护状态/上下文，以便您可以区分这些情况。
note, the other key to implementing a SAX handler is understanding that values may be split across multiplecharacter events.
请注意，实现 SAX 处理程序的另一个关键是理解值可以跨多个字符事件拆分。
回答by eon
Sax is event based, via callbacks you can read the XML document serially. Sax is good for reading large XML documents as the whole document is not loaded into memory. You might want to look at Xpath, e.g.
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，因为整个文档不会加载到内存中。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);
回答by vuhung3990
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(...);
}
}
its work with me
它和我一起工作
