Xerces 简明教程
Apache Xerces - XML Overview
What is XML?
XML 是一种简单的基于文本的语言,旨在以纯文本格式存储和传输数据。它代表可扩展标记语言。以下是 XML 的一些显著功能。
-
XML 是一种标记语言。
-
XML 是一种基于标记的语言,如 HTML。
-
XML 标记不是预定义的,如 HTML。
-
您可定义自己的标记,这就是为什么它被称为可扩展语言。
-
XML 标记旨在自我描述。
-
XML 是 W3C 对数据存储和传输的建议。
Example
<?xml version = "1.0"?>
<Class>
<Name>First</Name>
<Sections>
<Section>
<Name>A</Name>
<Students>
<Student>Rohan</Student>
<Student>Mohan</Student>
<Student>Sohan</Student>
<Student>Lalit</Student>
<Student>Vinay</Student>
</Students>
</Section>
<Section>
<Name>B</Name>
<Students>
<Student>Robert</Student>
<Student>Julie</Student>
<Student>Kalie</Student>
<Student>Michael</Student>
</Students>
</Section>
</Sections>
</Class>
Apache Xerces - Environment Setup
本教程将带你完成在 Windows 和基于 Linux 的系统中设置 Apache Xerces 的过程。按照几个简单的步骤,在没有复杂设置程序的情况下,可以轻松安装 Apache Xerces 并将其集成到你的当前 Java 环境中。安装过程中需要用户管理。
System Requirements
JDK |
Java SE 2 JDK 1.5 或更高版本 |
Memory |
1 GB RAM (recommended) |
Disk Space |
No minimum requirement |
Operating System Version |
Windows XP 或更高版本、Linux |
现在,让我们继续进行安装 Apache Xerces 的步骤。
Step 1: Verify your Java Installation
首先,你所使用的系统需要安装 Java 软件开发套件 (SDK)。要验证这一点,请根据你所使用的平台执行两个命令中的任何一个。
如果 Java 安装成功,那么它将显示你的 Java 安装的当前版本和规范。一个示例输出在以下表格中给出。
Platform |
Command |
Sample Output |
Windows |
打开命令控制台并输入− java -version |
Java 版本“1.7.0_60” Java™ SE 运行时环境(构建 1.7.0_60-b19)Java Hotspot™ 64 位服务器虚拟机(构建 24.60b09,混合模式) |
Linux |
打开命令终端并输入 − $java -version |
Java 版本“1.7.0_25”Open JDK 运行时环境(rhel-2.3.10.4.el6_4-x86_64)Open JDK 64 位服务器虚拟机(构建 23.7-b01,混合模式) |
-
我们假设本教程的读者已在他们的系统上安装了 Java SDK 版本 1.7.0_60。
-
如果您没有 Java SDK,请从 www.oracle.com/technetwork/java/javase/downloads/index.html 下载其当前版本并将其安装。
Step 2: Set your Java Environment
设置环境变量 JAVA_HOME 以指向计算机上安装 Java 的基本目录位置。例如,
Sr.No. |
Platform & Description |
1 |
Windows Set JAVA_HOME to C:\ProgramFiles\java\jdk1.7.0_60 |
2 |
Linux Export JAVA_HOME = /usr/local/java-current |
将 Java 编译器位置的完整路径附加到系统路径。
Sr.No. |
Platform & Description |
1 |
Windows 将字符串“C:\Program Files\Java\jdk1.7.0_60\bin”附加到系统变量 PATH 的末尾。 |
2 |
Linux Export PATH = $PATH:$JAVA_HOME/bin/ |
如上所示从命令提示符处执行命令 java version。
Step 3: Install Apache Xerces Library
从 https://xerces.apache.org/mirrors.cgi" 下载 Apache Xerces 的最新版本,并将其内容解压到一个文件夹中,以便从该文件夹链接必需的库到你的 Java 程序中。假设这些文件已经收集到 C 驱动器上的一个文件夹 xerces-2_12_1 中。
将上图中突出显示的五个 jar 的完整路径添加到 CLASSPATH。
Sr.No. |
Platform & Description |
1 |
Windows 在用户变量 CLASSPATH 后追加以下字符串 −C:\xerces-2_12_1\resolver.jar;C:\xerces-2_12_1\serializer.jar;C:\xerces-2_12_1\xercesImpl.jar;C:\xerces-2_12_1\xercesSamples.jar;C:\xerces-2_12_1\xml-apis.jar; |
2 |
Linux 导出 CLASSPATH = $CLASSPATH −/usr/share/xerces-2_12_1\resolver.jar;/usr/share/xerces-2_12_1\serializer.jar;/usr/share/xerces-2_12_1\xercesImpl.jar;/usr/share/xerces-2_12_1\xercesSamples.jar;/usr/share/xerces-2_12_1\xml-apis.jar; |
Apache Xerces - XML Parsers
Apache Xerces - DOM Parser Overview
DOM Parser - Parse XML Document
Steps to Use DOM
以下是使用 DOM 解析器解析文档时使用的步骤。
-
Import XML-related packages.
-
Create a DocumentBuilder
-
从文件或流创建一个文档
-
Extract the root element
-
Examine attributes
-
Examine sub-elements
Create a DocumentBuilder
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Create a Document from a file or stream
StringBuilder xmlStringBuilder = new StringBuilder();
xmlStringBuilder.append("<?xml version = "1.0"?> <class> </class>");
ByteArrayInputStream input = new ByteArrayInputStream(
xmlStringBuilder.toString().getBytes("UTF-8"));
Document doc = builder.parse(input);
Examine attributes
//returns specific attribute
getAttribute("attributeName");
//returns a Map (table) of names/values
getAttributes();
Examine sub-elements
//returns a list of subelements of specified name
getElementsByTagName("subelementName");
//returns a list of all child nodes
getChildNodes();
Demo Example
下面是需要解析的输入 xml 文件 −
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Demo Example
DomParserDemo.java
package com.tutorialspoint.xml;
import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
public class DomParserDemo {
public static void main(String[] args){
try {
File inputFile = new File("input.txt");
DocumentBuilderFactory dbFactory
= DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(inputFile);
doc.getDocumentElement().normalize();
System.out.println("Root element :"
+ doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("student");
System.out.println("----------------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
System.out.println("\nCurrent Element :"
+ nNode.getNodeName());
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Student roll no : "
+ eElement.getAttribute("rollno"));
System.out.println("First Name : "
+ eElement
.getElementsByTagName("firstname")
.item(0)
.getTextContent());
System.out.println("Last Name : "
+ eElement
.getElementsByTagName("lastname")
.item(0)
.getTextContent());
System.out.println("Nick Name : "
+ eElement
.getElementsByTagName("nickname")
.item(0)
.getTextContent());
System.out.println("Marks : "
+ eElement
.getElementsByTagName("marks")
.item(0)
.getTextContent());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
Root element :class
----------------------------
Current Element :student
Student roll no : 393
First Name : Dinkar
Last Name : Kad
Nick Name : Dinkar
Marks : 85
Current Element :student
Student roll no : 493
First Name : Vineet
Last Name : Gupta
Nick Name : Vinni
Marks : 95
Current Element :student
Student roll no : 593
First Name : Jasvir
Last Name : Singh
Nick Name : Jazz
Marks : 90
DOM Parser - Query XML Document
Demo Example
以下是我们必须查询的输入 xml 文件:
<?xml version = "1.0"?>
<cars>
<supercars company = "Ferrari">
<carname type = "formula one">Ferarri 101</carname>
<carname type = "sports car">Ferarri 201</carname>
<carname type = "sports car">Ferarri 301</carname>
</supercars>
<supercars company = "Lamborgini">
<carname>Lamborgini 001</carname>
<carname>Lamborgini 002</carname>
<carname>Lamborgini 003</carname>
</supercars>
<luxurycars company = "Benteley">
<carname>Benteley 1</carname>
<carname>Benteley 2</carname>
<carname>Benteley 3</carname>
</luxurycars>
</cars>
Demo Example
QueryXmlFileDemo.java
package com.tutorialspoint.xml;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;
public class QueryXmlFileDemo {
public static void main(String argv[]) {
try {
File inputFile = new File("input.txt");
DocumentBuilderFactory dbFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(inputFile);
doc.getDocumentElement().normalize();
System.out.print("Root element: ");
System.out.println(doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("supercars");
System.out.println("----------------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
System.out.println("\nCurrent Element :");
System.out.print(nNode.getNodeName());
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.print("company : ");
System.out.println(eElement.getAttribute("company"));
NodeList carNameList =
eElement.getElementsByTagName("carname");
for (int count = 0;
count < carNameList.getLength(); count++) {
Node node1 = carNameList.item(count);
if (node1.getNodeType() ==
node1.ELEMENT_NODE) {
Element car = (Element) node1;
System.out.print("car name : ");
System.out.println(car.getTextContent());
System.out.print("car type : ");
System.out.println(car.getAttribute("type"));
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
Root element :cars
----------------------------
Current Element :supercars
company : Ferrari
car name : Ferarri 101
car type : formula one
car name : Ferarri 201
car type : sports car
car name : Ferarri 301
car type : sports car
Current Element :supercars
company : Lamborgini
car name : Lamborgini 001
car type :
car name : Lamborgini 002
car type :
car name : Lamborgini 003
car type :
DOM Parser - Create XML Document
Demo Example
以下是我们需要创建的 XML -
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?>
<cars><supercars company = "Ferrari">
<carname type = "formula one">Ferrari 101</carname>
<carname type = "sports">Ferrari 202</carname>
</supercars></cars>
Demo Example
CreateXmlFileDemo.java
package com.tutorialspoint.xml;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import java.io.File;
public class CreateXmlFileDemo {
public static void main(String argv[]) {
try {
DocumentBuilderFactory dbFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder =
dbFactory.newDocumentBuilder();
Document doc = dBuilder.newDocument();
// root element
Element rootElement = doc.createElement("cars");
doc.appendChild(rootElement);
// supercars element
Element supercar = doc.createElement("supercars");
rootElement.appendChild(supercar);
// setting attribute to element
Attr attr = doc.createAttribute("company");
attr.setValue("Ferrari");
supercar.setAttributeNode(attr);
// carname element
Element carname = doc.createElement("carname");
Attr attrType = doc.createAttribute("type");
attrType.setValue("formula one");
carname.setAttributeNode(attrType);
carname.appendChild(
doc.createTextNode("Ferrari 101"));
supercar.appendChild(carname);
Element carname1 = doc.createElement("carname");
Attr attrType1 = doc.createAttribute("type");
attrType1.setValue("sports");
carname1.setAttributeNode(attrType1);
carname1.appendChild(
doc.createTextNode("Ferrari 202"));
supercar.appendChild(carname1);
// write the content into xml file
TransformerFactory transformerFactory =
TransformerFactory.newInstance();
Transformer transformer =
transformerFactory.newTransformer();
DOMSource source = new DOMSource(doc);
StreamResult result =
new StreamResult(new File("C:\\cars.xml"));
transformer.transform(source, result);
// Output to console for testing
StreamResult consoleResult =
new StreamResult(System.out);
transformer.transform(source, consoleResult);
} catch (Exception e) {
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?>
<cars><supercars company = "Ferrari">
<carname type = "formula one">Ferrari 101</carname>
<carname type = "sports">Ferrari 202</carname>
</supercars></cars>
DOM Parser - Modify XML Document
Demo Example
以下是我们需要修改的输入 XML 文件 -
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?>
<cars>
<supercars company = "Ferrari">
<carname type = "formula one">Ferrari 101</carname>
<carname type = "sports">Ferrari 202</carname>
</supercars>
<luxurycars company = "Benteley">
<carname>Benteley 1</carname>
<carname>Benteley 2</carname>
<carname>Benteley 3</carname>
</luxurycars>
</cars>
Demo Example
ModifyXmlFileDemo.java
package com.tutorialspoint.xml;
import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class ModifyXmlFileDemo {
public static void main(String argv[]) {
try {
File inputFile = new File("input.txt");
DocumentBuilderFactory docFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder =
docFactory.newDocumentBuilder();
Document doc = docBuilder.parse(inputFile);
Node cars = doc.getFirstChild();
Node supercar = doc.getElementsByTagName("supercars").item(0);
// update supercar attribute
NamedNodeMap attr = supercar.getAttributes();
Node nodeAttr = attr.getNamedItem("company");
nodeAttr.setTextContent("Lamborigini");
// loop the supercar child node
NodeList list = supercar.getChildNodes();
for (int temp = 0; temp < list.getLength(); temp++) {
Node node = list.item(temp);
if (node.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) node;
if ("carname".equals(eElement.getNodeName())){
if("Ferrari 101".equals(eElement.getTextContent())){
eElement.setTextContent("Lamborigini 001");
}
if("Ferrari 202".equals(eElement.getTextContent()))
eElement.setTextContent("Lamborigini 002");
}
}
}
NodeList childNodes = cars.getChildNodes();
for(int count = 0; count < childNodes.getLength(); count++){
Node node = childNodes.item(count);
if("luxurycars".equals(node.getNodeName()))
cars.removeChild(node);
}
// write the content on console
TransformerFactory transformerFactory =
TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
DOMSource source = new DOMSource(doc);
System.out.println("-----------Modified File-----------");
StreamResult consoleResult = new StreamResult(System.out);
transformer.transform(source, consoleResult);
} catch (Exception e) {
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
-----------Modified File-----------
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?>
<cars>
<supercars company = "Lamborigini">
<carname type = "formula one">Lamborigini 001</carname>
<carname type = "sports">Lamborigini 002</carname>
</supercars></cars>
SAX Parser - Overview
SAX(XML 简单 API)是基于事件的 XML 文档解析器。与 DOM 解析器不同,SAX 解析器不创建解析树。SAX 是一个 XML 流传输接口,这意味着使用 SAX 的应用程序会针对正在处理的 XML 文档接收事件通知,包括元素、属性以及从文档顶部开始、以 ROOT 元素的结束为结尾的顺序排列的时间。
-
从上到下读取 XML 文档,识别构成良好形成的 XML 文档的标记。
-
标记按其出现在文档中的顺序进行处理。
-
向应用程序报告解析器在遇到解析标记时发现的标记的类型。
-
应用程序提供了一个“事件”处理程序,该处理程序必须在解析器中注册。
-
随着标记被识别,带有相关信息的回调方法将被调用。
When to use?
以下情况应使用 SAX 解析器 -
-
你可以从上到下线性处理 XML 文档。
-
文档没有深度嵌套。
-
您正在处理一个非常大的 XML 文档,它对应的 DOM 树会占用大量的内存。典型的 DOM 实现使用 10 个字节的内存表示一个字节的 XML。
-
需要解决的问题仅涉及 XML 文档的一部分。
-
数据一旦被解析器看到就可用,因此 SAX 非常适用于通过流到达的 XML 文档。
ContentHandler Interface
此接口指定 SAX 解析器用于通知应用程序程序其看到的 XML 文档组件的回调方法。
-
void startDocument() − 在文档开头调用。
-
void endDocument() − 在文档开头调用。
-
void startElement(String uri, String localName, String qName, Attributes atts) − 在元素开头调用。
-
void endElement(String uri, String localName,String qName) − 在元素结尾调用。
-
void characters(char[] ch, int start, int length) − 在遇到字符数据时调用。
-
void ignorableWhitespace( char[] ch, int start, int length) − 在存在 DTD 且遇到可忽略空白时调用。
-
void processingInstruction(String target, String data) − 在识别出处理指令时调用。
-
void setDocumentLocator(Locator locator)) − 提供一个用于标识文档中位置的定位器。
-
void skippedEntity(String name) − 在遇到未解析的实体时调用。
-
void startPrefixMapping(String prefix, String uri) − 在定义新的命名空间映射时调用。
-
void endPrefixMapping(String prefix) − 在命名空间定义结束其作用域时调用。
SAX Parser - Parse XML Document
Demo Example
下面是需要解析的输入 xml 文件 −
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
UserHandler.java
package com.tutorialspoint.xml;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
String rollNo = attributes.getValue("rollno");
System.out.println("Roll No : " + rollNo);
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri,
String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[], int start, int length) throws SAXException {
if (bFirstName) {
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
SAXParserDemo.java
package com.tutorialspoint.xml;
import java.io.File;
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){
try {
File inputFile = new File("input.txt");
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
UserHandler userhandler = new UserHandler();
saxParser.parse(inputFile, userhandler);
} catch (Exception e) {
e.printStackTrace();
}
}
}
class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
String rollNo = attributes.getValue("rollno");
System.out.println("Roll No : " + rollNo);
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri,
String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[], int start, int length) throws SAXException {
if (bFirstName) {
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
以上程序将生成以下结果:
Roll No : 393
First Name: Dinkar
Last Name: Kad
Nick Name: Dinkar
Marks: 85
End Element :student
Roll No : 493
First Name: Vineet
Last Name: Gupta
Nick Name: Vinni
Marks: 95
End Element :student
Roll No : 593
First Name: Jasvir
Last Name: Singh
Nick Name: Jazz
Marks: 90
End Element :student
SAX Parser - Query XML Document
Demo Example
以下是我们要查询学号的输入文本文件:393 -
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
UserHandler.java
package com.tutorialspoint.xml;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
String rollNo = null;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
rollNo = attributes.getValue("rollno");
}
if(("393").equals(rollNo) && qName.equalsIgnoreCase("student")){
System.out.println("Start Element :" + qName);
}
if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
if(("393").equals(rollNo)
&& qName.equalsIgnoreCase("student"))
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[], int start, int length) throws SAXException {
if (bFirstName && ("393").equals(rollNo)) {
//age element, set Employee age
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName && ("393").equals(rollNo)) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName && ("393").equals(rollNo)) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks && ("393").equals(rollNo)) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
SAXQueryDemo.java
package com.tutorialspoint.xml;
import java.io.File;
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 SAXQueryDemo {
public static void main(String[] args){
try {
File inputFile = new File("input.txt");
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
UserHandler userhandler = new UserHandler();
saxParser.parse(inputFile, userhandler);
} catch (Exception e) {
e.printStackTrace();
}
}
}
class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
String rollNo = null;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
rollNo = attributes.getValue("rollno");
}
if(("393").equals(rollNo) &&
qName.equalsIgnoreCase("student")){
System.out.println("Start Element :" + qName);
}
if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri,
String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
if(("393").equals(rollNo)
&& qName.equalsIgnoreCase("student"))
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[], int start, int length) throws SAXException {
if (bFirstName && ("393").equals(rollNo)) {
//age element, set Employee age
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName && ("393").equals(rollNo)) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName && ("393").equals(rollNo)) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks && ("393").equals(rollNo)) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
以上程序将生成以下结果:
Start Element :student
First Name: Dinkar
Last Name: Kad
Nick Name: Dinkar
Marks: 85
End Element :student
SAX Parser - Modify XML Document
Demo Example
以下是我们必须在 </marks> tag 末尾附加 <Result>Pass<Result/> 以进行修改的输入 xml 文件。
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
SAXModifyDemo.java
package com.tutorialspoint.xml;
import java.io.*;
import org.xml.sax.*;
import javax.xml.parsers.*;
import org.xml.sax.helpers.DefaultHandler;
public class SAXModifyDemo extends DefaultHandler {
static String displayText[] = new String[1000];
static int numberLines = 0;
static String indentation = "";
public static void main(String args[]) {
try {
File inputFile = new File("input.txt");
SAXParserFactory factory =
SAXParserFactory.newInstance();
SAXModifyDemo obj = new SAXModifyDemo();
obj.childLoop(inputFile);
FileWriter filewriter = new FileWriter("newfile.xml");
for(int loopIndex = 0; loopIndex < numberLines; loopIndex++){
filewriter.write(displayText[loopIndex].toCharArray());
filewriter.write('\n');
System.out.println(displayText[loopIndex].toString());
}
filewriter.close();
} catch (Exception e) {
e.printStackTrace(System.err);
}
}
public void childLoop(File input){
DefaultHandler handler = this;
SAXParserFactory factory = SAXParserFactory.newInstance();
try {
SAXParser saxParser = factory.newSAXParser();
saxParser.parse(input, handler);
} catch (Throwable t) {}
}
public void startDocument() {
displayText[numberLines] = indentation;
displayText[numberLines] += "<?xml version=\"1.0\" encoding=\""+
"UTF-8" + "\"?>";
numberLines++;
}
public void processingInstruction(String target, String data) {
displayText[numberLines] = indentation;
displayText[numberLines] += "<?";
displayText[numberLines] += target;
if (data != null && data.length() > 0) {
displayText[numberLines] += ' ';
displayText[numberLines] += data;
}
displayText[numberLines] += "?>";
numberLines++;
}
public void startElement(String uri, String localName,
String qualifiedName, Attributes attributes) {
displayText[numberLines] = indentation;
indentation += " ";
displayText[numberLines] += '<';
displayText[numberLines] += qualifiedName;
if (attributes != null) {
int numberAttributes = attributes.getLength();
for (int loopIndex = 0; loopIndex < numberAttributes;
loopIndex++){
displayText[numberLines] += ' ';
displayText[numberLines] += attributes.getQName(loopIndex);
displayText[numberLines] += "=\"";
displayText[numberLines] += attributes.getValue(loopIndex);
displayText[numberLines] += '"';
}
}
displayText[numberLines] += '>';
numberLines++;
}
public void characters(char characters[], int start, int length) {
String characterData = (new String(characters, start, length)).trim();
if(characterData.indexOf("\n") < 0 && characterData.length() > 0) {
displayText[numberLines] = indentation;
displayText[numberLines] += characterData;
numberLines++;
}
}
public void endElement(String uri, String localName, String qualifiedName) {
indentation = indentation.substring(0, indentation.length() - 4);
displayText[numberLines] = indentation;
displayText[numberLines] += "</";
displayText[numberLines] += qualifiedName;
displayText[numberLines] += '>';
numberLines++;
if (qualifiedName.equals("marks")) {
startElement("", "Result", "Result", null);
characters("Pass".toCharArray(), 0, "Pass".length());
endElement("", "Result", "Result");
}
}
}
以上程序将生成以下结果:
<?xml version = "1.0" encoding = "UTF-8"?>
<class>
<student rollno = "393">
<firstname>
Dinkar
</firstname>
<lastname>
Kad
</lastname>
<nickname>
Dinkar
</nickname>
<marks>
85
</marks>
<Result>
Pass
</Result>
</student>
<student rollno = "493">
<firstname>
Vineet
</firstname>
<lastname>
Gupta
</lastname>
<nickname>
Vinni
</nickname>
<marks>
95
</marks>
<Result>
Pass
</Result>
</student>
<student rollno = "593">
<firstname>
Jasvir
</firstname>
<lastname>
Singh
</lastname>
<nickname>
Jazz
</nickname>
<marks>
90
</marks>
<Result>
Pass
</Result>
</student>
</class>
StAX Parser - Overview
StAX 是一个基于 JAVA 的 API,它以与 SAX 解析器类似的方式来解析 XML 文档。但这两个 API 之间有两个主要的差异点 −
-
StAX 是一种 PULL API,而 SAX 是一种 PUSH API。这意味着对于 StAX 解析器,客户端应用程序需要在需要时要求 StAX 解析器从 XML 中获取信息,而对于 SAX 解析器,当 SAX 解析器通知客户端应用程序信息可用时,则要求客户端应用程序获取信息。
-
StAX API 可以对 XML 文档进行读取和写入。使用 SAX API,只能读取 xml。
以下是 StAX API 的特性:
-
从上到下读取 XML 文档,识别构成良好形成的 XML 文档的标记。
-
标记按其出现在文档中的顺序进行处理。
-
向应用程序报告解析器遇到的令牌的性质,因为它们会发生。
-
应用程序提供一个充当迭代器的“事件”读取器,该读取器在事件上进行迭代以获取所需信息。另一个可用的读取器是充当指向 xml 节点的指针的“游标”读取器。
-
随着事件的标识,可以从事件对象中检索 xml 元素,并可以进一步处理。
When to use?
您应该在以下情况下使用 StAX 解析器:
-
你可以从上到下线性处理 XML 文档。
-
文档没有深度嵌套。
-
你正在处理一个非常大的 XML 文档,其 DOM 树会占用过多的内存。典型的 DOM 实现使用 10 个字节的内存来表示 1 字节的 XML。
-
需要解决的问题仅涉及 XML 文档的一部分。
-
解析器一看到数据便立即能用,因此 StAX 非常适用于流式传输的 XML 文档。
XMLEventReader Class
该类提供事件的迭代器,可用在解析 XML 文档时用于迭代遇到的事件
-
StartElement asStartElement() − 用于检索元素的值和属性。
-
EndElement asEndElement() − 在元素结尾处调用。
-
Characters asCharacters() − 可用于获取字符,如 CDATA、空白等。
StAX Parser - Parse XML Document
Demo Example
下面是需要解析的输入 xml 文件 −
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
StAXParserDemo.java
package com.tutorialspoint.xml;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Iterator;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
public class StAXParserDemo {
public static void main(String[] args) {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
try {
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLEventReader eventReader =
factory.createXMLEventReader(new FileReader("input.txt"));
while(eventReader.hasNext()){
XMLEvent event = eventReader.nextEvent();
switch(event.getEventType()){
case XMLStreamConstants.START_ELEMENT:
StartElement startElement = event.asStartElement();
String qName = startElement.getName().getLocalPart();
if (qName.equalsIgnoreCase("student")) {
System.out.println("Start Element : student");
Iterator<Attribute> attributes = startElement.getAttributes();
String rollNo = attributes.next().getValue();
System.out.println("Roll No : " + rollNo);
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
break;
case XMLStreamConstants.CHARACTERS:
Characters characters = event.asCharacters();
if(bFirstName){
System.out.println("First Name: " + characters.getData());
bFirstName = false;
}
if(bLastName){
System.out.println("Last Name: " + characters.getData());
bLastName = false;
}
if(bNickName){
System.out.println("Nick Name: " + characters.getData());
bNickName = false;
}
if(bMarks){
System.out.println("Marks: " + characters.getData());
bMarks = false;
}
break;
case XMLStreamConstants.END_ELEMENT:
EndElement endElement = event.asEndElement();
if(endElement.getName().getLocalPart().equalsIgnoreCase("student")){
System.out.println("End Element : student");
System.out.println();
}
break;
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
Start Element : student
Roll No : 393
First Name: Dinkar
Last Name: Kad
Nick Name: Dinkar
Marks: 85
End Element : student
Start Element : student
Roll No : 493
First Name: Vineet
Last Name: Gupta
Nick Name: Vinni
Marks: 95
End Element : student
Start Element : student
Roll No : 593
First Name: Jasvir
Last Name: Singh
Nick Name: Jazz
Marks: 90
End Element : student
StAX Parser - Query XML Document
Demo Example
下面是需要解析的输入 xml 文件 −
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
StAXParserDemo.java
package com.tutorialspoint.xml;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Iterator;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
public class StAXQueryDemo {
public static void main(String[] args) {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
boolean isRequestRollNo = false;
try {
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLEventReader eventReader = factory.createXMLEventReader(
new FileReader("input.txt"));
String requestedRollNo = "393";
while(eventReader.hasNext()){
XMLEvent event = eventReader.nextEvent();
switch(event.getEventType()){
case XMLStreamConstants.START_ELEMENT:
StartElement startElement = event.asStartElement();
String qName = startElement.getName().getLocalPart();
if (qName.equalsIgnoreCase("student")) {
Iterator<Attribute> attributes = startElement.getAttributes();
String rollNo = attributes.next().getValue();
if(rollNo.equalsIgnoreCase(requestedRollNo)){
System.out.println("Start Element : student");
System.out.println("Roll No : " + rollNo);
isRequestRollNo = true;
}
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
break;
case XMLStreamConstants.CHARACTERS:
Characters characters = event.asCharacters();
if(bFirstName && isRequestRollNo){
System.out.println("First Name: " + characters.getData());
bFirstName = false;
}
if(bLastName && isRequestRollNo){
System.out.println("Last Name: " + characters.getData());
bLastName = false;
}
if(bNickName && isRequestRollNo){
System.out.println("Nick Name: " + characters.getData());
bNickName = false;
}
if(bMarks && isRequestRollNo){
System.out.println("Marks: " + characters.getData());
bMarks = false;
}
break;
case XMLStreamConstants.END_ELEMENT:
EndElement endElement = event.asEndElement();
if(endElement.getName().getLocalPart().equalsIgnoreCase("student") && isRequestRollNo){
System.out.println("End Element : student");
System.out.println();
isRequestRollNo = false;
}
break;
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
Start Element : student
Roll No : 393
First Name: Dinkar
Last Name: Kad
Nick Name: Dinkar
Marks: 85
End Element : student
StAX Parser - Create XML Document
Demo Example
Here is the XML we need to create −
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?>
<cars><supercars company = "Ferrari">
<carname type = "formula one">Ferrari 101</carname>
<carname type = "sports">Ferrari 202</carname>
</supercars></cars>
Demo Example
StAXCreateXMLDemo.java
package com.tutorialspoint.xml;
import java.io.IOException;
import java.io.StringWriter;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;
public class StAXCreateXMLDemo {
public static void main(String[] args) {
try {
StringWriter stringWriter = new StringWriter();
XMLOutputFactory xMLOutputFactory = XMLOutputFactory.newInstance();
XMLStreamWriter xMLStreamWriter = xMLOutputFactory.createXMLStreamWriter(stringWriter);
xMLStreamWriter.writeStartDocument();
xMLStreamWriter.writeStartElement("cars");
xMLStreamWriter.writeStartElement("supercars");
xMLStreamWriter.writeAttribute("company", "Ferrari");
xMLStreamWriter.writeStartElement("carname");
xMLStreamWriter.writeAttribute("type", "formula one");
xMLStreamWriter.writeCharacters("Ferrari 101");
xMLStreamWriter.writeEndElement();
xMLStreamWriter.writeStartElement("carname");
xMLStreamWriter.writeAttribute("type", "sports");
xMLStreamWriter.writeCharacters("Ferrari 202");
xMLStreamWriter.writeEndElement();
xMLStreamWriter.writeEndElement();
xMLStreamWriter.writeEndDocument();
xMLStreamWriter.flush();
xMLStreamWriter.close();
String xmlString = stringWriter.getBuffer().toString();
stringWriter.close();
System.out.println(xmlString);
} catch (XMLStreamException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?>
<cars><supercars company = "Ferrari">
<carname type = "formula one">Ferrari 101</carname>
<carname type = "sports">Ferrari 202</carname>
</supercars></cars>
StAX Parser - Modify XML Document
Demo Example
为了运行此示例,您应该在应用程序的类路径中有 jdom.jar。下载 jdom-2.0.5.zip.
以下是我们要修改的 XML -
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Demo Example
StAXModifyDemo.java
package com.tutorialspoint.xml;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;
public class StAXModifyDemo {
public static void main(String[] args) {
try {
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLEventReader eventReader =
factory.createXMLEventReader(
new FileReader("input.txt"));
SAXBuilder saxBuilder = new SAXBuilder();
Document document = saxBuilder.build(new File("input.txt"));
Element rootElement = document.getRootElement();
List<Element> studentElements = rootElement.getChildren("student");
while(eventReader.hasNext()){
XMLEvent event = eventReader.nextEvent();
switch(event.getEventType()){
case XMLStreamConstants.START_ELEMENT:
StartElement startElement = event.asStartElement();
String qName = startElement.getName().getLocalPart();
if (qName.equalsIgnoreCase("student")) {
Iterator<Attribute> attributes = startElement.getAttributes();
String rollNo = attributes.next().getValue();
if(rollNo.equalsIgnoreCase("393")){
//get the student with roll no 393
for(int i=0;i < studentElements.size();i++){
Element studentElement = studentElements.get(i);
if(studentElement.getAttribute("rollno").getValue().equalsIgnoreCase("393")){
studentElement.removeChild("marks");
studentElement.addContent(new Element("marks").setText("80"));
}
}
}
}
break;
}
}
XMLOutputter xmlOutput = new XMLOutputter();
// display xml
xmlOutput.setFormat(Format.getPrettyFormat());
xmlOutput.output(document, System.out);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
} catch (JDOMException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
以上程序将生成以下结果:
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>80</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>