内容
1. XML
1. 概念
2. 语法
3. 解析
XML:
1. 概念:Extensible Markup Language 可扩展标记语言
* 可扩展:标签都是自定义的。 <user> <student>
* 功能
* 存储数据
1. 配置文件
2. 在网络中传输
* xml与html的区别
1. xml标签都是自定义的,html标签是预定义。
2. xml的语法严格,html语法松散
3. xml是存储数据的,html是展示数据
* w3c:万维网联盟
2. 语法:
* 基本语法:
1. xml文档的后缀名 .xml
2. xml第一行必须定义为文档声明
3. xml文档中有且仅有一个根标签
4. 属性值必须使用引号(单双都可)引起来
5. 标签必须正确关闭
6. xml标签名称区分大小写
* 快速入门:
<?xml version='1.0' ?>
< users>
< user id = ' 1' >
< name> zhangsan</ name>
< age> 23</ age>
< gender> male</ gender>
< br/>
</ user>
< user id = ' 2' >
< name> lisi</ name>
< age> 24</ age>
< gender> female</ gender>
</ user>
</ users>
* 组成部分:
1. 文档声明
1. 格式:<?xml 属性列表 ?>
2. 属性列表:
* version:版本号,必须的属性
* encoding:编码方式。告知解析引擎当前文档使用的字符集,默认值:ISO-8859-1
* standalone:是否独立
* 取值:
* yes:不依赖其他文件
* no:依赖其他文件
2. 指令(了解):结合css的
* <?xml-stylesheet type="text/css" href="a.css" ?>
3. 标签:标签名称自定义的
* 规则:
* 名称可以包含字母、数字以及其他的字符
* 名称不能以数字或者标点符号开始
* 名称不能以字母 xml(或者 XML、Xml 等等)开始
* 名称不能包含空格
4. 属性:
id属性值唯一
5. 文本:
* CDATA区:在该区域中的数据会被原样展示
* 格式: <![CDATA[ 数据 ]]>
<?xml version="1.0" encoding="utf-8" standalone='no' ?>
< users>
< user id = ' 1' >
< name> 张三</ name>
< age> 23</ age>
< gender> male</ gender>
< br/>
</ user>
< user id = ' 2' >
< name> lisi</ name>
< age> 24</ age>
< gender> female</ gender>
< code>
<![CDATA[
if(a < b && a > c) {}
]]>
</ code>
</ user>
</ users>
* 约束:规定xml文档的书写规则
* 作为框架的使用者(程序员):
1. 能够在xml中引入约束文档
2. 能够简单的读懂约束文档
* 分类:
1. DTD:一种简单的约束技术
2. Schema:一种复杂的约束技术
* DTD:
* 引入dtd文档到xml文档中
* 内部dtd:将约束规则定义在xml文档中
* 外部dtd:将约束的规则定义在外部的dtd文件中
* 本地:<!DOCTYPE 根标签名 SYSTEM "dtd文件的位置">
* 网络:<!DOCTYPE 根标签名 PUBLIC "dtd文件名字" "dtd文件的位置URL">
< !ELEMENT students (student+) >
< !ELEMENT student (name,age,sex) >
< !ELEMENT name (#PCDATA) >
< !ELEMENT age (#PCDATA) >
< !ELEMENT sex (#PCDATA) >
< !ATTLIST student number ID #REQUIRED >
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE students SYSTEM "student.dtd">
< students>
< student number = " s001" >
< name> zhangsan</ name>
< age> abc</ age>
< sex> hehe</ sex>
</ student>
< student number = " s002" >
< name> lisi</ name>
< age> 24</ age>
< sex> female</ sex>
</ student>
</ students>
* Schema:
* 引入:
1.填写xml文档的根元素
2.引入xsi前缀. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3.引入xsd文件命名空间. xsi:schemaLocation="http://www.itcast.cn/xml student.xsd"
4.为每一个xsd约束声明一个前缀,作为标识 xmlns="http://www.itcast.cn/xml"
<students xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.itcast.cn/xml"
xsi:schemaLocation="http://www.itcast.cn/xml student.xsd">
<?xml version="1.0"?>
< xsd: schema xmlns = " http://www.itcast.cn/xml"
xmlns: xsd= " http://www.w3.org/2001/XMLSchema"
targetNamespace = " http://www.itcast.cn/xml" elementFormDefault = " qualified" >
< xsd: element name = " students" type = " studentsType" />
< xsd: complexType name = " studentsType" >
< xsd: sequence>
< xsd: element name = " student" type = " studentType" minOccurs = " 0" maxOccurs = " unbounded" />
</ xsd: sequence>
</ xsd: complexType>
< xsd: complexType name = " studentType" >
< xsd: sequence>
< xsd: element name = " name" type = " xsd:string" />
< xsd: element name = " age" type = " ageType" />
< xsd: element name = " sex" type = " sexType" />
</ xsd: sequence>
< xsd: attribute name = " number" type = " numberType" use = " required" />
</ xsd: complexType>
< xsd: simpleType name = " sexType" >
< xsd: restriction base = " xsd:string" >
< xsd: enumeration value = " male" />
< xsd: enumeration value = " female" />
</ xsd: restriction>
</ xsd: simpleType>
< xsd: simpleType name = " ageType" >
< xsd: restriction base = " xsd:integer" >
< xsd: minInclusive value = " 0" />
< xsd: maxInclusive value = " 256" />
</ xsd: restriction>
</ xsd: simpleType>
< xsd: simpleType name = " numberType" >
< xsd: restriction base = " xsd:string" >
< xsd: pattern value = " heima_\d{4}" />
</ xsd: restriction>
</ xsd: simpleType>
</ xsd: schema>
<?xml version="1.0" encoding="UTF-8" ?>
< students xmlns: xsi= " http://www.w3.org/2001/XMLSchema-instance"
xmlns = " http://www.itcast.cn/xml"
xsi: schemaLocation= " http://www.itcast.cn/xml student.xsd"
>
< student number = " heima_0001" >
< name> tom</ name>
< age> 18</ age>
< sex> male</ sex>
</ student>
</ students>
3. 解析:操作xml文档,将文档中的数据读取到内存中
* 操作xml文档
1. 解析(读取):将文档中的数据读取到内存中
2. 写入:将内存中的数据保存到xml文档中。持久化的存储
* 解析xml的方式:
1. DOM:将标记语言文档一次性加载进内存,在内存中形成一颗dom树
* 优点:操作方便,可以对文档进行CRUD的所有操作
* 缺点:占内存
2. SAX:逐行读取,基于事件驱动的。
* 优点:不占内存。
* 缺点:只能读取,不能增删改
* xml常见的解析器:
1. JAXP:sun公司提供的解析器,支持dom和sax两种思想,不常用性能低
2. DOM4J:一款非常优秀的解析器
3. Jsoup:jsoup 是一款Java 的HTML解析器,可直接解析某个URL地址、HTML文本内容。它提供了一套非常省力的API,可通过DOM,CSS以及类似于jQuery的操作方法来取出和操作数据。
4. PULL:Android操作系统内置的解析器,sax方式的。
* Jsoup:jsoup 是一款Java 的HTML解析器,可直接解析某个URL地址、HTML文本内容。它提供了一套非常省力的API,可通过DOM,CSS以及类似于jQuery的操作方法来取出和操作数据。
* 快速入门:
* 步骤:
1. 导入jar包: jsoup-1.11.2.jar
2. 获取Document对象
3. 获取对应的标签Element对象
4. 获取数据
* 代码:
<?xml version="1.0" encoding="UTF-8" ?>
< students>
< student number = " heima_0001" >
< name id = " itcast" >
< xing> 张</ xing>
< ming> 三</ ming>
</ name>
< age> 18</ age>
< sex> male</ sex>
</ student>
< student number = " heima_0002" >
< name> jack</ name>
< age> 18</ age>
< sex> female</ sex>
</ student>
</ students>
import org. jsoup. Jsoup;
import org. jsoup. nodes. Document;
import org. jsoup. nodes. Element;
import org. jsoup. select. Elements;
import java. io. File;
import java. io. IOException;
public class JsoupDemo1 {
public static void main ( String[ ] args) throws IOException {
String path = JsoupDemo1. class . getClassLoader ( ) . getResource ( "student.xml" ) . getPath ( ) ;
Document document = Jsoup. parse ( new File ( path) , "utf-8" ) ;
Elements elements = document. getElementsByTag ( "name" ) ;
System. out. println ( elements. size ( ) ) ;
Element element = elements. get ( 0 ) ;
String name = element. text ( ) ;
System. out. println ( name) ;
}
}
* 对象的使用:
1. Jsoup:工具类,可以解析html或xml文档,返回Document
* parse:解析html或xml文档,返回Document
* parse(File in, String charsetName):解析xml或html文件的。
* parse(String html):解析xml或html字符串
* parse(URL url, int timeoutMillis):通过网络路径获取指定的html或xml的文档对象
import org. jsoup. Jsoup;
import org. jsoup. nodes. Document;
import org. jsoup. nodes. Element;
import org. jsoup. select. Elements;
import java. io. File;
import java. io. IOException;
import java. net. URL;
public class JsoupDemo2 {
public static void main ( String[ ] args) throws IOException {
String path = JsoupDemo2. class . getClassLoader ( ) . getResource ( "student.xml" ) . getPath ( ) ;
Document document = Jsoup. parse ( new File ( path) , "utf-8" ) ;
System. out. println ( document) ;
String str = "<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n" +
"\n" +
"<students>\n" +
"\t<student number=\"heima_0001\">\n" +
"\t\t<name>tom</name>\n" +
"\t\t<age>18</age>\n" +
"\t\t<sex>male</sex>\n" +
"\t</student>\n" +
"\t<student number=\"heima_0002\">\n" +
"\t\t<name>jack</name>\n" +
"\t\t<age>18</age>\n" +
"\t\t<sex>female</sex>\n" +
"\t</student>\n" +
"\n" +
"</students>" ;
Document document1 = Jsoup. parse ( str) ;
System. out. println ( document1) ;
URL url = new URL ( "https://baike.baidu.com/item/jsoup/9012509?fr=aladdin" ) ;
Document document2 = Jsoup. parse ( url, 10000 ) ;
System. out. println ( document2) ;
}
}
2. Document:文档对象。代表内存中的dom树
* 获取Element对象
* getElementById(String id):根据id属性值获取唯一的element对象
* getElementsByTag(String tagName):根据标签名称获取元素对象集合
* getElementsByAttribute(String key):根据属性名称获取元素对象集合
* getElementsByAttributeValue(String key, String value):根据对应的属性名和属性值获取元素对象集合
import org. jsoup. Jsoup;
import org. jsoup. nodes. Document;
import org. jsoup. nodes. Element;
import org. jsoup. select. Elements;
import java. io. File;
import java. io. IOException;
import java. net. URL;
public class JsoupDemo3 {
public static void main ( String[ ] args) throws IOException {
String path = JsoupDemo3. class . getClassLoader ( ) . getResource ( "student.xml" ) . getPath ( ) ;
Document document = Jsoup. parse ( new File ( path) , "utf-8" ) ;
Elements elements = document. getElementsByTag ( "student" ) ;
System. out. println ( elements) ;
System. out. println ( "-----------" ) ;
Elements elements1 = document. getElementsByAttribute ( "id" ) ;
System. out. println ( elements1) ;
System. out. println ( "-----------" ) ;
Elements elements2 = document. getElementsByAttributeValue ( "number" , "heima_0001" ) ;
System. out. println ( elements2) ;
System. out. println ( "-----------" ) ;
Element itcast = document. getElementById ( "itcast" ) ;
System. out. println ( itcast) ;
}
}
3. Elements:元素Element对象的集合。可以当做 ArrayList<Element>来使用
4. Element:元素对象
1. 获取子元素对象
* getElementById(String id):根据id属性值获取唯一的element对象
* getElementsByTag(String tagName):根据标签名称获取元素对象集合
* getElementsByAttribute(String key):根据属性名称获取元素对象集合
* getElementsByAttributeValue(String key, String value):根据对应的属性名和属性值获取元素对象集合
2. 获取属性值
* String attr(String key):根据属性名称获取属性值
3. 获取文本内容
* String text():获取文本内容
* String html():获取标签体的所有内容(包括子标签的字符串内容)
import org. jsoup. Jsoup;
import org. jsoup. nodes. Document;
import org. jsoup. nodes. Element;
import org. jsoup. select. Elements;
import java. io. File;
import java. io. IOException;
public class JsoupDemo4 {
public static void main ( String[ ] args) throws IOException {
String path = JsoupDemo4. class . getClassLoader ( ) . getResource ( "student.xml" ) . getPath ( ) ;
Document document = Jsoup. parse ( new File ( path) , "utf-8" ) ;
Elements elements = document. getElementsByTag ( "name" ) ;
System. out. println ( elements. size ( ) ) ;
System. out. println ( "----------------" ) ;
Element element_student = document. getElementsByTag ( "student" ) . get ( 0 ) ;
Elements ele_name = element_student. getElementsByTag ( "name" ) ;
System. out. println ( ele_name. size ( ) ) ;
String number = element_student. attr ( "NUMBER" ) ;
System. out. println ( number) ;
System. out. println ( "------------" ) ;
String text = ele_name. text ( ) ;
String html = ele_name. html ( ) ;
System. out. println ( text) ;
System. out. println ( html) ;
}
}
5. Node:节点对象
* 是Document和Element的父类
* 快捷查询方式:
1. selector:选择器
* 使用的方法:Elements select(String cssQuery)
* 语法:参考Selector类中定义的语法
import org. jsoup. Jsoup;
import org. jsoup. nodes. Document;
import org. jsoup. nodes. Element;
import org. jsoup. select. Elements;
import java. io. File;
import java. io. IOException;
public class JsoupDemo5 {
public static void main ( String[ ] args) throws IOException {
String path = JsoupDemo5. class . getClassLoader ( ) . getResource ( "student.xml" ) . getPath ( ) ;
Document document = Jsoup. parse ( new File ( path) , "utf-8" ) ;
Elements elements = document. select ( "name" ) ;
System. out. println ( elements) ;
System. out. println ( "=----------------" ) ;
Elements elements1 = document. select ( "#itcast" ) ;
System. out. println ( elements1) ;
System. out. println ( "----------------" ) ;
Elements elements2 = document. select ( "student[number='heima_0001']" ) ;
System. out. println ( elements2) ;
System. out. println ( "----------------" ) ;
Elements elements3 = document. select ( "student[number='heima_0001'] > age" ) ;
System. out. println ( elements3) ;
}
}
结果:
< name id= "itcast" >
< xing>
张
< / xing>
< ming>
三
< / ming>
< / name>
< name>
jack
< / name>
= -- -- -- -- -- -- -- --
< name id= "itcast" >
< xing>
张
< / xing>
< ming>
三
< / ming>
< / name>
-- -- -- -- -- -- -- --
< student number= "heima_0001" >
< name id= "itcast" >
< xing>
张
< / xing>
< ming>
三
< / ming>
< / name>
< age>
18
< / age>
< sex>
male
< / sex>
< / student>
-- -- -- -- -- -- -- --
< age>
18
< / age>
2. XPath:XPath即为XML路径语言,它是一种用来确定XML(标准通用标记语言的子集)文档中某部分位置的语言
* 使用Jsoup的Xpath需要额外导入jar包。 JsoupXpath-0.3.2.jar
* 查询w3cshool参考手册,使用xpath的语法完成查询
* 代码:
import cn. wanghaomiao. xpath. exception. XpathSyntaxErrorException;
import cn. wanghaomiao. xpath. model. JXDocument;
import cn. wanghaomiao. xpath. model. JXNode;
import org. jsoup. Jsoup;
import org. jsoup. nodes. Document;
import org. jsoup. select. Elements;
import java. io. File;
import java. io. IOException;
import java. util. List;
public class JsoupDemo6 {
public static void main ( String[ ] args) throws IOException, XpathSyntaxErrorException {
String path = JsoupDemo6. class . getClassLoader ( ) . getResource ( "student.xml" ) . getPath ( ) ;
Document document = Jsoup. parse ( new File ( path) , "utf-8" ) ;
JXDocument jxDocument = new JXDocument ( document) ;
List< JXNode> jxNodes = jxDocument. selN ( "//student" ) ;
for ( JXNode jxNode : jxNodes) {
System. out. println ( jxNode) ;
}
System. out. println ( "--------------------" ) ;
List< JXNode> jxNodes2 = jxDocument. selN ( "//student/name" ) ;
for ( JXNode jxNode : jxNodes2) {
System. out. println ( jxNode) ;
}
System. out. println ( "--------------------" ) ;
List< JXNode> jxNodes3 = jxDocument. selN ( "//student/name[@id]" ) ;
for ( JXNode jxNode : jxNodes3) {
System. out. println ( jxNode) ;
}
System. out. println ( "--------------------" ) ;
List< JXNode> jxNodes4 = jxDocument. selN ( "//student/name[@id='itcast']" ) ;
for ( JXNode jxNode : jxNodes4) {
System. out. println ( jxNode) ;
}
}
}
结果:
< student number= "heima_0001" >
< name id= "itcast" >
< xing>
张
< / xing>
< ming>
三
< / ming>
< / name>
< age>
18
< / age>
< sex>
male
< / sex>
< / student>
< student number= "heima_0002" >
< name>
jack
< / name>
< age>
18
< / age>
< sex>
female
< / sex>
< / student>
-- -- -- -- -- -- -- -- -- --
< name id= "itcast" >
< xing>
张
< / xing>
< ming>
三
< / ming>
< / name>
< name>
jack
< / name>
-- -- -- -- -- -- -- -- -- --
< name id= "itcast" >
< xing>
张
< / xing>
< ming>
三
< / ming>
< / name>
-- -- -- -- -- -- -- -- -- --
< name id= "itcast" >
< xing>
张
< / xing>
< ming>
三
< / ming>
< / name>
Process finished with exit code 0