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1. XML: extensible markup language version="1.0"
Constraints are the writing rules of xml
Classification of constraints:
Write root tag
Introducing the instance namespace xmlns:xsi="www.w3.org/2001/XMLSchema-instance"
<?xml version="1.0"?> <xsd:schema xmlns="www.itheima.cn/xml" xmlns:xsd="www.w3.org/2001/XMLSchema" targetNamespace="www.itheima.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="itheima_\d{4}"/> </xsd:restriction> </xsd:simpleType> </xsd:schema> <?xml version="1.0" encoding="UTF-8" ?>
<students xmlns="www.itheima.cn/xml" xsi:schemaLocation="www.itheima.cn/xml student.xsd" xmlns:xsi="www.w3.org/2001/XMLSchema-instance" > <student number="itheima_1001"> <name>asfd</name> <age>12</age> <sex>male</sex> </student> </students> <students xmlns:itheima="www.itheima.cn/xml" xsi:schemaLocation="www.itheima.cn/xml student.xsd" xmlns:xsi="www.w3.org/2001/XMLSchema-instance" > <itheima:student number="itheima_1001"> <itheima:name>asfd</itheima:name> <itheima:age>12</itheima:age> <theima:sex>male</itheima:sex> </itheima:student> </itheima:students>
<!ELEMENT students (student*) > <!ELEMENT student (name,age,sex)> <!ELEMENT name (#PCDATA)> <!ELEMENT age (#PCDATA)> <!ELEMENT sex (#PCDATA)> <!ATTLIST student number ID #REQUIRED> 唯一的,必须的 <?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE students SYSTEM "student.dtd"> <students> <student number="s0001" > <name>zs</name> <age>abc</age> <sex>yao</sex> </student> </students>
public classTestXPath2 { @Test publicvoidtest()throwsException{ SAXReaderread= new SAXReader(); Documentdocument= read.read("src/Dom4jTest.xml"); Listnodes= document.selectNodes("/bookstore//book/title"); for(inti= 0;i< nodes.size();i++) { Nodenode= (Node)nodes.get(i); System.out.println(node.getText()); } } }
selectSingleNode()
创建解析器 SAXReader reader = new SAXReader()
解析xml 获得document对象 Document document = reader.read(url)
// nodename 选取此节点。
// / 从根节点选取。
// // 从匹配选择的当前节点选择文档中的节点,而不考虑它们的位置。
// .. 选取当前节点的父节点。
// @ 选取属性。
// [@属性名] 属性过滤
// [标签名] 子元素过滤
@Test
//遍历所有元素节点
publicvoidtest2()throwsException{ //创建一个xml解析对象 SAXReaderreader= new SAXReader(); //把xml文档加载到document对象中 Documentdocument= reader.read("src/Book.xml"); Elementroot= document.getRootElement(); treeWalk(root); } privatevoidtreeWalk(Elementele){ //输出当前节点的名字 System.out.println(ele.getName()); //ele.nodeCount()得到当前节点的所有子节点的数量 for(inti= 0;i<ele.nodeCount();i++){ //取出下标为i的节点 Nodenode= ele.node(i); //判断当前节点是否为标签 if(nodeinstanceofElement){ //把node强转为标签(Element) treeWalk((Element)node); } } } }
public classTestDom4j { @Test publicvoidtest1()throwsException{ //创建一个xml解析对象 SAXReaderreader= new SAXReader(); //把xml文档加载到document对象中 Documentdocument= reader.read("src/Book.xml"); Elementroot= document.getRootElement(); // Element bookNode = root.element("书"); // System.out.println(bookNode.getName()); //得到当前节点所有的子节点 Listlist= root.elements(); //得到第二本书对象 ElementsecondBook= (Element)list.get(1); //得到当前节点的文本内容 Stringname= secondBook.element("书名").getText(); System.out.println(name); }
导入jar包 dom4j.jar
创建解析器
解析xml 获得document对象
SAXReader reader = new SAXReader()
Document document = reader.read(url)
JAXP sun公司提供的解析 支持dom和sax
JDOM
DOM4J dom for java民间方式,但是是事实方式,非常好,支持dom
解析xml
XPATH 专门用于查询
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