xml function and syntax
2 XML作用 2.1 描述带关系的数据(软件的配置文件) web服务器(PC): 学生管理系统 -> 添加学生功能 -> 添加学生页面 -> name=eric&email=eric@qq.com 前提: 网络(IP地址: oracle:255.43.12.54 端口:1521 ) java代码:使用ip(255.43.12.54)地址和端口(1521),连接oracle数据库,保存学生数据。 把ip地址端口配置到xml文件: host.xml <host> <ip>255.43.12.55</ip> <port>1521</port> </host> 数据库服务器(PC): 主服务器(255.43.12.54):Oracle数据库软件(负载) 副服务器(255.43.12.55):Oracle数据库软件 2.2 数据的载体(小型的“数据库”) 教师管理系统: 姓名 工龄+1 邮箱 发教师数据给财务管理系统: String teacher = name=张三&email=zhangsan@qq.com&workage=2 字符串 (问题: 1)不好解析 2)不是规范) teacher.xml <teacher> <name>张三</name> <email>zhangsan@qq.com</email> <workage>2</workage> </teacher> 这种一种规范 财务管理系统: 姓名 工龄+1 邮箱 发奖金: 统计奖金。 工龄 发邮件功能: 邮箱 姓名 金额 方案一: 在财务管理系统中维护了一套教师信息。 每年 : 工龄增加 维护了两个系统的信息。 方案二: 教师信息只在教学管理系统中维护。 3 XML语法 xml文件以xml后缀名结尾。 xml文件需要使用xml解析器去解析。浏览器内置了xml解析器。 3.1 标签 语法: <student></student> 开始标签 标签体内容 结束标签 1)<student/> 或 <student></student> 空标签。没有标签体内容 2)xml标签名称区分大小写。 3)xml标签一定要正确配对。 4)xml标签名中间不能使用空格 5)xml标签名不能以数字开头 6)注意: 在一个xml文档中,有且仅有一个根标签 3.2 属性 语法: <Student name="eric">student</Student> name:属性名。name="eric"属性值 注意: 1)属性值必须以引号包含,不能省略,也不能单双引号混用!!! 2)【一个标签】内可以有多个属性,但不能出现重复的属性名!!! 3.3 注释 语言: <!-- xml注释 --> 练习: 通讯录系统 联系人数据:编号 (唯一的) 姓名 年龄 电话 邮箱 QQ 要求: contact.xml 1)设计一个xml文件,用于存储联系人数据 2)这个xml文件可以存取多个联系人。 3.4 文档声明 语法: <?xml version="1.0" encoding="utf-8"?> version: xml的版本号 encoding: 解析xml文件时查询的码表(解码过程时查询的码表),浏览器打开时候的编码方式 注意: 1)如果在ecplise工具中开发xml文件,保存xml文件时自动按照文档声明的encoding来保存文件。 2)如果用记事本工具修改xml文件,注意【保存xml文件】按照文档声明的encoding的码表来保存。 3.5 转义字符 在xml中内置了一些特殊字符,这些特殊字符不能直接被浏览器原样输出。如果希望把这些特殊字符按照原样输出到浏览器,对这些特殊字符进行转义。 转义之后的字符就叫转义字节。 特殊字符 转义字符 < < > > " " & & 空格 &nsbp; 3.6 CDATA块 作用: 可以让一些需要进行包含特殊字符的内容统一进行[原样输出]。 <![CDATA[ <itcast> <br/> </itcast> ]]> 3.7 处理指令 作用: 告诉xml解析如果解析xml文档 处理指令,简称PI (processing instruction)。处理指令用来指挥解析引擎如何解析XML文档内容。 例如,在XML文档中可以使用xml-stylesheet指令,通知XML解析引擎,应用css文件显示xml文档内容。 <?xml-stylesheet type="text/css" href="1.css"?> 处理指令必须以“<?”作为开头,以“?>”作为结尾,XML声明语句就是最常见的一种处理指令。
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