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xml讲解.md

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+# XML
+
+语法：
+
+## XML约束-schema约束
+
+本质还是一个xml文件
+
+![image-20260106164151697](https://gitee.com/icecat2233/picture/raw/master/20260106164155129.png)
+
+### 代码演示：
+
+**此为xsd文件**
+
+complexType:复杂属性
+
+sequence：序列  后可加maxOccurs来表示元素是否可为多个
+
+attribute：属性 后可加属性标签来约束xml标签属性有什么为什么类型是否是必需
+
+element：元素 后写名称来标识你在xml中应有的元素
+
+```xml
+<?xml version="1.0" encoding="UTF-8" ?>
+<schema xmlns="http://www.w3.org/2001/XMLSchema"
+        targetNamespace="ice.cat.home"
+        elementFormDefault="qualified">
+<element name="students">
+    <complexType>
+        <sequence maxOccurs="unbounded">
+            <element name="Student">
+                <complexType>
+                    <sequence maxOccurs="unbounded">
+                        <element name="name"></element>
+                        <element name="age"></element>
+                    </sequence>
+                    <attribute name="id" type="string" use="required"/>
+                </complexType>
+            </element>
+        </sequence>
+    </complexType>
+</element>
+</schema>
+```
+
+**下方为约束效果**
+
+```xml
+<?xml version="1.0" encoding="UTF-8" ?>
+<students xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
+          xmlns = "ice.cat.home"
+          xsi:schemaLocation="ice.cat.home schema.xsd">
+<Student id="1">
+    <name>张三</name>
+    <age>12</age>
+    <name>杏菜</name>
+    <age>14</age>
+</Student>
+</students>
+```
+
+## 解析：
+
+将xml文件读取到Java
+
+### SAX解析：
+
+![image-20260106170911320](https://gitee.com/icecat2233/picture/raw/master/20260106170912993.png)
+
+### DOM解析：
+
+![image-20260106170924376](https://gitee.com/icecat2233/picture/raw/master/20260106170928898.png)
+
+**一般用DOM**
+
+**首先导入DOM4j的jar包**
+
+方法：
+
+<img src="imgh/image-20260106172208442.png" alt="image-20260106172208442" style="zoom: 67%;" />
+
+### DOM解析代码：
+
+<img src="https://gitee.com/icecat2233/picture/raw/master/20260106172046827.png" alt="image-20260106172045711" style="zoom:150%;" />
+