学习笔记：javaEE基础1 XML

这里是xml专场！

声明

1	<?xml version="1.0" encoding="UTF-8"?>

转义

实体引用
- < <
- > >
- & &
- ' '
- " "
CDATA标签

<![CDATA[ .... ]]>

<?xml version="1.0" encoding="UTF-8"?>
<lesson>
  <content>
    <![CDATA[
      <html><body>Test</body></html>
    ]]>
  </content>
</lesson>

语义约束

DTD

数量限制
- <!ELEMENT hr (employee)> 只能1个
- <!ELEMENT hr (employee+)> 最少1个
- <!ELEMENT hr (employee*)> 最少0个
- <!ELEMENT hr (employee?)> 最多一个
引入DTD文件
- <!DOCTYPE 根节点 SYSTEM ”路径“> system代表来自本地
属性设置
- <!ATTLIST employee no CDATA "">
节点所包括的值设置
- <!ELEMENT employee (name, age)>
变量声明
- <!ELEMENT age (#PCDATA)>

<!-- DTD文档 -->
<?xml version="1.0" encoding="UTF-8"?>
        <!--s声明子节点的个数-->
        <!ELEMENT hr (employee+)>
        <!--声明变量-->
        <!ELEMENT name (#PCDATA)>
        <!ELEMENT age (#PCDATA)>
        <!--声明节点所包含的值-->
        <!ELEMENT employee (name, age)>
        <!--声明属性-->
        <!ATTLIST employee no CDATA "">

<!-- 对应的xml文件 -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hr SYSTEM "hr.dtd">
<hr>
  <employee no="12">
    <name>aaaa</name>
    <age>12</age>
  </employee>
</hr>

XML Schema

W3C标准规范 .xsd 比较常用的，但是结构比较复

注意：如果不添加命名空间的话Intellij IDEA会报错

<!-- XML Schema，文件名为hr.xsd，在第二段代码开头需要引入 -->
<?xml version="1.0" encoding="utf-8" ?>
<xs:schema
        xmlns:xs="http://www.w3.org/2001/XMLSchema"
        targetNamespace="http://www.w3school.com.cn"
        xmlns="http://www.w3school.com.cn"
        elementFormDefault="qualified"
>
    <xs:element name="hr">
        <!-- 复杂节点声明 -->
        <xs:complexType>
            <xs:sequence>
                <xs:element name="employee" minOccurs="1" maxOccurs="999">
                    <xs:complexType>
                    <!-- 这样子声明的话写xml时顺序不能搞错 -->
                        <xs:sequence>
                            <xs:element name="name" type="xs:string"/>
                            <!-- 对类型进行一些条件限制 -->
                            <xs:element name="age">
                                <xs:simpleType>
                                    <xs:restriction base="xs:integer">
                                        <xs:minInclusive value="18"/>
                                        <xs:maxInclusive value="60"/>
                                    </xs:restriction>
                                </xs:simpleType>
                            </xs:element>

                            <!-- 可以进行嵌套 -->
                            <xs:element name="department">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="dname" type="xs:string"/>
                                        <xs:element name="local" type="xs:string"/>
                                    </xs:sequence>
                                </xs:complexType>
                            </xs:element>
                        </xs:sequence>
                        <!-- 声明标签 -->
                        <xs:attribute type="xs:string" name="id" use="required"/>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

对应的xml数据

<!-- hr.xsd.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<hr xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.w3school.com.cn"
        xsi:schemaLocation="http://www.w3school.com.cn hr.xsd">
    <employee id="122">
        <name>aaaa</name>
        <age>55</age>
        <department>
            <dname>研发部</dname>
            <local>xx大厦200</local>
        </department>
    </employee>
    <employee id="123">
        <name>bbb</name>
        <age>25</age>
        <department>
            <dname>市场部</dname>
            <local>xx大厦201</local>
        </department>
    </employee>
    <employee id="3322">
        <name>2233</name>
        <age>45</age>
        <department>
            <dname>运营部</dname>
            <local>XX大厦</local>
        </department>
    </employee>
</hr>

使用dom4j读写xml

对上面的 hr.xsd.xml 进行操作，没什么好说的，就是那个库把xml文件读入进内存封装成Document，然后你就可以像js操作dom一样对它进行操作了

public class App {
    private String filePath = "xml/hr.xsd.xml";

    // 读文件
    public void readXml() {
        // 解析，生成树结构
        SAXReader reader = new SAXReader();
        // 生成document
        Document document = null;
        try {
            document = reader.read(filePath);
            // 获取根节点
            Element root = document.getRootElement();
            List<Element> employees = root.elements("employee");

            for (Element employee : employees) {
                Element name = employee.element("name");
                String empName = name.getText();
                System.out.print(
                        empName + " " + employee.elementText("age") + " "
                                + employee.attribute("id").getText() + " " + employee.element("department").elementText("dname"));

                System.out.println();
            }
        } catch (DocumentException e) {
            e.printStackTrace();
        }
    }

    // 写文件
    public void writeXml() {
        try {
            SAXReader reader = new SAXReader();
            Document document = null;
            document = reader.read(filePath);

            Element root = document.getRootElement();
            Element employee = root.addElement("employee");
            employee.addElement("name").setText("2233");
            employee.addElement("age").setText("45");
            employee.addAttribute("id", "3322");
            Element department = employee.addElement("department");
            department.addElement("dname").setText("运营部");
            department.addElement("local").setText("XX大厦");

            Writer writer = new OutputStreamWriter(new FileOutputStream(this.filePath), "UTF-8");
            document.write(writer);
            writer.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
       App app = new App();
       app.writeXml();
       app.readXml();
    }

}

使用xpath解析xml

关于xpath的部分语法如下

这里需要使用到dom4j和jaxen两个java包，在解析的时候需要注入，如果xml使用了命名空间，需要对其进行额外处理，详见此链接

public class XPathTester {

    public void xpathTest(String xpathStr) {
        String file = "xml/hr.xsd.xml";
        SAXReader reader = new SAXReader();
        // 对命名空间进行处理
        Map map = new HashMap();
        map.put("xs","http://www.w3school.com.cn");
        try {
            Document document = reader.read(file);
            XPath x = document.createXPath(xpathStr);
            x.setNamespaceURIs(map);
            List<Node> nodes = x.selectNodes(document);
            for (Node node: nodes) {
                Element emp = (Element)node;
                System.out.println(emp.elementText("name") + " " + emp.elementText("age"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        XPathTester tester = new XPathTester();
        // 使用xpath
        tester.xpathTest("//xs:employee");
        System.out.println("======");
        tester.xpathTest("//xs:employee[xs:age<40]");
        System.out.println("======");
        tester.xpathTest("//xs:employee[position()<3]");
        System.out.println("======");
        tester.xpathTest("//xs:employee[last()]");
        System.out.println("======");
        tester.xpathTest("//xs:employee[@id=3322]");

    }
}

Schwarzeni

声明

转义

语义约束

DTD

XML Schema

使用dom4j读写xml

使用xpath解析xml