使用dom4j解析mybatis核心配置文件

1. 代码   32-34

test代码在com.powernode.xml.test

ParseXMLByDom4jTest

package com.powernode.xml.test;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.Test;

import java.io.InputStream;
import java.util.List;

//使用dom4j解析mybatis核心配置文件   32
public class ParseXMLByDom4jTest {

    //解析CarMapper.xml  34
    @Test
    public void testParseSqlMapperXML() throws Exception{
        SAXReader reader = new SAXReader();
        InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("CarMapper.xml");
        Document document = reader.read(is);
        // 获取namespace
        String xpath = "/mapper";
        Element mapper = (Element) document.selectSingleNode(xpath);
        String namespace = mapper.attributeValue("namespace");
        System.out.println(namespace);
        // 获取mapper节点下所有的子节点
        List elements = mapper.elements();
        // 遍历
        elements.forEach(element -> {
            // 获取sqlId
            String id = element.attributeValue("id");
            System.out.println(id);
            // 获取resultType
            // 没有这个属性的话，会自动返回"null"
            String resultType = element.attributeValue("resultType"); 
            System.out.println(resultType);
            // 获取标签中的sql语句（表示获取标签中的文本内容，而且去除前后空白）
            String sql = element.getTextTrim();
            System.out.println(sql);
            
            // insert into t_car values(null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})
            // insert into t_car values(null,?,?,?,?,?)
            // mybaits封装了jdbc。早晚要执行带有?的sql语句。
            // 转换
            String newSql = sql.replaceAll("#\\{[0-9A-Za-z_$]*}", "?");
            System.out.println(newSql);
        });
    }


    //使用dom4j解析mybatis核心配置文件   32
    @Test
    public void testParseMyBatisConfigXML() throws Exception{
        // 创建SAXReader对象
        SAXReader reader = new SAXReader();
        // 获取输入流
        InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("mybatis-config.xml");
        // 读XML文件，返回document对象。document对象是文档对象，代表了整个XML文件。
        Document document = reader.read(is);

        //System.out.println(document);

//        // 获取文档当中的根标签
//        Element rootElt = document.getRootElement();
//        String rootEltName = rootElt.getName();
//        System.out.println("根节点的名字：" + rootEltName);
//
        //获取default默认的环境id
        // xpath是做标签路径匹配的。能够让我们快速定位XML文件中的元素。
        // 以下的xpath代表了：从根下开始找configuration标签，然后找configuration标签下
        // 的子标签environments
        String xpath = "/configuration/environments";
        // Element是Node类的子类，方法更多，使用更便捷。
        Element environments = (Element) document.selectSingleNode(xpath);
        // 获取属性的值
        String defaultEnvironmentId = environments.attributeValue("default");
        System.out.println("默认环境的id：" + defaultEnvironmentId);

        // 获取具体的环境environment
        xpath = "/configuration/environments/environment[@id='"+defaultEnvironmentId+"']";
        //System.out.println(xpath);
        Element environment = (Element) document.selectSingleNode(xpath);

        // 33
        // 获取environment节点下的transactionManager节点(Element的element()方法用来获取孩子节点)
        Element transactionManager = environment.element("transactionManager");
        String transactionType = transactionManager.attributeValue("type");
        System.out.println("事务管理器的类型：" + transactionType);
        // 获取dataSource节点
        Element dataSource = environment.element("dataSource");
        String dataSourceType = dataSource.attributeValue("type");
        System.out.println("数据源的类型：" + dataSourceType);
        // 获取dataSource节点下的所有子节点
        List propertyElts = dataSource.elements();
        // 遍历
        propertyElts.forEach(propertyElt -> {
            String name = propertyElt.attributeValue("name");
            String value = propertyElt.attributeValue("value");
            System.out.println(name + "=" + value);
        });
        // 获取所有的mapper标签
        // 不想从根下开始获取，你想从任意位置开始，获取所有的某个标签，xpath该这样写
        xpath = "//mapper";
        List mappers = document.selectNodes(xpath);
        // 遍历
        mappers.forEach(mapper -> {
            Element mapperElt = (Element) mapper;
            String resource = mapperElt.attributeValue("resource");
            System.out.println(resource);
        });
    }
}

resources目录下

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <environments default="powernodeDB">
        <environment id="powernodeDB">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/powernode"/>
                <property name="username" value="root"/>
                <property name="password" value="lzl"/>
            </dataSource>
        </environment>

        <!--这是mybatis的另一个环境，也就是连接的数据库是另一个数据库mybatis-->
        <environment id="mybatisDB">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="lzl"/>
            </dataSource>
        </environment>

    </environments>

    <mappers>
        <!--resource属性自动会从类的根路径下开始查找资源。-->
        <mapper resource="CarMapper.xml"/>
    </mappers>

</configuration>

CarMappper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="car">

    <insert id="insertCar">
        insert into t_car values(null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})
    </insert>

    <select id="selectById" resultType="com.powernode.mybatis.pojo.Car">
        select
            id,car_num as carNum,brand,guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id}
    </select>

</mapper>

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.powernode</groupId>
    <artifactId>course6</artifactId>
    <version>1.0-SNAPSHOT</version>

    <packaging>jar</packaging>

    <!--依赖-->
    <dependencies>
        <!--dom4j的依赖-->
        <dependency>
            <groupId>org.dom4j</groupId>
            <artifactId>dom4j</artifactId>
            <version>2.1.3</version>
        </dependency>
        <!--jaxen依赖-->
        <dependency>
            <groupId>jaxen</groupId>
            <artifactId>jaxen</artifactId>
            <version>1.2.0</version>
        </dependency>
        <!--junit依赖-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <properties>
        <!--    编译代码使用的jdk版本-->
        <maven.compiler.source>1.8</maven.compiler.source>
        <!--    运行程序使用的jdk版本-->
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>


</project>