mybatis 配置文件 mybatis-config.xmljava
<?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"> <!-- 配置文件的根元素 --> <configuration> <!-- 屬性:定義配置外在化 --> <properties></properties> <!-- 設置:定義mybatis的一些全局性設置 --> <settings> <!-- 具體的參數名和參數值 --> <setting name="" value=""/> </settings> <!-- 類型名稱:爲一些類定義別名 --> <typeAliases></typeAliases> <!-- 類型處理器:定義Java類型與數據庫中的數據類型之間的轉換關係 --> <typeHandlers></typeHandlers> <!-- 對象工廠 --> <objectFactory type=""></objectFactory> <!-- 插件:mybatis的插件,插件能夠修改mybatis的內部運行規則 --> <plugins> <plugin interceptor=""></plugin> </plugins> <!-- 環境:配置mybatis的環境 --> <environments default=""> <!-- 環境變量:能夠配置多個環境變量,好比使用多數據源時,就須要配置多個環境變量 --> <environment id=""> <!-- 事務管理器 --> <transactionManager type=""></transactionManager> <!-- 數據源 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver"/> <property name="url" value="jdbc:mysql://120.78.83.28:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false"/> <property name="username" value="root"/> <property name="password" value="Dsk741852!"/> </dataSource> </environment> </environments> <!-- 數據庫廠商標識 --> <databaseIdProvider type=""></databaseIdProvider> <!-- 映射器:指定映射文件或者映射類 --> <mappers></mappers> </configuration>
Mybatis 在初始化過程當中處理mybatis-Config.xml 配置文件以及映射文件時,使用的是DOM解析,並結合XPath 解析XML配置文件。DOM會將整個XML文檔加載到內存並造成數據結構。XPath 是XML查詢語句,實現對XML的解析,功能相似SQL語句。EntityResolver 用於加載本地dtd。mysql
Mybatis 提供的XpathParser 類封裝 前面涉及的XPath,Document 和EntityResolversql
public class XPathParser { private Document document; private boolean validation; private EntityResolver entityResolver; private Properties variables; private XPath xpath;
默認狀況下,對XML文檔進行驗證時,會根據XML文檔開始位置指定的網址加載對應的DTD文件或XSD文件。當網絡比較慢時,在實踐中提早設置EntityResolver 接口對象加載本地DTD文件。數據庫
package xml; import org.apache.ibatis.io.Resources; import org.apache.ibatis.parsing.XPathParser; import org.xml.sax.EntityResolver; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import java.io.IOException; import java.io.InputStream; import java.util.Locale; /** * Created by dingshuangkun on 2017/12/10. */ public class XMLMapperEntityResolver implements EntityResolver { private static final String IBATIS_CONFIG_SYSTEM="ibatis-3-cofig.dtd"; private static final String IBATIS_MAPPER_SYSTEM="ibatis-3-mapper.dtd"; private static final String MYBATIS_CONFIG_SYSTEM="mybatis-3-cofig.dtd"; private static final String MYBATIS_MAPPER_SYSTEM="mybatis-3-mybatis.dtd"; private static final String MYBATIS_CONFIG_DTD="org/apache/ibatis/builder/xml/mybatis-3-cofig.dtd"; private static final String MYBATIS_MAPPER_DTD="org/apache/ibatis/builder/xml/mybatis-3-mapper.dtd"; @Override public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException { if(systemId!=null){ String lowerCaseSystemId=systemId.toLowerCase(Locale.ENGLISH); if(lowerCaseSystemId.contains(MYBATIS_CONFIG_SYSTEM) || lowerCaseSystemId.contains(IBATIS_CONFIG_SYSTEM)){ return getInputSource(MYBATIS_CONFIG_DTD,publicId,systemId); }else if(lowerCaseSystemId.contains(MYBATIS_MAPPER_SYSTEM) || lowerCaseSystemId.contains(IBATIS_MAPPER_SYSTEM)){ return getInputSource(MYBATIS_MAPPER_DTD,publicId,systemId); } } return null; } public InputSource getInputSource(String path,String publicId,String systemId){ InputSource source=null; try { InputStream in= Resources.getResourceAsStream(path); source=new InputSource(in); source.setPublicId(publicId); source.setSystemId(systemId); }catch (Exception e){ e.printStackTrace(); } return source; } }