Mybaitis 源码分析

前提文件：对应项目为mybatis-01
其中配置xml文件为

<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            dataSource>
        environment>
    environments>
    <mappers>
        <mapper resource="com/wang/Dao/UserMapper.xml"/>
    mappers>
configuration>

Dao接口层Mapper.xml为：

<mapper namespace="com.wang.Dao.UserMapper">
    <select id="getUserLike">
        select * from mybatis.user where like #{value}
    select>
    <select id="getUserList" resultType="com.wang.pojo.User">
        select * from mybatis.user;
    select>
    <select id="getUserById" resultType="com.wang.pojo.User" parameterType="int">
        select * from mybatis.user where id = #{id};
    select>
    <select id="getUserById2" resultType="com.wang.pojo.User" parameterType="map">
        select * from mybatis.user where id = #{id} and name=#{name};
    select>

    <insert id="addUser" parameterType="com.wang.pojo.User" >
        insert into mybatis.user (id, name ,pwd) values (#{id}, #{name}, #{pwd});
    insert>
    <insert id="addUser2" parameterType="map" >
        insert into mybatis.user (id, name ,pwd) values (#{userid}, #{username}, #{userpwd});
    insert>
    <update id="updateUser" parameterType="com.wang.pojo.User">
        update mybatis.user set name=#{name },pwd=#{pwd} where id=#{id};
    update>
    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id=@{id}
    delete>
mapper>

技术拆解
首先对mybatis进行技术拆解，可分为如下部分：

一、对数据源部分进行分析：该部分整体的解析步骤为：

mybatis是如一步一步何处理数据源的：
org.apache.ibatis.session.SqlSessionFactoryBuilder.build(java.io.Reader)
    >org.apache.ibatis.builder.xml.XMLConfigBuilder
        >org.apache.ibatis.builder.xml.XMLConfigBuilder.parse
            >org.apache.ibatis.builder.xml.XMLConfigBuilder.environmentsElement
                >org.apache.ibatis.builder.xml.XMLConfigBuilder.dataSourceElement
                    >org.apache.ibatis.datasource.unpooled.UnpooledDataSourceFactory.getDataSource
                        >org.apache.ibatis.session.Configuration.setEnvironment   #####这里是set
总结：解析xml文件，将文件内容给到Java对象Configuration，通过setEnvironment给到的

第一步：

可以得到如下内容：

<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>            
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>                
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf8"/>                
                <property name="username" value="root"/>                
                <property name="password" value="123456"/>                
            dataSource>
        environment>
    environments>
    <mappers>
        <mapper resource="com/wang/Dao/UserMapper.xml"/>        
    mappers>
configuration>

第二步得到该内容：

<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC"/>        
        <dataSource type="POOLED">
            <property name="driver" value="com.mysql.cj.jdbc.Driver"/>            
            <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf8"/>            
            <property name="username" value="root"/>            
            <property name="password" value="123456"/>            
        dataSource>
    environment>
environments>

第三步：得到该内容

<dataSource type="POOLED">
    <property name="driver" value="com.mysql.cj.jdbc.Driver"/>    
    <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf8"/>    
    <property name="username" value="root"/>    
    <property name="password" value="123456"/>    
dataSource>

第四步得到该内容：

<transactionManager type="JDBC"/>
<dataSource type="POOLED">
    <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf8"/>
    <property name="username" value="root"/>
    <property name="password" value="123456"/>
dataSource>

第五步得到该内容：

这个就和我们的配置文件一一对应的！！！！

二，执行语句

是如何执行sql语句：
org.apache.ibatis.session.SqlSessionFactoryBuilder.build(java.io.Reader)
    >org.apache.ibatis.builder.xml.XMLConfigBuilder
        >org.apache.ibatis.builder.xml.XMLConfigBuilder.parse
             >org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement
                >org.apache.ibatis.builder.xml.XMLMapperBuilder.XMLMapperBuilder(java.io.InputStream, org.apache.ibatis.session.Configuration, java.lang.String, java.util.Map<java.lang.String,org.apache.ibatis.parsing.XNode>)
                    >org.apache.ibatis.builder.xml.XMLMapperBuilder.parse
                        >org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement
                            >org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(java.util.List<org.apache.ibatis.parsing.XNode>)
                                >org.apache.ibatis.builder.xml.XMLStatementBuilder.XMLStatementBuilder(org.apache.ibatis.session.Configuration, org.apache.ibatis.builder.MapperBuilderAssistant, org.apache.ibatis.parsing.XNode, java.lang.String)
                                    >org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode
                                        >org.apache.ibatis.session.Configuration.addMappedStatement  ####这里是add                                        

第一步得到该内容：

<mappers>
    <mapper resource="com/wang/Dao/UserMapper.xml"/>    
mappers>

补充知识（源码分析得到）：
mybatis解析mapper文件有几种方式：4种，以及优先级


第二步得到该内容：

<mapper namespace="com.wang.Dao.UserMapper">
    <select id="getUserLike">
        select * from mybatis.user where like #{value}
    select>
    <select resultType="com.wang.pojo.User" id="getUserList">
        select * from mybatis.user;
    select>
    <select resultType="com.wang.pojo.User" parameterType="int" id="getUserById">
        select * from mybatis.user where id = #{id};
    select>
    <select resultType="com.wang.pojo.User" parameterType="map" id="getUserById2">
        select * from mybatis.user where id = #{id} and name=#{name};
    select>
    <insert parameterType="com.wang.pojo.User" id="addUser">
        insert into mybatis.user (id, name ,pwd) values (#{id}, #{name}, #{pwd});
    insert>
    <insert parameterType="map" id="addUser2">
        insert into mybatis.user (id, name ,pwd) values (#{userid}, #{username}, #{userpwd});
    insert>
    <update parameterType="com.wang.pojo.User" id="updateUser">
        update mybatis.user set name=#{name },pwd=#{pwd} where id=#{id};
    update>
    <delete parameterType="int" id="deleteUser">
        delete from mybatis.user where id=@{id}
    delete>
mapper>

第三步得到该内容：

对应我的Mapper.xml文件中的标签！！
mapper标签中的子标签都在这里！！！


org.apache.ibatis.mapping.MappedStatement中的内容对应mapper.xml中的select内容

补充知识二：

org.apache.ibatis.session.Configuration#newExecutor(org.apache.ibatis.transaction.Transaction, org.apache.ibatis.session.ExecutorType)
mybiatis的核心是执行器，执行器有3种
org.apache.ibatis.session.ExecutorType下有三种SIMPLE, REUSE, BATCH
SIMPLE是默认的执行器
org.apache.ibatis.executor.Executor执行器接口

mybatis一级缓存是否默认开启呢，默认开启。
if (cacheEnabled) {
     
  executor = new CachingExecutor(executor);
}
protected boolean cacheEnabled = true;

补充1.
补充2.