mybatis源码 (一) —— SqlSessionFactory创建和mapper的解析

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这篇主要分析SqlSessionFactory的构建过程,以及mybatis mapper文件的解析
先来看SqlSessionFactory的创建过程

String resource = "org/mybatis/example/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

org.apache.ibatis.session.SqlSessionFactoryBuilder#build(java.io.Reader,java.lang.String,java.util.Properties)

  public SqlSessionFactory build(Reader reader, String environment, Properties properties) {try {//委托XMLConfigBuilder来解析xml文件，并构建XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);return build(parser.parse());} catch (Exception e) {//这里是捕获异常，包装成自己的异常并抛出的idiom？，最后还要reset ErrorContextthrow ExceptionFactory.wrapException("Error building SqlSession.", e);} finally {ErrorContext.instance().reset();try {reader.close();} catch (IOException e) {// Intentionally ignore. Prefer previous error.}}}

可以看到SqlSessionFactoryBuilder委托XMLConfigBuilder来解析xml文件,下面我们跟进去查看解析过程

  //构造函数，转换成XPathParser再去调用构造函数public XMLConfigBuilder(Reader reader, String environment, Properties props) {//构造一个需要验证，XMLMapperEntityResolver的XPathParserthis(new XPathParser(reader, true, props, new XMLMapperEntityResolver()), environment, props);}

最终调用的构造方法是:

  //上面6个构造函数最后都合流到这个函数，传入XPathParserprivate XMLConfigBuilder(XPathParser parser, String environment, Properties props) {//首先调用父类初始化Configurationsuper(new Configuration());//错误上下文设置成SQL Mapper Configuration(XML文件配置),以便后面出错了报错用吧ErrorContext.instance().resource("SQL Mapper Configuration");//将Properties全部设置到Configuration里面去this.configuration.setVariables(props);this.parsed = false;this.environment = environment;this.parser = parser;}

创建一个Configuration对象,
然后会调用父类的构造org.apache.ibatis.builder.BaseBuilder#BaseBuilder

  //需要配置，类型别名注册，类型处理器注册3个东西protected final Configuration configuration;protected final TypeAliasRegistry typeAliasRegistry;protected final TypeHandlerRegistry typeHandlerRegistry;public BaseBuilder(Configuration configuration) {this.configuration = configuration;this.typeAliasRegistry = this.configuration.getTypeAliasRegistry();this.typeHandlerRegistry = this.configuration.getTypeHandlerRegistry();}

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  //映射的语句,存在Map里protected final Map<String, MappedStatement> mappedStatements = new StrictMap<MappedStatement>("Mapped Statements collection");//缓存,存在Map里protected final Map<String, Cache> caches = new StrictMap<Cache>("Caches collection");

这是Configuration对象的成员变量,mapper中配置的sql解析出来之后会存在mappedStatements 中
org.apache.ibatis.builder.xml.XMLConfigBuilder#parse

 //解析配置public Configuration parse() {//如果已经解析过了，报错if (parsed) {throw new BuilderException("Each XMLConfigBuilder can only be used once.");}parsed = true;
//  <?xml version="1.0" encoding="UTF-8" ?> 
//  <!DOCTYPE configuration PUBLIC "-//mybat

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