mybatis源码核心代码

/**
     * mybatis源码测试类
     * @param args
     * @throws IOException
     * @see org.apache.ibatis.session.Configuration
     * @see org.apache.ibatis.binding.MapperRegistry
     */
    public static void main(String[] args) throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession sqlSession = factory.openSession();

        sqlSession.selectOne("com.log.mybatis.mapper.CarMapper.getList");

        CarMapper carMapper = sqlSession.getMapper(CarMapper.class);
        carMapper.countTheData(new HashMap<>());
    }

0.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 {
      XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        reader.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }

1.org.apache.ibatis.builder.xml.XMLConfigBuilder#parse

  public Configuration parse() {
    if (parsed) {
      throw new BuilderException("Each XMLConfigBuilder can only be used once.");
    }
    parsed = true;
    parseConfiguration(parser.evalNode("/configuration"));
    return configuration;
  }

2.org.apache.ibatis.builder.xml.XMLConfigBuilder#mapperElement

private void mapperElement(XNode parent) throws Exception {
    if (parent != null) {
      for (XNode child : parent.getChildren()) {
        if ("package".equals(child.getName())) {
          String mapperPackage = child.getStringAttribute("name");
          configuration.addMappers(mapperPackage);
        } else {
          String resource = child.getStringAttribute("resource");
          String url = child.getStringAttribute("url");
          String mapperClass = child.getStringAttribute("class");
          if (resource != null && url == null && mapperClass == null) {
            ErrorContext.instance().resource(resource);
            InputStream inputStream = Resources.getResourceAsStream(resource);
            XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
            //核心代码
            mapperParser.parse();
          } else if (resource == null && url != null && mapperClass == null) {
            ErrorContext.instance().resource(url);
            InputStream inputStream = Resources.getUrlAsStream(url);
            XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
            mapperParser.parse();
          } else if (resource == null && url == null && mapperClass != null) {
            Class<?> mapperInterface = Resources.classForName(mapperClass);
            configuration.addMapper(mapperInterface);
          } else {
            throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
          }
        }
      }
    }
  }

  public void parse() {
    if (!configuration.isResourceLoaded(resource)) {
      //所有xml的statement写入org.apache.ibatis.session.Configuration#mappedStatements  无mapper接口类的主要靠这个访问
      configurationElement(parser.evalNode("/mapper"));
      configuration.addLoadedResource(resource);
      //看看xml的namespace是否对应的mapper类
      bindMapperForNamespace();
    }

    parsePendingResultMaps();
    parsePendingChacheRefs();
    parsePendingStatements();
  }

3.xml中所有的动作用configuration.addMappedStatement(statement) 写入org.apache.ibatis.session.Configuration#mappedStatements 对于没有mapper类的只能从中取

public void parseStatementNode() {
    String id = context.getStringAttribute("id");
    String databaseId = context.getStringAttribute("databaseId");

    if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) return;

    Integer fetchSize = context.getIntAttribute("fetchSize");
    Integer timeout = context.getIntAttribute("timeout");
    String parameterMap = context.getStringAttribute("parameterMap");
    String parameterType = context.getStringAttribute("parameterType");
    Class<?> parameterTypeClass = resolveClass(parameterType);
    String resultMap = context.getStringAttribute("resultMap");
    String resultType = context.getStringAttribute("resultType");
    String lang = context.getStringAttribute("lang");
    LanguageDriver langDriver = getLanguageDriver(lang);

    Class<?> resultTypeClass = resolveClass(resultType);
    String resultSetType = context.getStringAttribute("resultSetType");
    StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
    ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);

    String nodeName = context.getNode().getNodeName();
    SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
    boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
    boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
    boolean useCache = context.getBooleanAttribute("useCache", isSelect);
    boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);

    // Include Fragments before parsing
    XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
    includeParser.applyIncludes(context.getNode());

    // Parse selectKey after includes and remove them.
    processSelectKeyNodes(id, parameterTypeClass, langDriver);
    
    // Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
    SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
    String resultSets = context.getStringAttribute("resultSets");
    String keyProperty = context.getStringAttribute("keyProperty");
    String keyColumn = context.getStringAttribute("keyColumn");
    KeyGenerator keyGenerator;
    String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
    keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
    if (configuration.hasKeyGenerator(keyStatementId)) {
      keyGenerator = configuration.getKeyGenerator(keyStatementId);
    } else {
      keyGenerator = context.getBooleanAttribute("useGeneratedKeys",
          configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))
          ? new Jdbc3KeyGenerator() : new NoKeyGenerator();
    }

    //核心代码，生成xml的Statement的id
    builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
        fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
        resultSetTypeEnum, flushCache, useCache, resultOrdered, 
        keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
  }


public MappedStatement addMappedStatement(
      String id,
      SqlSource sqlSource,
      StatementType statementType,
      SqlCommandType sqlCommandType,
      Integer fetchSize,
      Integer timeout,
      String parameterMap,
      Class<?> parameterType,
      String resultMap,
      Class<?> resultType,
      ResultSetType resultSetType,
      boolean flushCache,
      boolean useCache,
      boolean resultOrdered,
      KeyGenerator keyGenerator,
      String keyProperty,
      String keyColumn,
      String databaseId,
      LanguageDriver lang,
      String resultSets) {
    
    if (unresolvedCacheRef) throw new IncompleteElementException("Cache-ref not yet resolved");
    
    id = applyCurrentNamespace(id, false);
    boolean isSelect = sqlCommandType == SqlCommandType.SELECT;

    MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType);
    statementBuilder.resource(resource);
    statementBuilder.fetchSize(fetchSize);
    statementBuilder.statementType(statementType);
    statementBuilder.keyGenerator(keyGenerator);
    statementBuilder.keyProperty(keyProperty);
    statementBuilder.keyColumn(keyColumn);
    statementBuilder.databaseId(databaseId);
    statementBuilder.lang(lang);
    statementBuilder.resultOrdered(resultOrdered);
    statementBuilder.resulSets(resultSets);
    setStatementTimeout(timeout, statementBuilder);

    setStatementParameterMap(parameterMap, parameterType, statementBuilder);
    setStatementResultMap(resultMap, resultType, resultSetType, statementBuilder);
    setStatementCache(isSelect, flushCache, useCache, currentCache, statementBuilder);

    MappedStatement statement = statementBuilder.build();
    configuration.addMappedStatement(statement);//mappedStatements = new StrictMap<MappedStatement>
    return statement;
  }

4.有mapper接口类的 用mapperRegistry.addMapper(Class clz)写入org.apache.ibatis.binding.MapperRegistry#knownMappers

  private void bindMapperForNamespace() {
    String namespace = builderAssistant.getCurrentNamespace();
    if (namespace != null) {
      Class<?> boundType = null;
      try {
        boundType = Resources.classForName(namespace);
      } catch (ClassNotFoundException e) {
        //ignore, bound type is not required
      }
      if (boundType != null) {
        if (!configuration.hasMapper(boundType)) {
          // Spring may not know the real resource name so we set a flag
          // to prevent loading again this resource from the mapper interface
          // look at MapperAnnotationBuilder#loadXmlResource
          configuration.addLoadedResource("namespace:" + namespace);
          configuration.addMapper(boundType);//private final Map<Class<?>, MapperProxyFactory<?>> knownMappers = new HashMap<Class<?>, MapperProxyFactory<?>>();
        }
      }
    }
  }

附mybatis配置文件：

<?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>
    <!-- 引入外部资源文件-->
    <properties resource="jdbc.properties"/>

    <!-- 配置数据源环境 -->
    <environments default="development">
        <environment id="development">
            <!-- 数据库事务管理类型 -->
            <transactionManager type="JDBC"/>
            <!-- 数据源，type=pooled 说明是使用连接池方式，可以节省资源 -->
            <dataSource type="POOLED">
                <!-- 调用资源文件里的用户信息-->
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="sqlMap/CarMapper.xml" />
    </mappers>
</configuration>