MyBatis10mybatis的执行流程

String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);

• 源码

public static InputStream getResourceAsStream(String resource) throws IOException {
  return getResourceAsStream(null, resource);
}
// 向下调用 ↓
public static InputStream getResourceAsStream(ClassLoader loader, String resource) throws IOException {
  InputStream in = classLoaderWrapper.getResourceAsStream(resource, loader);
  if (in == null) {
    throw new IOException("Could not find resource " + resource);
  }
  return in;
}
// 向下调用 ↓
public InputStream getResourceAsStream(String resource, ClassLoader classLoader) {
  return getResourceAsStream(resource, getClassLoaders(classLoader));
}
// 向下调用 ↓
InputStream getResourceAsStream(String resource, ClassLoader[] classLoader) {
  for (ClassLoader cl : classLoader) {
    if (null != cl) {

      // try to find the resource as passed
      InputStream returnValue = cl.getResourceAsStream(resource);

      // now, some class loaders want this leading "/", so we'll add it and try again if we didn't find the resource
      if (null == returnValue) {
        returnValue = cl.getResourceAsStream("/" + resource);
      }

      if (null != returnValue) {
        return returnValue;
      }
    }
  }
  return null;
}

2、实例化SqlSessionFactoryBuilder构造器

new SqlSessionFactoryBuilder()

3、通过build(inputStream)方法,构建SqlSessionFactory

sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

• 源码

public SqlSessionFactory build(InputStream inputStream) {
  return build(inputStream, null, null);
}
// 向下调用 ↓
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
  try {
    // XMLConfigBuilder 解析输入流
    XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
    return build(parser.parse());
  } catch (Exception e) {
    throw ExceptionFactory.wrapException("Error building SqlSession.", e);
  } finally {
    ErrorContext.instance().reset();
    try {
      inputStream.close();
    } catch (IOException e) {
      // Intentionally ignore. Prefer previous error.
    }
  }
}
// parser.parse() 解析mybatis配置文件
private void parseConfiguration(XNode root) {
  try {
    //issue #117 read properties first
    propertiesElement(root.evalNode("properties"));
    Properties settings = settingsAsProperties(root.evalNode("settings"));
    loadCustomVfs(settings);
    loadCustomLogImpl(settings);
    typeAliasesElement(root.evalNode("typeAliases"));
    pluginElement(root.evalNode("plugins"));
    objectFactoryElement(root.evalNode("objectFactory"));
    objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
    reflectorFactoryElement(root.evalNode("reflectorFactory"));
    settingsElement(settings);
    // read it after objectFactory and objectWrapperFactory issue #631
    environmentsElement(root.evalNode("environments"));
    databaseIdProviderElement(root.evalNode("databaseIdProvider"));
    typeHandlerElement(root.evalNode("typeHandlers"));
    mapperElement(root.evalNode("mappers"));
  } catch (Exception e) {
    throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
  }
}
// 向下调用 ↓
public SqlSessionFactory build(Configuration config) {
  return new DefaultSqlSessionFactory(config);
}

4、在openSession()时,通过openSessionFromDataSource配置事务相关信息,返回DefaultSqlSession

@Override
public SqlSession openSession() {
  return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
}

// 向下调用 ↓
private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
  Transaction tx = null;
  try {
    final Environment environment = configuration.getEnvironment();
    final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
    tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
    final Executor executor = configuration.newExecutor(tx, execType);
    return new DefaultSqlSession(configuration, executor, autoCommit);
  } catch (Exception e) {
    closeTransaction(tx); // may have fetched a connection so lets call close()
    throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
  } finally {
    ErrorContext.instance().reset();
  }
}

5、getMapper通过配置文件配置的class类型,通过动态代理获取接口

UserMapper mapper = sqlSession.getMapper(UserMapper.class);

• 源码

@Override
public <T> T getMapper(Class<T> type) {
  return configuration.getMapper(type, this);
}

public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
  return mapperRegistry.getMapper(type, sqlSession);
}

@SuppressWarnings("unchecked")
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
  final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
  if (mapperProxyFactory == null) {
    throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
  }
  try {
    return mapperProxyFactory.newInstance(sqlSession);
  } catch (Exception e) {
    throw new BindingException("Error getting mapper instance. Cause: " + e, e);
  }
}
@SuppressWarnings("unchecked")
protected T newInstance(MapperProxy<T> mapperProxy) {
// 动态代理获取接口
  return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}

6、通过接口与绑定的sql-mapper文件调用具体的sql

User user = mapper.selectUserById(1);