chenxingxing6/mybatis-3

MyBatis源码分析...

mybatis-3源码分析

1.mybatis运行流程大致了解
2.TypeHandler自己定义
3.plugin自己定义
4.源码追踪，debug大致看一下关键代码

快捷链接：https://www.cnblogs.com/zhjh256/p/8512392.html

1.解析xml,全局配置

XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);

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2.xml解析对应的java对象Configuration

protected Environment environment;    
protected Properties variables = new Properties();   
protected final Map<String, MappedStatement> mappedStatements = new StrictMap<MappedStatement>   
protected final Map<String, Cache> caches = new StrictMap<>("Caches collection");   
protected final Map<String, ResultMap> resultMaps = new StrictMap<>("Result Maps collection");   
protected final Map<String, ParameterMap> parameterMaps = new StrictMap<>("Parameter Maps collection");    

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3.获取sqlSqssion

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();
}
}

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4.创建代理对象

BunkTypeMapper bunkTypeMapper = sqlSession.getMapper(BunkTypeMapper.class);

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

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);
    }
} 


public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
    switch (ms.getStatementType()) {
      case STATEMENT:
        delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      case PREPARED:
        delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      case CALLABLE:
        delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      default:
        throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
    }
} 

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5.Mapper接口是怎么给Spring进行管理的？

5.1 xml挂载点，MapperScannerConfigurer
5.2 注解方式，MapperScannerRegistrar

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6.sqlSession生命周期在加事务有什么变化？

6.1 在没有Transaction情况下生命周期是request/method级别的
6.2 在有Transaction情况下生命周期是Transaction范围里面的

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