使用MyBatis和logBack时在日志中输出sql

测试环境：MyBatis3.2.7+logBack1.1.3

1. 在MyBatis的配置文件中增加setting配置
注意：dao.中的字符“.”是必须的

2.在logBack的配置文件中增加logger配置

3.源码解析
ConnectionLogger

public Object invoke(Object proxy, Method method, Object[] params)
      throws Throwable {
    try {
      if (Object.class.equals(method.getDeclaringClass())) {
        return method.invoke(this, params);
      }    
      if ("prepareStatement".equals(method.getName())) {
        if (isDebugEnabled()) {
          debug(" Preparing: " + removeBreakingWhitespace((String) params[0]), true);
        }        
        PreparedStatement stmt = (PreparedStatement) method.invoke(connection, params);
        stmt = PreparedStatementLogger.newInstance(stmt, statementLog, queryStack);
        return stmt;
      }

其中的isDebugEnabled()指的是

protected boolean isDebugEnabled() {
    return statementLog.isDebugEnabled();
}

注意这里的statementLog，看SimpleExecutor的prepareStatement(handler, ms.getStatementLog());

public  List doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
    Statement stmt = null;
    try {
      Configuration configuration = ms.getConfiguration();
      StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
      stmt = prepareStatement(handler, ms.getStatementLog());
      return handler.query(stmt, resultHandler);
    } finally {
      closeStatement(stmt);
    }
  }

这个statementLog是ms.getStatementLog()而来的。而MappedStatement的StatementLog

String logId = id;
if (configuration.getLogPrefix() != null) logId = configuration.getLogPrefix() + id;
mappedStatement.statementLog = LogFactory.getLog(logId);

这里可以看到，logPrefix决定了所有log前缀，所以只需要配置logPrefix就行了

参考资料：

1. myBatis3.2.7如何打印sql http://www.cnblogs.com/beiyeren/p/4196134.html