该文中使用的log框架为logback

myBatis3.0.6左右的版本时

打印sql的时候只需要配置如下属性：

<logger name="java.sql.Connection" level="DEBUG" /><logger name="java.sql.Statement" level="DEBUG" /><logger name="java.sql.PreparedStatement" level="DEBUG" />

源码解析：

PreparedStatementLogger里面看这个log.isDebugEnabled()

public Object invoke(Object proxy, Method method, Object[] params) throws Throwable {    try {      if (EXECUTE_METHODS.contains(method.getName())) {        if (log.isDebugEnabled()) {          log.debug("==>  Executing: " + removeBreakingWhitespace(sql));          log.debug("==> Parameters: " + getParameterValueString());        }        clearColumnInfo();        if ("executeQuery".equals(method.getName())) {          ResultSet rs = (ResultSet) method.invoke(statement, params);          if (rs != null) {            return ResultSetLogger.newInstance(rs);          } else {            return null;          }        } else {          return method.invoke(statement, params);        }      }

这个log定义的是PreparedStatement

private static final Log log = LogFactory.getLog(PreparedStatement.class);

在myBatis3.2.7左右版本

更改了打印Sql的模式，它将sql打印细化到了每一个mapperStatement的每一个方法上。

如果你打算有一个全局配置打印所有的sql，则需要如下配置

在mybatis的configuration中增加setting配置

<settings>        <setting name="logPrefix" value="http://www.mamicode.com/dao."/></settings>

然后增加配置

<logger name="dao" level="DEBUG"/>

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 <E> List<E> 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.<E>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