public List<Message> queryMessageList(String command, String description) {
		DBAccess dbAccess = new DBAccess();
		List<Message> messageList = new ArrayList<Message>();
		SqlSession sqlSession = null;
		try {
			sqlSession = dbAccess.getSqlSession();
			Message message = new Message();
			message.setCommand(command);
			message.setDescription(description);
			//通过sqlSession执行SQL语句
			messageList = sqlSession.selectList("Message.queryMessageList",message);
		} catch (IOException e) {
			e.printStackTrace();
		}finally{
			if(sqlSession!=null){
				sqlSession.close();
			}
			
		}
		return messageList;
	}
	public static void main(String[] args) {
		MessageDao messageDao = new MessageDao();
		messageDao.queryMessageList("", "");
	}

<mapper namespace="Message">

  <resultMap type="com.imooc.bean.Message" id="MessageResult">
    <id column="ID" jdbcType="INTEGER" property="id"/>
    <result column="COMMAND" jdbcType="VARCHAR" property="command"/>
    <result column="DESCRIPTION" jdbcType="VARCHAR" property="description"/>
    <result column="CONTENT" jdbcType="VARCHAR" property="content"/>
  </resultMap>

  <select id="queryMessageList" parameterType="com.imooc.bean.Message" resultMap="MessageResult">
    select ID,COMMAND,DESCRIPTION,CONTENT from MESSAGE where 1=1
    <if test="command != null and !&quot;&quot;.equals(command.trim())">
    	and COMMAND=#{command}
    </if>
     <if test="description != null and !&quot;&quot;.equals(description.trim())">
    	and DESCRIPTION like '%' #{description} '%'
    </if>
  </select>
</mapper>


 <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC">
        <property name="" value=""/>
      </transactionManager>
      <dataSource type="UNPOOLED">
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/micro_message?useUnicode=true&amp;characterEncoding=UTF-8"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
      </dataSource>
    </environment>
  </environments>

  <mappers>
    <mapper resource="com/imooc/config/sqlxml/Message.xml"/>
  </mappers>

</configuration>