tmpSql = oSql.substring(oSql.indexOf("<if")) + "</if>";

Element root = DocumentHelper.parseText(tmpSql).getRootElement();

String condition = root.attribute("test").getValue();

Object condObj = Ognl.parseExpression(condition);
Object value = Ognl.getValue(condObj, requestParams);
 if (value instanceof Boolean) {
                conditionResult = (Boolean) value;

tmpSql =
<if test=\"pwd != null and pwd != ''\">
and a.password = #pwd#
</if>
//  然后将tempSql转成 xml 之后 再获取 test 
也就是此时的condition = pwd != null and pwd != ''
condObj = (pwd != null) && (pwd != "")
//-------------------------------------------------->
requestParams 是一个类似于Map的结构 里面保存着 pwd 的值
 
 可能 Mybatis底层 解析 if标签就这么做的吧 
 但是此时我也没找到一个合适的例子
 ------------------------------------》
 留作 问题  标注一个

 

  但是我始终没有想到 这个工具类有什么用  可能大佬的想法 我这个应用操作人员用不到
    public static void main(String[] args) throws Exception {
        JSONObject jsObject = new JSONObject();
//        jsObject.put("username","2");
        jsObject.put("password","1");
//        Object username = Ognl.parseExpression("username !=null && username !=''");
//        Object value = Ognl.getValue(username, jsObject);
        String username = jsObject.getString("username");
        if(null==username){
            System.out.println("x");
        }

    /**
     * 处理SQL语句
     *
     * @param oldSql
     * 	 select * from s_a a
     *               where <if test="name != null && name != ''">
     *               a.name = #name#
     *               </if>
     * @return
     */
    public String dealSqlIf(String oldSql, JSONObject requestParams) throws DocumentException, OgnlException {
        StringBuffer newSql = new StringBuffer();
        String tmpSql = "";
        Boolean conditionResult = false;
        // 未包含 条件语句
        if (!oldSql.contains("<if")) {
            return oldSql;
        }

        String[] oSqls = oldSql.split("</if>");
        for (String oSql : oSqls) {
            logger.debug("处理if 节点，当前处理的oSql=" + oSql + "总的oSqls = " + oSqls);

            if (StringUtil.isNullOrNone(oSql) || !oSql.contains("<if")) {
                newSql.append(oSql);
                continue;
            }
                if (!oSql.startsWith("<if")) {
                newSql.append(oSql.substring(0, oSql.indexOf("<if")));
            }

            tmpSql = oSql.substring(oSql.indexOf("<if")) + "</if>";

            Element root = DocumentHelper.parseText(tmpSql).getRootElement();

            String condition = root.attribute("test").getValue();

            Object condObj = Ognl.parseExpression(condition);

            Object value = Ognl.getValue(condObj, requestParams);

            if (value instanceof Boolean) {
                conditionResult = (Boolean) value;
            } else {
                throw new BusinessException(ResponseConstant.RESULT_CODE_INNER_ERROR, "配置错误，if语句配置错误 " + condition);
            }

            if (conditionResult) {
                newSql.append(root.getText());
            }


        }
 //  mybatis 可能就是通过 ognl来解析这个动态标签  比如说< if>