请求各位解读一小段代码

解读这段代码，这段我有些不太清楚
public String lianxi1() {
HttpServletRequest request = ServletActionContext.getRequest();
String shan= request.getParameter("shan");

    StringBuffer sb = new StringBuffer();
    sb.append(" where ");
    if(shenhe!=null&&!"".equals(shan)){
        sb.append("shan like '%"+shan+"%'");
        sb.append(" and ");


        request.setAttribute("shan", shan);
    }


public String lianxi1() {
//获取request 对象
HttpServletRequest request = ServletActionContext.getRequest();
//通过request 对象，获取Shan的属性值
String shan= request.getParameter("shan");
//创建字符串缓存对象
    StringBuffer sb = new StringBuffer();
//拼接字符串
    sb.append(" where ");
    //判断request 请求中的Shan属性值是否为空，不为空则执行if语句
    if(shenhe!=null&&!"".equals(shan)){
        //拼接Shan 字段模糊查询
        sb.append("shan like '%"+shan+"%'");
        sb.append(" and ");
        request.setAttribute("shan", shan);
    }

不清楚什么

这段代码是拼接 sql 语句的。不清楚可以问额。
where shan like '%"+shan+"%'

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