Java Web开发之信息查询方式总结

<p>请输入要查询的姓名：</p>
<form action="select.jsp" method="POST">
 <p><input type="text" name="username" size="20"><input type="submit" value="提交" name="B1"><input type="reset" value="全部重写" name="B2"></p>
</form>

<%@ page contentType="text/html;charset=gb2312"%>
<%
  StringBuffer sql=new StringBuffer();
  //查询字符串
  String username = request.getParameter("username");
  //查询的条件
  if(username==null||username.length()==0)
  {
   out.println("请输入查询条件！");
  }
  else
  {
   sql.append("select * from user where username like '");
   sql.append(username);
   sql.append("'");
  }
  //接下来根据上面生成的sql进行查询即可
%>

sql.append("select * from user where username like '%");
sql.append(username);
sql.append("%'");

<p>请输入要查询的关键字：</p>
<form action="select.jsp" method="POST">
 <p><input type="text" name="condition" size="20"><input type="submit" value="提交" name="B1"><input type="reset" value="全部重写" name="B2"></p>
</form>

<%@ page contentType="text/html;charset=gb2312"%>
<%
  StringBuffer sql=new StringBuffer();
  //查询字符串
  String condition =request.getParameter("condition");
  //查询的条件
  if(condition==null||condition.length()==0)
  {
   out.println("请输入查询条件！");
  }
  else
  {
   sql.append("select * from user where title like '%");
   sql.append(condition);
   sql.append("%' and summary like '%");
   sql.append(condition);
   sql.append("%' and detail like '%");
   sql.append(condition);
   sql.append("%'");
  }
  //接下来根据上面生成的sql进行查询即可
%>

<%@ page contentType="text/html;charset=gb2312"%>
<%
  StringBuffer sql=new StringBuffer();
  //查询字符串
  String condition = request.getParameter("condition");
  //查询的字段
  String v = request.getParameter("v");
  //查询的值
  if(v.length()==0)
  {
   out.println("请输入查询条件！");
  }
  else
  {
   sql.append("select * from user where ");
   //根据用户选择的字段进行处理
   if(condition.equals("a"))
     sql.append(" a like '");
   else if(condition.equals("b"))
     sql.append(" b like '");
   else
     sql.append(" c like '");
   sql.append(v);
   sql.append("'");
   /*
   如果界面中下拉列表中的条件是数据库中字段的名字，上面的代码会非常简单：
   sql.append("select * from user where ");
   sql.append(condition);
   sql.append(" like '");
   sql.append(v);
   sql.append("'");
   */
  }
  //接下来根据上面生成的sql进行查询即可
%>

<%@ page contentType="text/html;charset=gb2312"%>
<%
  StringBuffer sql=new StringBuffer();
  //查询字符串
  String a = request.getParameter("a");
  String b = request.getParameter("b");
  String c = request.getParameter("c");
  String d = request.getParameter("d");
  //获取用户输入的查询条件
  sql.append("select * from user where");
  if(a.length()!=0)
  {
   sql.append(" a like '");
   sql.append(a);
   sql.append("' and");
  }
  if(b.length()!=0)
  {
   sql.append(" b like '");
   sql.append(b);
   sql.append("' and");
  }
  if(c.length()!=0)
  {
   sql.append(" c like '");
   sql.append(c);
   sql.append("' and");
  }
  if(d.length()!=0)
  {
   sql.append(" d like '");
   sql.append(d);
   sql.append("' and");
  }
  sql.trim(sql.length-3,3);
  //删除最后的4个字母（" and"）
  //接下来根据上面生成的sql进行查询即可
%>

<%@ page contentType="text/html;charset=gb2312"%>
<%
  StringBuffer sql=new StringBuffer();
  //查询字符串
  String condition = request.getParameter("condition");
  //获取查询条件
  int index = condition.indexof(" ");
  //查找空格位置，空格作为两个数字的分隔符
  String min=condition.subString(1,index);
  //前面的值
  String max=condition.subString(index+1,condition.length-1);
  //后面的值
  try
  {
   Integer.parseInt(min);
   Integer.parseInt(max);
  }catch(Exception e)
  {
   out.println("输入的信息不合法！");
   return;
  }
  sql.append("select * from user where age between ");
  sql.append(min);
  sql.append(" and ");
  sql.append(max);
  //构造查询字符串
  //接下来根据上面生成的sql进行查询即可
%>