ajax文档

package ajax; import java.io.IOException; import java.io.PrintWriter; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class SelectServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html; charset=UTF-8"); PrintWriter out = response.getWriter(); String selectedId = request.getParameter("selectedId"); //获取selectedId参数 out.println(getOptions(selectedId)); out.flush(); out.close(); } String getOptions(String selectedId) { int counter = 0; //计数器 StringBuffer opts = new StringBuffer("{"); //保存选项信息 String sql = "select * from select_menu where pid = ? order by seq asc";//定义查询数据库的SQL语句 Connection conn = null; //声明Connection对象 PreparedStatement pstmt = null; //声明PreparedStatement对象 ResultSet rs = null; //声明ResultSet对象 try { Class.forName("com.mysql.jdbc.Driver"); conn = DriverManager.getConnection("jdbc:mysql:///ajax" , "root" , "root"); pstmt = conn.prepareStatement(sql); //根据sql创建PreparedStatement pstmt.setString(1, selectedId); //设置参数 rs = pstmt.executeQuery(); //执行查询，返回结果集 while (rs.next()) { //遍历结果集 //如果不是第一项，追加一个“,”用于分隔选项 if (counter > 0) { opts.append(","); } opts.append("'"); opts.append(rs.getString("id")); opts.append("':'"); opts.append(rs.getString("text")); opts.append("'"); counter++; //计数器加1 } } catch (Exception e) { System.out.println(e.toString()); } finally { try { rs.close(); pstmt.close(); conn.close(); } catch (SQLException e) { } } opts.append("}"); return opts.toString(); } }