有没有更有效的方法在servlet中输出html？

时间：2016-01-22 04:20:44

标签： java html jsp servlets

我在下面有一个servlet，它从数据库中检索大量信息，然后以表格形式打印出来。我正在使用out.println（html代码）输出此页面上的所有内容。有没有更有效的方法在servlet中编写这个HTML代码？对于我想要添加的每个html元素/属性等，我必须使用out.println(<head>)作为示例。 

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

public class PersonalInfoOutput extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            response.setContentType("text/html;charset=UTF-8");
            PrintWriter out = response.getWriter();

            HttpSession session = request.getSession(false);
            String employeeid = ""; 

                       if(session != null) { 
                           employeeid = (String)session.getAttribute("employeeid"); 
                       }


            boolean st = false;
            try { 
                Class.forName("com.mysql.jdbc.Driver").newInstance(); 
                Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/payroll_system", "root", ""); 
                PreparedStatement ps = con.prepareStatement("select employeeID,  FirstName, LastName, Admin, DOB, Address, Email, HourlyRate, Gender, ALeaveBalance, SLeaveBalance, ActiveStatus, Role, BSB, BankName, AccNumber, SuperNumber, SuperCompany from payroll_system.employee_info where employeeID = ?");
                ps.setString(1, employeeid);
                ResultSet rs = ps.executeQuery(); 
                st = rs.next(); 
                if(st){
                boolean adminTrue = rs.getBoolean("Admin"); 
                boolean activeTrue = rs.getBoolean("ActiveStatus"); 

                out.println("<html>");
                out.println("<head>");
                out.println("<style>"); 
                out.println("table { border-collapse: collapse; width: 50%; } th, td { text-align: left; padding: 8px; } tr:nth-child(even){background-color: #f2f2f2}");
                out.println("tr:hover {background-color: #e2f4ff;}");
                out.println("</style>");
                out.println("<link rel = stylesheet type = text/css href = main.css>");
                out.println("<link rel = stylesheet type = text/css href = sidebar.css>");
                out.println("<title>Personal Information</title>");
                out.print("</head>");

                out.println("<body>");

                if(adminTrue){ 
                    out.println("<ul>");
                    out.println("<li><a class=active >View Personal Information</a></li>");
                    out.println("<li><a href=xyz>View Expense Claims</a></li>");
                    out.println("<li><a href=xyz>View Payslips</a></li>");
                    out.println("<li><a href=changePassAdmin.html>Change Password</a></li>");
                    out.println("<li><a href=xyz>Maintain Employee Information</a></li>");
                    out.println("<li><a href=xyz>Maintain Tax Information</a></li>");
                    out.println("<li><a href=xyz>Maintain Payroll Items</a></li>");
                    out.println("<li><a href=xyz>Maintain Timesheet</a></li>");
                    out.println("<li><a href=xyz>Maintain Employee Expenses</a></li>");
                    out.println("<li><a href=xyz>Run Payroll</a></li>");
                    out.println("<li><a href=xyz>Generate Reports</a></li>");
                    out.println("</ul>");
                    out.println("<div style=margin-left:25%;padding:1px 16px;height:1000px;>");
                    out.println("</div>");
                }
                else if(!adminTrue){ 
                    out.println("<ul>");
                    out.println("<li><a class=active href=PersonalInfoOutput>View Personal Information</a></li>");
                    out.println("<li><a href=xyz>View Expense Claims</a></li>");
                    out.println("<li><a href=xyz>View Payslips</a></li>");
                    out.println("<li><a href=.html>Change Password</a></li>");
                    out.println("</ul>");
                    out.println("<div style=margin-left:25%;padding:1px 16px;height:1000px;>");
                    out.println("</div>");

                }


                out.println("<h1>Personal Information</h1>");
                out.println("<table border =1>");

                out.println("<tr>");
                out.println("<td>Name</td>");
                out.println("<td>"+ rs.getString("FirstName") + " " + rs.getString("LastName") + "</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Employee ID</td>");
                out.println("<td>"+ rs.getString("employeeID")+"</td>");
                out.println("</tr>");

                if(adminTrue) { 
                    out.println("<tr>");
                    out.println("<td>Admin</td>");
                    out.println("<td>Yes</td>");
                    out.println("</tr>");
                }
                else{ 
                    out.println("<tr>");
                    out.println("<td>Admin</td>");
                    out.println("<td>No</td>");
                    out.println("</tr>");
                }

                out.println("<tr>");
                out.println("<td>Date Of Birth</td>");
                out.println("<td>"+ rs.getString("DOB")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Residential Address</td>");
                out.println("<td>"+ rs.getString("Address")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Email</td>");
                out.println("<td>"+ rs.getString("Email")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Hourly Income</td>");
                out.println("<td>"+ "$" + rs.getString("HourlyRate")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Gender</td>");
                out.println("<td>"+ rs.getString("Gender")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Annual Leave Balance</td>");
                out.println("<td>"+ rs.getString("ALeaveBalance")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Sick Leave Balance</td>");
                out.println("<td>"+ rs.getString("SLeaveBalance")+"</td>");
                out.println("</tr>");

                if(activeTrue) { 
                    out.println("<tr>");
                    out.println("<td>Currently Active</td>");
                    out.println("<td>Yes</td>");
                    out.println("</tr>");
                }
                else { 
                    out.println("<tr>");
                    out.println("<td>Currently Active</td>");
                    out.println("<td>No</td>");
                    out.println("</tr>");
                }

                out.println("<tr>");
                out.println("<td>Role</td>");
                out.println("<td>"+ rs.getString("Role")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>BSB</td>");
                out.println("<td>"+ rs.getString("BSB")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Bank Name</td>");
                out.println("<td>"+ rs.getString("BankName")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Bank Account Number</td>");
                out.println("<td>"+ rs.getString("AccNumber")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Superannuation Company</td>");
                out.println("<td>"+ rs.getString("SuperCompany")+"</td>");
                out.println("</tr>");

                out.println("<tr>");
                out.println("<td>Superannuation Number</td>");
                out.println("<td>"+ rs.getString("SuperNumber")+"</td>");
                out.println("</tr>");

                out.println("</table>");
                out.println("</body>");
                out.println("</html>");

                }
             }catch(Exception e)
              {
                  e.printStackTrace();
              }
            out.close();
    }

    }

2 个答案:

答案 0 :(得分：3)

out.println（）在可读性方面有点难看 - 但与I / O时间相比，这些调用的成本会很小。

在循环中使用+进行字符串连接可能会损害您的内存占用（并且它也不是最快的方式）。考虑一下你有这条线：

     out.println("<td>"+ rs.getString("FirstName") + " " + rs.getString("LastName") + "</td>");

您可以获得可读性和速度，并且通过使用format()进行编码可以减少垃圾收集的剩余时间：

    out.format ("<td>%s %s</td>", rs.getString  ("FirstName"), rs.getString  ("LastName"));

更多备注

每次调用servlet时都会创建并连接新的数据库连接。这将严重影响您的性能和可伸缩性。您应该考虑使用从中获取预连接​​Connections的连接池。您获得的性能将弥补很多String concats或println调用。

答案 1 :(得分：0)

如果你看一下Jasper JSP编译器的预编译输出（Apache Tomcat中的JSP编译器），这就是它将JSP转化为的内容。提高效率的唯一有效策略是考虑在服务器中传输表的数据，并在浏览器中将其转换为带有JavaScript的表。我将这种方法用于运送超过10,000行的系统（我也使用分页来保持有效负载的可管理性）

相关问题
最新问题