java - JAVA:使用 IntelliJ IDEA 在 JSP 中显示 mysql 数据
问题描述
所以我使用 intelliJ 和 Java 作为编程语言已经快 2 个月了。我正在开发一个 Web 应用程序,并且我已经成功实现了使用LoginServlet.java
. 但是我想COUNT(*)
在 JSP 中显示一个输出,但是我在如何显示数据输出方面遇到了一些问题。我不确定我的 servlet 是否允许多个request.getRequestDispatcher
,或者我需要在 servlet 之外编写代码(可能在 jsp 中)。一些方向将不胜感激。
这是我的代码
UserLogin.java Servlet
@WebServlet("/organizer")
public class UserLogin extends HttpServlet {
@SuppressWarnings("Duplicates")
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try{
String email = request.getParameter("email");
String password = request.getParameter("password");
OrganizerDao e = new OrganizerDao();
HttpSession session = request.getSession();
session.setAttribute("email", email);
Connection con= OrganizerDao.getConnection();
PreparedStatement st=con.prepareStatement("select id, firstname, lastname from users where email=? and password=?");
st.setString(1,email);
st.setString(2,password);
ResultSet rs=st.executeQuery();
if (rs.next()) {
request.setAttribute("id",rs.getInt("id"));
request.setAttribute("firstname",rs.getString("firstname"));
request.setAttribute("lastname",rs.getString("lastname"));
RequestDispatcher rd = request.getRequestDispatcher("dashboard.jsp");
rd.include(request, response);
} else {
out.println("<div class=\"alert alert-danger\" role=\"alert\">");
out.println("<center>Oh snap! Change a few things and try submitting again.</center>");
out.println("</div>");
request.getRequestDispatcher("login.jsp").include(request, response);
}
con.close();
}catch(Exception ex){ex.printStackTrace();}
}
@SuppressWarnings("Duplicates")
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processRequest(request,response);
getEventsCount(request,response);
getAffiliatesCount(request,response);
}
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processRequest(request,response);
getEventsCount(request,response);
getAffiliatesCount(request, response);
}
@SuppressWarnings("Duplicates")
protected void getEventsCount(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//call ConnectToDatabase
try {
String email = request.getParameter("email");
String password = request.getParameter("password");
HttpSession session = request.getSession();
session.setAttribute("email", email);
try {
String query = "SELECT count(events.userid) AS etotal from events, users where events.userid=users.id and users.email=? and users.password=?";
int count = 0;
Connection connection = EventsDAO.getConnection();
PreparedStatement st = connection.prepareStatement(query);
st.setString(1, email);
st.setString(2, password);
ResultSet rs = st.executeQuery();
while (rs.next()) {
count = rs.getInt("etotal");
request.setAttribute("count", count);
RequestDispatcher rd = request.getRequestDispatcher("dashboard.jsp");
rd.include(request, response);
}
} catch (SQLException e) {
e.printStackTrace();
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
@SuppressWarnings("Duplicates")
protected void getAffiliatesCount(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//call ConnectToDatabase
try {
String email = request.getParameter("email");
String password = request.getParameter("password");
HttpSession session = request.getSession();
session.setAttribute("email", email);
try {
String query = "SELECT count(affiliates.userid) AS affiliatestotal from affiliates, users where affiliates.userid=users.id and users.email=? and users.password=?";
int affiliatescount = 0;
Connection connection = EventsDAO.getConnection();
PreparedStatement st = connection.prepareStatement(query);
st.setString(1, email);
st.setString(2, password);
ResultSet rs = st.executeQuery();
while (rs.next()){
affiliatescount = rs.getInt("affiliatestotal");
request.setAttribute("affiliatescount",affiliatescount);
RequestDispatcher rd = request.getRequestDispatcher("dashboard.jsp");
rd.include(request, response);
}
} catch (SQLException e) {
e.printStackTrace();
}
}catch(Exception ex){ex.printStackTrace();}
}
}
仪表板.jsp
<div class="card card-sm">
<div class="card-body">
<div class="d-flex justify-content-between mb-5">
<div>
<span class="d-block font-15 text-dark font-weight-500">My Events</span>
</div>
<div>
<span class="text-warning font-14 font-weight-500">-2.8%</span>
</div>
</div>
<div>
<span class="d-block display-4 text-dark mb-5">${count}</span>
<small class="d-block">100 Targeted</small>
</div>
</div>
</div>
编辑:我还想知道是否允许使用重定向到同一页面的请求调度程序显示 3 个方法,如下面的代码所示
UserLogin.java Servlet
@SuppressWarnings("Duplicates")
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processRequest(request,response);
getEventsCount(request,response);
getAffiliatesCount(request,response);
}
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processRequest(request,response);
getEventsCount(request,response);
getAffiliatesCount(request, response);
}
更新:我能够通过使用字符串作为所有 getDispatcher 转发器的占位符来解决数据显示问题。但是错误页面现在无法正确显示。这是我的代码:
用户登录.java
String page = "";
@SuppressWarnings("Duplicates")
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//call ConnectToDatabase
try{
String email = request.getParameter("email");
String password = request.getParameter("password");
OrganizerDao e = new OrganizerDao();
HttpSession session = request.getSession();
session.setAttribute("email", email);
Connection con= OrganizerDao.getConnection();
PreparedStatement st=con.prepareStatement("select id, firstname, lastname from users where email=? and password=?");
st.setString(1,email);
st.setString(2,password);
ResultSet rs=st.executeQuery();
if (rs.next()) {
request.setAttribute("id",rs.getInt("id"));
request.setAttribute("firstname",rs.getString("firstname"));
request.setAttribute("lastname",rs.getString("lastname"));
//RequestDispatcher rd = request.getRequestDispatcher("dashboard.jsp");
//rd.include(request, response);
page = "dashboard.jsp";
} else {
out.println("<div class=\"alert alert-danger\" role=\"alert\">");
out.println("<center>Oh snap! Change a few things and try submitting again.</center>");
out.println("</div>");
//request.getRequestDispatcher("/login.jsp").include(request, response);
page = "/login.jsp";
}
con.close();
}catch(Exception ex){ex.printStackTrace();}
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//call ConnectToDatabase
processRequest(request,response);
getEventsCount(request,response);
getAffiliatesCount(request,response);
getTotalWithdrawal(request, response);
if(page!=null){
request.getRequestDispatcher("/dashboard.jsp").include(request, response);
}else {
out.println("<div class=\"alert alert-danger\" role=\"alert\">");
out.println("<center>Oh snap! Change a few things and try submitting again.</center>");
out.println("</div>");
request.getRequestDispatcher("/login.jsp").include(request, response);
}
}
解决方案
你的实现在这里很遥远。您需要执行以下操作。您可以使用 JSP EL 访问请求属性:
<p>Event Count is ${eventCount}</p>
<p>Affiliate Count is ${affiliateCount}</p>
<p>User Name is ${user.forename} ${user.surname}</p>
小服务程序
@WebServlet("/organizer")
public class UserLogin extends HttpServlet {
protected void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
@SuppressWarnings("Duplicates")
protected void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
String email = request.getParameter("email");
String password = request.getParameter("password");
User user = getUsert(emil password)
if(user != null){
request.setAttributes("eventCount", getEventsCount(email, password));
request.setAttributes("affiliateCount", getAffiliatesCount(email,password));
request.getRequestDispatcher("/dashboard.jsp").forward(request, response);
}else{
request.setAttribute("failedLogin", true);
request.getRequestDispatcher("/login.jsp").forward(request, response);
}
}
protected User getUser(String email String password){}
User user = null; //create a class user with 3 fields
// Query
if(rs.next()){
user = new User(rs.getInt("id"),
rs.getString("firstname"),
rs.getString("lastname"))
}
return user;
}
protected int getEventsCount(String email, String password)
throws ServletException, IOException {
// query and return result
return count;
}
protected void getAffiliatesCount(String email, String password)
throws ServletException, IOException {
// query and return result
return count;
}
}
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