java 在同一页面上获取、处理和显示结果
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/11177971/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Fetch, process and display the result on the same page
提问by Chitransh Saurabh
I have a jsp page containing a form where a user fills in some value. Now i pass these values into a servlet which processes it and retieves a related set of data. Now, i am able to retrieve the data in the servlet page, but am not able to display it on the same jsp page at which i fetched the request.
我有一个包含用户填写一些值的表单的 jsp 页面。现在我将这些值传递到一个 servlet 中，该 servlet 处理它并检索一组相关的数据。现在，我能够在 servlet 页面中检索数据，但无法在我获取请求的同一个 jsp 页面上显示它。
I do not want to use java code inside jsp. I wish to do the same using servlets only. I do not want to do something like this
我不想在jsp中使用java代码。我希望只使用 servlet 来做同样的事情。我不想做这样的事情
<% if(rollno==null)
// then display the form
else
// process the request on the jsp page itself
%>
I want to process all my reults in a servlet file and then dispaly the result on the jsp page by passing data from servlet to jsp. I am posting my code below :
我想在一个 servlet 文件中处理我的所有结果，然后通过将数据从 servlet 传递到 jsp 来在 jsp 页面上显示结果。我在下面发布我的代码：
<form id="form" method="post" action="searchServlet">
Student Roll No :<br><input type="text" value="" name="rollno"><br><br>
<input type="submit" value="SHOW DETAILS" />
</form>
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
String rollno=request.getParameter("rollno");
ResultSet rs=null;
Class.forName("com.mysql.jdbc.Driver");
String url="jdbc:mysql://localhost/schooldatabase";
Connection con = DriverManager.getConnection(url,"root","passwd");
Statement st= (Statement) con.createStatement();
String strquery="SELECT name,regno FROM `schooldatabase`.`student_info` WHERE rollno="+ rollno+ ";";
if(!con.isClosed()) {
rs=st.executeQuery(strquery);
while(rs.next())
{
out.println(rs.getString("name"));
out.println(rs.getString("regno"));
}
}
else
{ // The connection is closed
}
}
catch(Exception e)
{
out.println(e);
}
finally {
out.close();
}
}
回答by BalusC
You shouldn't be doing the presentation in the servlet. You should nothave anyof those lines in the servlet.
您不应该在 servlet 中进行演示。你应该不会有任何在servlet的线。
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
// ...
out.println(rs.getString("name"));
out.println(rs.getString("regno"));
// ...
out.println(e);
You should instead be storing the data in a sensible collection and be setting it as a request attribute and finally forward the request/response to a JSP which in turn generates the proper HTML around all those data. Something like this:
相反，您应该将数据存储在一个合理的集合中，并将其设置为请求属性，最后将请求/响应转发到 JSP，后者又会围绕所有这些数据生成正确的 HTML。像这样的东西：
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
List<Student> students = studentDAO.find(request.getParameter("rollno"));
request.setAttribute("students", students); // Will be available as ${students} in JSP
request.getRequestDispatcher("/WEB-INF/students.jsp").forward(request, response);
} catch (SQLException e) {
throw new ServletException("Cannot obtain students from DB", e);
}
}
with this in the students.jsp
有了这个 students.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
...
<table>
<c:forEach items="${students}" var="student">
<tr>
<td>${student.name}</td>
<td>${student.regno}</td>
</tr>
</c:forEach>
</table>
For a more concrete example, see also this answer: Show JDBC ResultSet in HTML in JSP page using MVC and DAO pattern
有关更具体的示例，另请参阅此答案：使用 MVC 和 DAO 模式在 JSP 页面中的 HTML 中显示 JDBC ResultSet
See also:
也可以看看：
- Our Servlets wiki page- Contains several Hello World examples
- 我们的 Servlets wiki 页面- 包含几个 Hello World 示例
