本文介绍了将整数变量从jsp传递到servlet的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个jsp页面，其中有两个变量是标志变量....我想将这些变量传递给servlet.我应该如何将这些变量传递给servlet?
I have a jsp page where there are two variables which are flag variables....I want to pass these variables to a servlet. How should I pass these variables to a servlet?
这是我的jsp页面.
<html>
<head>
<title>Student Registration Form</title>
<style type="text/css">
h3{font-family: Calibri; font-size: 22pt; font-style: normal; font-weight: bold; color:SlateBlue;
text-align: center; text-decoration: underline }
table{font-family: Calibri; color:white; font-size: 11pt; font-style: normal;
text-align:; background-color: SlateBlue; border-collapse: collapse; border: 2px solid navy}
table.inner{border: 0px}
</style>
</head>
<body>
<h3>Create Category</h3>
<form action="insert_category" method="POST">
<table align="center" cellpadding = "10">
<tr>
<td>Category Name</td>
<td><input type="text" name="category_name" maxlength="30"/>
(max 30 characters a-z and A-Z)
</td>
</tr>
<%
int flag=1;
int operation=1;
request.setAttribute("flag", String.valueOf(flag));
request.setAttribute("operation", String.valueOf(operation));
%>
<tr>
<td>Category Code</td>
<td><input type="text" name="category_code" maxlength="30"/>
(max 30 characters a-z and A-Z)
</td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" value="Submit">
<input type="reset" value="Reset">
</td>
</tr>
</table>
</form>
</body>
</html>
Servlet
package com.kunal.servlet;
import java.io.IOException;
import java.sql.*;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class CreateCategory
*/
@WebServlet("/CreateCategory")
public class InsertCategory extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public InsertCategory() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String category__name=request.getParameter("category_name");
String category_code=request.getParameter("category_code");
int flag=(int)request.getAttribute("flag");
int operation=(int)request.getAttribute("operation");
if(flag==1 && operation==1)
{
String connectionURL = "jdbc:mysql://localhost:3306/agro";
Connection connection = null;
long catcode=Integer.parseInt(category_code);
try {
// Load the database driver
Class.forName("com.mysql.jdbc.Driver");
// Get a Connection to the database
connection = DriverManager.getConnection(connectionURL, "root", "");
//Add the data into the database
//String sql = "insert into sample values(?,?)";
PreparedStatement pst = connection.prepareStatement("INSERT into tbl_category VALUES(?,?,?)");
pst.setString(1,null);
pst.setString(2,category__name);
pst.setLong(3,catcode);
int numRowsChanged = pst.executeUpdate();
if(numRowsChanged!=0){
System.out.println("Successfull execution");
RequestDispatcher rd = request.getRequestDispatcher("adminhome.jsp");
rd.forward(request, response);
}
else{
System.err.println("Problem with the insertion query");
}
pst.close();
}
catch(ClassNotFoundException e){
e.printStackTrace();
}
catch(SQLException e){
e.printStackTrace();
}
catch (Exception e){
e.printStackTrace();
}
finally {
// Always close the database connection.
try {
if (connection != null) connection.close();
}
catch (SQLException ignored){
}
}
}
}
}
我不能使用getParameters()方法，因为它们只是两个变量.有什么方法可以将这些传递给servlet吗?我收到NullPointerException
I cannot use getParameters() method because these are simply two variables. Is there any way to pass these to servlet? I am getting a NullPointerException
StackTrace
StackTrace
Aug 12, 2014 1:22:10 PM org.apache.catalina.core.AprLifecycleListener init
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
Aug 12, 2014 1:22:11 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:Agro' did not find a matching property.
Aug 12, 2014 1:22:11 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-nio-8080"]
Aug 12, 2014 1:22:11 PM org.apache.tomcat.util.net.NioSelectorPool getSharedSelector
INFO: Using a shared selector for servlet write/read
Aug 12, 2014 1:22:11 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-nio-8009"]
Aug 12, 2014 1:22:11 PM org.apache.tomcat.util.net.NioSelectorPool getSharedSelector
INFO: Using a shared selector for servlet write/read
Aug 12, 2014 1:22:11 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 673 ms
Aug 12, 2014 1:22:11 PM org.apache.catalina.core.StandardService startInternal
INFO: Starting service Catalina
Aug 12, 2014 1:22:11 PM org.apache.catalina.core.StandardEngine startInternal
INFO: Starting Servlet Engine: Apache Tomcat/8.0.9
Aug 12, 2014 1:22:11 PM org.apache.jasper.servlet.TldScanner scanJars
INFO: At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
Aug 12, 2014 1:22:11 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["http-nio-8080"]
Aug 12, 2014 1:22:11 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["ajp-nio-8009"]
Aug 12, 2014 1:22:11 PM org.apache.catalina.startup.Catalina start
INFO: Server startup in 675 ms
Aug 12, 2014 1:22:25 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [InsertServlet] in context with path [/Agro] threw exception
java.lang.NullPointerException
at com.kunal.servlet.InsertCategory.doPost(InsertCategory.java:42)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:644)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:136)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:526)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:655)
at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
推荐答案
如果要在提交表单时传递flag和operation参数，则可以将其存储在隐藏字段中，以便在提交时它会与您的form参数一起发送.
If you want to passed flag and operation parameter at the time of form submit than you can store it in hidden field, so that when you submit form it will send with your form parameter.
<form action="insert_category">
<input type="hidden" name="flag" value="1">
<input type="hidden" name="operation" value="1">
....rest of your code
</form>
在服务器端，您可以通过request.getParameter()来获得此参数，如下所示:
at server side you get this parameter by request.getParameter() like below :
int flag=(int)request.getParameter("flag");
int operation=(int)request.getParameter("operation");
OR
您可以将该参数存储在session中，并从服务器端的会话获取值，例如:
OR
you may store this parameter in session and get value from session on server side for example :
在您的JSP中:
<%
session.setAttribute("flag", String.valueOf(flag));
session.setAttribute("operation", String.valueOf(operation));
%>
在servlet的服务器端:
On server side in servlet :
HttpSession session = request.getSession();
int flag=(int)session.getAttribute("flag");
int operation=(int)session.getAttribute("operation");
愿这对您有帮助.
这篇关于将整数变量从jsp传递到servlet的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！