Servlet JSP getparameter getattribute returning null
Question
I'm having trouble with passing servlet variables to jsp.
Of course, I also have the web.xml set for the servlet already
<servlet>
<servlet-name>databaseServlet</servlet-name>
<servlet-class>Servlet.databaseServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>databaseServlet</servlet-name>
<url-pattern>/dbServlet</url-pattern>
</servlet-mapping>
The result is all of the name, owner, species and sex values are null. Can someone help me with this? Thanks
PS: I also tried to use request.getSession().setAttribute in the servlet, didn't work either
PPS: So if I make the following changes:
databaseServlet.java
package Servlet;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import java.util.ArrayList;
@SuppressWarnings("serial")
public class databaseServlet extends HttpServlet {
private Connection conn;
private Statement statement;
String name;
String owner;
String species;
String sex;
String birth;
String death;
public void init(ServletConfig config) throws ServletException {
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(
"jdbc:mysql://localhost/STUDENTS",
"root",
"");
statement = conn.createStatement();
String sql = "SELECT name, owner, species, sex, birth, death FROM pet";
ResultSet rs = statement.executeQuery(sql);
//STEP 5: Extract data from result set
while(rs.next()){
//Retrieve by column name
name = rs.getString("name");
owner = rs.getString("owner");
species = rs.getString("species");
sex = rs.getString("sex");
birth = rs.getString("birth");
death = rs.getString("death");
}
rs.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setAttribute("NAME", "Hello");
System.out.println(name);
request.setAttribute("OWNER",owner);
request.setAttribute("SPECIES",species);
request.setAttribute("SEX", sex);
RequestDispatcher dispatcher=getServletConfig().getServletContext().getRequestDispatcher("/dbServlet.jsp");
dispatcher.forward(request, response);
}
}
and this is my new jsp:
<body>
Name="${databaseServlet.NAME}"
Owner="${databaseServlet.OWNER}"
Species="<%= request.getAttribute("SPECIES") %>"
Sex="<%= request.getSession().getAttribute("SEX") %>"
</body>
both Name and Owner returns empty string, while Species and Sex still returns NULL
basically what I'm trying to do is to access MySQL database to retrieve variables from a table, and display it using JSP
3 answers
solution1
0 2014-01-08 07:37:21
Make sure that you have valid values for name , owner , species and sex when setting request attribute inside doPost method.
Use EL syntax like
${NAME}
${OWNER}
${SPECIES}
${SEX}
Do not write scriptlets in JSP , because scriptlets shouldn't be used in JSPs for more than a decade. Learn the JSP EL , the JSTL , and use servlet for the Java code. How to avoid Java Code in JSP-Files?
solution2
0 2014-01-08 07:46:18
Try using
RequestDispatcher dispatcher=getServletConfig().getServletContext().getRequestDispatcher("/dbServlet.jsp");
I guess it should work. And use request.getAttribute() only, it will return Object type, you will have to cast it
solution3
0 2017-05-23 00:35:24
Just give a scope to your attributes, and you can change your code like this :
protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.getSession().setAttribute("NAME", "Hello");
System.out.println(name);
request.getSession().setAttribute("OWNER",owner);
request.getSession().setAttribute("SPECIES",species);
request.getSession().setAttribute("SEX", sex);
RequestDispatcher dispatcher=getServletConfig().getServletContext().getRequestDispatcher("/dbServlet.jsp");
dispatcher.forward(request, response);
}
And when you handling the attribute make it sessionScope like :
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<body>
<c:set var="myName" value="NAME" />
<c:set var="myOwner" value="OWNER" />
Name="${sessionScope[myName]}"
Owner="${sessionScope[myOwner]}"
//etc...
</body>
I hope this helps you.
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