Sending request.setAttribute?

What I am trying to do is read file and send the text to jsp

first, I read the context of my text file from fileGet.java. Then using request.setAttribute(“chat”, chat), I want to send the context to Live_index6.jsp

However, as I use request.getAttribute(“chat”) in Live_index6.jsp to receive the data, it kept print “null”

I checked that request.getAtrribute successfully printed the data I wanted in fileController.java, but it does not in Live_index6.jsp

I searched internet and it said code in controller

RequestDispatcher rd1 = request.getRequestDispatcher(str);
rd1.forward(request, response);

JavaScript
​x
 
RequestDispatcher rd1 = request.getRequestDispatcher(str);
rd1.forward(request, response);
​

will send the request data to place where I directed, which is str == “Live_index6.jsp” that I setted.

can you guys please check my code and what is the problem?

Thank you so much!

this is my Live_index6.jsp

<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=EUC-KR"
    pageEncoding="EUC-KR"%>
 <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 
<!DOCTYPE html>
<html>
<head>
<meta charset="EUC-KR">
<title>Insert title here</title>
<script src="jquery-3.3.1.js"></script>
<style>

 textarea {
    width: 300px;
    height: 300px;
  }

</style>

</head>
<body>

<% String user = request.getParameter("userName"); 
user = "hong";
%>
<%=request.getAttribute("chat")  %>
 <h3>Chat</h3>
 <textarea row = "20" col="50" readonly id = "ta1">
 

 
 
 </textarea><br>
 <h3>Who?</h3>
 <input type = "Text" id = "who1" value = "<%=user%>" height = "300px" disabled>
 <h4>보낼 글</h4>
<input type = "text" id = "chat1" onkeyup="enterkey()">
<input type = "button" value = "가자" onclick="insertFile(); kajaChool()">

 
 
 <br>
 귓속말시 /wnickname (chatting)을 해야합니다. 닉네임과 chatting에 빈공간이 없을시 귓속말이 안보내집니다.

<script>
    window.onload = function(){
        const name = document.getElementById("who1").value;
        $.ajax({ // $.ajax() $.get $.post
            url:"getAllFile.do",
            data: { 
                name : name
            }, // kaja.jsp?irum=hong&na2=35
            dataType:"text",
            type:"post",
            success: function(result1){ 
                //place where I want to print my file context
                alert();
            },
            error: function(xhr1,status){
                alert("에러상태: " + "t" + xhr1.status);
            }
        });
    }
    
    function enterkey(){
        if(window.event.keyCode == 13){
            insertFile();
            kajaChool();
        }
    }
    
    function insertFile(){
        const name = document.getElementById("who1").value;
        const chat = document.getElementById("chat1").value;
        $.ajax({ // $.ajax() $.get $.post
            url:"insertFile.do",
            data: { 
                name : name,
                chat : chat
            }, // kaja.jsp?irum=hong&na2=35
            dataType:"text",
            type:"post",
            success: function(result1){ 
                
            },
            error: function(xhr1,status){
                alert("error: " + "t" + xhr1.status);
            }
        });
    }
    
    function kajaChool(){
        document.getElementById("who1").disabled = true; 
        var tmp = document.getElementById("chat1").value;
        
        
        if(tmp.substring(0,2) != "/w"){
            ta1.value += "[" + who1.value + "]" + chat1.value + "n";
            ws1.send("[" + who1.value + "]" + chat1.value);
        }else{
            var index = tmp.indexOf(" ") + 1;
            var toNickName = tmp.substring(2,index-1);
            
            if(true){
                ta1.value += "[" + who1.value + "]" + " >> " + "[" + toNickName + "]" + tmp.substring(index) + "n";
                ws1.send("[" + who1.value + "]" + chat1.value);
            }else{
                alert("존재하지 않는 닉네임입니다.");
                chat1.value = "";
                chat1.focuse();
                return;
            }
        }
        /*
        if(tmp.indexOf("/w") == -1){
            ta1.value += "[" + who1.value + "]" + chat1.value + "n";
        }else{
            var index = tmp.indexOf(" ") + 1;
            var toNickName = tmp.substring(2,index-1);
            ta1.value += "[" + who1.value + "]" + " >> " + "[" + toNickName + "]" + tmp.substring(index) + "n";
        }
        */
        // ws1.send("[" + who1.value + "]" + chat1.value);
        
        chat1.value = "";
        chat1.focuse();
    }


</script>

<script>

    const ws1 = new WebSocket("ws://localhost:8080/Live_Chat6/kaja");
    
    
    const ta1 = document.getElementById("ta1");
    
    ws1.onerror = function(aa){
        alert("error");
    };
    ws1.onopen = function(aa){
        alert("[chat]");
        who1.focus();
        who1.select();
    };
    
    ws1.onmessage = function(aa){ 
        const name = document.getElementById("who1").value;
        const arr = aa.data.split("]");
        const tmp = arr[1];
        const comp = tmp.substring(0,2) == "/w" ;
        
        //ta1.value += comp + "n";
        
        
        if(comp){
            var index = tmp.indexOf(" ") + 1;
            var toNickName = tmp.substring(2,index-1);
            if(name == toNickName){
                ta1.value += "["+arr[0].substring(1)+"] >> " + "[" + toNickName + "]" + tmp.substring(index) + "n";
            }
        }else{
            ta1.value += aa.data + "n";
        }
        
    
    };
    
</script>


</body>
</html>

JavaScript
 
<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=EUC-KR"
    pageEncoding="EUC-KR"%>
 <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 
<!DOCTYPE html>
<html>
<head>
<meta charset="EUC-KR">
<title>Insert title here</title>
<script src="jquery-3.3.1.js"></script>
<style>
​
 textarea {
    width: 300px;
    height: 300px;
  }
​
</style>
​
</head>
<body>
​
<% String user = request.getParameter("userName"); 
user = "hong";
%>
<%=request.getAttribute("chat")  %>
 <h3>Chat</h3>
 <textarea row = "20" col="50" readonly id = "ta1">
 
​
 
 
 </textarea><br>
 <h3>Who?</h3>
 <input type = "Text" id = "who1" value = "<%=user%>" height = "300px" disabled>
 <h4>보낼 글</h4>
<input type = "text" id = "chat1" onkeyup="enterkey()">
<input type = "button" value = "가자" onclick="insertFile(); kajaChool()">
​
 
 
 <br>
 귓속말시 /wnickname (chatting)을 해야합니다. 닉네임과 chatting에 빈공간이 없을시 귓속말이 안보내집니다.
​
<script>
    window.onload = function(){
        const name = document.getElementById("who1").value;
        $.ajax({ // $.ajax() $.get $.post
            url:"getAllFile.do",
            data: { 
                name : name
            }, // kaja.jsp?irum=hong&na2=35
            dataType:"text",
            type:"post",
            success: function(result1){ 
                //place where I want to print my file context
                alert();
            },
            error: function(xhr1,status){
                alert("에러상태: " + "t" + xhr1.status);
            }
        });
    }
    
    function enterkey(){
        if(window.event.keyCode == 13){
            insertFile();
            kajaChool();
        }
    }
    
    function insertFile(){
        const name = document.getElementById("who1").value;
        const chat = document.getElementById("chat1").value;
        $.ajax({ // $.ajax() $.get $.post
            url:"insertFile.do",
            data: { 
                name : name,
                chat : chat
            }, // kaja.jsp?irum=hong&na2=35
            dataType:"text",
            type:"post",
            success: function(result1){ 
                
            },
            error: function(xhr1,status){
                alert("error: " + "t" + xhr1.status);
            }
        });
    }
    
    function kajaChool(){
        document.getElementById("who1").disabled = true; 
        var tmp = document.getElementById("chat1").value;
        
        
        if(tmp.substring(0,2) != "/w"){
            ta1.value += "[" + who1.value + "]" + chat1.value + "n";
            ws1.send("[" + who1.value + "]" + chat1.value);
        }else{
            var index = tmp.indexOf(" ") + 1;
            var toNickName = tmp.substring(2,index-1);
            
            if(true){
                ta1.value += "[" + who1.value + "]" + " >> " + "[" + toNickName + "]" + tmp.substring(index) + "n";
                ws1.send("[" + who1.value + "]" + chat1.value);
            }else{
                alert("존재하지 않는 닉네임입니다.");
                chat1.value = "";
                chat1.focuse();
                return;
            }
        }
        /*
        if(tmp.indexOf("/w") == -1){
            ta1.value += "[" + who1.value + "]" + chat1.value + "n";
        }else{
            var index = tmp.indexOf(" ") + 1;
            var toNickName = tmp.substring(2,index-1);
            ta1.value += "[" + who1.value + "]" + " >> " + "[" + toNickName + "]" + tmp.substring(index) + "n";
        }
        */
        // ws1.send("[" + who1.value + "]" + chat1.value);
        
        chat1.value = "";
        chat1.focuse();
    }
​
​
</script>
​
<script>
​
    const ws1 = new WebSocket("ws://localhost:8080/Live_Chat6/kaja");
    
    
    const ta1 = document.getElementById("ta1");
    
    ws1.onerror = function(aa){
        alert("error");
    };
    ws1.onopen = function(aa){
        alert("[chat]");
        who1.focus();
        who1.select();
    };
    
    ws1.onmessage = function(aa){ 
        const name = document.getElementById("who1").value;
        const arr = aa.data.split("]");
        const tmp = arr[1];
        const comp = tmp.substring(0,2) == "/w" ;
        
        //ta1.value += comp + "n";
        
        
        if(comp){
            var index = tmp.indexOf(" ") + 1;
            var toNickName = tmp.substring(2,index-1);
            if(name == toNickName){
                ta1.value += "["+arr[0].substring(1)+"] >> " + "[" + toNickName + "]" + tmp.substring(index) + "n";
            }
        }else{
            ta1.value += aa.data + "n";
        }
        
    
    };
    
</script>
​
​
</body>
</html>
​
​

my FileController.java

package frontController;

import java.io.IOException;

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;

import Services.fileGet;
import Services.fileImpl;
import Services.fileInsert;

/**
 * Servlet implementation class FileController
 */
@WebServlet("*.do")
public class FileController extends HttpServlet {
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public FileController() {
        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
        //response.getWriter().append("Served at: ").append(request.getContextPath());
        System.out.println("완료");
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //doGet(request, response);
        
        
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        /*******************************/
        String c =request.getRequestURI().substring
                     (request.getContextPath().length());
        /**********************************/
        
        String str = "Live_index6.jsp";  ///////////
        fileImpl fi = null; 
        switch(c) {
        
        case "/insertFile.do":
            fi = new fileInsert();
            try {
                fi.fileWork(request, response);
            }catch(Exception e){
                System.out.println(e.getMessage());
            }
            break;  
            
            
        case "/getAllFile.do":
            fi = new fileGet();
            try {
                fi.fileWork(request, response);
            }catch(Exception e) {
                System.out.println(e.getMessage());
            }
            break;
        } //swich -end 
        //String chat = (String) request.getAttribute("chat");
        //System.out.println(chat);
        
        RequestDispatcher rd1 = request.getRequestDispatcher(str);
        rd1.forward(request, response);
        
    }

}

JavaScript
 
package frontController;
​
import java.io.IOException;
​
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;
​
import Services.fileGet;
import Services.fileImpl;
import Services.fileInsert;
​
/**
 * Servlet implementation class FileController
 */
@WebServlet("*.do")
public class FileController extends HttpServlet {
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public FileController() {
        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
        //response.getWriter().append("Served at: ").append(request.getContextPath());
        System.out.println("완료");
    }
​
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //doGet(request, response);
        
        
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        /*******************************/
        String c =request.getRequestURI().substring
                     (request.getContextPath().length());
        /**********************************/
        
        String str = "Live_index6.jsp";  ///////////
        fileImpl fi = null; 
        switch(c) {
        
        case "/insertFile.do":
            fi = new fileInsert();
            try {
                fi.fileWork(request, response);
            }catch(Exception e){
                System.out.println(e.getMessage());
            }
            break;  
            
            
        case "/getAllFile.do":
            fi = new fileGet();
            try {
                fi.fileWork(request, response);
            }catch(Exception e) {
                System.out.println(e.getMessage());
            }
            break;
        } //swich -end 
        //String chat = (String) request.getAttribute("chat");
        //System.out.println(chat);
        
        RequestDispatcher rd1 = request.getRequestDispatcher(str);
        rd1.forward(request, response);
        
    }
​
}
​
​

My fileGet.java

package Services;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.util.ArrayList;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class fileGet implements fileImpl{

    @Override
    public void fileWork(HttpServletRequest request, HttpServletResponse response) throws Exception {
        // TODO Auto-generated method stub
        
        String path = request.getSession().getServletContext().getRealPath("/") + "/Chat_Log/chat_log.txt";
        //String path = "c:/Chat_Log/chat_log.txt";
        //ArrayList<String> chat = new ArrayList<String>();
        String chat = "";
        try{
            
            File file = new File(path);
            
            FileReader filereader = new FileReader(file);
                        BufferedReader bufReader = new BufferedReader(filereader);
            String line = "";
            while((line = bufReader.readLine()) != null){
                chat += line + "n";
            }            
            bufReader.close();
        }catch (Exception e) {
            System.out.println(e.getMessage());
        }
        request.setAttribute("chat", chat);
        
    }
    

}

JavaScript
 
package Services;
​
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.util.ArrayList;
​
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
​
public class fileGet implements fileImpl{
​
    @Override
    public void fileWork(HttpServletRequest request, HttpServletResponse response) throws Exception {
        // TODO Auto-generated method stub
        
        String path = request.getSession().getServletContext().getRealPath("/") + "/Chat_Log/chat_log.txt";
        //String path = "c:/Chat_Log/chat_log.txt";
        //ArrayList<String> chat = new ArrayList<String>();
        String chat = "";
        try{
            
            File file = new File(path);
            
            FileReader filereader = new FileReader(file);
                        BufferedReader bufReader = new BufferedReader(filereader);
            String line = "";
            while((line = bufReader.readLine()) != null){
                chat += line + "n";
            }            
            bufReader.close();
        }catch (Exception e) {
            System.out.println(e.getMessage());
        }
        request.setAttribute("chat", chat);
        
    }
    
​
}
​
​

Answer

I faced same problem and to solve it I used HttpSession instead of request and response.sendRedirect instead of requestDispatcher this is the code that I used, you need only to reform it

session.setAttribute("eqmsg", "Equipment Added Successfully");
                response.sendRedirect("http://localhost:8080/SmartFarmManagementSystem/addView.jsp");

JavaScript
 
session.setAttribute("eqmsg", "Equipment Added Successfully");
                response.sendRedirect("http://localhost:8080/SmartFarmManagementSystem/addView.jsp");
​

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Answer