Servlet example to perform Edit, Add operation on File

Requirement :- User has a course and can add course in it dependend on other. User can edit also the same course. Text file can have commented code like starting with # in the text file, So neglect such tile

Following are the servlet code

1:- ReadTextFileServlet

package com.test;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Vector;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ReadTextFileServlet extends HttpServlet {

//Vector av = new Vector();
HtmlUtils hu = new HtmlUtils();
PrintWriter out;
ServletContext context;
String filename = "/WEB-INF/Course1.txt";

/* protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html");

// We are going to read a file called configuration.properties. This
// file is placed under the WEB-INF directory.
String filename = "/WEB-INF/Course.txt";

ServletContext context = getServletContext();

// First get the file InputStream using ServletContext.getResourceAsStream()
// method.
InputStream is = context.getResourceAsStream(filename);
if (is != null) {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader reader = new BufferedReader(isr);
PrintWriter writer = response.getWriter();
String text;

// We read the file line by line and later will be displayed on the
// browser page.
while ((text = reader.readLine()) != null) {
writer.println(text + "");
}
}
}*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
printTable(request, response);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
printTable(request, response);
}

public void printTable(HttpServletRequest request,
HttpServletResponse response) throws IOException {

response.setContentType("text/html");
PrintWriter out = response.getWriter();
Vector av = new Vector();

out.print(hu.createHtmlHeader("Print Table"));

out.print(hu.getTableHead("center", 1));

out.print(hu.getTH("center", "Code"));
out.print(hu.getTH("center", "Title"));
out.print(hu.getTH("center", "Prerequisites"));
out.print(hu.getTH("center", "Operation"));

ServletContext context = getServletContext();
InputStream is = context.getResourceAsStream(filename);
if (is != null) {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader reader = new BufferedReader(isr);
//PrintWriter writer = response.getWriter();
String text;

while ((text = reader.readLine()) != null) {

if(text.length() > 0 && text.trim().indexOf('#') != 0) {
//writer.println(text + "");
String[] sArray = text.split(",",0);
if(sArray.length==1)
{
String parameter = "";
for(int i=0;iav.addElement(sArray[0]);
parameter = sArray[0];
}
av.addElement("");
av.addElement("");
av.addElement("Edit");

}else if (sArray.length==2)
{
String parameter1 = "";
for(int i=0;iav.addElement(sArray[i]);
parameter1 = parameter1 + "-" + sArray[i];
}
av.addElement("");
av.addElement("Edit");

}else
{
String parameter2 = "";
for(int i=0;iav.addElement(sArray[i]);
parameter2 = parameter2 + "-" +sArray[i];
}
av.addElement("Edit");

}

}
}
}

out.print(hu.getTableContents("center", av, 4));
out.print(hu.getTR());
out.print(hu.getTD());
out.println("Add Course");
out.print(hu.getClosedTD());
out.print(hu.getClosedTR());
out.print(hu.getHtmlFooter());

}

class HtmlUtils {

public String createHtmlHeader(String title) {

String htmlHeader = null;
htmlHeader = "";
return htmlHeader;
}

public String getHtmlFooter() {

String htmlFooter = "

";
return htmlFooter;
}

public String getHead(int level, String heading) {
return " " + heading + "";
}

public String getTableHead(String align, int border) {

String tableHeader = null;
tableHeader = "";
return tableHeader;

}

public String getTR(String align) {
String TRCell = null;
TRCell = " ";
return TRCell;
}

public String getTR() {
String TRCell = null;
TRCell = " ";
return TRCell;
}

public String getTD(String align, String value) {
String TDCell = null;
TDCell = "
" + value + "
";
return TDCell;
}

public String getTD() {
String TDCell = null;
TDCell = "
";
return TDCell;
}

public String getTD(int width) {
String TDCell = null;
TDCell = "
";
return TDCell;
}

public String getTH(String align, String value) {
String THCell = null;
THCell = "
" + value + "
";
return THCell;
}

public String getTableContents(String align, Vector values, int elementCounter) throws IOException {

StringWriter Cells = new StringWriter();
String contents = new String();
int vsize = values.size();

Cells.write(" ");

for (int i = 0; i < vsize; i++) {
String value = values.elementAt(i).toString();

if (i != 0) {
if (i >= elementCounter) {

if (i % elementCounter == 0) {
Cells.write("

\n\n ");
}
}
}

Cells.write("
" + value + "
\n");
}

Cells.write("

");

contents = Cells.toString();
Cells.flush();
Cells.close();

return contents;
}

public String getClosedTR() {
String TRCell = null;
TRCell = "

";
return TRCell;
}

public String getClosedTD() {
String TDCell = null;
TDCell = "

";
return TDCell;
}

public String getBR(int lines) {

StringWriter lineBR = new StringWriter();
String lineBRs = new String();

for (int i = 0; i <= lines; i++) {
lineBR.write("
\n");
}
lineBRs = lineBR.toString();

return lineBRs;
}

public String getLI(String item) {

String li = new String("

");
li += item;
return li;

}
}
}

2:- AddCourseTextFileServlet

package com.test;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Vector;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AddCourseTextFileServlet extends HttpServlet {

/**
*
*/
private static final long serialVersionUID = 1L;

Vector

ServletContext context;
String filename = "/WEB-INF/Course1.txt";

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
context = getServletContext();
printTable(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//printTable(request, response);
String finalCheckBox="";
PrintWriter out = response.getWriter();
String button1Click = request.getParameter("Submit");
System.out.println("button1Click"+button1Click);

File outputFile = new File(getServletContext().getRealPath("/WEB-INF/")
+ "/Course1.txt");
FileWriter fout = new FileWriter(outputFile,true);

try {

InputStream is = context.getResourceAsStream(filename);
if (is != null) {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader reader = new BufferedReader(isr);

String text;
int k=0;
while ((text = reader.readLine()) != null) {

if(text.length() > 0 && text.trim().indexOf('#') != 0) {
k = k +1 ;
String[] sArray = text.split(",",2);
String [] checkboxNamesList = new String[sArray.length];

for(int i=0;i{
checkboxNamesList= request.getParameterValues(sArray[i]);

if(null != checkboxNamesList)
{
finalCheckBox = finalCheckBox + sArray[i].toString() + " ";
}
else
{
finalCheckBox = finalCheckBox;
}

}

}
}
System.out.println("Value of record is:"+k);
}

} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

String finalString = request.getParameter("Code") + "," + request.getParameter("Title") + "," + finalCheckBox;
fout.write("\n");
fout.write(finalString);
fout.close();
RequestDispatcher rd = request.getRequestDispatcher("readTextFileServlet");
rd.forward(request,response);

}

public void printTable(HttpServletRequest request,
HttpServletResponse response) throws IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("");
out.println("");
out.println("");
out.println("");
out.println("");
out.println("

");

out.println("");

out.println("
Code:
");
out.println("
");
out.println(" ");

out.println("
Title:
");
out.println("
");
out.println(" ");

out.println("
Prerequisite(s):
");
try {

InputStream is = context.getResourceAsStream(filename);
if (is != null) {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader reader = new BufferedReader(isr);

String text;
int k=0;
while ((text = reader.readLine()) != null) {

if(text.length() > 0 && text.trim().indexOf('#') != 0) {
//writer.println(text + "");
k = k +1 ;
String[] sArray = text.split(",",2);

out.print("
");
for(int i=0;i{
out.print("");
out.print(" ");
//out.print(" ");

out.print("
");
out.print("

"); out.println("

"); out.print(sArray[i].toString()); out.print("

");
}
out.print("
");

}
}
System.out.println("Value of record is:"+k);
}
out.println("

");
out.println("

");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

out.println("

");

out.println("

");

}

}

3:- EditCourseTextFileServlet

package com.test;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Vector;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class EditCourseTextFileServlet extends HttpServlet {

/**
*
*/
private static final long serialVersionUID = 1L;

Vector

ServletContext context;
String filename = "/WEB-INF/Course1.txt";

String sUrlParam="";

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
context = getServletContext();
printTable(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//printTable(request, response); //To Lead the table as per the data available from URL
request.setAttribute("param",sUrlParam);
RequestDispatcher rd = request.getRequestDispatcher("editSaveCourseTextFileServlet");
rd.forward(request,response);
}

public void printTable(HttpServletRequest request,
HttpServletResponse response) throws IOException {
response.setContentType("text/html");
sUrlParam = request.getParameter("param");
PrintWriter out = response.getWriter();
out.println("");
out.println("");
out.println("");
out.println("");
out.println("");
out.println("

");
out.println("");

String[] urlArray = sUrlParam.split("-",0);
//for(int i=0;iif(urlArray.length > 0)
{
//System.out.println(urlArray[i]);
if((urlArray.length == 2 || urlArray.length == 3) && urlArray[0] != null)
{
out.println("
Code:
");
out.println("
");
out.println(" ");
}
if((urlArray.length == 2 || urlArray.length == 3) && urlArray[1] != null)
{
out.println(" Title:
");
String textValue = urlArray[1].trim();//.toString().replaceAll(" ", " ");
out.println("
");
out.println(" ");
}
if(urlArray.length == 3 && urlArray[2]!= null)
{

//Showing all Check Box

InputStream is = context.getResourceAsStream(filename);
if (is != null) {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader reader = new BufferedReader(isr);

String text;
out.println("
Prerequisite(s):
");
out.print("");
String checkBoxString = urlArray[2].trim().toString();
String[] sArray1 = checkBoxString.split(" ",0);
out.print("
");

while ((text = reader.readLine()) != null) {
if(text.length() > 0 && text.trim().indexOf('#') != 0) {
//writer.println(text + "");
String[] sArray = text.split(",",2);
for(int i=0;i{

out.print(" ");
//cheking if the check box need to clicked start[
boolean flag = false;
for(int m=0;mif(sArray[i].toString().equals(sArray1[m].toString()))
{
out.println("
");
out.print(sArray[i].toString());
flag = true;
}
}
//cheking if the check box need to clicked end]
if(!flag)
{
out.println("
");
out.print(sArray[i].toString());
flag= false;

}
out.print("

");
out.print("");
}
}
}
out.print("");
out.print("");
}

}
else
{
try {

InputStream is = context.getResourceAsStream(filename);
if (is != null) {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader reader = new BufferedReader(isr);

String text;
int k=0;
out.println("
Prerequisite(s):
");
while ((text = reader.readLine()) != null) {

if(text.length() > 0 && text.trim().indexOf('#') != 0) {
//writer.println(text + "");
k = k +1 ;
String[] sArray = text.split(",",2);

out.print("
");
for(int i=0;i{
out.print("");
out.print(" ");
//out.print(" ");

out.print("
");
out.print("

"); out.println("

"); out.print(sArray[i].toString()); out.print("

");
}
out.print("
");

}
}
out.print("

");
System.out.println("Value of record is:"+k);
}

} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
out.println("

");
out.println("

");
out.println("");

out.println("

");

}

}
}

4:- EditSaveCourseTextFileServlet

package com.test;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Vector;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class EditSaveCourseTextFileServlet extends HttpServlet {

/**
*
*/
private static final long serialVersionUID = 1L;

Vector

ServletContext context;
String filename = "/WEB-INF/Course1.txt";

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
context = getServletContext();
}

private void updateLine(String toUpdate, String updated) throws IOException {
InputStream is = context.getResourceAsStream(filename);
InputStreamReader isr = new InputStreamReader(is);
BufferedReader file = new BufferedReader(isr);
String my_new_str = toUpdate.replaceAll("-", ",");
String line;
String input = "";

while ((line = file.readLine()) != null)
input += line + "\n";

input = input.replace(my_new_str, updated);

File outputFile = new File(getServletContext().getRealPath("/WEB-INF/")
+ "/Course1.txt");
//FileWriter fout = new FileWriter(outputFile,true);

FileOutputStream os = new FileOutputStream(outputFile);
os.write(input.getBytes());

file.close();
os.close();

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

String sOldValue = ""+request.getAttribute("param");

//printTable(request, response);
String finalCheckBox="";
PrintWriter out = response.getWriter();
String button1Click = request.getParameter("Submit");
System.out.println("button1Click"+button1Click);

File outputFile = new File(getServletContext().getRealPath("/WEB-INF/")
+ "/Course1.txt");
FileWriter fout = new FileWriter(outputFile,true);

try {
context = getServletContext();
InputStream is = context.getResourceAsStream(filename);
if (is != null) {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader reader = new BufferedReader(isr);

String text;
int k=0;
while ((text = reader.readLine()) != null) {

if(text.length() > 0 && text.trim().indexOf('#') != 0) {

k = k +1 ;
String[] sArray = text.split(",",2);
String [] checkboxNamesList = new String[sArray.length];

for(int i=0;i{
checkboxNamesList= request.getParameterValues(sArray[i]);

if(null != checkboxNamesList)
{
finalCheckBox = finalCheckBox + sArray[i].toString() + " ";
}
else
{
finalCheckBox = finalCheckBox;
}

}

}
}
System.out.println("Value of record is:"+k);
}

} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

String finalString = request.getParameter("Code") + "," + request.getParameter("Title") + "," + finalCheckBox;
this.updateLine(sOldValue, finalString);

RequestDispatcher rd = request.getRequestDispatcher("readTextFileServlet");
rd.forward(request,response);
}

}

5- web.xml

   

6:- Course1.txt

# This is commented line no need to read it

Siddhu120,Comment 1
Siddhu122,Comment 2
Siddhu201,Comment 3
Siddhu202,Comment 4,Siddhu120 Siddhu201
Siddhu203,Comment 6,Siddhu202
Siddhu320,Comment ,Siddhu120 Siddhu122 Siddhu203