java.lang.IllegalStateException

[Farakh khan]

Hello,

I did lot of changes by implementing many ways by searching this error on google but still exists in my code. Please help me to fix this problem

Articles.java java.lang.IllegalStateException
java.lang.IllegalStateException
	at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:435)
	at Articles.doGet(Articles.java:186)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
	at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
	at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
	at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:769)
	at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:698)
	at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:891)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
	at java.lang.Thread.run(Thread.java:619)

My code is as follow:

import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class Articles extends HttpServlet{

	Connection 	cnn=null;
	ResultSet 	 rs=null;
	
public void doGet(HttpServletRequest req, HttpServletResponse res)throws IOException, ServletException{

	res.setContentType("text/html");
	PrintWriter out=res.getWriter();

try{
	
	if ((cnn==null)||cnn.isClosed()){
	cnn=DB.getOracleConnection();
	}
	
	SiteTemplate st=new SiteTemplate();
	CategoriesDAO cd = new CategoriesDAO();

	String catId = req.getParameter("catId");

	out.print(st.header()+st.leftBar()+

	"<!.....Main Started.....>"+

	"<!.....Leftbar Started.....>"+	
	"<table border=0    >"+
	"<tr>"+
	
	"<td >");	
		
	
	int start=0,end=0,currentPage=0,next=0,previous=0,pages=0,totalPages=0,lastPage=0,i=0;

	String pageNo=req.getParameter("pageNo");
	if(pageNo != null){
	currentPage=Integer.parseInt(pageNo);

	String query1="select count(*) from Articles where active=1 and cat_id=?";


	int totalRecords=0;

	PreparedStatement ps1=cnn.prepareStatement(query1);
	ps1.setString(1, catId);

	rs=ps1.executeQuery();
	if(rs.next()){
	totalRecords=rs.getInt(1);
	}
	ps1.close();

	totalPages= (totalRecords / 14) +1;
	end=(currentPage * 14);
	start=(end-14) +1;	
	next=currentPage+1;
	previous=currentPage-1;
	lastPage=totalPages;

		out.println(
		"<table border=0 ><tr><td class=pageHeading >"+
		cd.ViewSpecificCategory(catId)+" (Articles)</td>"+
		"<td  class=bigFont>");
		
		if((previous<=totalPages) && (previous>0)){
		out.print("<a >Previous</a>"+
		"<font size=2 color=blue>«|</font>  ");
		out.println(" <a ><b>1..,  </b></a><b></b>");
		}
			
	if(totalPages>5 && totalPages<=lastPage){	
		if(currentPage==1){
		out.println("<a href=/servlet/Articles?pageNo=1&catId="+catId+"><b>1</b></a>  "+
		"<a href=/servlet/Articles?pageNo=2&catId="+catId+"><b>2</b></a>  "+
		"<a href=/servlet/Articles?pageNo=3&catId="+catId+"><b>3</b></a>  "+
		"<a href=/servlet/Articles?pageNo=4&catId="+catId+"><b>4</b></a>  "+
		"<a href=/servlet/Articles?pageNo=5&catId="+catId+"><b>5</b></a>");
		}
	

		else{
			for(i=1;i<=5;i++){
			out.print("  "+
			"<a href=/servlet/Articles?pageNo=" + ((currentPage+i)-1) +"&catId="+catId+"><b>"+
			((currentPage+i)-1)+"</b></a>");

			if((currentPage+i)>=lastPage){
			break;		
		}	}
		}
		}else{
			if((totalPages * 5) +1>=totalRecords){
			totalPages++;
			}

			for(i = 1; i < totalPages; i++){
			out.print("   <a  + i  rel="nofollow">"+ i +"</a>");
			}
		}
		
		if((next<totalPages) && (totalPages>1) && (currentPage<lastPage)){
		out.print("  ><font size=2 color=blue>|» </font>"+
	"<a >Next</a>     <br>");
		}
		out.println("</td></tr></table>");
					
	int count=1;
	String query="select * from(select zafar.*,rownum khan from("+
	" select Articles_id,subject,substr(article,1,250),picture from Articles "+
	" where active=1 and cat_id=? order by Articles_date desc) zafar where rownum<="+end+") where khan>="+start;

		PreparedStatement ps=cnn.prepareStatement(query);
		ps.setString(1, catId);

		rs=ps.executeQuery();
		while(rs.next()){						
		String articleId=rs.getString(1);
		String articleName=rs.getString(2);
		String article=rs.getString(3);		
		String picture=rs.getString(4);
		
		count+=1;
	
		article=article.replaceAll("<br>"," ");
		article=article.replaceAll(
		"<table border=1   ","       ");

	
		if(article.equals("") || 
		;
		}else{
			 || picture.equals("null")){
			out.println("><a >"+
			"<span class=bigFont>"+articleName+"</span></a><br>"+
						
			article+
			"<a 
			" rel="nofollow"><b>   Details.....</b></a><br><br>");
			}else{

			if(count%2==0){
			out.println("<table border=0   >"+
			"<tr><td class=text2>"+
			"<br><br><a >"+
			"<span class=bigFont>"+articleName+"</span></a><br>"+
						
			article+
			"<a 
			" rel="nofollow"><b>   Details.....</b></a><br><br></td>"+
			"<td ><br><br><img "+			
			" 
			picture+"\"  >"+
			"</td></tr></table>");

			}
			else
			{						
			out.println("<table border=0   >"+
			"<tr><td ><br><br>"+
			"<img 
			picture+"\"  >"+
			"</td>"+

			"<td class=text2><br><br>"+
			"<a >"+
			"<span class=bigFont>"+articleName+"</span></a><br>"+
						
			article+
			"<a 
			" rel="nofollow"><b>   Details.....</b></a><br><br></td>"+
			"</tr></table>");
			}
			}
			
		}

		}//psLoop	
		ps.close();
		
	}else{
	res.sendRedirect("/servlet/Articles?pageNo=1&catId="+catId);
	}
	out.println("</td></tr></table>");
	out.println("<br><br>"+st.rightBar()+st.footer());		
	

}catch(Exception e){
	out.println("Articles.java "+e.toString()); 
	System.out.println("Articles.java "+e.toString()); 
	e.printStackTrace(); 
}

finally  {      
	try{        
		if ( rs  != null ) 	rs.close();        		
		if ( cnn != null )  	cnn.close();      
	}catch(SQLException ex) {          
	out.println("Articles..java "+ex.toString()); 
	System.out.println("Articles..java "+ex.toString());  
	}
}
}

}

Thanks & best regards

[David O'Meara]

You can't call sendRedirect if you have written to the output stream, or in your case the Writer.
It is bad practice to put HTML in a servlet, and if you gather the data ready to display and pass to a JSP then your code becomes:

// gather data and set on the request ready to display
if(all data is ok)
{
    requestdispatcher.forward(req,res);
}
else
{
    sendRedirect();
}

You can call one or the other, but not both.

[David O'Meara]

Taking it a step further, the HTTP response that you send back to the client is made up of a HTTP header and a HTTP body. Note we're talking about HTTP, not HTML. The HTTP body is typically but not necessarily text/html content.
So as I just said, the page information goes in the HTTP body, but in order to perform a sendRedirect operation, the servlet container needs to write information to the HTTP header.

If you start writing to the HTTP body, then the container can buffer the response and hold off sending to the client in case you change your mind, but at some stage the buffer will fill and it will be too late to change your mind. Trigger an IllegalStateException. I have seen people increase the size of the buffer but this is hiding the problem, not solving it. It is better to get out of the habit beforehand. Also, increasing the size of the buffer will increase the memory that the application will need to run without any real benefit.

[Farakh khan]

David O'Meara wrote:You can't call sendRedirect if you have written to the output stream, or in your case the Writer.
It is bad practice to put HTML in a servlet, and if you gather the data ready to display and pass to a JSP then your code becomes:

// gather data and set on the request ready to display
if(all data is ok)
{
    requestdispatcher.forward(req,res);
}
else
{
    sendRedirect();
}

You can call one or the other, but not both.

I am doing the same if you recheck please

[Farakh khan]

David O'Meara wrote:Taking it a step further, the HTTP response that you send back to the client is made up of a HTTP header and a HTTP body. Note we're talking about HTTP, not HTML. The HTTP body is typically but not necessarily text/html content.
So as I just said, the page information goes in the HTTP body, but in order to perform a sendRedirect operation, the servlet container needs to write information to the HTTP header.

My code is just sending the pageNo and catId as HTTP response not HTTP body

David O'Meara wrote:If you start writing to the HTTP body, then the container can buffer the response and hold off sending to the client in case you change your mind, but at some stage the buffer will fill and it will be too late to change your mind. Trigger an IllegalStateException. I have seen people increase the size of the buffer but this is hiding the problem, not solving it. It is better to get out of the habit beforehand. Also, increasing the size of the buffer will increase the memory that the application will need to run without any real benefit.

I not increase any buffer size but are you sure this is the case with my code?

Best regards

[David O'Meara]

out.print(st.header()+st.leftBar()+  
  
    "<!.....Main Started.....>"+  
  
    "<!.....Leftbar Started.....>"+     
    "<table border=0    >"+  
    "<tr>"+  
      
    "<td >");   
          

Anything written to the output stream or writer goes to the HTTP body. Your code is full of text written to the Writer and should be moved to a JSP instead.

[Pete Nelson]

When you see "IllegalStateException" in a servlet (or JSP), look for where you're setting a response header, after writing to the reponse's PrintWriter. 99% of the time, this is the cause of the IllegalStateException.

On line 27:

 out.print(st.header()+st.leftBar()+  

... followed by a lot more printing to that PrintWriter. Then on line 186:

 res.sendRedirect("/servlet/Articles?pageNo=1&catId="+catId); 

Your error log is even telling you that this is where the exception is occurring:

    at Articles.doGet(Articles.java:186)  

One quick solution to fix this code might be instead of writing directly to the response's PrintWriter, write to a local StringWriter as a buffer instead. Once all the logic that might send a redirect is complete, then write the StringWriter's contents out to the response's PrintWriter. The biggest advantage of that approach to you is that it would be relatively simple to change in your code:

#line 14
StringWriter out = new StringWriter();

... leave all the "out.println" statements the same ...

#line 207
res.getWriter().print(out.toString());

[Farakh khan]

Pete Nelson wrote:
One quick solution to fix this code might be instead of writing directly to the response's PrintWriter, write to a local StringWriter as a buffer instead. Once all the logic that might send a redirect is complete, then write the StringWriter's contents out to the response's PrintWriter. The biggest advantage of that approach to you is that it would be relatively simple to change in your code:

#line 14
StringWriter out = new StringWriter();

... leave all the "out.println" statements the same ...

#line 207
res.getWriter().print(out.toString());

Thanks from the bottom of my heart to post such precious opinion and helping me.

I applied your directives but its throwing 16 errors at compile time and the message is same:

Articles.java: 205: can not find symbol
symbol: method println(java.lang.string)
location: class java.io.StringWriter

Thanks again for helping

Best regards

[Pete Nelson]

My Bad! I missed a step! You need to wrap the StringWriter in a PrintWriter in order to get the println method. Try this instead:

// line 14
StringWriter sWriter = new StringWriter();
PrintWriter out = new PrintWriter(sWriter);

// ... and then on line 207, make sure to use the underlying sWriter
res.getWriter().print(sWriter.toString());

Sorry to lead you astray! I had forgotten, all Writers are not created equal.

[Farakh khan]

Now compiled and hopefully will fix the error.

Thanks from the bottom of my heart