I am using Eclipse dynamic web project with tomcat 7. I am extremely new at this and slowly working through tutorials.
I am trying to make a simple webapp where a user enters information which is used to generate a QR code. I can make the image and save it to the WebContent folder. I want to show this image to the user and store it. Eventually I will have an account for each user with their stored QR codes and other images. I have an index.html that takes the information through a form and passes it to a servlet that creates the image and saves it in my WebContent folder, then builds a simple HTML to show the image. However, the image is not shown unless I tell eclipse to refresh the project. My guess is that eclipse doesn't know about the new image file until it gets refreshed, and for some reason the HTML generated by the servlet isn't picking up on the image even though it's in the right place.
The answer here suggests storing the data outside the webapp folders and streaming it. This is something I am unfamiliar with. I have tried to store the image in an outside folder and refer to it using both absolute and relative paths from the WebContent folder to the image file, neither works. And the QR code I was able to show from inside the WebContent folder doesn't update when I give it different data to build the image from, I have to refresh the project in eclipse even though the file name and location is the same. When I use the file browser to open the image file it has the new data.
I am asking for very basic help, I'm not incompetent but I've never done internet programming before and this is a lot to learn. In general I need to know how to get and store data and generate new data and then call it back up dynamically to display to the user. Thank you.
Here is my doPost method for the servlet:
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
username = request.getParameter("userName");
password = request.getParameter("password");
PrintWriter out = response.getWriter();
response.setContentType("text/html");
// check the input and create the html
checkFormData();
// Unless something goes very wrong, this string should be replaced.
String html = "<html><p>SOMETHING BROKE!</p></html>";
if(usernameOK && passwordOK){
html = buildHTMLForGoodInfo();
}else{
html = buildHTMLForBadInfo();
}
out.println(html);
}
And here is where I generate the QR code and create the HTML to display it:
private String buildHTMLForGoodInfo(){
QRGenerator qrg = new QRGenerator();
// This file goes into the webcontent folder
File filename1 = new File("/home/NAME/Workspace/MyWebApp/WebContent/qr1.png");
// This file goes outside the webcontent folder
File filename2 = new File("/home/NAME/Workspace/Data/qr2.png");
String result = "User Name = " + username + " Password = " + password +".";
qrg.makeQR(result, filename1);
qrg.makeQR(result, filename2);
String html = "<html><head><title>Results Page</title></head>\n" +
"<body><center>\n" +
"<p>Your user name is " + username + ".<p>\n" +
"<br/>\n" +
"<p>Your password is " + password + ".<p>\n" +
"<br/>\n" +
"<p> Have a QR Code</p>\n" +
"<br/>\n" +
// Show the image from inside the webcontent folder
"<img src=\"qr1.png\" alt=\"qr1.png\" border=\"1\">\n" +
// show the image from outside the webcontent folder
"<img src=\"/home/NAME/Workspace/Data/qr2.png\" alt=\"qr2.png\" border=\"1\">\n" +
"</center></body></html>";
return html;
}
NOTE: I have obfuscated my linux username to provide me with a tiny sense of false security.
Here is a screenshot of the output:
The QR code on the left decodes to old data, it should show the new data, username = UserName, password = Password. The image on the right does not appear. When I use the file manager to navigate to both file's locations on my computer, both files have QR codes with the correct data. I don't know where the old incorrect QR code is being stored, it doesn't show up in the file manager and I have checked for hidden files.
EDIT:
I have solved my issue by using an image servlet, unfortunately I can't find the stackoverflow page that led me in that path. I made a simple servlet with this doGet method:
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
// In the event of an error, make a red square.
int[] pixels = new int[128*128*3];
for(int i = 0; i < 128*128; i++){
pixels[i] = 200 << 16 | 0 << 8 | 0;
}
BufferedImage image = new BufferedImage(128,128,BufferedImage.TYPE_INT_RGB);
image.setRGB(0,0,128,128, pixels,0,128);
// get the file's address from the request
File imageID = new File(request.getParameter("imageID"));
// Try to read the file into the image, if you can't read it, print an error
try{
image = ImageIO.read(imageID);
}catch(Exception e){
System.out.println("IMAGE IO ERROR");
e.printStackTrace();
}
System.out.println(imageID.toString());
// get the response output stream and pass the image to it
ServletOutputStream out = response.getOutputStream();
ImageIO.write(image, "png", out);
}
Then when I want to display an image, I use this html:
img src=\"ImageServlet?imageID= PUT YOUR IMAGE ADDRESS HERE "
