File download using Struts

In some developments, you have to prompt "OPEN/SAVE" dialog for file viewing.
Here is a sample code for file download with the support of the "DownloadAction".

import java.io.IOException;
import java.io.InputStream;
import java.io.ByteArrayInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.actions.DownloadAction;


public class ExampleByteArrayDownload extends DownloadAction {

    protected StreamInfo getStreamInfo(ActionMapping mapping, 
                                       ActionForm form,
                                       HttpServletRequest request, 
                                       HttpServletResponse response)
            throws Exception {
   
        String fileName = httpServletRequest.getParameter("fileName");

        String fileExtension =
            fileName.substring(fileName.lastIndexOf("."), fileName.length());

        httpServletResponse.setHeader("Content-Disposition",
                                      "attachment;filename=\"" + fileName +
                                      "\"");
        
        // Download a "pdf" file
        String contentType = "application/pdf";
        byte[] myPdfBytes  = null;              // Get the bytes from somewhere

        return new ByteArrayStreamInfo(contentType, myPdfBytes);
        
    }

    protected class ByteArrayStreamInfo implements StreamInfo {
        
        protected String contentType;
        protected byte[] bytes;
        
        public ByteArrayStreamInfo(String contentType, byte[] bytes) {
            this.contentType = contentType;
            this.bytes = bytes;
        }
        
        public String getContentType() {
            return contentType;
        }

        public InputStream getInputStream() throws IOException {
            return new ByteArrayInputStream(bytes);
        }
    }
}

Reference
http://wiki.apache.org/struts/StrutsFileDownload

Replace String pattern in "Vi"

1) Open the TEXT file using "vi" editor in linux.
2) Press ESC
3) Following command will replace "tab" character by "|".

    :%s/    /|/g

4) Save & quit file using following command.

    :wq!

Java property file usage

Use the below code to read the java property file and retrieve the property value.
 
      Properties properties = new Properties();
        FileInputStream in;
        try {
            in = new FileInputStream("app.properties");
            properties.load(in);
            in.close();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
        return properties.getProperty("appcode");

Sample "app.properties" file is shown below.

appcode=50
email=admin@yahoo.com

From date < To date validate using js

Use the below js code to validate date "From date < To date"

         var frmDate = document.getElementById("frmDate").value;
         var toDate = document.getElementById("toDate").value;

         if (frmDate < toDate) {
               alert("Invalid Date Range!\nStart Date cannot be after End Date!")
               return false;
           }

Solution to dwr session error

Edit your web.xml file and and the following code.

<init-param>
<param-name>crossDomainSessionSecurity</param-name>
<param-value>false</param-value>
</init-param>

Move large number of files in solaris using "awk"

• Change directory where your files are located.
• Use the following "awk" script to move files from one location to another.

  for k in `ls | awk '{print $1}'`; 
  do 
  mv $k destination;
  done

Use java 64 bit version

You have to use 64bit version of java when your memory allocation is larger than 4Gb.

Use -d64 parameter when running the application.

java -d64 -jar -Xms1024m -Xmx4096m Test.jar