Can the following Servlet be converted to a webservice call in spring framework?

[Jack Tauson]

I have the following servlet which is deployed on tomcat. And I can download a file by calling the servlet on the browser in the following manner :

https://myservername.com/DownloadFileFromServer/DownloadFileServlet?filename=Requested_files_80A50AD.zip&user=JACK

However, I want to convert this servlet into a webservice call in a spring framework. I already have a Spring framework with many GET and POST webservice end points, where I've defined controller, interface and implementation of the interface. Can I convert the following servlet into a webservice end point? How should I proceed? Just to show how my controller, DAOs etc are defined, I have pasted a sample GET request in the code below.

package com.mypackage.servlet;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class DownloadFileServlet
 */
@WebServlet("/DownloadFileServlet")
public class DownloadFileServlet extends HttpServlet {

    final String[][] contentTypes = {{"zip" ,"application/zip"},{"csv" ,"text/csv"},{"pdf","application/pdf"}};
    private static final long serialVersionUID = 1L;


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


        String param1 = request.getParameter("filename");
        String param2 = request.getParameter("user");

        System.out.println("File Name Retrieved is:"+param1);
        System.out.println("User Name Retrieved is:"+param2);

        //final String FILE_LOCATION = "/srv/my_users/param2/";
        //final String FILE_LOCATION = "/srv/my_users/param2/";

        final String FILE_LOCATION = "C:\\jack\\file\\AKHARE";
       



        if(param1 == null || param2 == null) {
            // The Request Parameters Were Not Present In The Query String. Do Something Or Exception Handling !!
            System.out.println("Request Parameter Not Found in first if!");
        } else if ("".equals(param1) || "".equals(param2)) {
            // The Request Parameters Were Present In The Query String But Has No Value. Do Something Or  Exception Handling !!
            System.out.println("Request Parameter Not Found in second if!");
        } else {

        /*if (param1 != null && param2 !=null) {*/
            String fileName = (String) param1;
            String contentType = getContentType(fileName.split("\\.")[1]);
            File file = new File(FILE_LOCATION + "/" +fileName);
            response.setContentType(contentType);
            response.addHeader("Content-Disposition","attachment; filename=" + fileName);
            response.setContentLength((int) file.length());
            ServletOutputStream servletOutputStream = response.getOutputStream();
            BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(file));
            int bytesRead = bufferedInputStream.read();
            while (bytesRead != -1) {
                servletOutputStream.write(bytesRead);
                bytesRead = bufferedInputStream.read();
            }
            if (servletOutputStream != null) servletOutputStream.close();
            if(bufferedInputStream != null) bufferedInputStream.close();

        }

        //response.getWriter().append("Served at: ").append(request.getContextPath());
    }


    private String getContentType(String fileType) {
        String returnType = null;
        for(int i = 0; i < contentTypes.length; i++) {
            if(fileType.equals(contentTypes[i][0])) returnType = contentTypes[i][1];
        }
        return returnType;
    }

}

Sample GET requests in my controller:

GetCompanyNamesController.java

@RequestMapping(value="/getCompanyNames", method=RequestMethod.GET)
    public String get_all_companynames
    (    	
        @RequestParam(value="user_name", defaultValue="") String user_name    	
    ) 
    {
    	
		
		GetCompanyNames companyNameInfo = new GetCompanyNames();
		String companyNameJsonString = "";
		
		try {
			
			
			
		    GetCompanyNamesDao companyNameDao = (GetCompanyNamesDao) context.getBean("GetCompanyNamesDao");	
			List<GetAllCompanyNames> companyLists = companyNameDao.getCompanyNamesQuery(user_name);
			companyNameInfo.setCompanyNameList(companyLists);
			
			companyNameJsonString = GetCompanyNamesView.getCompanyNamesToJsonString(companyNameInfo, true, Constants.EMPTY, true);
			if ((companyLists != null) && (companyLists.size() > 0)) {
				logger.info("Number of Patient Sets:" + companyLists.size());
			}	
			
			logger.debug(companyNameJsonString);					
		} catch (Throwable th) {
			th.printStackTrace();			
			companyNameJsonString = GetCompanyNamesView.getCompanyNamesToJsonString(companyNameInfo, false, th.getMessage(), true);
		}
		
        return companyNameJsonString;
    }

GetCompanyNamesDao.java

public interface GetCompanyNamesDao {
	
	List<GetAllCompanyNames> getCompanyNamesQuery(String user_name)throws DaoException;

    }
	

GetCompanyNamesDaoImpl.java

	@Override
	public List<GetAllCompanyNames> getCompanyNamesQuery(String user_name) throws DaoException {
								
		DataSource ds = null;
		Connection conn = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		
		
		List<GetAllCompanyNames> allCompanyNameslists = new ArrayList<GetAllCompanyNames>();
		
		try {
			ds = jdbcTemplate.getDataSource();
			conn = ds.getConnection();			
			pstmt = conn.prepareStatement(getSQL);
			pstmt.setString(1, user_name);
			rs = pstmt.executeQuery();	
			while(rs.next()) {
				//do something	
			}
			
		}
		catch(Throwable th) {
			throw new DaoException(th.getMessage(), th);
	    }
		finally {
			if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); }}
			if (pstmt != null) { try { pstmt.close(); } catch(SQLException sqe) { sqe.printStackTrace(); }}
			if (conn != null) { try { conn.close(); } catch (SQLException sqle) { sqle.printStackTrace(); }}
		}	
		
		return allCompanyNameslists;
		
		
		
	}

[Himai Minh]

You can have a controller:

public class DownloadFileController{

@GetMapping("/downloadFile/{filename}/{user}")
public void download (HttpServletRequest request, HttpServletResponse response, @PathVariable String filename, @PathVariable String user){
          …… 
    //Put your code here 
}

}

Here is an example:
https://howtodoinjava.com/spring-mvc/spring-mvc-download-file-controller-example/

[Jack Tauson]

Himai Minh wrote:You can have a controller:

public class DownloadFileController{

@GetMapping("/downloadFile/{filename}/{user}")
public void download (HttpServletRequest request, HttpServletResponse response, @PathVariable String filename, @PathVariable String user){
          …… 
    //Put your code here 
}

}

Here is an example:
https://howtodoinjava.com/spring-mvc/spring-mvc-download-file-controller-example/

Thanks. I tried doing it as you suggested as shown below. I don't see any errors, however, whenever Iam trying to call the end point, I'm getting 404 Not found for some reason.

@GetMapping("/downloadFile/{filename}/{user}")
	public void download (HttpServletRequest request, HttpServletResponse response, @PathVariable String filename, @PathVariable String user) throws IOException{
	          
		    //String param1 = request.getParameter("filename");
	        //String param2 = request.getParameter("user");
	        
	        String param1 = filename;
	        String param2 = user;

	        System.out.println("File Name Retrieved is:"+param1);
	        System.out.println("User Name Retrieved is:"+param2);
	        
	      //final String FILE_LOCATION = "/srv/my_users/param2/";
	        //final String FILE_LOCATION = "/srv/my_users/param2/";
	        
	        final String FILE_LOCATION = "C:\\jack\\file\\JACK";
	        
	        if(param1 == null || param2 == null) {
	            // The Request Parameters Were Not Present In The Query String. Do Something Or Exception Handling !!
	            System.out.println("Request Parameter Not Found in first if!");
	        } else if ("".equals(param1) || "".equals(param2)) {
	            // The Request Parameters Were Present In The Query String But Has No Value. Do Something Or  Exception Handling !!
	            System.out.println("Request Parameter Not Found in second if!");
	        } else {

	        
	            String fileName = (String) param1;
	            String contentType = getContentType(fileName.split("\\.")[1]);
	            File file = new File(FILE_LOCATION + "/" +fileName);
	            response.setContentType(contentType);
	            response.addHeader("Content-Disposition","attachment; filename=" + fileName);
	            response.setContentLength((int) file.length());
	            ServletOutputStream servletOutputStream = response.getOutputStream();
	            BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(file));
	            int bytesRead = bufferedInputStream.read();
	            while (bytesRead != -1) {
	                servletOutputStream.write(bytesRead);
	                bytesRead = bufferedInputStream.read();
	            }
	            if (servletOutputStream != null) servletOutputStream.close();
	            if(bufferedInputStream != null) bufferedInputStream.close();

	        }
	        
	        

Here's how I'm calling my file :

localhost:8080/MyFileDownloader/downloadFile?filename=file1_927204A50BB.zip&user=JACK


Another way I tried to convert it - just like I have been doing it using @RequestMapping annotation below, it's generating an error like this:

    //Testing with RequestMapping
    	@RequestMapping(value="/downloadFile", method=RequestMethod.GET)
        public void fileDownload
        (    	
            @RequestParam(value="fileName", defaultValue="") String filename,
            @RequestParam(value="user", defaultValue="") String user  
        ) throws IOException
        {
    		String param1 = filename;
            String param2 = user;
    
            System.out.println("File Name Retrieved is:"+param1);
            System.out.println("User Name Retrieved is:"+param2);
            
          //final String FILE_LOCATION = "/srv/my_users/param2/";
            //final String FILE_LOCATION = "/srv/my_users/param2/";
            
            final String FILE_LOCATION = "C:\\jack\\file\\JACK";
            
            if(param1 == null || param2 == null) {
                // The Request Parameters Were Not Present In The Query String. Do Something Or Exception Handling !!
                System.out.println("Request Parameter Not Found in first if!");
            } else if ("".equals(param1) || "".equals(param2)) {
                // The Request Parameters Were Present In The Query String But Has No Value. Do Something Or  Exception Handling !!
                System.out.println("Request Parameter Not Found in second if!");
            } else {
    
            
                String fileName = (String) param1;
                String contentType = getContentType(fileName.split("\\.")[1]);
                File file = new File(FILE_LOCATION + "/" +fileName);
                response.setContentType(contentType);
                response.addHeader("Content-Disposition","attachment; filename=" + fileName);
                response.setContentLength((int) file.length());
                ServletOutputStream servletOutputStream = response.getOutputStream();
                BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(file));
                int bytesRead = bufferedInputStream.read();
                while (bytesRead != -1) {
                    servletOutputStream.write(bytesRead);
                    bytesRead = bufferedInputStream.read();
                }
                if (servletOutputStream != null) servletOutputStream.close();
                if(bufferedInputStream != null) bufferedInputStream.close();
    
            }

It's resulting in the following error in ECLIPSE  -`response cannot be resolved`. What am I doing wrong here?Eclipse doesn't complain in the first conversion approach mentioned above.



       

[Stephan van Hulst]

Well, where did you declare response?

[Rob Spoor]

Jack Tauson wrote:[I'm getting 404 Not found for some reason.

@GetMapping("/downloadFile/{filename}/{user}")

localhost:8080/MyFileDownloader/downloadFile?filename=file1_927204A50BB.zip&user=JACK

Of course that gives you a 404, the paths don't match. Your new implementation has a correctly matching path, but this one requires the URL to be localhost:8080/MyFileDownloader/downloadFile/file1_927204A50BB.zip/JACK.

[Jack Tauson]

Rob Spoor wrote:

Jack Tauson wrote:[I'm getting 404 Not found for some reason.

@GetMapping("/downloadFile/{filename}/{user}")

localhost:8080/MyFileDownloader/downloadFile?filename=file1_927204A50BB.zip&user=JACK

Of course that gives you a 404, the paths don't match. Your new implementation has a correctly matching path, but this one requires the URL to be localhost:8080/MyFileDownloader/downloadFile/file1_927204A50BB.zip/JACK.

Thanks, that worked.

[Jack Tauson]

Stephan van Hulst wrote:Well, where did you declare response?

Sorry! My bad. I didn't notice that in the late evening hours of Sunday working on this.