Load a static file in a Spring Controller

Question

I'm pretty new to Spring, so apologies if I don't see the obvious answer here.

I set up small demo project with a Spring MVC controller and deployed it to App Engine. In my controller I would like to read the content of a static file into a String. What's the best way of doing that?

I googled a bit but I'm probably searching for the wrong thing. I tried the below, but it does not work:

@Controller
@RequestMapping("/myController")
public class MyController {

    @RequestMapping(value = "/test", method = RequestMethod.GET)
    public @ResponseBody String myTest() {

        FileReader fileReader = null;
        BufferedReader bufferedReader = null;
        String content = "";
        try {
            fileReader = new FileReader("file:/WEB-INF/content/somecontent.txt");
            bufferedReader = new BufferedReader(fileReader);
            content = bufferedReader.readLine();
            bufferedReader.close(); 
        }
        catch (Exception ignored) { 
            // ignore
        }
        return content;
    }
}

Any push into the right direction will be highly appreciated :-)

Answer 1

Servlet containers in general, and GAE in particular, won't let you use the File API from within the servlet container like that.

Instead, autowire your controller with the ServletContext, and fetch the resource from that. Also, your exception handling isn't great, you shouldn't ignore exceptions like that, they're there for a reason.

Something like should be OK:

@Controller
@RequestMapping("/myController")
public class MyController {

    private @Autowired ServletContext servletContext;

    @RequestMapping(value = "/test", method = RequestMethod.GET)
    public @ResponseBody String myTest() throws IOException {
        InputStream inputStream = null;
        try {
            inputStream = servletContext.getResourceAsStream("/WEB-INF/content/somecontent.txt");
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            return bufferedReader.readLine();
        } finally {
            if (inputStream != null) {
               inputStream.close();
            }
        }
    }
}

Alternatively, if you're using Spring 3.x, this might be even simpler:

<mvc:view-controller path="/test" view-name="/WEB-INF/content/somecontent.txt"/>

See docs for what this does, but it may mean you can avoid any code.

Answer 2

The notation "file:" and "classpath:" isn't right with FileReader. I suggest you to create a FileSystemResource

FileSystemResource resource = new FileSystemResource("/WEB-INF/content/somecontent.txt");

and then to use getFile() or getInputStream() to read file. This is very useful in a web application, because you can use relative path.