如果springboot应用程序打包为jar，则Thymeleaf无法访问模型属性

Question

I am building a springboot project with thymeleaf. The project runs as expected when running from within eclipse. ie I am able to access model attributes in thymeleaf.

However, when I package the above project as a jar, thymeleaf is unable to access model attributes added on the backend.

1) Java code on the backend:

@RequestMapping("/")
public String index(Model model) throws Exception {

    String headshotsfileNameStrings = "";
    InputStream resource = new ClassPathResource("static/images/xyz-headshots/").getInputStream();
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(resource))) {
         headshotsfileNameStrings = reader.lines().collect(Collectors.joining(","));
    }

    model.addAttribute("headshotsfileNameStrings", headshotsfileNameStrings);
    System.out.println(model);
    return "index";
}

EDIT 1: I updated above code to:

    try (BufferedReader reader = new BufferedReader(new InputStreamReader(resource))) {

System.out.println(reader.readLine()); //This prints 'null' when running application as a Jar 

         headshotsfileNameStrings = reader.lines().collect(Collectors.joining(","));
    }

2) Thymeleaf frontend code

<script>
        var headshotsfileNameStrings = "[[${headshotsfileNameStrings}]]";
    </script>

The variable 'headshotsfileNameStrings' has value "" when the application is run as a springboot jar and has value "some_string_here_xyz" when the application is run from Eclipse.

What could be going on here? I don't see any errors and I don't know where to start debugging this from. Any ideas?

Answer 1

My first check would be if the file is indeed found, you can put a debug point and see if your resource value indeed holds the file that you expect.

Also, add a catch clause and print the stacktrace instead of using throws Exception , right now if something goes wrong in this method it does so silently.

What I believe happens at the moment, is that you have an IOException file not found, but you cannot see it because you do not print the stacktrace.

UPDATE:

I expect that 'xyz-headshots' is a filename. If that is the case, add the file extension and remove the trailing "/". So if it is a text file for example it should look like this static/images/xyz-headshots.txt

Answer 2

This code worked for me in the IDE as well as when the application was run as a JAR:

@RequestMapping("/")
    public String index(Model model) {
        String headshotsfileNameStrings = "";
        ResourceLoader resourceLoader = new DefaultResourceLoader();
        Resource[] resources;
        try {
            resources = ResourcePatternUtils.getResourcePatternResolver(resourceLoader)
                    .getResources("classpath:" + "/static/images/xyz-headshots/*.jpg"); //get all files in the directory
            for (int i = 0; i < resources.length; i++) {
                String fileName = resources[i].getFilename(); //fileName gets populated now.
                headshotsfileNameStrings += fileName + ",";
            }


        } catch (Exception e) {
            e.printStackTrace();
        }

        model.addAttribute("headshotsfileNameStrings", headshotsfileNameStrings);
        return "index";
    }

I took help from the answers listed here: Classpath resource not found when running as jar