9 Proven Ways to Read Files from the Resources Folder in Spring Boot

This article provides nine approaches to read files from the resources directory in a Java/Spring Boot project, plus a helper method to output file content.

/**
 * Read file content by path
 *
 * @param fileInPath
 * @throws IOException
 */
public static void getFileContent(Object fileInPath) throws IOException {
    BufferedReader br = null;
    if (fileInPath == null) {
        return;
    }
    if (fileInPath instanceof String) {
        br = new BufferedReader(new FileReader(new File((String) fileInPath)));
    } else if (fileInPath instanceof InputStream) {
        br = new BufferedReader(new InputStreamReader((InputStream) fileInPath));
    }
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
    br.close();
}

Method One

Uses getClass().getClassLoader().getResource("") to obtain the base path, then appends the file name.

public void function1(String fileName) throws IOException {
    String path = this.getClass().getClassLoader().getResource("").getPath(); // empty string
    System.out.println(path);
    String filePath = path + fileName;
    System.out.println(filePath);
    getFileContent(filePath);
}

Method Two

Calls getResource(fileName) directly; if the path contains Chinese characters, decode it with URLDecoder.

public void function2(String fileName) throws IOException {
    String path = this.getClass().getClassLoader().getResource(fileName).getPath();
    System.out.println(path);
    String filePath = URLDecoder.decode(path, "UTF-8"); // decode Chinese characters
    System.out.println(filePath);
    getFileContent(filePath);
}

Method Three

Retrieves the file via getFile(); for URL paths, getPath() returns the path without query parameters.

public void function3(String fileName) throws IOException {
    String path = this.getClass().getClassLoader().getResource(fileName).getFile();
    System.out.println(path);
    String filePath = URLDecoder.decode(path, "UTF-8");
    System.out.println(filePath);
    getFileContent(filePath);
}

Method Four (Important)

Uses getResourceAsStream to obtain an InputStream, which works when files are packaged inside a JAR.

public void function4(String fileName) throws IOException {
    InputStream in = this.getClass().getClassLoader().getResourceAsStream(fileName);
    getFileContent(in);
}

Method Five (Important)

Calls getResourceAsStream on the class itself, allowing a leading slash to reference the root of resources.

public void function5(String fileName) throws IOException {
    InputStream in = this.getClass().getResourceAsStream("/" + fileName);
    getFileContent(in);
}

Method Six (Important)

Leverages Spring's ClassPathResource to obtain an input stream, suitable for Spring Boot applications.

public void function6(String fileName) throws IOException {
    ClassPathResource classPathResource = new ClassPathResource(fileName);
    InputStream inputStream = classPathResource.getInputStream();
    getFileContent(inputStream);
}

Method Seven

Builds an absolute path using the project's root directory; this works only locally and not on a server.

public void function7(String fileName) throws IOException {
    String rootPath = System.getProperty("user.dir");
    String filePath = rootPath + "\\chapter-2-springmvc-quickstart\\src\\main\\resources\\" + fileName;
    getFileContent(filePath);
}

Method Eight

Uses new File("") to get the current directory's canonical path, then constructs the absolute file path.

public void function8(String fileName) throws IOException {
    File directory = new File("");
    String rootCanonicalPath = directory.getCanonicalPath();
    String filePath = rootCanonicalPath + "\\chapter-2-springmvc-quickstart\\src\\main\\resources\\" + fileName;
    getFileContent(filePath);
}

Method Nine

Sets an environment variable (e.g., TEST_ROOT) and builds the file path from it.

public void function9(String fileName) throws IOException {
    System.setProperty("TEST_ROOT", "E:\\WorkSpace\\Git\\spring-framework-learning-example");
    String rootPath = System.getProperty("TEST_ROOT");
    System.out.println(rootPath);
    String filePath = rootPath + "\\chapter-2-springmvc-quickstart\\src\\main\\resources\\" + fileName;
    getFileContent(filePath);
}