SpringBoot项目中读取resource目录下的文件六种方法

    /**
     * 方法一：使用类加载器的getResource().getPath()获取全路径再拼接文件名，最后根据文件路径获取文件流
     * 备注：jar包不可用，因为jar包中没有一个实际的路径存放文件
     *
     * @param fileName
     * @return
     * @throws FileNotFoundException
     */
    public BufferedReader function1(String fileName) throws FileNotFoundException {

        //   /Users/zunf/code/read-resource/target/classes/
        String path = this.getClass().getClassLoader().getResource("").getPath();
        //   /Users/zunf/code/read-resource/target/classes/测试.txt
        String filePath = path + fileName;

        return new BufferedReader(new FileReader(filePath));
    }

    /**
     * 方法二：使用类加载器的getResource().getPath()，传参直接获取文件路径，再根据文件路径获取文件流
     * 备注：jar包不可用，因为jar包中没有一个实际的路径存放文件
     *
     * @param fileName
     * @return
     * @throws IOException
     */
    public BufferedReader function2(String fileName) throws IOException {

        //   /Users/zunf/code/read-resource/target/classes/%e6%b5%8b%e8%af%95.txt
        String filePath = this.getClass().getClassLoader().getResource(fileName).getPath();

        //可以看到上面读取到路径的中文被URLEncoder编码了，所以需要先用URLDecoder解码一下，恢复中文
        filePath = URLDecoder.decode(filePath, "UTF-8");

        return new BufferedReader(new FileReader(filePath));
    }

    /**
     * 方法三：使用类加载器的getResourceAsStream()，直接获取文件流
     * 备注：jar包可用
     *
     * @param fileName
     * @return
     * @throws IOException
     */
    public BufferedReader function3(String fileName) throws IOException {
        //getResourceAsStream(fileName) 等价于getResource(fileName).openStream()
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(fileName);
        if (inputStream == null) {
            throw new FileNotFoundException(fileName);
        }
        return new BufferedReader(new InputStreamReader(inputStream));
    }

    /**
     * 方法四：使用Class对象的getResourceAsStream()获取文件流
     * 备注：jar包可用
     *
     * @param fileName
     * @return
     * @throws IOException
     */
    public BufferedReader function4(String fileName) throws IOException {
        //getResourceAsStream(fileName) 等价于getResource(fileName).openStream()
        InputStream inputStream = this.getClass().getResourceAsStream("/" + fileName);
        if (inputStream == null) {
            throw new FileNotFoundException(fileName);
        }
        return new BufferedReader(new InputStreamReader(inputStream));
    }

    /**
     * 方法五：使用Spring提供的ClassPathResource获取
     * 备注：jar包可用
     *
     * @param fileName
     * @return
     * @throws IOException
     */
    public BufferedReader function5(String fileName) throws IOException {
        ClassPathResource classPathResource = new ClassPathResource(fileName);
        InputStream inputStream = classPathResource.getInputStream();
        return new BufferedReader(new InputStreamReader(inputStream));
    }

    /**
     * 方法六：使用Hutool的ResourceUtil
     * 备注：jar包可用
     *
     * @param fileName
     * @return
     * @throws IOException
     */
    public BufferedReader function6(String fileName) throws IOException {
        List<URL> resources = ResourceUtil.getResources(fileName);
        URL resource = resources.get(0);
        return new BufferedReader(new InputStreamReader(resource.openStream()));
    }

   //Jar包启动时根据传入的不同funcation值来选择调用哪个方法测试
    @Value("${function}")
    private int function;    


    @GetMapping("/test")
    public String test() throws IOException {
        //需要在resource里读取的文件
        String fileName = "测试.txt";

        //调用方法
        System.out.println("调用function" + function);
        BufferedReader bufferedReader = null;
        switch (function) {
            case 1:
                bufferedReader = function1(fileName);
                break;
            case 2:
                bufferedReader = function2(fileName);
                break;
            case 3:
                bufferedReader = function3(fileName);
                break;
            case 4:
                bufferedReader = function4(fileName);
                break;
            case 5:
                bufferedReader = function5(fileName);
                break;
            case 6:
                bufferedReader = function6(fileName);
                break;
            default:
        }

        //读取并输出
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            sb.append(line).append("\n");
        }
        System.out.println(sb);
        return sb.toString();
    }