Table of Contents
方式一
方式二
方式三
方式四(重要)
方式五(重要)
方式六(重要)
方式七
方式八
方式九
Home Java javaTutorial How to read the file path in the resources directory in Java

How to read the file path in the resources directory in Java

Apr 19, 2023 am 10:43 AM
java resources

打印文件的方法如下:

    /**
     * 根据文件路径读取文件内容
     *
     * @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();
    }
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方式一

主要核心方法是使用getResource和getPath方法,这里的getResource("")里面是空字符串

    public void function1(String fileName) throws IOException {
        String path = this.getClass().getClassLoader().getResource("").getPath();//注意getResource("")里面是空字符串
        System.out.println(path);
        String filePath = path + fileName;
        System.out.println(filePath);
        getFileContent(filePath);
    }
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方式二

主要核心方法是使用getResource和getPath方法,直接通过getResource(fileName)方法获取文件路径,注意如果是路径中带有中文一定要使用URLDecoder.decode解码。

    /**
     * 直接通过文件名getPath来获取路径
     *
     * @param fileName
     * @throws IOException
     */
    public void function2(String fileName) throws IOException {
        String path = this.getClass().getClassLoader().getResource(fileName).getPath();//注意getResource("")里面是空字符串
        System.out.println(path);
        String filePath = URLDecoder.decode(path, "UTF-8");//如果路径中带有中文会被URLEncoder,因此这里需要解码
        System.out.println(filePath);
        getFileContent(filePath);
    }
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方式三

直接通过文件名+getFile()来获取文件。如果是文件路径的话getFile和getPath效果是一样的,如果是URL路径的话getPath是带有参数的路径。如下所示:

url.getFile()=/pub/files/foobar.txt?id=123456
url.getPath()=/pub/files/foobar.txt
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使用getFile()方式获取文件的代码如下:

    /**
     * 直接通过文件名+getFile()来获取
     *
     * @param fileName
     * @throws IOException
     */
    public void function3(String fileName) throws IOException {
        String path = this.getClass().getClassLoader().getResource(fileName).getFile();//注意getResource("")里面是空字符串
        System.out.println(path);
        String filePath = URLDecoder.decode(path, "UTF-8");//如果路径中带有中文会被URLEncoder,因此这里需要解码
        System.out.println(filePath);
        getFileContent(filePath);
    }
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方式四(重要)

直接使用getResourceAsStream方法获取流,上面的几种方式都需要获取文件路径,但是在SpringBoot中所有文件都在jar包中,没有一个实际的路径,因此可以使用以下方式。

    /**
     * 直接使用getResourceAsStream方法获取流
     * springboot项目中需要使用此种方法,因为jar包中没有一个实际的路径存放文件
     *
     * @param fileName
     * @throws IOException
     */
    public void function4(String fileName) throws IOException {
        InputStream in = this.getClass().getClassLoader().getResourceAsStream(fileName);
        getFileContent(in);
    }
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方式五(重要)

主要也是使用getResourceAsStream方法获取流,不使用getClassLoader可以使用getResourceAsStream("/配置测试.txt")直接从resources根路径下获取,SpringBoot中所有文件都在jar包中,没有一个实际的路径,因此可以使用以下方式。

    /**
     * 直接使用getResourceAsStream方法获取流
     * 如果不使用getClassLoader,可以使用getResourceAsStream("/配置测试.txt")直接从resources根路径下获取
     *
     * @param fileName
     * @throws IOException
     */
    public void function5(String fileName) throws IOException {
        InputStream in = this.getClass().getResourceAsStream("/" + fileName);
        getFileContent(in);
    }
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方式六(重要)

通过ClassPathResource类获取文件流,SpringBoot中所有文件都在jar包中,没有一个实际的路径,因此可以使用以下方式。

    /**
     * 通过ClassPathResource类获取,建议SpringBoot中使用
     * springboot项目中需要使用此种方法,因为jar包中没有一个实际的路径存放文件
     *
     * @param fileName
     * @throws IOException
     */
    public void function6(String fileName) throws IOException {
        ClassPathResource classPathResource = new ClassPathResource(fileName);
        InputStream inputStream = classPathResource.getInputStream();
        getFileContent(inputStream);
    }
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方式七

通过绝对路径获取项目中文件的位置,只是本地绝对路径,不能用于服务器获取。

    /**
     * 通过绝对路径获取项目中文件的位置(不能用于服务器)
     * @param fileName
     * @throws IOException
     */
    public void function7(String fileName) throws IOException {
        String rootPath = System.getProperty("user.dir");//E:\WorkSpace\Git\spring-framework-learning-example
        String filePath = rootPath + "\\chapter-2-springmvc-quickstart\\src\\main\\resources\\"+fileName;
        getFileContent(filePath);
    }
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方式八

通过new File("")获取当前的绝对路径,只是本地绝对路径,不能用于服务器获取。

    /**
     * 通过绝对路径获取项目中文件的位置(不能用于服务器)
     * @param fileName
     * @throws IOException
     */
    public void function8(String fileName) throws IOException {
        //参数为空
        File directory = new File("");
        //规范路径:getCanonicalPath() 方法返回绝对路径,会把 ..\ 、.\ 这样的符号解析掉
        String rootCanonicalPath = directory.getCanonicalPath();
        //绝对路径:getAbsolutePath() 方法返回文件的绝对路径,如果构造的时候是全路径就直接返回全路径,如果构造时是相对路径,就返回当前目录的路径 + 构造 File 对象时的路径
        String rootAbsolutePath =directory.getAbsolutePath();
        System.out.println(rootCanonicalPath);
        System.out.println(rootAbsolutePath);
        String filePath = rootCanonicalPath + "\\chapter-2-springmvc-quickstart\\src\\main\\resources\\"+fileName;
        getFileContent(filePath);
    }
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方式九

主要是通过设置环境变量,将文件放在环境变量中,原理也是通过绝对路径获取。
示例中我设置了一个环境变量:TEST_ROOT=E:\\WorkSpace\\Git\\spring-framework-learning-example

 System.getenv("TEST_ROOT");
 System.getProperty("TEST_ROOT")
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通过设置环境变量的方式,然后通过绝对路径获取文件

    /**
     * 通过绝对路径获取项目中文件的位置
     *
     * @param fileName
     * @throws IOException
     */
    public void function9(String fileName) throws IOException {
        System.setProperty("TEST_ROOT","E:\\WorkSpace\\Git\\spring-framework-learning-example");
        //参数为空
        String rootPath = System.getProperty("TEST_ROOT");
        System.out.println(rootPath);
        String filePath = rootPath + "\\chapter-2-springmvc-quickstart\\src\\main\\resources\\"+fileName;
        getFileContent(filePath);
    }
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