Nine ways to read the file path under the resources directory

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This article provides nine ways to obtain resources How to file in the directory . The method of printing documents is as follows ：

/**
 *  Read the contents of the file according to the file 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();
}

Mode one

The main core method is to use getResource and getPath Method , there getResource("") There is an empty string

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

Mode two

The main core method is to use getResource and getPath Method , Directly through getResource(fileName) Method to get the file path , Note that if there is Chinese in the path, you must use URLDecoder.decode decode .

/**
 *  Directly through the file name getPath To get the path 
 *
 * @param fileName
 * @throws IOException
 */
public void function2(String fileName) throws IOException {
    String path = this.getClass().getClassLoader().getResource(fileName).getPath();// Be careful getResource("") There is an empty string 
    System.out.println(path);
    String filePath = URLDecoder.decode(path, "UTF-8");// If there is Chinese in the path, it will be URLEncoder, So here we need to decode 
    System.out.println(filePath);
    getFileContent(filePath);
}

Mode three

Directly through file name +getFile() To get the files . If it's a file path getFile and getPath The effect is the same , If it is URL In terms of path getPath Is a path with parameters .

As shown below ：

url.getFile()=/pub/files/foobar.txt?id=123456
url.getPath()=/pub/files/foobar.txt

Use getFile() The code to obtain the file is as follows ：

/**
 *  Directly through the file name +getFile() To get 
 *
 * @param fileName
 * @throws IOException
 */
public void function3(String fileName) throws IOException {
    String path = this.getClass().getClassLoader().getResource(fileName).getFile();// Be careful getResource("") There is an empty string 
    System.out.println(path);
    String filePath = URLDecoder.decode(path, "UTF-8");// If there is Chinese in the path, it will be URLEncoder, So here we need to decode 
    System.out.println(filePath);
    getFileContent(filePath);
}

Mode 4 （ important ）

Use it directly getResourceAsStream Method get stream , The above methods all need to get the file path , But in SpringBoot All the files in the are in jar In bag , There is no actual path , Therefore, the following methods can be used .

/**
 *  Use it directly getResourceAsStream Method get stream 
 * springboot This method needs to be used in the project , because jar There is no actual path in the package to store files 
 *
 * @param fileName
 * @throws IOException
 */
public void function4(String fileName) throws IOException {
    InputStream in = this.getClass().getClassLoader().getResourceAsStream(fileName);
    getFileContent(in);
}

Methods five （ important ）

Mainly used getResourceAsStream Method get stream , Don't use getClassLoader have access to getResourceAsStream("/ Configuration testing .txt") Directly from resources Get from the root path ,SpringBoot All the files in the are in jar In bag , There is no actual path , Therefore, the following methods can be used .

/**
 *  Use it directly getResourceAsStream Method get stream 
 *  If not used getClassLoader, have access to getResourceAsStream("/ Configuration testing .txt") Directly from resources Get from the root path 
 *
 * @param fileName
 * @throws IOException
 */
public void function5(String fileName) throws IOException {
    InputStream in = this.getClass().getResourceAsStream("/" + fileName);
    getFileContent(in);
}

Mode 6 （ important ）

adopt ClassPathResource Class to get the file stream ,SpringBoot All the files in the are in jar In bag , There is no actual path , Therefore, the following methods can be used .

/**
 *  adopt ClassPathResource Class gets , Suggest SpringBoot Use in 
 * springboot This method needs to be used in the project , because jar There is no actual path in the package to store files 
 *
 * @param fileName
 * @throws IOException
 */
public void function6(String fileName) throws IOException {
    ClassPathResource classPathResource = new ClassPathResource(fileName);
    InputStream inputStream = classPathResource.getInputStream();
    getFileContent(inputStream);
}

Mode 7

Get the location of files in the project through the absolute path , Only the local absolute path , Cannot be used for server acquisition .

/**
 *  Get the location of files in the project through the absolute path （ Cannot be used for server ）
 * @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);
}

Mode 8

adopt new File("") Get the current absolute path , Only the local absolute path , Cannot be used for server acquisition .

/**
 *  Get the location of files in the project through the absolute path （ Cannot be used for server ）
 * @param fileName
 * @throws IOException
 */
public void function8(String fileName) throws IOException {
    // The parameter is empty. 
    File directory = new File("");
    // Canonical path ：getCanonicalPath()  Method returns the absolute path , Will be able to  ..\ 、.\  Such symbols are resolved 
    String rootCanonicalPath = directory.getCanonicalPath();
    // Absolute path ：getAbsolutePath()  Method returns the absolute path of the file , If it is a full path when constructing, it will directly return to the full path , If the construction is a relative path , Return the path of the current directory  +  structure  File  Object 
    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);
}

Mode 9

Mainly by setting environment variables , Put the file in the environment variable , The principle is also obtained through absolute path .

In the example, I set an environment variable ：TEST_ROOT=E:\\WorkSpace\\Git\\spring-framework-learning-example

System.getenv("TEST_ROOT");
 System.getProperty("TEST_ROOT")

By setting environment variables , Then get the file through the absolute path

/**
 *  Get the location of files in the project through the absolute path 
 *
 * @param fileName
 * @throws IOException
 */
public void function9(String fileName) throws IOException {
    System.setProperty("TEST_ROOT","E:\\WorkSpace\\Git\\spring-framework-learning-example");
    // The parameter is empty. 
    String rootPath = System.getProperty("TEST_ROOT");
    System.out.println(rootPath);
    String filePath = rootPath + "\\chapter-2-springmvc-quickstart\\src\\main\\resources\\"+fileName;
    getFileContent(filePath);
}

source ：blog.csdn.net/u011047968/article/details/107311462

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