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文件的三种加载方式(全网讲解最全,最严谨)

程序员文章站 2022-03-10 09:03:54
1.通过文件系统加载,也就是File类@Test public void testFileSystem() { //1.File-用户根目录 String property = System.getProperty("user.dir"); System.out.println("property:"+property);//property:G:\IdeaProjects\poxiao-cloud\poxiao-service\poxiao-sys...

1.通过文件系统加载,也就是File类

@Test
    public void testFileSystem() {
        //1.File-用户根目录
        String property = System.getProperty("user.dir");
        System.out.println("property:"+property);//property:G:\IdeaProjects\poxiao-cloud\poxiao-service\poxiao-system

        //2.File-绝对路径
        String name = new File("/banner.txt").getAbsolutePath();
        System.out.println("name:"+name);//name:G:\banner.txt
        Assert.assertNotNull(name);

        String name0 = new File("banner.txt").getAbsolutePath();
        System.out.println("name0:"+name0);//name0:G:\IdeaProjects\poxiao-cloud\poxiao-service\poxiao-system\banner.txt
        Assert.assertNotNull(name0);

        //3.File-相对路径
        String name1 = new File("audio/explode.wav").getAbsolutePath();
        System.out.println("name1:"+name1);//name1:G:\IdeaProjects\poxiao-cloud\poxiao-service\poxiao-system\audio\explode.wav
        Assert.assertNotNull(name1);

        //4.File-相对路径-验证绝对路径
        String name2 = new File("/audio/explode.wav").getAbsolutePath();
        System.out.println("name2:"+name2);//name2:G:\audio\explode.wav
        Assert.assertNotNull(name2);

        //5.File-相对路径-验证绝对路径
        String name3 = new File("/audio/explode.wava").getAbsolutePath();
        System.out.println("name3:"+name3);//name3:G:\audio\explode.wava
        Assert.assertNotNull(name3);

        //结论:
        //使用file(文件系统)有相对路径和绝对路径
        //相对路径:指的是System.getProperty("user.dir")(用户当前路径)下的路径,也就是当前项目名之下
        //绝对路径:是指根目录下的路径,而根目录在window系统指c,d,e,f,在linux系统指/
    }

结论:

  • 使用file(文件系统)有相对路径和绝对路径
  • 相对路径:指的是System.getProperty(“user.dir”)(用户当前路径)下的路径,也就是当前项目名之下
  • 绝对路径:是指根目录下的路径,而根目录在window系统指c,d,e,f,在linux系统指/

2.使用class加载

@Test
    public void testClassFile() throws IOException {
        //1.class-绝对路径
        InputStream inputStream = this.getClass().getResourceAsStream("/banner.txt");
        byte[] bytes = new byte[1024];
        inputStream.read(bytes);
        System.out.println("bytes[0]:"+bytes[0]);
        Assert.assertNotNull("为空",inputStream);//not null
        //2.class-相对路径
        InputStream inputStream2 = this.getClass().getResourceAsStream("banner.txt");
        Assert.assertNull("不为空",inputStream2);//is null
        //3.class-相对路径-""
        String path = this.getClass().getResource("").getPath();
        System.out.println("path:"+path);//path:/G:/IdeaProjects/poxiao-cloud/poxiao-service/poxiao-system/target/test-classes/com/poxiao/system/
        //4.class-绝对路径-"/"
        String path1 = this.getClass().getResource("/").getPath();
        System.out.println("path1:"+path1);//path1:/G:/IdeaProjects/poxiao-cloud/poxiao-service/poxiao-system/target/test-classes/
        //5.class-相对路径-"banner.txt"
        String path2 = this.getClass().getResource("banner.txt").getPath();
        System.out.println("path2:"+path2);//null point
        //6.class-绝对路径-"/banner.txt"
        String path3 = this.getClass().getResource("/banner.txt").getPath();
        System.out.println("path3:"+path3);//path3:/G:/IdeaProjects/poxiao-cloud/poxiao-service/poxiao-system/target/classes/banner.txt

        //结论:
        //使用class加载有相对路径和绝对路径
        //相对路径:指的是当前类所在的包下
        //绝对路径:指的是当前类所在的根路径下,指的是classes或者test-classes
    }

结论:

  • 使用class加载有相对路径和绝对路径
  • 相对路径:指的是当前类所在的包下
  • 绝对路径:指的是当前类所在的根路径下,指的是classes或者test-classes

3.使用类加载器加载

@Test
    public void testClassLoader() throws IOException {
        //1.class-绝对路径
//        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("/banner.txt");
//        byte[] bytes = new byte[1024];
//        inputStream.read(bytes);//null point
//        System.out.println("bytes[0]:"+bytes[0]);
//        Assert.assertNotNull("为空",inputStream);
        //2.class-相对路径
        InputStream inputStream2 = this.getClass().getClassLoader().getResourceAsStream("banner.txt");
        Assert.assertNotNull("为空",inputStream2);//not null
        //3.class-相对路径-""
        String path = this.getClass().getClassLoader().getResource("").getPath();
        System.out.println("path:"+path);//path:/G:/IdeaProjects/poxiao-cloud/poxiao-service/poxiao-system/target/test-classes/
        //4.class-绝对路径-"/"
//        String path1 = this.getClass().getClassLoader().getResource("/").getPath();
//        System.out.println("path1:"+path1);//is null
        //5.class-相对路径-"banner.txt"
        String path2 = this.getClass().getClassLoader().getResource("banner.txt").getPath();
        System.out.println("path2:"+path2);//path2:/G:/IdeaProjects/poxiao-cloud/poxiao-service/poxiao-system/target/classes/banner.txt
        //6.class-绝对路径-"/banner.txt"
//        String path3 = this.getClass().getClassLoader().getResource("/banner.txt").getPath();
//        System.out.println("path3:"+path3);//null point

        //结论
        //classLoador只有相对路径,这个和类加载器所处的位置有关系
        //相对路径:相对于根路径,这个根路径指classes和test-classes的下面
    }

结论:

  • classLoador只有相对路径,这个和类加载器所处的位置有关系
  • 相对路径:相对于根路径,这个根路径指classes和test-classes的下面

本文地址:https://blog.csdn.net/qq_40321119/article/details/109840103