YYNET.WANG 编程学习
Java 获取文件Jar包中读取文件
2022-08-20
本文介绍java多种方式从classpath、url以及jar中读取文件。
各种路径获取方式
package com.theliang;
import java.io.File;
import java.io.InputStream;
import java.net.URL;
public class Main {
public static void main(String[] args) throws Exception {
//* 1. 获取项目的路径(非Jar包)
String path1 = System.getProperty("user.dir");
System.out.println("1.获取项目的路径 = " + path1);
//* 1. 获取项目的主路径(包级以上级别)(非Jar包)
String path1_1 = Main.class.getClassLoader().getResource(".").getFile();
System.out.println("1.获取项目的路径 = " + path1_1);
//* 2. 获取项目中当前类的路径(非Jar包)
String path2 = Main.class.getResource("Main.class").getPath();
System.out.println("2.获取项目中当前类的路径 = " + path2);
//* 3. 获取Jar包所在路径
String path3 = System.getProperty("user.dir");
System.out.println("3.获取Jar包所在路径 = " + path3);
//* 4. 获取Jar包路径
String path4 = Main.class.getProtectionDomain().getCodeSource().getLocation().getFile();
String path4_1 = Main.class.getProtectionDomain().getCodeSource().getLocation().getPath();//两个是相同的
System.out.println("4.获取Jar包路径 = " + path4);
System.out.println("4.获取Jar包路径 = " + path4_1);
//* 5. 获取Jar包中指定资源的路径
String path5 = Main.class.getClassLoader().getResource("hello.text").getPath();
String path5_1 = Main.class.getClassLoader().getResource("hello.text").getFile();
System.out.println("5.获取Jar包中指定资源的路径 = " + path5);
System.out.println("5.获取Jar包中指定资源的路径 = " + path5_1);
//* 6. 读取项目下的文件(非Jar包)
URL url = Main.class.getClassLoader().getResource("hello.text");
System.out.println("6.读取项目下的文件 = " + url.getPath());
InputStream is = url.openStream();
// is = Main.class.getClassLoader().getResourceAsStream("hello.text");//也可以写成这样
byte[] bytes = new byte[1024];
while (is.read(bytes) != -1) {
System.out.println(new String(bytes, "UTF-8"));
}
//* 7. 读取Jar包中的文件(执行的类也在相同的jar包中)
URL url2 = Main.class.getClassLoader().getResource("hello.text");
System.out.println("7.读取Jar包中的文件 = " + url2.getPath());
InputStream is2 = url2.openStream();
byte[] bytes2 = new byte[1024];
while (is2.read(bytes2) != -1) {
System.out.println(new String(bytes2, "UTF-8"));
}
//* 8. 外部类访问Jar包内的文件
String jarPath = "D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar";
URL url3 = new URL("jar:file:/" + jarPath + "!/hello.text");
System.out.println("8.访问Jar包内的文件 = " + url3.getPath());
InputStream is3 = url3.openStream();
byte[] bytes3 = new byte[1024];
while (is3.read(bytes3) != -1) {
System.out.println(new String(bytes3, "UTF-8"));
}
//* 9. 乱码问题
//如果路径包含Unicode字符，还需要将路径转码
path1 = java.net.URLDecoder.decode(path1, "UTF-8");
}
}IDEA中输出的结果
1.获取项目的路径 = D:\Project\JavaPath 2.获取项目中当前类的路径 = /D:/Project/JavaPath/out/production/JavaPath/com/theliang/Main.class 3.获取Jar包所在路径 = D:\Project\JavaPath 4.获取Jar包路径 = /D:/Project/JavaPath/out/production/JavaPath/ 4.获取Jar包路径 = /D:/Project/JavaPath/out/production/JavaPath/ 5.获取Jar包中指定资源的路径 = /D:/Project/JavaPath/out/production/JavaPath/hello.text 5.获取Jar包中指定资源的路径 = /D:/Project/JavaPath/out/production/JavaPath/hello.text 6.读取项目下的文件 = /D:/Project/JavaPath/out/production/JavaPath/hello.text Hello Test 测试文件 7.读取Jar包中的文件 = /D:/Project/JavaPath/out/production/JavaPath/hello.text Hello Test 测试文件 8.访问Jar包内的文件 = file:/D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar!/hello.text Hello Test 测试文件
执行JAR包所输出的结果
1.获取项目的路径 = D:\Project\JavaPath\out\artifacts\JavaPath_jar 2.获取项目中当前类的路径 = file:/D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar!/com/theliang/Main.class 3.获取Jar包所在路径 = D:\Project\JavaPath\out\artifacts\JavaPath_jar 4.获取Jar包路径 = /D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar 4.获取Jar包路径 = /D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar 5.获取Jar包中指定资源的路径 = file:/D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar!/hello.text 5.获取Jar包中指定资源的路径 = file:/D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar!/hello.text 6.读取项目下的文件 = file:/D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar!/hello.text Hello Test 测试文件 7.读取Jar包中的文件 = file:/D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar!/hello.text Hello Test 测试文件 8.访问Jar包内的文件 = file:/D:/Project/JavaPath/out/artifacts/JavaPath_jar/JavaPath.jar!/hello.text Hello Test 测试文件
外部类读取Jar包中的配置文件
Jar包中配置文件的路径格式是：jar:file/地址/Jar包.jar!/配置文件名
判断 是class文件执行还是jar文件执行
public class Main {
public static void main(String[] args) {
System.out.println(Main.class.getResource("Main.class").toString());
}
}在Class中会输出：
file:/D:/Project/JavaPath/out/production/JavaPath/com/theliang/Main.class
在Jar包中会输出：
jar:file:/D:/Project/JavaPath/out/production/JavaPath/com/theliang/JavaPath.jar!/com/theliang/Main.class
所以我们可以通过前缀判断执行环境
URL url = this.getClass().getResource("/file/test.txt");
String file = url.getFile();
System.out.println(file);来源：https://blog.csdn.net/the_liang/article/details/103957426
URL url = WebMvcConfig.class.getClassLoader().getResource("abc.txt");
try {
InputStream inputFile = url.openStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputFile));
while(reader.ready()) {
String line = reader.readLine();
if(line.length()>0 && line.trim().length()>0) {
System.out.println(line);
}
}
} catch (IOException e) {
e.printStackTrace();
}