前几天在写一个C/S的小工具,使用class.getClassLoader().getResource("")时,发现一个问题,程序如下:
package com.syj;
public class ClassLoaderTest {
public static void main(String[] args){
String classPath1 = ClassLoaderTest.class.getClassLoader().getResource(
"config.ini").toString();
System.out.println("classPath1:" + classPath1);
String classPath2 = ClassLoaderTest.class.getClassLoader().getResource(
"").toString();
System.out.println("classPath2:" + classPath2);
}
}
public class ClassLoaderTest {
public static void main(String[] args){
String classPath1 = ClassLoaderTest.class.getClassLoader().getResource(
"config.ini").toString();
System.out.println("classPath1:" + classPath1);
String classPath2 = ClassLoaderTest.class.getClassLoader().getResource(
"").toString();
System.out.println("classPath2:" + classPath2);
}
}
打成jar包test.jar后
执行
java -jar test.jar
pause
执行结果
classPath1:jar:file:/D:/DEV.WORK/works_acnt/Test/test.jar!/config
Exception in thread "main" java.lang.NullPointerException
at com.syj.ClassLoaderTest.main(ClassLoaderTest.java:9)
执行
set CLASSPATH=%CLASSPATH%;test.jar;
java com.syj.ClassLoaderTest
pause
执行结果
classPath1:file:/D:/DEV.WORK/works_acnt/Test/config.ini
classPath2:file:/D:/DEV.WORK/works_acnt/Test/
不难发现当使用java -jar test.jar启动程序时可以getResource一个具体文件是没有问题的但是getResource("")就会出问题,要把这个jar放
到ClassPath里面才行
可见用java -jar test.jar启动程序时程序并不知道当前这个test.jar的绝对路径
linux下路径为//home/hdfs/.....，否则也可能空异常
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