获取文件路径是很常用的操作,但在这之前你必须对url的相对路径和绝对路径有所了解。
如果我想获取工程的路径,或者说我想获取工程里某个文件应该怎么办呢?
方法就是用class获取Resource。
比如我们写个类叫XXX.java
获取资源文件就可以使用2个方法,分别是
XXX.class.getResource()与XXX.class.getClassLoader().getResource(url)。
关于怎么获取和这两者的区别,做个试验就很清楚了。
现在给出我的文件结构:
src(源文件夹)
|_org
|_path
| |_child
| | |FileTwo.txt
| |
| |PathUtil.java
| |FileOne.txt
|
|_path2
|fileThree.txt
如图:
废话不多说,看试验吧:
PathUtil
package org.path;
import java.io.File;
/**
* XXX.class.getResource()与XXX.class.getClassLoader().getResource(url)研究
* @author lushuaiyin
*
*/
public class PathUtil {
public static void main(String[] args) {
String path1=PathUtil.class.getResource("").getPath();
System.out.println("path1:"+path1);
String path2=PathUtil.class.getResource("/").getPath();
System.out.println("path2:"+path2);
String path3=PathUtil.class.getClassLoader().getResource("").getPath();
System.out.println("path3:"+path3);
// String path4=PathUtil.class.getClassLoader().getResource("/").getPath();
// System.out.println("path4:"+path4);//空指针报错
System.out.println("-------------------------------------------");
//知道XXX.class.getResource(url)和XXX.class.getClassLoader().getResource(url)的区别后,
//下面开始使用这2个方法找到我们想要的文件
//一:找和本class同包下的文件,例如FileOne.txt
//方式1(从本类路径开始找)
File fileOne1=new File(PathUtil.class.getResource("FileOne.txt").getFile());
System.out.println("fileOne1:"+PathUtil.class.getResource("FileOne.txt").getFile());
//方式2(从根路径开始找)
File fileOne2=new File(PathUtil.class.getClassLoader().getResource("org/path/FileOne.txt").getFile());
System.out.println("fileOne2:"+PathUtil.class.getClassLoader().getResource("org/path/FileOne.txt").getFile());
System.out.println("");
//二:找和本class同包下的子目录下的文件,例如FileTwo.txt
//方式1(从本类路径开始找)
File fileTwo1=new File(PathUtil.class.getResource("child/FileTwo.txt").getFile());
System.out.println("fileTwo1:"+PathUtil.class.getResource("child/FileTwo.txt").getFile());
//方式2(从根路径开始找)
File fileTwo2=new File(PathUtil.class.getClassLoader().getResource("org/path/child/FileTwo.txt").getFile());
System.out.println("fileTwo2:"+PathUtil.class.getClassLoader().getResource("org/path/child/FileTwo.txt").getFile());
System.out.println("");
//三:找和本class父目录同包下的文件,例如FileThree.txt
//方式1(从本类路径开始找)
File fileThree1=new File(PathUtil.class.getResource("../path2/FileThree.txt").getFile());
System.out.println("fileThree1:"+PathUtil.class.getResource("../path2/FileThree.txt").getFile());
//方式2(从根路径开始找)
File fileThree2=new File(PathUtil.class.getClassLoader().getResource("org/path2/FileThree.txt").getFile());
System.out.println("fileThree2:"+PathUtil.class.getClassLoader().getResource("org/path2/FileThree.txt").getFile());
}
/*
首先给出文件路径结构:
src(源文件夹)
|_org
|_path
| |_child
| | |FileTwo.txt
| |
| |PathUtil.java
| |FileOne.txt
|
|_path2
|fileThree.txt
XXX.class.getResource(url)
这个是从当前类XXX的路径开始找。
XXX.class.getClassLoader().getResource(url)
这个是从根目录开始找。
所以PathUtil.class.getClassLoader().getResource("/").getPath()会报错。
打印:
path1:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/org/path/
path2:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/
path3:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/
-------------------------------------------
fileOne1:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/org/path/FileOne.txt
fileOne2:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/org/path/FileOne.txt
fileTwo1:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/org/path/child/FileTwo.txt
fileTwo2:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/org/path/child/FileTwo.txt
fileThree1:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/org/path2/FileThree.txt
fileThree2:/D:/ChinaDevelopmentBankJBPM/workSpace/frame/webapp/WEB-INF/classes/org/path2/FileThree.txt
*/
}
上面的试验清楚明了,唯一要注意的地方就是:
PathUtil.class.getResource("").getPath() 得到本类路径
PathUtil.class.getResource("/").getPath() 得到根路径
PathUtil.class.getClassLoader().getResource("").getPath() 得到根路径
PathUtil.class.getClassLoader().getResource("/").getPath() 空指针报错,因为它从根路径找文件,你给的url不是文件的url
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