定位所用的class

方案

为解决类冲突，我们可以使用下述的方案定位一个class所在的位置

ClassName.class.getResource("").getPath();

获取ClassName所在的位置，即使它是在一个jar包中；如果所在jar包添加了安全保护，会获取失败。

ClassName.class.getProtectionDomain().getCodeSource().getLocation().getFile();

获取ClassName所在jar的位置，如果所在jar被安全保护，则获取失败。

DEMO

 1 package cn.j2se.junit.classpath;
 2
 3 import static org.junit.Assert.*;
 4
 5 import java.io.UnsupportedEncodingException;
 6
 7 import org.apache.commons.logging.Log;
 8 import org.apache.commons.logging.LogFactory;
 9 import org.junit.Test;
10
11 public class ClassPathTest {
12     private static final Log logger = LogFactory.getLog(ClassPathTest.class);
13     @Test
14     public void testClassPath() {
15         String classPath = ClassPathTest.class.getResource("").getPath();
16         logger.info("the classpath of ClassPathTest is:[" + classPath + "]");
17
18         assertEquals(1, 1);
19     }
20
21     @Test
22     public void testJarPath() throws UnsupportedEncodingException {
23         // System.class.getResource("") == null
24         String lfClassPath = LogFactory.class.getResource("").getPath();
25         logger.info("the classpath of LogFactory is:[" + lfClassPath + "]");
26
27         // System.class.getProtectionDomain().getCodeSource() == null
28         String lfJarPath = LogFactory.class.getProtectionDomain().getCodeSource().getLocation().getFile();
29         logger.info("the jar path of LogFactory is:[" + lfJarPath + "]");
30         assertEquals(1, 1);
31     }
32 }

 
测试结果：

1 [INFO ] 2015-08-25 14:26:30 CST
2         the classpath of ClassPathTest is:[/D:/develop/eclipse_jee_juno_SR2/workspace/lijinlong/j2se/bin/cn/j2se/junit/classpath/]
3
4 [INFO ] 2015-08-25 14:26:30 CST
5         the classpath of LogFactory is:[file:/D:/develop/eclipse_jee_juno_SR2/workspace/lijinlong/j2se/lib/commons-logging-1.1.1.jar!/org/apache/commons/logging/]
6
7 [INFO ] 2015-08-25 14:26:30 CST
8         the jar path of LogFactory is:[/D:/develop/eclipse_jee_juno_SR2/workspace/lijinlong/j2se/lib/commons-logging-1.1.1.jar]