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

package cn.j2se.junit.classpath;

import static org.junit.Assert.*;

import java.io.UnsupportedEncodingException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.junit.Test;

public class ClassPathTest {
    private static final Log logger = LogFactory.getLog(ClassPathTest.class);
    @Test
    public void testClassPath() {
        String classPath = ClassPathTest.class.getResource("").getPath();
        logger.info("the classpath of ClassPathTest is:[" + classPath + "]");
        
        assertEquals(1, 1);
    }
    
    @Test
    public void testJarPath() throws UnsupportedEncodingException {
        // System.class.getResource("") == null
        String lfClassPath = LogFactory.class.getResource("").getPath();
        logger.info("the classpath of LogFactory is:[" + lfClassPath + "]");
        
        // System.class.getProtectionDomain().getCodeSource() == null
        String lfJarPath = LogFactory.class.getProtectionDomain().getCodeSource().getLocation().getFile();
        logger.info("the jar path of LogFactory is:[" + lfJarPath + "]");
        assertEquals(1, 1);
    }
}

 
测试结果：

[INFO ] 2015-08-25 14:26:30 CST
        the classpath of ClassPathTest is:[/D:/develop/eclipse_jee_juno_SR2/workspace/lijinlong/j2se/bin/cn/j2se/junit/classpath/]

[INFO ] 2015-08-25 14:26:30 CST
        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/]

[INFO ] 2015-08-25 14:26:30 CST
        the jar path of LogFactory is:[/D:/develop/eclipse_jee_juno_SR2/workspace/lijinlong/j2se/lib/commons-logging-1.1.1.jar]