在URL中想访问getCodeBase()的上级目录，help

Question

没明白，我现在手头没有api和参考书，能写详细一点？

Answer 1

不知道是不是这个意思哈！URL url = new URL(codeBase.toString()+"../dat/output.txt");

Answer 2

URL url = new URL(codeBase.toString()+"/../dat/output.txt");

Answer 3

URL u1 = new URL("http://archive.ncsa.uiuc.edu/SDG/url-primer.html");
      URL u2 = new URL(u1,"../dat/output.txt");
      System.out.println(u2);
===============================================
输出是：
http://archive.ncsa.uiuc.edu/dat/output.txt不知道是你要的效果否？

Answer 4

error！！！！！！！！！！！！！！！！！！！！E:\weblab\Telelab\lab7\PID\java\Djbh.java:165: cannot resolve symbol
symbol  : variable codeBase 
location: class Djbh
                URL url = new URL(codeBase.toString()+"../dat/output.txt");
HELP!!!!!!!!!!!!!!!!!!!!!!!!

Answer 5

URL url = new URL(getCodeBase(),"../dat/output.txt");

Answer 6

java.security.AccessControlException: access denied (java.io.FilePermissi
eblab\Telelab\lab7\PID\dat\output.txt read)
        at java.security.AccessControlContext.checkPermission(AccessContr
xt.java:270)
        at java.security.AccessController.checkPermission(AccessControlle
401)
        at java.lang.SecurityManager.checkPermission(SecurityManager.java
        at java.lang.SecurityManager.checkRead(SecurityManager.java:887)
        at java.io.File.isDirectory(File.java:698)
        at sun.net.www.protocol.file.FileURLConnection.connect(FileURLCon
.java:65)
        at sun.net.www.protocol.file.FileURLConnection.getInputStream(Fil
nection.java:156)
        at java.net.URL.openStream(URL.java:960)
        at Djbh.paint(Djbh.java:167)
        at sun.awt.RepaintArea.paint(RepaintArea.java:177)
        at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java
        at java.awt.Component.dispatchEventImpl(Component.java:3699)
        at java.awt.Container.dispatchEventImpl(Container.java:1623)
        at java.awt.Component.dispatchEvent(Component.java:3480)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:450)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDis
read.java:197)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispa
ad.java:150)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.ja        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.ja        at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

Answer 7

编译能通过，显示如下
file:/E:/weblab/Telelab/lab7/PID/dat/output.txt
file:/E:/weblab/Telelab/lab7/PID/java/output.dat
oo0.249055
oo0.862702
oo1.662471
oo2.548436
oo3.462989
oo4.371207
oo5.250439
oo6.084794
oo6.862256
附：相关代码
＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃
import java.io.*;
import java.util.StringTokenizer;
import java.lang.Double;
import java.lang.Integer;
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.net.*;
public class Ceshi extends Applet
{
public void init()
    {
try
{
                String delim1 = ",";   
                String shu,time;
                double a=0;
               URL url = new URL(getCodeBase(),"output.dat");    
                   URL u2 = new URL(url,"../dat/output.txt");
                   System.out.println(u2);
                   System.out.println(url);
InputStreamReader reader = new InputStreamReader ( url.openStream( ));
BufferedReader bufReader = new BufferedReader ( reader );
String name = bufReader.readLine();
StringTokenizer tokenizer;
tokenizer = new StringTokenizer(name, delim1);
for (int i=0;tokenizer.hasMoreTokens();i++)
 {
                        shu = tokenizer.nextToken(delim1);                        
                        a=Double.valueOf(shu).doubleValue();//°ü×°Æ÷ÀàDouble.valueOf
                         System.out.println("oo"+a);
                        } 
                }
catch (IOException ioe)
{
System.out.println ("I/O error : " + ioe);
} 
   
}
}

//<applet code=Ceshi  NAME = "TestApplet" width=561  height=410 ALIGN = middle></applet>//appletviewer Ceshi.java
＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃
dat和txt中存0.249055,0.862702,1.662471,2.548436,3.462989,等数字

Answer 8

若把上面测试程序中InputStreamReader reader = new InputStreamReader ( url.openStream( ));
改为InputStreamReader reader = new InputStreamReader ( u2.openStream( ));
即，连到新的dat文件时出错
文件结构：E:/weblab/Telelab/lab7/PID/dat/output.dat－－－－－－对应u2
         E:/weblab/Telelab/lab7/PID/java/output.txt－－－－－对应url
报错如下：（编译能通过，执行时报错！）file:/E:/weblab/Telelab/lab7/PID/dat/output.txt
file:/E:/weblab/Telelab/lab7/PID/java/output.dat
java.security.AccessControlException: access denied (java.io.FilePermission E:\w
eblab\Telelab\lab7\PID\dat\output.txt read)
        at java.security.AccessControlContext.checkPermission(AccessControlConte
xt.java:270)
        at java.security.AccessController.checkPermission(AccessController.java:
401)
        at java.lang.SecurityManager.checkPermission(SecurityManager.java:542)
        at java.lang.SecurityManager.checkRead(SecurityManager.java:887)
        at java.io.File.isDirectory(File.java:698)
        at sun.net.www.protocol.file.FileURLConnection.connect(FileURLConnection
.java:65)
        at sun.net.www.protocol.file.FileURLConnection.getInputStream(FileURLCon
nection.java:156)
        at java.net.URL.openStream(URL.java:960)
        at Ceshi.init(Ceshi.java:24)
        at sun.applet.AppletPanel.run(AppletPanel.java:348)
        at java.lang.Thread.run(Thread.java:536)
看来是java.security.AccessControlException，请达人解释一下！