?? classorigin.html
字號:
<HTML>
<HEAD>
<META http-equiv="Content-Type" content="text/html; charset=UTF-8">
<TITLE>Determining from Where a Class Was Loaded
(Java Developers Almanac Example)
</TITLE>
<META CONTENT="Patrick Chan" NAME="AUTHOR">
<META CONTENT="Code Examples from The Java Developers Almanac 1.4" NAME="DESCRIPTION">
<META CONTENT="Addison-Wesley/Patrick Chan" NAME="OWNER">
<META CONTENT="3/20/02" NAME="revision">
<STYLE TYPE="text/css">
<!-- BODY CODE {font-family: Courier, Monospace; font-size: 11pt} TABLE, BODY {font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt} PRE {font-family: Courier, Monospace; font-size: 10pt} H3 {font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 11pt} A.eglink {text-decoration: none} A:hover.eglink {text-decoration: underline} -->
</STYLE>
</HEAD>
<BODY>
<TABLE CELLSPACING="0" CELLPADDING="0" BORDER="0">
<TR>
<TD rowspan="3"><A HREF="/?l=ex"><IMG BORDER="0" ALIGN="BOTTOM" HSPACE="10" SRC="/egs/almanac14a.jpg"></A></TD><TD VALIGN="top"><font face="Times" size="6"><b>The Java Developers Almanac 1.4</b></font>
<br>
Order this book from <a href="/cgi-bin/scripts/redirect.pl?l=ex&url=http://www.amazon.com/exec/obidos/ASIN/0201752808/xeo">Amazon</a>.
</TD>
</TR>
<TR>
<TD align="right" valign="bottom">
<FORM method="get" action="/cgi-bin/search/find.pl">
<INPUT size="25" name="words" type="text"><INPUT value="Search" type="submit">
</FORM>
</TD>
</TR>
</TABLE>
<HR color="#6666cc">
<DIV ALIGN="LEFT">
<A HREF="/">Home</A>
>
<A HREF="../index.html">List of Packages</A>
>
<B><A HREF="../java.lang/pkg.html">java.lang</A></B><font color="#666666" SIZE="-2">
[58 examples]
</font>
>
<B><A HREF="../java.lang/pkg.html#Classes">Classes</A></B><font color="#666666" SIZE="-2">
[11 examples]
</font>
</DIV><P>
<h3>
e67.
Determining from Where a Class Was Loaded</h3>
<pre>
// Get the location of this class
Class cls = this.getClass();
ProtectionDomain pDomain = cls.getProtectionDomain();
CodeSource cSource = pDomain.getCodeSource();
URL loc = cSource.getLocation(); // file:/c:/almanac14/examples/
</pre>
It is not possible to determine the location of classes loaded by the
system class loader in the same way since the class' code source is
<code>null</code>. The only other method is to use the <code>-verbose</code> option on the
<code>java</code> command. This causes the Java virtual machine to print a message
every time a class is loaded.
<pre>
> java -verbose <font color="#0066ff"><i>MyApp</i></font>
</pre>
Here's a sample of the output:
<pre>
[Opened c:\jdk1.4\jre\lib\rt.jar]
[Opened c:\jdk1.4\jre\lib\sunrsasign.jar]
[Opened c:\jdk1.4\jre\lib\jsse.jar]
[Opened c:\jdk1.4\jre\lib\jce.jar]
[Opened c:\jdk1.4\jre\lib\charsets.jar]
[Loaded java.lang.Object from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.io.Serializable from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.Comparable from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.CharSequence from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.String from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.Class from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.Cloneable from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.ClassLoader from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.System from c:\jdk1.4\jre\lib\rt.jar]
[Loaded java.lang.Throwable from c:\jdk1.4\jre\lib\rt.jar]
</pre>
<P><table width="600" CELLSPACING="0" CELLPADDING="2" BORDER="0">
<tr>
<td bgcolor="#6666cc" align="center"><font color="#ffffff">
Related Examples
</font></td>
</tr>
</table>
e59. <a class="eglink" href="GetClass.html?l=rel">
Getting a Class Object
</a>
<br>
e60. <a class="eglink" href="GetClassName.html?l=rel">
Getting the Name of a Class Object
</a>
<br>
e61. <a class="eglink" href="IsClass.html?l=rel">
Determining If a Class Object Represents a Class or Interface
</a>
<br>
e62. <a class="eglink" href="SuperClass.html?l=rel">
Getting the Superclass of an Object
</a>
<br>
e63. <a class="eglink" href="SuperClass2.html?l=rel">
Getting the Superclass of a Class Object
</a>
<br>
e64. <a class="eglink" href="GetImplements2.html?l=rel">
Listing the Interfaces That a Class Implements
</a>
<br>
e65. <a class="eglink" href="GetImplements.html?l=rel">
Listing the Interfaces That an Interface Extends
</a>
<br>
e66. <a class="eglink" href="GetPkg.html?l=rel">
Getting the Package of a Class
</a>
<br>
e68. <a class="eglink" href="LoadClass.html?l=rel">
Loading a Class That Is Not on the Classpath
</a>
<br>
e69. <a class="eglink" href="ReloadClass.html?l=rel">
Dynamically Reloading a Modified Class
</a>
<br>
<table width="600" CELLSPACING="0" CELLPADDING="2" BORDER="0">
<tr>
<td align="left">
<br>
See also:
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Arrays">
Arrays
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Assertions">
Assertions
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Commands">
Commands
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Numbers">
Numbers
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Objects">
Objects
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Strings">
Strings
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#System%20Properties">
System Properties
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Threads">
Threads
</a>
</td>
</tr>
</table>
<br>
<br>
<FONT FACE="Verdana, Arial, Helvetica, sans-serif" SIZE="0">
© 2002 Addison-Wesley.
</FONT>
</BODY>
</HTML>
?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -