Java - Classpath variable
Table of Contents
1 - About
Java classes needed to execute a Java program can be physically located in different file system directories. When Java classes are loaded, it searches different file system directories specified in the CLASSPATH variable to resolve references to the classes needed for execution.
2 - Articles Related
3 - Management
3.1 - Set
The class path can be set using either the:
3.1.1 - JVM cp Options
- -classpath option (shortened -cp) when calling an SDK tool
sdkTool -classpath classpath1;classpath2...
The -classpath option is present in the following sdk (java, jdb, javac, and javah ). Example:
# Windows with ;
java -cp /directory/with/my/class;anotherDirToaJar path/To/MainClass
# Linux with :
java -cp /directory/with/my/class:anotherDirToaJar path/To/MainClass
3.1.2 - Environment variable
By setting the CLASSPATH environment variable in a command line
C:> set CLASSPATH=classpath1;classpath2...
3.1.3 - Manifest file
in a manifest file
Class-Path: lib/supportLib.jar lib/supportLib2.jar
3.2 - Add
3.2.1 - Class
You need to add the directory root of the class definition.
Example for the class <wrap box>utility.myapp</note> located in the directory <wrap box>c:\java\MyClasses\utility\myapp</note>, you need to add the directory <wrap box>c:\java\MyClasses\</note>
java -classpath C:\java\myClasses utility.myapp.Cool
3.2.2 - Jar
- Adding one jar
In an archive file (a .zip or .jar file) the class path entry is the path to and including the .zip or .jar file. For example, to use a class library that is in a .jar file, the command would look something like this:
java -classpath C:\java\myClasses\myClasses.jar utility.myapp.Cool
- Adding all JAR files in a directory (since Java 6)
REM Windows
java -classpath ".;c:\mylib\*" MyApp
echo Linux example
java -classpath '.:/mylib/*' MyApp
3.3 - Get
System.getProperty("java.class.path")
4 - Snippet
4.1 - DOS: Building a classpath from a directory of library
@REM Appending additional jar files to the CLASSPATH...
IF EXIST %MY_DIR%\lib FOR %%G IN (%MY_DIR%\lib\*.jar) DO (CALL :APPEND_CLASSPATH %%~FSG)
echo %CLASSPATH%
java ....
:APPEND_CLASSPATH
SET CLASSPATH=%CLASSPATH%;%1
GOTO :EOF
5 - Support
5.1 - You cannot use both -jar and -cp on the command line
6 - Documentation / Reference
- Setting the Classpath: Solaris and Linux - Windows