Java Class-Path tells Java where to look on the file system for files defining these classes. For generic java application, all class files are searched/loaded from the jar files, or class folders, based on these path item sequence.
Usually, the developer would like to find class in one or many jar files, like the following situation,
- Know which class is loaded, if same class name hosted in different jar files;
- List all duplicated class names to eliminate incorrect class loading issue;
- Find class full name based on specified Simple class name or name with wild card character;
- List some class with specified constant string;
- List classes that using other class, method or field;
The classfinder library/tool is helping Java developer to find class easily inside or outside JVM without source code provided. This manual is mainly to introduce the core function for this tool running as standalone application from command line.
NOTE: It only supports Java 8+ (including Java 11). For prior Java version, please download classfinder v1.2.2 from https://github.com/feng-zh/classfinder/releases/download/v1.2.2/classfinder.jar
Download classfinder latest version (Java 8+ is required) from https://jitpack.io/com/github/feng-zh/classfinder/v2.1.0/classfinder-v2.1.0-jar-with-dependencies.jar
The classfinder support two ways by specifying jar files.
-
Add jar files as parameter
-classpathjava -jar classfinder.jar -classpath file1.jar;file2.jar;file3.jar NameToSearch -
Use jar file list from Std in (or pipeline)
dir /b path\to\folder\*.jar | java -jar classfinder.jar NameToSearchor recursive search from current work directory by enabling
/soptiondir /b /s *.jar | java -jar classfinder.jar NameToSearchor more powerful command
findin Unix/Linuxfind /path/to/folder -name "*.jar" | java -jar classfinder.jar NameToSearch
To know which jar files are involved, use "-verbose" parameter to enable file list:
$ find /path/to/folder -name "*.jar" | java -jar classfinder.jar -verbose NameToSearch1 NameSearch2
***** START CLASSPATH *****
/path/to/folder/file1.jar
/path/to/folder/file2.jar
/path/to/folder/sub/file3.jar
***** END CLASSPATH *****
***** START ARGUMENTS *****
NameToSearch1
NameToSearch2
***** END ARGUMENTS *****
The command can display full class name by specify simple class name, or with wild card character. The candidate full class name list, with the source file name will be shown. If same class find different jar files, the file name will be displayed by sequence of path order.
C:\> dir /b *.jar | java -jar classfinder.jar String
[com.sun.org.apache.xpath.internal.operations.String]
C:\Program Files (x86)\Java\jre6\lib\rt.jar
[java.lang.String]
C:\Program Files (x86)\Java\jre6\lib\rt.jar
In addition, a switch flag -group can group result by jar file name.
C:\> dir /b *.jar | java -jar classfinder.jar -group Util*
-- From [C:\classfinder.jar]
Util
...
Util$SuffixFilter
-- From [C:\rt.jar]
com.sun.corba.se.impl.javax.rmi.CORBA.Util
com.sun.corba.se.impl.javax.rmi.CORBA.Util$1
...
sun.rmi.server.Util
sun.text.normalizer.Utility
To list duplicate class by its simple name, or wild card names, use -duplicate parameter with name parameter can list all duplicated class. The jar file name is listed by its path order, which means the effective one is in the first.
C:\>dir /b *.jar | java -jar classfinder.jar -duplicate Util*
[Util]
C:\classfinder-dup.jar
C:\classfinder.jar
...
[Util$SuffixFilter]
C:\classfinder-dup.jar
C:\classfinder.jar
All class under the specified package (and its sub-packages) can be displayed over all jar files with -package parameter and name parameter.
C:\>dir /b *.jar | java -jar classfinder.jar -package java.lang
-- Class in package [java.lang]
java.lang.StackTraceElement
java.lang.ApplicationShutdownHooks$1
java.lang.StrictMath
...
To see all super class and interface names for the specified class, use -super parameter and full class name.
C:\>dir /b *.jar | java -jar classfinder.jar -super java.util.Properties
-- Super class for [java.util.Properties]
java.util.Hashtable
java.util.Dictionary
java.lang.Object
java.io.Serializable
java.lang.Cloneable
java.util.Map
To see all sub class or interface names for the specified class, use -sub parameter and full class name.
C:\>dir /b *.jar | java -jar classfinder.jar -super java.util.Properties
-- Sub class for [java.util.Properties]
com.sun.security.sasl.Provider
java.security.AuthProvider
java.security.Provider
...
sun.security.smartcardio.SunPCSC
To get reference of the specified class over the jar files, use -ref parameter and full class name can provide all class which depends on this class.
C:\>dir /b *.jar | java -jar classfinder.jar -ref java.lang.Shutdown
-- Reference class for [java.lang.Shutdown]
java.lang.ApplicationShutdownHooks
java.lang.Runtime
java.lang.Shutdown
java.lang.Shutdown$1
java.lang.Shutdown$Lock
java.lang.System$2
java.lang.Terminator$1
Also to know all depending classes over the jar files, use -depend parameter and full class name can provide all class which used by this class. That means if no such class in classpath, it may trigger class not found error.
The result shows existing dependence class name, and non-founded dependence class names (some may related to JRE).
C:\>dir /b *.jar | java -jar classfinder.jar -depend Util
-- Dependence class for [Util]
AbstractClassFinder
ClassFinder
ClassLoaderFinder
...
-- Non-founded dependence class for [Util]
com.sun.org.apache.bcel.internal.classfile.Attribute
com.sun.org.apache.bcel.internal.classfile.ClassParser
...
To get reference of the specified method in the class, use -mref parameter and full method with class name can provide related class name list.
C:\>dir /b *.jar | java -jar classfinder.jar -mref java.lang.System.exit
-- Reference class for Method [java.lang.System.exit]
ClassPathFinderMain
JarCat
com.sun.corba.se.impl.activation.Quit
com.sun.corba.se.impl.activation.ServerMain
com.sun.corba.se.impl.naming.cosnaming.TransientNameServer
...
To get reference of the specified field in the class, use -fref parameter and full field with class name can provide related class name list.
C:\>dir /b *.jar | java -jar classfinder.jar -fref java.lang.System.out
-- Reference class for Field [java.lang.System.out]
ClassPathFinderMain
JarCat
...
During some application running, if want to know where the log string is created, we can first use -strings to find possible class, then look into them (or source code) by using other tools.
C:\>dir /b *.jar | java -jar classfinder.jar -strings "Options:"
-- Class contains text "Options:"
[com.sun.servicetag.Installer]
Internal Options:
[sun.tools.jar.resources.jar]
Usage: jar {ctxui}[vfm0Me] [jar-file] [manifest-file] [entry-point] [-C dir] files ...
Options:
...
If the jar file contains some property file, XML file, or java source file, use -cat parameter can help to view its text directly without extracting them.
C:\>dir /b *.jar | java -jar classfinder.jar -cat ClassFinder
::[1] com/hp/it/gadsc/et/ei/tools/classfinder/ClassFinder.class
::Warn: "com/hp/it/gadsc/et/ei/tools/classfinder/ClassFinder.class" is not a text file, may be content type of application/java-vm
::[2] com/hp/it/gadsc/et/ei/tools/classfinder/ClassFinder.java
package com.hp.it.gadsc.et.ei.tools.classfinder;
import java.net.URL;
import java.util.List;
import java.util.Map;
public interface ClassFinder {
...
Here are the full usage for reference. Type java -jar classfinder.jar or incorrect parameter can also print these information in console.
Usage: classfinder [SCOPE] [OPTION] NAME...
Find class name from classpath.
SCOPE:
-classpath <PATH LIST> [-jre <JAVA HOME>]
Lookup class from the provided class path
(EMPTY)
Find class from the class path loaded from std in. It accept path separator or new line separator
OPTION:
(EMPTY)
List class names and group by name
-group
Group class by its source
-package
List class names by package name, which is specified in NAME
-super
List all super class or interface names
-sub
List all children class or interface names
-duplicate
List all duplicated class or interface names
-ref
List all incoming referring class or interface names
-mref
List all incoming referring class or interface names for the full method name
-fref
List all incoming referring class or interface names for the full field name
-depend
List all outgoing depending class or interface names
-strings
List class or interface contains the string text
-cat
Print text file with name matching the string text
-verbose
List class path will be searched
-current
Add current java home into classpath if no explicit java home specified
NAME:
java.lang.Object The full class name
'Object*' The class name with wildcards, but without package name.
This is only support for class name finding.
'java.util.*List' The full class name with wildcards(like '*', or '?'). This is only support for class name finding.
'java.util.Collection.toArray' The full method name. This is only support for method name based finding.
'java.lang.System.out' The full field name. This is only support for field name based finding.