javah Man page

javah Basic Tools javah

NAME

javah – Generates C header and source files from a Java class.

SYNOPSIS

javah [ options ] fully-qualified-class-name …

options
The command-line options. See Options.

fully-qualified-class-name
The fully qualified location of the classes to be converted to C
header and source files.

DESCRIPTION

The javah command generates C header and source files that are needed
to implement native methods. The generated header and source files are
used by C programs to reference an object’s instance variables from
native source code. The .h file contains a struct definition with a
layout that parallels the layout of the corresponding class. The fields
in the struct correspond to instance variables in the class.

The name of the header file and the structure declared within it are
derived from the name of the class. When the class passed to the javah
command is inside a package, the package name is added to the beginning
of both the header file name and the structure name. Underscores (_)
are used as name delimiters.

By default the javah command creates a header file for each class
listed on the command line and puts the files in the current directory.
Use the -stubs option to create source files. Use the -o option to
concatenate the results for all listed classes into a single file.

The Java Native Interface (JNI) does not require header information or
stub files. The javah command can still be used to generate native
method function prototypes needed for JNI-style native methods. The
javah command produces JNI-style output by default and places the
result in the .h file.

OPTIONS

-o outputfile
Concatenates the resulting header or source files for all the
classes listed on the command line into an output file. Only one
of -o or -d can be used.

-d directory
Sets the directory where the javah command saves the header
files or the stub files. Only one of -d or -o can be used.

-stubs
Causes the javah command to generate C declarations from the
Java object file.

-verbose
Indicates verbose output and causes the javah command to print a
message to stdout about the status of the generated files.

-help
Prints a help message for javah usage.

-version
Prints javah command release information.

-jni
Causes the javah command to create an output file containing
JNI-style native method function prototypes. This is the default
output; use of -jni is optional.

-classpath path
Specifies the path the javah command uses to look up classes.
Overrides the default or the CLASSPATH environment variable when
it is set. Directories are separated by colons on Oracle Solaris
and semicolons on Windows. The general format for path is:

Oracle Solaris:

.:your-path

Example: .:/home/avh/classes:/usr/local/java/classes

Windows:

.;your-path

Example: .;C:\users\dac\classes;C:\tools\java\classes

As a special convenience, a class path element that contains a
base name of * is considered equivalent to specifying a list of
all the files in the directory with the extension .jar or .JAR.

For example, if directory mydir contains a.jar and b.JAR, then
the class path element mydir/* is expanded to a A.jar:b.JAR,
except that the order of jar files is unspecified. All JAR files
in the specified directory, including hidden ones, are included
in the list. A class path entry that consists of * expands to a
list of all the JAR files in the current directory. The
CLASSPATH environment variable, where defined, is similarly
expanded. Any class path wild card expansion occurs before the
Java Virtual Machine (JVM) is started. A Java program will never
see unexpanded wild cards except by querying the environment.
For example, by calling System.getenv(“CLASSPATH”).

-bootclasspath path
Specifies the path from which to load bootstrap classes. By
default, the bootstrap classes are the classes that implement
the core Java platform located in jre\lib\rt.jar and several
other JAR files.

-old
Specifies that old JDK 1.0-style header files should be
generated.

-force
Specifies that output files should always be written.

-Joption
Passes option to the Java Virtual Machine, where option is one
of the options described on the reference page for the Java
application launcher. For example, -J-Xms48m sets the startup
memory to 48 MB. See java.

SEE ALSO

· javah

· java

· jdb

· javap

· javadoc

JDK 8 21 November 2013 javah