linux/Documentation/java.txt
<<
>>
Prefs
   1               Java(tm) Binary Kernel Support for Linux v1.03
   2               ----------------------------------------------
   3
   4Linux beats them ALL! While all other OS's are TALKING about direct
   5support of Java Binaries in the OS, Linux is doing it!
   6
   7You can execute Java applications and Java Applets just like any
   8other program after you have done the following:
   9
  101) You MUST FIRST install the Java Developers Kit for Linux.
  11   The Java on Linux HOWTO gives the details on getting and
  12   installing this. This HOWTO can be found at:
  13
  14        ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/Java-HOWTO
  15
  16   You should also set up a reasonable CLASSPATH environment
  17   variable to use Java applications that make use of any
  18   nonstandard classes (not included in the same directory
  19   as the application itself).
  20
  212) You have to compile BINFMT_MISC either as a module or into
  22   the kernel (CONFIG_BINFMT_MISC) and set it up properly.
  23   If you choose to compile it as a module, you will have
  24   to insert it manually with modprobe/insmod, as kmod
  25   cannot easily be supported with binfmt_misc. 
  26   Read the file 'binfmt_misc.txt' in this directory to know
  27   more about the configuration process.
  28
  293) Add the following configuration items to binfmt_misc
  30   (you should really have read binfmt_misc.txt now):
  31   support for Java applications:
  32     ':Java:M::\xca\xfe\xba\xbe::/usr/local/bin/javawrapper:'
  33   support for executable Jar files:
  34     ':ExecutableJAR:E::jar::/usr/local/bin/jarwrapper:'
  35   support for Java Applets:
  36     ':Applet:E::html::/usr/bin/appletviewer:'
  37   or the following, if you want to be more selective:
  38     ':Applet:M::<!--applet::/usr/bin/appletviewer:'
  39
  40   Of course you have to fix the path names. The path/file names given in this
  41   document match the Debian 2.1 system. (i.e. jdk installed in /usr,
  42   custom wrappers from this document in /usr/local)
  43
  44   Note, that for the more selective applet support you have to modify
  45   existing html-files to contain <!--applet--> in the first line
  46   ('<' has to be the first character!) to let this work!
  47
  48   For the compiled Java programs you need a wrapper script like the
  49   following (this is because Java is broken in case of the filename
  50   handling), again fix the path names, both in the script and in the
  51   above given configuration string.
  52
  53   You, too, need the little program after the script. Compile like
  54   gcc -O2 -o javaclassname javaclassname.c
  55   and stick it to /usr/local/bin.
  56
  57   Both the javawrapper shellscript and the javaclassname program
  58   were supplied by Colin J. Watson <cjw44@cam.ac.uk>.
  59
  60====================== Cut here ===================
  61#!/bin/bash
  62# /usr/local/bin/javawrapper - the wrapper for binfmt_misc/java
  63
  64if [ -z "$1" ]; then
  65        exec 1>&2
  66        echo Usage: $0 class-file
  67        exit 1
  68fi
  69
  70CLASS=$1
  71FQCLASS=`/usr/local/bin/javaclassname $1`
  72FQCLASSN=`echo $FQCLASS | sed -e 's/^.*\.\([^.]*\)$/\1/'`
  73FQCLASSP=`echo $FQCLASS | sed -e 's-\.-/-g' -e 's-^[^/]*$--' -e 's-/[^/]*$--'`
  74
  75# for example:
  76# CLASS=Test.class
  77# FQCLASS=foo.bar.Test
  78# FQCLASSN=Test
  79# FQCLASSP=foo/bar
  80
  81unset CLASSBASE
  82
  83declare -i LINKLEVEL=0
  84
  85while :; do
  86        if [ "`basename $CLASS .class`" == "$FQCLASSN" ]; then
  87                # See if this directory works straight off
  88                cd -L `dirname $CLASS`
  89                CLASSDIR=$PWD
  90                cd $OLDPWD
  91                if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
  92                        CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
  93                        break;
  94                fi
  95                # Try dereferencing the directory name
  96                cd -P `dirname $CLASS`
  97                CLASSDIR=$PWD
  98                cd $OLDPWD
  99                if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
 100                        CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
 101                        break;
 102                fi
 103                # If no other possible filename exists
 104                if [ ! -L $CLASS ]; then
 105                        exec 1>&2
 106                        echo $0:
 107                        echo "  $CLASS should be in a" \
 108                             "directory tree called $FQCLASSP"
 109                        exit 1
 110                fi
 111        fi
 112        if [ ! -L $CLASS ]; then break; fi
 113        # Go down one more level of symbolic links
 114        let LINKLEVEL+=1
 115        if [ $LINKLEVEL -gt 5 ]; then
 116                exec 1>&2
 117                echo $0:
 118                echo "  Too many symbolic links encountered"
 119                exit 1
 120        fi
 121        CLASS=`ls --color=no -l $CLASS | sed -e 's/^.* \([^ ]*\)$/\1/'`
 122done
 123
 124if [ -z "$CLASSBASE" ]; then
 125        if [ -z "$FQCLASSP" ]; then
 126                GOODNAME=$FQCLASSN.class
 127        else
 128                GOODNAME=$FQCLASSP/$FQCLASSN.class
 129        fi
 130        exec 1>&2
 131        echo $0:
 132        echo "  $FQCLASS should be in a file called $GOODNAME"
 133        exit 1
 134fi
 135
 136if ! echo $CLASSPATH | grep -q "^\(.*:\)*$CLASSBASE\(:.*\)*"; then
 137        # class is not in CLASSPATH, so prepend dir of class to CLASSPATH
 138        if [ -z "${CLASSPATH}" ] ; then
 139                export CLASSPATH=$CLASSBASE
 140        else
 141                export CLASSPATH=$CLASSBASE:$CLASSPATH
 142        fi
 143fi
 144
 145shift
 146/usr/bin/java $FQCLASS "$@"
 147====================== Cut here ===================
 148
 149
 150====================== Cut here ===================
 151/* javaclassname.c
 152 *
 153 * Extracts the class name from a Java class file; intended for use in a Java
 154 * wrapper of the type supported by the binfmt_misc option in the Linux kernel.
 155 *
 156 * Copyright (C) 1999 Colin J. Watson <cjw44@cam.ac.uk>.
 157 *
 158 * This program is free software; you can redistribute it and/or modify
 159 * it under the terms of the GNU General Public License as published by
 160 * the Free Software Foundation; either version 2 of the License, or
 161 * (at your option) any later version.
 162 *
 163 * This program is distributed in the hope that it will be useful,
 164 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 165 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 166 * GNU General Public License for more details.
 167 *
 168 * You should have received a copy of the GNU General Public License
 169 * along with this program; if not, write to the Free Software
 170 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 171 */
 172
 173#include <stdlib.h>
 174#include <stdio.h>
 175#include <stdarg.h>
 176#include <sys/types.h>
 177
 178/* From Sun's Java VM Specification, as tag entries in the constant pool. */
 179
 180#define CP_UTF8 1
 181#define CP_INTEGER 3
 182#define CP_FLOAT 4
 183#define CP_LONG 5
 184#define CP_DOUBLE 6
 185#define CP_CLASS 7
 186#define CP_STRING 8
 187#define CP_FIELDREF 9
 188#define CP_METHODREF 10
 189#define CP_INTERFACEMETHODREF 11
 190#define CP_NAMEANDTYPE 12
 191#define CP_METHODHANDLE 15
 192#define CP_METHODTYPE 16
 193#define CP_INVOKEDYNAMIC 18
 194
 195/* Define some commonly used error messages */
 196
 197#define seek_error() error("%s: Cannot seek\n", program)
 198#define corrupt_error() error("%s: Class file corrupt\n", program)
 199#define eof_error() error("%s: Unexpected end of file\n", program)
 200#define utf8_error() error("%s: Only ASCII 1-255 supported\n", program);
 201
 202char *program;
 203
 204long *pool;
 205
 206u_int8_t read_8(FILE *classfile);
 207u_int16_t read_16(FILE *classfile);
 208void skip_constant(FILE *classfile, u_int16_t *cur);
 209void error(const char *format, ...);
 210int main(int argc, char **argv);
 211
 212/* Reads in an unsigned 8-bit integer. */
 213u_int8_t read_8(FILE *classfile)
 214{
 215        int b = fgetc(classfile);
 216        if(b == EOF)
 217                eof_error();
 218        return (u_int8_t)b;
 219}
 220
 221/* Reads in an unsigned 16-bit integer. */
 222u_int16_t read_16(FILE *classfile)
 223{
 224        int b1, b2;
 225        b1 = fgetc(classfile);
 226        if(b1 == EOF)
 227                eof_error();
 228        b2 = fgetc(classfile);
 229        if(b2 == EOF)
 230                eof_error();
 231        return (u_int16_t)((b1 << 8) | b2);
 232}
 233
 234/* Reads in a value from the constant pool. */
 235void skip_constant(FILE *classfile, u_int16_t *cur)
 236{
 237        u_int16_t len;
 238        int seekerr = 1;
 239        pool[*cur] = ftell(classfile);
 240        switch(read_8(classfile))
 241        {
 242        case CP_UTF8:
 243                len = read_16(classfile);
 244                seekerr = fseek(classfile, len, SEEK_CUR);
 245                break;
 246        case CP_CLASS:
 247        case CP_STRING:
 248        case CP_METHODTYPE:
 249                seekerr = fseek(classfile, 2, SEEK_CUR);
 250                break;
 251        case CP_METHODHANDLE:
 252                seekerr = fseek(classfile, 3, SEEK_CUR);
 253                break;
 254        case CP_INTEGER:
 255        case CP_FLOAT:
 256        case CP_FIELDREF:
 257        case CP_METHODREF:
 258        case CP_INTERFACEMETHODREF:
 259        case CP_NAMEANDTYPE:
 260        case CP_INVOKEDYNAMIC:
 261                seekerr = fseek(classfile, 4, SEEK_CUR);
 262                break;
 263        case CP_LONG:
 264        case CP_DOUBLE:
 265                seekerr = fseek(classfile, 8, SEEK_CUR);
 266                ++(*cur);
 267                break;
 268        default:
 269                corrupt_error();
 270        }
 271        if(seekerr)
 272                seek_error();
 273}
 274
 275void error(const char *format, ...)
 276{
 277        va_list ap;
 278        va_start(ap, format);
 279        vfprintf(stderr, format, ap);
 280        va_end(ap);
 281        exit(1);
 282}
 283
 284int main(int argc, char **argv)
 285{
 286        FILE *classfile;
 287        u_int16_t cp_count, i, this_class, classinfo_ptr;
 288        u_int8_t length;
 289
 290        program = argv[0];
 291
 292        if(!argv[1])
 293                error("%s: Missing input file\n", program);
 294        classfile = fopen(argv[1], "rb");
 295        if(!classfile)
 296                error("%s: Error opening %s\n", program, argv[1]);
 297
 298        if(fseek(classfile, 8, SEEK_SET))  /* skip magic and version numbers */
 299                seek_error();
 300        cp_count = read_16(classfile);
 301        pool = calloc(cp_count, sizeof(long));
 302        if(!pool)
 303                error("%s: Out of memory for constant pool\n", program);
 304
 305        for(i = 1; i < cp_count; ++i)
 306                skip_constant(classfile, &i);
 307        if(fseek(classfile, 2, SEEK_CUR))       /* skip access flags */
 308                seek_error();
 309
 310        this_class = read_16(classfile);
 311        if(this_class < 1 || this_class >= cp_count)
 312                corrupt_error();
 313        if(!pool[this_class] || pool[this_class] == -1)
 314                corrupt_error();
 315        if(fseek(classfile, pool[this_class] + 1, SEEK_SET))
 316                seek_error();
 317
 318        classinfo_ptr = read_16(classfile);
 319        if(classinfo_ptr < 1 || classinfo_ptr >= cp_count)
 320                corrupt_error();
 321        if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1)
 322                corrupt_error();
 323        if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET))
 324                seek_error();
 325
 326        length = read_16(classfile);
 327        for(i = 0; i < length; ++i)
 328        {
 329                u_int8_t x = read_8(classfile);
 330                if((x & 0x80) || !x)
 331                {
 332                        if((x & 0xE0) == 0xC0)
 333                        {
 334                                u_int8_t y = read_8(classfile);
 335                                if((y & 0xC0) == 0x80)
 336                                {
 337                                        int c = ((x & 0x1f) << 6) + (y & 0x3f);
 338                                        if(c) putchar(c);
 339                                        else utf8_error();
 340                                }
 341                                else utf8_error();
 342                        }
 343                        else utf8_error();
 344                }
 345                else if(x == '/') putchar('.');
 346                else putchar(x);
 347        }
 348        putchar('\n');
 349        free(pool);
 350        fclose(classfile);
 351        return 0;
 352}
 353====================== Cut here ===================
 354
 355
 356====================== Cut here ===================
 357#!/bin/bash
 358# /usr/local/java/bin/jarwrapper - the wrapper for binfmt_misc/jar
 359
 360java -jar $1
 361====================== Cut here ===================
 362
 363
 364Now simply chmod +x the .class, .jar and/or .html files you want to execute.
 365To add a Java program to your path best put a symbolic link to the main
 366.class file into /usr/bin (or another place you like) omitting the .class
 367extension. The directory containing the original .class file will be
 368added to your CLASSPATH during execution.
 369
 370
 371To test your new setup, enter in the following simple Java app, and name
 372it "HelloWorld.java":
 373
 374        class HelloWorld {
 375                public static void main(String args[]) {
 376                        System.out.println("Hello World!");
 377                }
 378        }
 379
 380Now compile the application with:
 381        javac HelloWorld.java
 382
 383Set the executable permissions of the binary file, with:
 384        chmod 755 HelloWorld.class
 385
 386And then execute it:
 387        ./HelloWorld.class
 388
 389
 390To execute Java Jar files, simple chmod the *.jar files to include
 391the execution bit, then just do
 392       ./Application.jar
 393
 394
 395To execute Java Applets, simple chmod the *.html files to include
 396the execution bit, then just do
 397        ./Applet.html
 398
 399
 400originally by Brian A. Lantz, brian@lantz.com
 401heavily edited for binfmt_misc by Richard G√ľnther
 402new scripts by Colin J. Watson <cjw44@cam.ac.uk>
 403added executable Jar file support by Kurt Huwig <kurt@iku-netz.de>
 404
 405