Php word to pdf-php execute exec to convert word to pdf permission

Server: ubuntu14.04PHP: 5.4 apache: invalid varwwwwwwrootUploaddoc & #39; tes execphp word to redirect phpexec permission

Server: ubuntu14.04
PHP 5.4
Apache: 2.0
I follow the methods found on the Internet to jdk1.7.0 _ 79, jodconverter-2.2.2 have been installed, and then use root login server, enter the command java-jar/alidata1/source/jodconverter-2.2.2/lib/jodconverter-cli-2.2.2.jar/var/www/wwwroot/Upload/doc/test.doc/var/www/wwwroot/Upload/doc/'testbench yes, however, you cannot run this command in the PHP file. The return value is always int (127). the result returned by whoami is www-data, then I changed wwwroot and source on the server from root to www-data. The result is still int (127 ),
// Shell_exec ('whoam ');
Exec ('Java-jar/alidata1/source/jodconverter-2.2.2/lib/jodconverter-cli-2.2.2.jar/var/www/wwwroot/Upload/doc/test.doc/var/www/wwwroot/Upload/doc/testbench 2>/var/www/wwwroot/log.txt ', $ arr, $ res );
Var_dump ($ arr, $ res );
?>
In this way, sh: 1: java: not found is obtained.
Which of the following Experts knows whether this is a permission issue? How should I adjust it? Thank you!