Execute another jar in a Java program

Question

I had written several simple java applications named as A jar  B jar   Now i want to write a GUI java program so that user can press button A to execute A jar and button B to execute B jar   Also i want to output the run-time process detail in my GUI program    Any suggestion

User · Answer

If the jar s in your classpath  and you know its Main class  you can just invoke the main class   Using DITA-OT as an example   import org dita dost invoker CommandLineInvoker       CommandLineInvoker main  -f    html5    -i    samples sequence ditamap    -o    test     Note this will make the subordinate jar share memory space and a classpath with your jar  with all the potential for interference that can cause   If you don t want that stuff polluted  you have other options  as mentioned above - namely    create a new ClassLoader with the jar in it   This is more safe  you can at least isolate the new jar s knowledge to a core classloader if you architect things with the knowledge that you ll be making use of alien jars   It s what we do in my shop for our plugins system  the main application is a tiny shell with a ClassLoader factory  a copy of the API  and knowledge that the real application is the first plugin for which it should build a ClassLoader   Plugins are a pair of jars - interface and implementation - that are zipped up together   The ClassLoaders all share all the interfaces  while each ClassLoader only has knowledge of its own implementation   The stack s a little complex  but it passes all tests and works beautifully  use Runtime getRuntime exec       which wholly isolates the jar  but has the normal  find the application    escape your strings right    platform-specific WTF   and  OMG System Threads  pitfalls of running system commands

User · Answer

If you are java 1 6 then the following can also be done   import javax tools JavaCompiler   import javax tools ToolProvider    public class CompilerExample        public static void main String   args            String fileToCompile     Users rupas VolatileExample java            JavaCompiler compiler   ToolProvider getSystemJavaCompiler             int compilationResult   compiler run null  null  null  fileToCompile            if  compilationResult    0                System out println  Compilation is successful              else               System out println  Compilation Failed

User · Answer

jar isn t executable  Instantiate classes or make call to any static method   EDIT  Add Main-Class entry while creating a JAR    p mf  content of p mf      Main-Class  pk Test    gt Test java  package pk  public class Test    public static void main String   args       System out println  Hello from Test            Use Process class and it s methods   public class Exec      public static void main String   args  throws Exception               Process ps Runtime getRuntime   exec new String    java   -jar   A jar             ps waitFor            java io InputStream is ps getInputStream            byte b   new byte is available             is read b 0 b length           System out println new String b

User · Answer

The following works by starting the jar with a batch file  in case the program runs as a stand alone   public static void startExtJarProgram            String extJar   Paths get  C   absolute  path  to  batchfile bat   toString            ProcessBuilder processBuilder   new ProcessBuilder extJar           processBuilder redirectError new File Paths get  C   path  to  JavaProcessOutput  extJar out put txt   toString              processBuilder redirectInput            try              final Process process   processBuilder start                try                   final int exitStatus   process waitFor                    if exitStatus  0                       System out println  External Jar Started Successfully                         System exit 0     or whatever suits                   else                      System out println  There was an error starting external Jar  Perhaps path issues  Use exit code   exitStatus   for details                         System out println  Check also C   path  to  JavaProcessOutput  extJar out put txt file for additional details                         System exit 1    whatever                                 catch  InterruptedException ex                    System out println  InterruptedException    ex getMessage                             catch  IOException ex                System out println  IOException  Faild to start process  Reason    ex getMessage                       System out println  Process Terminated             System exit 0           In the batchfile bat then we can say    echo off start  min C  path to jarprogram jar

User · Answer

If I understand correctly it appears you want to run the jars in a separate process from inside your java GUI application    To do this you can use      Run a java app in a separate system process Process proc   Runtime getRuntime   exec  java -jar A jar       Then retreive the process output InputStream in   proc getInputStream    InputStream err   proc getErrorStream      Its always good practice to buffer the output of the process

User · Answer

Hope this helps   public class JarExecutor    private BufferedReader error  private BufferedReader op  private int exitVal   public void executeJar String jarFilePath  List lt String gt  args  throws JarExecutorException          Create run arguments for the      final List lt String gt  actualArgs   new ArrayList lt String gt         actualArgs add 0   java        actualArgs add 1   -jar        actualArgs add 2  jarFilePath       actualArgs addAll args       try           final Runtime re   Runtime getRuntime              final Process command   re exec cmdString  args toArray new String 0             final Process command   re exec actualArgs toArray new String 0             this error   new BufferedReader new InputStreamReader command getErrorStream              this op   new BufferedReader new InputStreamReader command getInputStream                 Wait for the application to Finish         command waitFor            this exitVal   command exitValue            if  this exitVal    0                throw new IOException  Failed to execure jar      this getExecutionLog                      catch  final IOException   InterruptedException e            throw new JarExecutorException e            public String getExecutionLog         String error           String line      try           while  line   this error readLine       null                error   error     n    line                  catch  final IOException e              String output           try           while  line   this op readLine       null                output   output     n    line                  catch  final IOException e              try           this error close            this op close          catch  final IOException e              return  exitVal      this exitVal      error      error      output      output

[java] Execute another jar in a Java program

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