Add a basic implement of CommandLauncher.

This merges the Ant1.x VM launchers into one class. If working on older JVMs (pre jdk1.3) and try to execute outside the current directory then an exception will be thrown.


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@270278 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/myrmidon/framework/exec/launchers/DefaultCommandLauncher.java

@@ -0,0 +1,122 @@
+/*
+ * Copyright (C) The Apache Software Foundation. All rights reserved.
+ *
+ * This software is published under the terms of the Apache Software License
+ * version 1.1, a copy of which has been included  with this distribution in
+ * the LICENSE.txt file.
+ */
+package org.apache.myrmidon.framework.exec.launchers;
+
+import java.io.File;
+import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import org.apache.myrmidon.api.TaskException;
+import org.apache.myrmidon.framework.exec.CommandLauncher;
+import org.apache.myrmidon.framework.exec.ExecMetaData;
+import org.apache.tools.ant.Project;
+import org.apache.tools.ant.types.Commandline;
+
+/**
+ * A command launcher for a particular JVM/OS platform. This class is a
+ * general purpose command launcher which can only launch commands in the
+ * current working directory.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @author <a href="mailto:thomas.haas@softwired-inc.com">Thomas Haas</a>
+ * @version $Revision$ $Date$
+ */
+public class DefaultCommandLauncher
+    implements CommandLauncher
+{
+    private static final Method c_execWithCWD;
+
+    static
+    {
+        // Locate method Runtime.exec(String[] cmdarray, String[] envp, File dir)
+        Method method = null;
+        try
+        {
+            final Class[] types =
+                new Class[]{String[].class, String[].class, File.class};
+            method = Runtime.class.getMethod( "exec", types );
+        }
+        catch( final NoSuchMethodException nsme )
+        {
+            //ignore
+        }
+
+        c_execWithCWD = method;
+    }
+
+    /**
+     * Execute the specified native command.
+     *
+     * @param metaData the native command to execute
+     * @return the Process launched by the CommandLauncher
+     * @exception IOException is thrown when the native code can not
+     *            launch the application for some reason. Usually due
+     *            to the command not being fully specified and not in
+     *            the PATH env var.
+     * @exception TaskException if the command launcher detects that
+     *            it can not execute the native command for some reason.
+     */
+    public Process exec( final ExecMetaData metaData )
+        throws IOException, TaskException
+    {
+        if( ExecUtil.isCwd( metaData.getWorkingDirectory() ) )
+        {
+            return Runtime.getRuntime().
+                exec( metaData.getCommand(), metaData.getEnvironment() );
+        }
+        else if( null == c_execWithCWD )
+        {
+            final String message = "Unable to launch native command in a " +
+                "working directory other than \".\"";
+            throw new TaskException( message );
+        }
+        else
+        {
+            return execJava13( metaData );
+        }
+    }
+
+    /**
+     * Execute the Java1.3 Runtime.exec() 3 parame method that sets working
+     * directory. This needs to be done via reflection so that it can compile
+     * under 1.2.
+     */
+    private Process execJava13( final ExecMetaData metaData )
+        throws IOException, TaskException
+    {
+        final Object[] args =
+            {metaData.getCommand(),
+             metaData.getEnvironment(),
+             metaData.getWorkingDirectory()};
+        try
+        {
+            return (Process)c_execWithCWD.invoke( Runtime.getRuntime(), args );
+        }
+        catch( final IllegalAccessException iae )
+        {
+            throw new TaskException( iae.getMessage(), iae );
+        }
+        catch( final IllegalArgumentException iae )
+        {
+            throw new TaskException( iae.getMessage(), iae );
+        }
+        catch( final InvocationTargetException ite )
+        {
+            final Throwable t = ite.getTargetException();
+            if( t instanceof IOException )
+            {
+                t.fillInStackTrace();
+                throw (IOException)t;
+            }
+            else
+            {
+                throw new TaskException( t.getMessage(), t );
+            }
+        }
+    }
+}