1 /*
   2  * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package jdk.internal.jshell.jdi;
  26 
  27 import java.util.ArrayList;
  28 import java.util.Collection;
  29 import java.util.List;
  30 import jdk.internal.jshell.debug.InternalDebugControl;
  31 import jdk.jshell.JShellException;
  32 import jdk.jshell.spi.ExecutionControl;
  33 import jdk.jshell.spi.ExecutionEnv;
  34 
  35 /**
  36  * A meta implementation of ExecutionControl which cycles through the specified
  37  * ExecutionControl instances until it finds one that starts.
  38  */
  39 public class FailOverExecutionControl implements ExecutionControl {
  40 
  41     private final List<ExecutionControl> ecl = new ArrayList<>();
  42     private ExecutionControl active = null;
  43     private final List<Exception> thrown = new ArrayList<>();
  44 
  45     /**
  46      * Create the ExecutionControl instance with at least one actual
  47      * ExecutionControl instance.
  48      *
  49      * @param ec0 the first instance to try
  50      * @param ecs the second and on instance to try
  51      */
  52     public FailOverExecutionControl(ExecutionControl ec0, ExecutionControl... ecs) {
  53         ecl.add(ec0);
  54         for (ExecutionControl ec : ecs) {
  55             ecl.add(ec);
  56         }
  57     }
  58 
  59     @Override
  60     public void start(ExecutionEnv env) throws Exception {
  61         for (ExecutionControl ec : ecl) {
  62             try {
  63                 ec.start(env);
  64                 // Success! This is our active ExecutionControl
  65                 active = ec;
  66                 return;
  67             } catch (Exception ex) {
  68                 thrown.add(ex);
  69             } catch (Throwable ex) {
  70                 thrown.add(new RuntimeException(ex));
  71             }
  72             InternalDebugControl.debug(env.state(), env.userErr(),
  73                     thrown.get(thrown.size() - 1), "failed one in FailOverExecutionControl");
  74         }
  75         // They have all failed -- rethrow the first exception we encountered
  76         throw thrown.get(0);
  77     }
  78 
  79     @Override
  80     public void close() {
  81         active.close();
  82     }
  83 
  84     @Override
  85     public boolean addToClasspath(String path) {
  86         return active.addToClasspath(path);
  87     }
  88 
  89     @Override
  90     public String invoke(String classname, String methodname) throws JShellException {
  91         return active.invoke(classname, methodname);
  92     }
  93 
  94     @Override
  95     public boolean load(Collection<String> classes) {
  96         return active.load(classes);
  97     }
  98 
  99     @Override
 100     public boolean redefine(Collection<String> classes) {
 101         return active.redefine(classes);
 102     }
 103 
 104     @Override
 105     public ClassStatus getClassStatus(String classname) {
 106         return active.getClassStatus(classname);
 107     }
 108 
 109     @Override
 110     public void stop() {
 111         active.stop();
 112     }
 113 
 114     @Override
 115     public String varValue(String classname, String varname) {
 116         return active.varValue(classname, varname);
 117     }
 118 
 119 }