BshService.java

/***
  Copyright (c) 2008-2012 CommonsWare, LLC
  Licensed under the Apache License, Version 2.0 (the "License"); you may not
  use this file except in compliance with the License. You may obtain a copy
  of the License at http://www.apache.org/licenses/LICENSE-2.0. Unless required
  by applicable law or agreed to in writing, software distributed under the
  License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
  OF ANY KIND, either express or implied. See the License for the specific
  language governing permissions and limitations under the License.
  
  From _The Busy Coder's Guide to Advanced Android Development_
    http://commonsware.com/AdvAndroid
*/

package com.commonsware.android.advservice;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import java.util.concurrent.LinkedBlockingQueue;
import bsh.Interpreter;

public class BshService extends Service {
  private final IScript.Stub binder=new IScript.Stub() {
    public void executeScript(String script, IScriptResult cb) {
      executeScriptImpl(script, cb);
    }
  };
  private Interpreter i=new Interpreter();
  private LinkedBlockingQueue<Job> q=new LinkedBlockingQueue<Job>();
  
  @Override
  public void onCreate() {
    super.onCreate();
    
    new Thread(qProcessor).start();
    
    try {
      i.set("context", this);
    }
    catch (bsh.EvalError e) {
      Log.e("BshService", "Error executing script", e);
    }
  }
  
  @Override
  public IBinder onBind(Intent intent) {
    return(binder);
  }
  
  @Override
  public void onDestroy() {
    super.onDestroy();
    
    q.add(new KillJob());
  }
  
  private void executeScriptImpl(String script,
                                  IScriptResult cb) {
    q.add(new ExecuteScriptJob(script, cb));    
  }
  
  Runnable qProcessor=new Runnable() {
    public void run() {
      while (true) {
        try {
          Job j=q.take();
          
          if (j.stopThread()) {
            break;
          }
          else {
            j.process();
          }
        }
        catch (InterruptedException e) {
          break;
        }
      }
    }
  };
  
  class Job {
    boolean stopThread() {
      return(false);
    }
    
    void process() {
      // no-op
    }
  }
  
  class KillJob extends Job {
    @Override
    boolean stopThread() {
      return(true);
    }
  }
  
  class ExecuteScriptJob extends Job {
    IScriptResult cb;
    String script;
    
    ExecuteScriptJob(String script, IScriptResult cb) {
      this.script=script;
      this.cb=cb;
    }
    
    void process() {
      try {
        cb.success(i.eval(script).toString());
      }
      catch (Throwable e) {
        Log.e("BshService", "Error executing script", e);
        
        try {
          cb.failure(e.getMessage());
        }
        catch (Throwable t) {
          Log.e("BshService",
                "Error returning exception to client",
                t);
        }
      }
    }
  }
}