Examples of org.apache.commons.chain.Command

org.apache.commons.chain.Command
A {@link Command} encapsulates a unit of processing work to beperformed, whose purpose is to examine and/or modify the state of a transaction that is represented by a {@link Context}. Individual {@link Command}s can be assembled into a {@link Chain}, which allows them to either complete the required processing or delegate further processing to the next {@link Command} in the {@link Chain}.

{@link Command} implementations should be designed in a thread-safemanner, suitable for inclusion in multiple {@link Chain}s that might be processed by different threads simultaneously. In general, this implies that {@link Command} classes should not maintain state information ininstance variables. Instead, state information should be maintained via suitable modifications to the attributes of the {@link Context} that ispassed to the execute() command.

{@link Command} implementations typically retrieve and store stateinformation in the {@link Context} instance that is passed as a parameterto the execute() method, using particular keys into the Map that can be acquired via Context.getAttributes(). To improve interoperability of {@link Command} implementations, a useful design pattern is to expose thekey values used as JavaBeans properties of the {@link Command}implementation class itself. For example, a {@link Command} that requiresan input and an output key might implement the following properties:
```
 private String inputKey = "input"; public String getInputKey() { return (this.inputKey); } public void setInputKey(String inputKey) { this.inputKey = inputKey; } private String outputKey = "output"; public String getOutputKey() { return (this.outputKey); } public void setOutputKey(String outputKey) { this.outputKey = outputKey; } 
```
And the operation of accessing the "input" information in the context would be executed by calling:
```
 String input = (String) context.get(getInputKey()); 
```
instead of hard coding the attribute name. The use of the "Key" suffix on such property names is a useful convention to identify properties being used in this fashion, as opposed to JavaBeans properties that simply configure the internal operation of this {@link Command}.
@author Craig R. McClanahan @version $Revision: 1.5 $ $Date: 2004/02/25 00:01:07 $


    actionCtx.setException(exception);


    // Execute the specified command
    try {
      Command command = lookupExceptionCommand();


      if (command == null) {
        LOG.error("Cannot find exceptionCommand '" + exceptionCommand + "'");
        throw new IllegalStateException("Cannot find exceptionCommand '" + exceptionCommand + "'");
      }


      if (LOG.isTraceEnabled()) {
        LOG.trace("Calling exceptionCommand '" + exceptionCommand + "'");
      }


      command.execute(context);
    } catch (Exception e) {
      LOG.warn("Exception from exceptionCommand '" + exceptionCommand + "'", e);
      throw new IllegalStateException("Exception chain threw exception");
    }

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  public boolean execute(Context context) throws Exception {
    if (LOG.isTraceEnabled()) {
      LOG.trace("execute [" + this + "]");
    }


    Command command = getCommand(context);


    if (command != null) {
      return command.execute(getContext(context));
    } else {
      return false;
    }
  }

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   * @param exception
   *            The Exception thrown by another Comamnd in a Chain
   * @return TRUE if there is a Filter to process
   */
  public boolean postprocess(Context context, Exception exception) {
    Command command = getCommand(context);


    if ((command != null) && (command instanceof Filter)) {
      try {
        return ((Filter) command).postprocess(getContext(context), exception);
      } catch (NoSuchMethodException ex) {

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    if (catalog == null) {
      throw new IllegalArgumentException("Cannot find catalog '" + catalogName + "'");
    }


    Command command;
    String name = getName();


    if (name == null) {
      name = (String) context.get(getNameKey());
    }

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        throw new IllegalArgumentException("Duplicate Catalog name found: " + catalog.getName());
      }
      catMap.put(catalog.getName(), catalog);


      for (final String commandName : catalog.getCommandNames()) {
        final Command command = catalog.getCommand(commandName);
        Assert.notNull(command);
        final CommandKey commandKey = new CommandKey(catalog.getName(), commandName);
        cmdMap.put(commandKey, command);
        log.info("registered CommandKey: {}", commandKey);
      }

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      // command from context
      String commandName = (String)ctx.get("Command");
      if (commandName == null)
         throw new ServletException("No Command found at the Context");
      Command cmd;
      if (catalogName == null)
         cmd = commandService.getCatalog().getCommand(commandName);
      else
         cmd = commandService.getCatalog(catalogName).getCommand(commandName);


      if (cmd == null)
         throw new ServletException("No Command found " + commandName);
      try
      {
         if (pcClassLoader != null)
         {
            // Set the portal classloader to get all the resources defined within the portal context
            Thread.currentThread().setContextClassLoader(pcClassLoader);
            hasChanged = true;
         }         
         cmd.execute(ctx);
      }
      catch (Exception e)
      {
         log.error("An error occurs while executing the command " + commandName, e);
         throw new ServletException(e);

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   public void testExcecute() throws Exception
   {


      CommandService cservice = (CommandService)container.getComponentInstanceOfType(CommandService.class);
      Command c1 = cservice.getCatalog().getCommand("Execute2");
      Command c2 = cservice.getCatalog().getCommand("Command1");


      Catalog c = cservice.getCatalog();


      Context ctx = new ContextBase();
      ctx.put("test", Integer.valueOf(0));
      c1.execute(ctx);
      c2.execute(ctx);
      assertEquals(3, ((Integer)ctx.get("test")).intValue());


   }

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         throw new ServletException("Path undefined " + request.getParameter("path") + " Request: "
            + request.getRequestURI());


      try
      {
         Command cmd;
         if (catalogName == null)
            cmd = commandService.getCatalog().getCommand("displayResource");
         else
            cmd = commandService.getCatalog(catalogName).getCommand("displayResource");


         if (cmd == null)
            throw new Exception("No 'displayResource' command found");
         ctx.put("path", currentPath);
         ctx.put("cache-control-max-age", getServletConfig().getInitParameter("cache-control-max-age"));
         cmd.execute(ctx);
      }
      catch (Exception e)
      {
         e.printStackTrace(); //NOSONAR
         throw new ServletException(e);

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      // command from context
      String commandName = (String)ctx.get("Command");
      if (commandName == null)
         throw new ServletException("No Command found at the Context");
      Command cmd;
      if (catalogName == null)
         cmd = commandService.getCatalog().getCommand(commandName);
      else
         cmd = commandService.getCatalog(catalogName).getCommand(commandName);


      if (cmd == null)
         throw new ServletException("No Command found " + commandName);
      try
      {
         if (pcClassLoader != null)
         {
            // Set the portal classloader to get all the resources defined within the portal context
            Thread.currentThread().setContextClassLoader(pcClassLoader);
            hasChanged = true;
         }         
         cmd.execute(ctx);
      }
      catch (Exception e)
      {
         log.error("An error occurs while executing the command " + commandName, e);
         throw new ServletException(e);

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   }


   public void testSetProperty() throws Exception
   {


      Command c = cservice.getCatalog().getCommand("setProperty");
      ctx.put("currentNode", "/foo");
      ctx.put("name", "testProperty");
      ctx.put("propertyType", PropertyType.TYPENAME_STRING);
      ctx.put("values", "testValue");
      ctx.put("multiValued", Boolean.FALSE);


      c.execute(ctx);


      Command save = cservice.getCatalog().getCommand("save");
      save.execute(ctx);


   }

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