Class DispatchLookupCommand

java.lang.Object
org.apache.commons.chain.generic.LookupCommand
org.apache.commons.chain.generic.DispatchLookupCommand
All Implemented Interfaces:
Command, Filter
public class DispatchLookupCommand extends LookupCommand implements Filter

This command combines elements of the LookupCommand with the DispatchCommand. Look up a specified Command (which could also be a Chain) in a Catalog, and delegate execution to it. Introspection is used to lookup the appropriate method to delegate execution to. If the delegated-to Command is also a Filter, its postprocess() method will also be invoked at the appropriate time.

The name of the Command can be specified either directly (via the name property) or indirectly (via the nameKey property). Exactly one of these must be set.

The name of the method to be called can be specified either directly (via the method property) or indirectly (via the methodKey property). Exactly one of these must be set.

If the optional property is set to true, failure to find the specified command in the specified catalog will be silently ignored. Otherwise, a lookup failure will trigger an IllegalArgumentException.

Since:
Chain 1.1
Version:
$Revision: 480477 $
Author:
Sean Schofield

  • Field Details

    • DEFAULT_SIGNATURE

      private static final Class[] DEFAULT_SIGNATURE
      The base implementation expects dispatch methods to take a Context as their only argument.

    • methods

      private WeakHashMap methods

    • method

      private String method

    • methodKey

      private String methodKey

  • Constructor Details

    • DispatchLookupCommand

      public DispatchLookupCommand()
      Create an instance with an unspecified catalogFactory property. This property can be set later using setProperty, or if it is not set, the static singleton instance from CatalogFactory.getInstance() will be used.

    • DispatchLookupCommand

      public DispatchLookupCommand(CatalogFactory factory)
      Create an instance and initialize the catalogFactory property to given factory.
      Parameters:
      factory - The Catalog Factory.

  • Method Details

    • getMethod

      public String getMethod()
      Return the method name.
      Returns:
      The method name.

    • getMethodKey

      public String getMethodKey()
      Return the Context key for the method name.
      Returns:
      The Context key for the method name.

    • setMethod

      public void setMethod(String method)
      Set the method name.
      Parameters:
      method - The method name.

    • setMethodKey

      public void setMethodKey(String methodKey)
      Set the Context key for the method name.
      Parameters:
      methodKey - The Context key for the method name.

    • execute

      public boolean execute(Context context) throws Exception

      Look up the specified command, and (if found) execute it.

      Specified by:
      execute in interface Command
      Overrides:
      execute in class LookupCommand
      Parameters:
      context - The context for this request
      Returns:
      the result of executing the looked-up command's method, or false if no command is found.
      Throws:
      Exception - if no such Command can be found and the optional property is set to false

    • getSignature

      protected Class[] getSignature()

      Return a Class[] describing the expected signature of the method. The default is a signature that just accepts the command's Context. The method can be overidden to provide a different method signature.

      Returns:
      the expected method signature

    • getArguments

      protected Object[] getArguments(Context context)
      Get the arguments to be passed into the dispatch method. Default implementation simply returns the context which was passed in, but subclasses could use this to wrap the context in some other type, or extract key values from the context to pass in. The length and types of values returned by this must coordinate with the return value of getSignature()
      Parameters:
      context - The context associated with the request
      Returns:
      the method arguments to be used

    • extractMethod

      private Method extractMethod(Command command, Context context) throws NoSuchMethodException
      Extract the dispatch method. The base implementation uses the command's method property at the name of a method to look up, or, if that is not defined, uses the methodKey to lookup the method name in the context.
      Parameters:
      command - The commmand that contains the method to be executed.
      context - The context associated with this request
      Returns:
      the dispatch method
      Throws:
      NoSuchMethodException - if no method can be found under the specified name.
      NullPointerException - if no methodName can be determined