Package org.apache.commons.chain.generic

Class 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 Detail

      • DEFAULT_SIGNATURE

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

      • methods

        private java.util.WeakHashMap methods

      • method

        private java.lang.String method

      • methodKey

        private java.lang.String methodKey

    • Constructor Detail

      • 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 Detail

      • getMethod

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

      • getMethodKey

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

      • setMethod

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

      • setMethodKey

        public void setMethodKey​(java.lang.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 java.lang.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:
        java.lang.Exception - if no such Command can be found and the optional property is set to false

      • getSignature

        protected java.lang.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 java.lang.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 java.lang.reflect.Method extractMethod​(Command command,
                                               Context context)
                                        throws java.lang.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:
        java.lang.NoSuchMethodException - if no method can be found under the specified name.
        java.lang.NullPointerException - if no methodName can be determined