org.apache.turbine.pipeline

## Interface Pipeline

- All Known Implementing Classes:
    TurbinePipeline

      public interface Pipeline

  The idea of a pipeline is being taken from Catalina in its entirety :-) I would like to take the idea further and implement Valves instead of hardcoding particular methods in a pipeline. It would be more flexible to specify Valves for a pipeline in an XML file (we can also rip off the digester rules from T4) and have invoke() as part of the interface. So a set of Valves would be added to the pipeline and the pipeline would 'invoke' each valve. In the case Turbine each Valve would produce some output to be sent out the pipe. I think with another days work this can be fully working. The first pipeline to be fully implemented will the ClassicPipeline will emulate the Turbine 2.1 way of doing things.
  Author:
    Jason van Zyl, Daniel Rall, Peter Courcoux

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addValve(Valve valve)` Add a new Valve to the end of the pipeline.
    `Valve[]` | `getValves()` Return the set of all Valves in the pipeline.
    `void` | `initialize()` Initializes this instance.
    `void` | `invoke(PipelineData pipelineData)` Cause the specified request and response to be processed by the sequence of Valves associated with this pipeline, until one of these Valves decides to end the processing.
    `void` | `removeValve(Valve valve)` Remove the specified Valve from the pipeline, if it is found; otherwise, do nothing.

- - ### Method Detail

    - #### initialize

          void initialize()
                          throws Exception

      Initializes this instance. Called once by the Turbine servlet.
      Throws:
        `Exception` - if the initialization fails

    - #### addValve

          void addValve(Valve valve)

      Add a new Valve to the end of the pipeline.

      Parameters:
        `valve` - Valve to be added.
      Throws:
        `IllegalStateException` - If the pipeline has not been initialized.

    - #### getValves

          Valve[] getValves()

      Return the set of all Valves in the pipeline. If there are no such Valves, a zero-length array is returned.
      Returns:
        An array of valves.

    - #### invoke

          void invoke(PipelineData pipelineData)
                      throws TurbineException,
                             IOException

      Cause the specified request and response to be processed by the sequence of Valves associated with this pipeline, until one of these Valves decides to end the processing.

      The implementation must ensure that multiple simultaneous requests (on different threads) can be processed through the same Pipeline without interfering with each other's control flow.

      Parameters:
        `pipelineData` - The run-time information, including the servlet request and response we are processing.
      Throws:
        `TurbineException` - if the invocation fails
        `IOException` - an input/output error occurred.

    - #### removeValve

          void removeValve(Valve valve)

      Remove the specified Valve from the pipeline, if it is found; otherwise, do nothing.
      Parameters:
        `valve` - Valve to be removed.

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