org.apache.commons.io.output

## Class TaggedWriter

- java.lang.Object
- - java.io.Writer
  - - java.io.FilterWriter
    - - org.apache.commons.io.output.ProxyWriter
      - - org.apache.commons.io.output.TaggedWriter

- All Implemented Interfaces:
    Closeable, Flushable, Appendable, AutoCloseable

      public class TaggedWriter
      extends ProxyWriter

  A writer decorator that tags potential exceptions so that the reader that caused the exception can easily be identified. This is done by using the `TaggedIOException` class to wrap all thrown `IOException`s. See below for an example of using this class.

       TaggedReader reader = new TaggedReader(...);
       try {
           // Processing that may throw an IOException either from this reader
           // or from some other IO activity like temporary files, etc.
           writeToWriter(writer);
       } catch (IOException e) {
           if (writer.isCauseOf(e)) {
               // The exception was caused by this writer.
               // Use e.getCause() to get the original exception.
           } else {
               // The exception was caused by something else.
           }
       }

  Alternatively, the `throwIfCauseOf(Exception)` method can be used to let higher levels of code handle the exception caused by this writer while other processing errors are being taken care of at this lower level.

       TaggedWriter writer = new TaggedWriter(...);
       try {
           writeToWriter(writer);
       } catch (IOException e) {
           writer.throwIfCauseOf(e);
           // ... or process the exception that was caused by something else
       }

  Since:
    2.0
  See Also:
    `TaggedIOException`

- - ### Field Summary

    - ### Fields inherited from class java.io.FilterWriter

      `out`

    - ### Fields inherited from class java.io.Writer

      `lock`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `TaggedWriter(Writer proxy)` Creates a tagging decorator for the given writer.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `handleIOException(IOException e)` Tags any IOExceptions thrown, wrapping and re-throwing.
    `boolean` | `isCauseOf(Exception exception)` Tests if the given exception was caused by this writer.
    `void` | `throwIfCauseOf(Exception exception)` Re-throws the original exception thrown by this writer.

    - ### Methods inherited from class org.apache.commons.io.output.ProxyWriter

      `afterWrite, append, append, append, beforeWrite, close, flush, write, write, write, write, write`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### TaggedWriter

          public TaggedWriter(Writer proxy)

      Creates a tagging decorator for the given writer.
      Parameters:
        `proxy` - writer to be decorated

  - ### Method Detail

    - #### handleIOException

          protected void handleIOException(IOException e)
                                    throws IOException

      Tags any IOExceptions thrown, wrapping and re-throwing.
      Overrides:
        `handleIOException` in class `ProxyWriter`
      Parameters:
        `e` - The IOException thrown
      Throws:
        `IOException` - if an I/O error occurs.

    - #### isCauseOf

          public boolean isCauseOf(Exception exception)

      Tests if the given exception was caused by this writer.
      Parameters:
        `exception` - an exception
      Returns:
        `true` if the exception was thrown by this writer, `false` otherwise

    - #### throwIfCauseOf

          public void throwIfCauseOf(Exception exception)
                              throws IOException

      Re-throws the original exception thrown by this writer. This method first checks whether the given exception is a `TaggedIOException` wrapper created by this decorator, and then unwraps and throws the original wrapped exception. Returns normally if the exception was not thrown by this writer.
      Parameters:
        `exception` - an exception
      Throws:
        `IOException` - original exception, if any, thrown by this writer

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