## net.sf.saxon.trace
Class AbstractTraceListener

    java.lang.Object
      net.sf.saxon.trace.AbstractTraceListener

All Implemented Interfaces:
  java.util.EventListener, TraceListener

Direct Known Subclasses:
  XQueryTraceListener, XSLTTraceListener

public abstract class AbstractTraceListener
extends java.lang.Object
implements TraceListener

This is the standard trace listener used when the -T option is specified on the command line. There are two variants, represented by subclasses: one for XSLT, and one for XQuery. The two variants differ in that they present the trace output in terms of constructs used in the relevant host language.

Constructor Summary
`AbstractTraceListener()`

Method Summary
`void` `close()` Called at end
`void` `endCurrentItem(Item item)` Called after a node of the source tree got processed
`void` `enter(InstructionInfo info, XPathContext context)` Called when an instruction in the stylesheet gets processed
`java.lang.String` `escape(java.lang.String in)` Escape a string for XML output (in an attribute delimited by double quotes).
`protected abstract java.lang.String` `getOpeningAttributes()`
`java.io.PrintStream` `getOutputDestination()` Get the output destination
`void` `leave(InstructionInfo info)` Called after an instruction of the stylesheet got processed
`void` `open()` Called at start
`void` `setOutputDestination(java.io.PrintStream stream)` Set the output destination (default is System.err)
`void` `startCurrentItem(Item item)` Called when an item becomes the context item
`protected abstract java.lang.String` `tag(int construct)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### AbstractTraceListener

    public AbstractTraceListener()

Method Detail

### open

    public void open()

  Called at start

  Specified by:
    `open` in interface `TraceListener`

### getOpeningAttributes

    protected abstract java.lang.String getOpeningAttributes()

### close

    public void close()

  Called at end

  Specified by:
    `close` in interface `TraceListener`

### enter

    public void enter(InstructionInfo info,
                      XPathContext context)

  Called when an instruction in the stylesheet gets processed

  Specified by:
    `enter` in interface `TraceListener`
  Parameters:
    `info` - gives information about the instruction being executed, and about the context in which it is executed. This object is mutable, so if information from the InstructionInfo is to be retained, it must be copied.

### escape

    public java.lang.String escape(java.lang.String in)

  Escape a string for XML output (in an attribute delimited by double quotes). This method also collapses whitespace (since the value may be an XPath expression that was originally written over several lines).

### leave

    public void leave(InstructionInfo info)

  Called after an instruction of the stylesheet got processed

  Specified by:
    `leave` in interface `TraceListener`
  Parameters:
    `info` - gives the same information that was supplied to the enter method, though it is not necessarily the same object. Note that the line number of the instruction is that of the start tag in the source stylesheet, not the line number of the end tag.

### tag

    protected abstract java.lang.String tag(int construct)

### startCurrentItem

    public void startCurrentItem(Item item)

  Called when an item becomes the context item

  Specified by:
    `startCurrentItem` in interface `TraceListener`
  Parameters:
    `item` - the new current item. Item objects are not mutable; it is safe to retain a reference to the Item for later use.

### endCurrentItem

    public void endCurrentItem(Item item)

  Called after a node of the source tree got processed

  Specified by:
    `endCurrentItem` in interface `TraceListener`
  Parameters:
    `item` - the item that was current, whose processing is now complete. This will represent the same underlying item as the corresponding startCurrentItem() call, though it will not necessarily be the same actual object.

### setOutputDestination

    public void setOutputDestination(java.io.PrintStream stream)

  Set the output destination (default is System.err)

  Parameters:
    `stream` - the output destination for tracing output

### getOutputDestination

    public java.io.PrintStream getOutputDestination()

  Get the output destination