nestabledelegate.java

一个Java持久层类库

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 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
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 *    Alternately, this acknowledgement may appear in the software itself,
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package org.hibernate.exception;

import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.Serializable;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * <p>A shared implementation of the nestable exception functionality.</p>
 * <p/>
 * The code is shared between
 * {@link org.apache.commons.lang.exception.NestableError NestableError},
 * {@link org.apache.commons.lang.exception.NestableException NestableException} and
 * {@link org.apache.commons.lang.exception.NestableRuntimeException NestableRuntimeException}.
 * </p>
 *
 * @author <a href="mailto:[e-mail]">Rafal Krzewski</a>
 * @author <a href="mailto:[e-mail]">Daniel Rall</a>
 * @author <a href="mailto:[e-mail]">Kasper Nielsen</a>
 * @author <a href="mailto:[e-mail]">Steven Caswell</a>
 * @author Sean C. Sullivan
 * @author Stephen Colebourne
 * @version $Id: NestableDelegate.java 4782 2004-11-21 00:11:27Z pgmjsd $
 * @since 1.0
 */
public class NestableDelegate implements Serializable {

	/**
	 * Constructor error message.
	 */
	private static final String MUST_BE_THROWABLE =
			"The Nestable implementation passed to the NestableDelegate(Nestable) "
			+ "constructor must extend java.lang.Throwable";

	/**
	 * Holds the reference to the exception or error that we're
	 * wrapping (which must be a {@link
	 * org.apache.commons.lang.exception.Nestable} implementation).
	 */
	private Throwable nestable = null;

	/**
	 * Whether to print the stack trace top-down.
	 * This public flag may be set by calling code, typically in initialisation.
	 *
	 * @since 2.0
	 */
	private static boolean topDown = true;

	/**
	 * Whether to trim the repeated stack trace.
	 * This public flag may be set by calling code, typically in initialisation.
	 *
	 * @since 2.0
	 */
	private static boolean trimStackFrames = true;

	/**
	 * Constructs a new <code>NestableDelegate</code> instance to manage the
	 * specified <code>Nestable</code>.
	 *
	 * @param nestable the Nestable implementation (<i>must</i> extend
	 *                 {@link java.lang.Throwable})
	 * @since 2.0
	 */
	public NestableDelegate(Nestable nestable) {
		if ( nestable instanceof Throwable ) {
			this.nestable = ( Throwable ) nestable;
		}
		else {
			throw new IllegalArgumentException( MUST_BE_THROWABLE );
		}
	}

	/**
	 * Returns the error message of the <code>Throwable</code> in the chain
	 * of <code>Throwable</code>s at the specified index, numbererd from 0.
	 *
	 * @param index the index of the <code>Throwable</code> in the chain of
	 *              <code>Throwable</code>s
	 * @return the error message, or null if the <code>Throwable</code> at the
	 *         specified index in the chain does not contain a message
	 * @throws IndexOutOfBoundsException if the <code>index</code> argument is
	 *                                   negative or not less than the count of <code>Throwable</code>s in the
	 *                                   chain
	 * @since 2.0
	 */
	public String getMessage(int index) {
		Throwable t = this.getThrowable( index );
		if ( Nestable.class.isInstance( t ) ) {
			return ( ( Nestable ) t ).getMessage( 0 );
		}
		else {
			return t.getMessage();
		}
	}

	/**
	 * Returns the full message contained by the <code>Nestable</code>
	 * and any nested <code>Throwable</code>s.
	 *
	 * @param baseMsg the base message to use when creating the full
	 *                message. Should be generally be called via
	 *                <code>nestableHelper.getMessage( super.getMessage() )</code>,
	 *                where <code>super</code> is an instance of {@link
	 *                java.lang.Throwable}.
	 * @return The concatenated message for this and all nested
	 *         <code>Throwable</code>s
	 * @since 2.0
	 */
	public String getMessage(String baseMsg) {
		StringBuffer msg = new StringBuffer();
		if ( baseMsg != null ) {
			msg.append( baseMsg );
		}

		Throwable nestedCause = ExceptionUtils.getCause( this.nestable );
		if ( nestedCause != null ) {
			String causeMsg = nestedCause.getMessage();
			if ( causeMsg != null ) {
				if ( baseMsg != null ) {
					msg.append( ": " );
				}
				msg.append( causeMsg );
			}

		}
		return ( msg.length() > 0 ? msg.toString() : null );
	}

	/**
	 * Returns the error message of this and any nested <code>Throwable</code>s
	 * in an array of Strings, one element for each message. Any
	 * <code>Throwable</code> not containing a message is represented in the
	 * array by a null. This has the effect of cause the length of the returned
	 * array to be equal to the result of the {@link #getThrowableCount()}
	 * operation.
	 *
	 * @return the error messages
	 * @since 2.0
	 */
	public String[] getMessages() {
		Throwable[] throwables = this.getThrowables();
		String[] msgs = new String[throwables.length];
		for ( int i = 0; i < throwables.length; i++ ) {
			msgs[i] = Nestable.class.isInstance( throwables[i] ) ?
					( ( Nestable ) throwables[i] ).getMessage( 0 ) :
					throwables[i].getMessage();
		}
		return msgs;
	}

	/**
	 * Returns the <code>Throwable</code> in the chain of
	 * <code>Throwable</code>s at the specified index, numbererd from 0.
	 *
	 * @param index the index, numbered from 0, of the <code>Throwable</code> in
	 *              the chain of <code>Throwable</code>s
	 * @return the <code>Throwable</code>
	 * @throws IndexOutOfBoundsException if the <code>index</code> argument is
	 *                                   negative or not less than the count of <code>Throwable</code>s in the
	 *                                   chain
	 * @since 2.0
	 */
	public Throwable getThrowable(int index) {
		if ( index == 0 ) {
			return this.nestable;
		}
		Throwable[] throwables = this.getThrowables();
		return throwables[index];
	}

	/**
	 * Returns the number of <code>Throwable</code>s contained in the
	 * <code>Nestable</code> contained by this delegate.
	 *
	 * @return the throwable count
	 * @since 2.0
	 */
	public int getThrowableCount() {
		return ExceptionUtils.getThrowableCount( this.nestable );
	}

	/**
	 * Returns this delegate's <code>Nestable</code> and any nested
	 * <code>Throwable</code>s in an array of <code>Throwable</code>s, one
	 * element for each <code>Throwable</code>.
	 *
	 * @return the <code>Throwable</code>s
	 * @since 2.0
	 */
	public Throwable[] getThrowables() {
		return ExceptionUtils.getThrowables( this.nestable );
	}

	/**
	 * Returns the index, numbered from 0, of the first <code>Throwable</code>
	 * that matches the specified type in the chain of <code>Throwable</code>s
	 * held in this delegate's <code>Nestable</code> with an index greater than
	 * or equal to the specified index, or -1 if the type is not found.
	 *
	 * @param type      <code>Class</code> to be found
	 * @param fromIndex the index, numbered from 0, of the starting position in
	 *                  the chain to be searched
	 * @return index of the first occurrence of the type in the chain, or -1 if
	 *         the type is not found
	 * @throws IndexOutOfBoundsException if the <code>fromIndex</code> argument
	 *                                   is negative or not less than the count of <code>Throwable</code>s in the
	 *                                   chain
	 * @since 2.0
	 */
	public int indexOfThrowable(Class type, int fromIndex) {
		if ( fromIndex < 0 ) {
			throw new IndexOutOfBoundsException( "The start index was out of bounds: " + fromIndex );
		}
		Throwable[] throwables = ExceptionUtils.getThrowables( this.nestable );
		if ( fromIndex >= throwables.length ) {
			throw new IndexOutOfBoundsException( "The start index was out of bounds: "
					+ fromIndex + " >= " + throwables.length );
		}
		for ( int i = fromIndex; i < throwables.length; i++ ) {
			if ( throwables[i].getClass().equals( type ) ) {
				return i;
			}
		}
		return -1;
	}

	/**
	 * Prints the stack trace of this exception the the standar error
	 * stream.
	 */
	public void printStackTrace() {
		printStackTrace( System.err );
	}

	/**
	 * Prints the stack trace of this exception to the specified
	 * stream.
	 *
	 * @param out <code>PrintStream</code> to use for output.
	 * @see #printStackTrace(PrintWriter)
	 */
	public void printStackTrace(PrintStream out) {
		synchronized ( out ) {
			PrintWriter pw = new PrintWriter( out, false );
			printStackTrace( pw );
			// Flush the PrintWriter before it's GC'ed.
			pw.flush();
		}
	}

	/**
	 * Prints the stack trace of this exception to the specified
	 * writer. If the Throwable class has a <code>getCause</code>
	 * method (i.e. running on jre1.4 or higher), this method just
	 * uses Throwable's printStackTrace() method. Otherwise, generates
	 * the stack-trace, by taking into account the 'topDown' and
	 * 'trimStackFrames' parameters. The topDown and trimStackFrames
	 * are set to 'true' by default (produces jre1.4-like stack trace).
	 *
	 * @param out <code>PrintWriter</code> to use for output.
	 */
	public void printStackTrace(PrintWriter out) {
		Throwable throwable = this.nestable;
		// if running on jre1.4 or higher, use default printStackTrace
		if ( ExceptionUtils.isThrowableNested() ) {
			if ( throwable instanceof Nestable ) {
				( ( Nestable ) throwable ).printPartialStackTrace( out );
			}
			else {
				throwable.printStackTrace( out );
			}
			return;
		}

		// generating the nested stack trace
		List stacks = new ArrayList();
		while ( throwable != null ) {
			String[] st = getStackFrames( throwable );
			stacks.add( st );
			throwable = ExceptionUtils.getCause( throwable );
		}

		// If NOT topDown, reverse the stack
		String separatorLine = "Caused by: ";
		if ( !topDown ) {
			separatorLine = "Rethrown as: ";
			Collections.reverse( stacks );
		}

		// Remove the repeated lines in the stack
		if ( trimStackFrames ) trimStackFrames( stacks );

		synchronized ( out ) {
			for ( Iterator iter = stacks.iterator(); iter.hasNext(); ) {
				String[] st = ( String[] ) iter.next();
				for ( int i = 0, len = st.length; i < len; i++ ) {
					out.println( st[i] );
				}
				if ( iter.hasNext() ) out.print( separatorLine );
			}
		}
	}

	/**
	 * Captures the stack trace associated with the specified
	 * <code>Throwable</code> object, decomposing it into a list of
	 * stack frames.
	 *
	 * @param t The <code>Throwable</code>.
	 * @return An array of strings describing each stack frame.
	 * @since 2.0
	 */
	protected String[] getStackFrames(Throwable t) {
		StringWriter sw = new StringWriter();
		PrintWriter pw = new PrintWriter( sw, true );

		// Avoid infinite loop between decompose() and printStackTrace().
		if ( t instanceof Nestable ) {
			( ( Nestable ) t ).printPartialStackTrace( pw );
		}
		else {
			t.printStackTrace( pw );
		}
		return ExceptionUtils.getStackFrames( sw.getBuffer().toString() );
	}

	/**
	 * Trims the stack frames. The first set is left untouched. The rest
	 * of the frames are truncated from the bottom by comparing with
	 * one just on top.
	 *
	 * @param stacks The list containing String[] elements
	 * @since 2.0
	 */
	protected void trimStackFrames(List stacks) {
		for ( int size = stacks.size(), i = size - 1; i > 0; i-- ) {
			String[] curr = ( String[] ) stacks.get( i );
			String[] next = ( String[] ) stacks.get( i - 1 );

			List currList = new ArrayList( Arrays.asList( curr ) );
			List nextList = new ArrayList( Arrays.asList( next ) );
			ExceptionUtils.removeCommonFrames( currList, nextList );

			int trimmed = curr.length - currList.size();
			if ( trimmed > 0 ) {
				currList.add( "\t... " + trimmed + " more" );
				stacks.set( i,
						currList.toArray( new String[currList.size()] ) );
			}
		}
	}
}