java.lang.NoClassDefFoundError: javax.swing.tree.TreeNode is a restricted class

今天在GAE中配置Struts中出现了不少问题，以下是其中一个

Problem accessing /hello.action. Reason: 

    java.lang.NoClassDefFoundError: javax.swing.tree.TreeNode is a restricted class. 
    Please see the Google  App Engine developer's guide for more details.

Caused by:
javax.servlet.ServletException: java.lang.NoClassDefFoundError: javax.swing.tree.TreeNode 
is a restricted class. Please see the Google  App Engine developer's guide for more details.
	at org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:825)
	at org.apache.jasper.runtime.PageContextImpl.access$1100(PageContextImpl.java:64)
	at org.apache.jasper.runtime.PageContextImpl$12.run(PageContextImpl.java:745)

 解决方法是增加一个freemarker.core.TextBlock.

也就是先在src下建包 freemarker.core,然后增加一个TextBlock类

package freemarker.core;

import java.io.IOException;

public class TextBlock extends TemplateElement {
	private static final char[] EMPTY_CHAR_ARRAY = new char[0];
	static final TextBlock EMPTY_BLOCK = new TextBlock(EMPTY_CHAR_ARRAY, false);
	// We're using char[] instead of String for storing the text block because
	// Writer.write(String) involves copying the String contents to a char[]
	// using String.getChars(), and then calling Writer.write(char[]).By
	// using Writer.write(char[]) directly, we avoid array copying on each
	// write.
	private char[] text;
	private final boolean unparsed;

	public TextBlock(String text) {
		this(text, false);
	}

	public TextBlock(String text, boolean unparsed) {
		this(text.toCharArray(), unparsed);
	}

	private TextBlock(char[] text, boolean unparsed) {
		this.text = text;
		this.unparsed = unparsed;
	}

	/**
	 * Simply outputs the text.
	 */
	public void accept(Environment env) throws IOException {
		env.getOut().write(text);
	}

	public String getCanonicalForm() {
		String text = new String(this.text);
		if (unparsed) {
			return "<#noparse>" + text + "</#noparse>";
		}
		return text;
	}

	public String getDescription() {
		String s = new String(text).trim();
		if (s.length() == 0) {
			return "whitespace";
		}
		if (s.length() > 20) {
			s = s.substring(0, 20) + "...";
			s = s.replace('\n', ' ');
			s = s.replace('\r', ' ');
		}
		return "text block (" + s + ")";
	}

	TemplateElement postParseCleanup(boolean stripWhitespace) {
		if (text.length == 0)
			return this;
		int openingCharsToStrip = 0, trailingCharsToStrip = 0;
		boolean deliberateLeftTrim = deliberateLeftTrim();
		boolean deliberateRightTrim = deliberateRightTrim();
		if (!stripWhitespace || text.length == 0) {
			return this;
		}
		if (parent.parent == null && previousSibling() == null)
			return this;
		if (!deliberateLeftTrim) {
			trailingCharsToStrip = trailingCharsToStrip();
		}
		if (!deliberateRightTrim) {
			openingCharsToStrip = openingCharsToStrip();
		}
		if (openingCharsToStrip == 0 && trailingCharsToStrip == 0) {
			return this;
		}
		this.text = substring(text, openingCharsToStrip, text.length
				- trailingCharsToStrip);
		if (openingCharsToStrip > 0) {
			this.beginLine++;
			this.beginColumn = 1;
		}
		if (trailingCharsToStrip > 0) {
			this.endColumn = 0;
		}
		return this;
	}

	/**
	 * Scans forward the nodes on the same line to see whether there is a
	 * deliberate left trim in effect. Returns true if the left trim was
	 * present.
	 */
	private boolean deliberateLeftTrim() {
		boolean result = false;
		for (TemplateElement elem = this.nextTerminalNode(); elem != null
				&& elem.beginLine == this.endLine; elem = elem
				.nextTerminalNode()) {
			if (elem instanceof TrimInstruction) {
				TrimInstruction ti = (TrimInstruction) elem;
				if (!ti.left && !ti.right) {
					result = true;
				}
				if (ti.left) {
					result = true;
					int lastNewLineIndex = lastNewLineIndex();
					if (lastNewLineIndex >= 0 || beginColumn == 1) {
						char[] firstPart = substring(text, 0,
								lastNewLineIndex + 1);
						char[] lastLine = substring(text, 1 + lastNewLineIndex);
						if (trim(lastLine).length == 0) {
							this.text = firstPart;
							this.endColumn = 0;
						} else {
							int i = 0;
							while (Character.isWhitespace(lastLine[i])) {
								i++;
							}
							char[] printablePart = substring(lastLine, i);
							this.text = concat(firstPart, printablePart);
						}
					}
				}
			}
		}
		if (result) {
		}
		return result;
	}

	/**
	 * Checks for the presence of a t or rt directive on the same line. Returns
	 * true if the right trim directive was present.
	 */
	private boolean deliberateRightTrim() {
		boolean result = false;
		for (TemplateElement elem = this.prevTerminalNode(); elem != null
				&& elem.endLine == this.beginLine; elem = elem
				.prevTerminalNode()) {
			if (elem instanceof TrimInstruction) {
				TrimInstruction ti = (TrimInstruction) elem;
				if (!ti.left && !ti.right) {
					result = true;
				}
				if (ti.right) {
					result = true;
					int firstLineIndex = firstNewLineIndex() + 1;
					if (firstLineIndex == 0) {
						return false;
					}
					if (text.length > firstLineIndex
							&& text[firstLineIndex - 1] == '\r'
							&& text[firstLineIndex] == '\n') {
						firstLineIndex++;
					}
					char[] trailingPart = substring(text, firstLineIndex);
					char[] openingPart = substring(text, 0, firstLineIndex);
					if (trim(openingPart).length == 0) {
						this.text = trailingPart;
						this.beginLine++;
						this.beginColumn = 1;
					} else {
						int lastNonWS = openingPart.length - 1;
						while (Character.isWhitespace(text[lastNonWS])) {
							lastNonWS--;
						}
						char[] printablePart = substring(text, 0, lastNonWS + 1);
						if (trim(trailingPart).length == 0) {
							// THIS BLOCK IS HEINOUS! THERE MUST BE A BETTER
							// WAY! REVISIT (JR)
							boolean trimTrailingPart = true;
							for (TemplateElement te = this.nextTerminalNode(); te != null
									&& te.beginLine == this.endLine; te = te
									.nextTerminalNode()) {
								if (te.heedsOpeningWhitespace()) {
									trimTrailingPart = false;
								}
								if (te instanceof TrimInstruction
										&& ((TrimInstruction) te).left) {
									trimTrailingPart = true;
									break;
								}
							}
							if (trimTrailingPart)
								trailingPart = EMPTY_CHAR_ARRAY;
						}
						this.text = concat(printablePart, trailingPart);
					}
				}
			}
		}
		return result;
	}

	/*
	 * private String leftTrim(String s) { int i =0; while (i<s.length()) { if
	 * (!Character.isWhitespace(s.charAt(i))) break; ++i; } return
	 * s.substring(i); }
	 */
	private int firstNewLineIndex() {
		String content = new String(text);
		int newlineIndex1 = content.indexOf('\n');
		int newlineIndex2 = content.indexOf('\r');
		int result = newlineIndex1 >= 0 ? newlineIndex1 : newlineIndex2;
		if (newlineIndex1 >= 0 && newlineIndex2 >= 0) {
			result = Math.min(newlineIndex1, newlineIndex2);
		}
		return result;
	}

	private int lastNewLineIndex() {
		String content = new String(text);
		return Math.max(content.lastIndexOf('\r'), content.lastIndexOf('\n'));
	}

	/**
	 * figures out how many opening whitespace characters to strip in the
	 * post-parse cleanup phase.
	 */
	private int openingCharsToStrip() {
		int newlineIndex = firstNewLineIndex();
		if (newlineIndex == -1 && beginColumn != 1) {
			return 0;
		}
		++newlineIndex;
		if (text.length > newlineIndex) {
			if (newlineIndex > 0 && text[newlineIndex - 1] == '\r'
					&& text[newlineIndex] == '\n') {
				++newlineIndex;
			}
		}
		if (new String(text).substring(0, newlineIndex).trim().length() > 0) {
			return 0;
		}
		// We look at the preceding elements on the line to see if we should
		// strip the opening newline and any whitespace preceding it.
		for (TemplateElement elem = this.prevTerminalNode(); elem != null
				&& elem.endLine == this.beginLine; elem = elem
				.prevTerminalNode()) {
			if (elem.heedsOpeningWhitespace()) {
				return 0;
			}
		}
		return newlineIndex;
	}

	/**
	 * figures out how many trailing whitespace characters to strip in the
	 * post-parse cleanup phase.
	 */
	private int trailingCharsToStrip() {
		String content = new String(text);
		int lastNewlineIndex = lastNewLineIndex();
		if (lastNewlineIndex == -1 && beginColumn != 1) {
			return 0;
		}
		String substring = content.substring(lastNewlineIndex + 1);
		if (substring.trim().length() > 0) {
			return 0;
		}
		// We look at the elements afterward on the same line to see if we
		// should strip any whitespace after the last newline
		for (TemplateElement elem = this.nextTerminalNode(); elem != null
				&& elem.beginLine == this.endLine; elem = elem
				.nextTerminalNode()) {
			if (elem.heedsTrailingWhitespace()) {
				return 0;
			}
		}
		return substring.length();
	}

	boolean heedsTrailingWhitespace() {
		if (isIgnorable()) {
			return false;
		}
		for (int i = 0; i < text.length; i++) {
			char c = text[i];
			if (c == '\n' || c == '\r') {
				return false;
			}
			if (!Character.isWhitespace(c)) {
				return true;
			}
		}
		return true;
	}

	boolean heedsOpeningWhitespace() {
		if (isIgnorable()) {
			return false;
		}
		for (int i = text.length - 1; i >= 0; i--) {
			char c = text[i];
			if (c == '\n' || c == '\r') {
				return false;
			}
			if (!Character.isWhitespace(c)) {
				return true;
			}
		}
		return true;
	}

	boolean isIgnorable() {
		if (text == null || text.length == 0) {
			return true;
		}
		if (!isWhitespace()) {
			return false;
		}
		// trick here
		boolean atTopLevel = true;
		TemplateElement prevSibling = previousSibling();
		TemplateElement nextSibling = nextSibling();
		return ((prevSibling == null && atTopLevel) || nonOutputtingType(prevSibling))
				&& ((nextSibling == null && atTopLevel) || nonOutputtingType(nextSibling));
	}

	private boolean nonOutputtingType(TemplateElement element) {
		return (element instanceof Macro || element instanceof Assignment
				|| element instanceof AssignmentInstruction
				|| element instanceof PropertySetting
				|| element instanceof LibraryLoad || element instanceof Comment);
	}

	private static char[] substring(char[] c, int from, int to) {
		char[] c2 = new char[to - from];
		System.arraycopy(c, from, c2, 0, c2.length);
		return c2;
	}

	private static char[] substring(char[] c, int from) {
		return substring(c, from, c.length);
	}

	private static char[] trim(char[] c) {
		if (c.length == 0) {
			return c;
		}
		return new String(c).trim().toCharArray();
	}

	private static char[] concat(char[] c1, char[] c2) {
		char[] c = new char[c1.length + c2.length];
		System.arraycopy(c1, 0, c, 0, c1.length);
		System.arraycopy(c2, 0, c, c1.length, c2.length);
		return c;
	}

	boolean isWhitespace() {
		return text == null || trim(text).length == 0;
	}

}

 

强烈建议参考以下文章在GAE中配置Struts2

http://whyjava.wordpress.com/2009/08/30/creating-struts2-application-on-google-app-engine-gae/