通过Java压缩JavaScript代码实例分享

/** * This file is part of the Echo Web Application Framework (hereinafter /"Echo/"). * Copyright (C) 2002-2009 NextApp, Inc. * * Compresses a String containing JavaScript by removing comments and whitespace. */public class JavaScriptCompressor {	private static final char LINE_FEED = /'//n/';	private static final char CARRIAGE_RETURN = /'//r/';	private static final char SPACE = /' /';	private static final char TAB = /'//t/';	/**   * Compresses a String containing JavaScript by removing comments and    * whitespace.   *    * @param script the String to compress   * @return a compressed version   */	public static String compress(String script) {		JavaScriptCompressor jsc = new JavaScriptCompressor(script);		return jsc.outputBuffer.toString();	}	/** Original JavaScript text. */	private String script;	/**    * Compressed output buffer.   * This buffer may only be modified by invoking the <code>append()</code>   * method.   */	private StringBuffer outputBuffer;	/** Current parser cursor position in original text. */	private int pos;	/** Character at parser cursor position. */	private char ch;	/** Last character appended to buffer. */	private char lastAppend;	/** Flag indicating if end-of-buffer has been reached. */	private Boolean endReached;	/** Flag indicating whether content has been appended after last identifier. */	private Boolean contentAppendedAfterLastIdentifier = true;	/**   * Creates a new <code>JavaScriptCompressor</code> instance.   *    * @param script   */	private JavaScriptCompressor(String script) {		this.script = script;		outputBuffer = new StringBuffer(script.length());		nextchar();		while (!endReached) {			if (Character.isJavaIdentifierStart(ch)) {				renderIdentifier();			} else if (ch == /' /') {				skipWhiteSpace();			} else if (isWhitespace()) {				// Compress whitespace				skipWhiteSpace();			} else if ((ch == /'/"/') || (ch == /'///'/')) {        // Handle strings        renderString();      } else if (ch == /'//') {        // Handle comments        nextChar();        if (ch == /'//') {          nextChar();          skipLineComment();        } else if (ch == /'*/') {          nextChar();          skipBlockComment();        } else {          append(/'//');        }      } else {        append(ch);        nextChar();      }    }  }  /**   * Append character to output.   *    * @param ch the character to append   */  private void append(char ch) {    lastAppend = ch;    outputBuffer.append(ch);    contentAppendedAfterLastIdentifier = true;  }  /**   * Determines if current character is whitespace.   *    * @return true if the character is whitespace   */  private boolean isWhitespace() {    return ch == CARRIAGE_RETURN || ch == SPACE || ch == TAB || ch == LINE_FEED;      }  /**   * Load next character.   */  private void nextChar() {    if (!endReached) {      if (pos < script.length()) {        ch = script.charAt(pos++);      } else {        endReached = true;        ch = 0;      }    }  }  /**   * Adds an identifier to output.   */  private void renderIdentifier() {    if (!contentAppendedAfterLastIdentifier)      append(SPACE);    append(ch);    nextChar();    while (Character.isJavaIdentifierPart(ch)) {      append(ch);      nextChar();    }    contentAppendedAfterLastIdentifier = false;  }  /**   * Adds quoted String starting at current character to output.   */  private void renderString() {    char startCh = ch; // Save quote char    append(ch);    nextChar();    while (true) {      if ((ch == LINE_FEED) || (ch == CARRIAGE_RETURN) || (endReached)) {        // JavaScript error: string not terminated        return;      } else {        if (ch == /'/////') {          append(ch);          nextChar();          if ((ch == LINE_FEED) || (ch == CARRIAGE_RETURN) || (endReached)) {            // JavaScript error: string not terminated            return;          }          append(ch);          nextChar();        } else {          append(ch);          if (ch == startCh) {            nextChar();            return;          }          nextChar();        }      }    }  }  /**   * Moves cursor past a line comment.   */  private void skipLineComment() {    while ((ch != CARRIAGE_RETURN) && (ch != LINE_FEED)) {      if (endReached) {        return;      }      nextChar();    }  }  /**   * Moves cursor past a block comment.   */  private void skipBlockComment() {    while (true) {      if (endReached) {        return;      }      if (ch == /'*/') {        nextChar();        if (ch == /'//') {          nextChar();          return;        }      } else        nextChar();    }  }  /**   * Renders a new line character, provided previously rendered character    * is not a newline.   */  private void renderNewLine() {    if (lastAppend != /'//n/' && lastAppend != /'//r/') {      append(/'//n/');    }  }  /**   * Moves cursor past white space (including newlines).   */  private void skipWhiteSpace() {    if (ch == LINE_FEED || ch == CARRIAGE_RETURN) {      renderNewLine();    } else {      append(ch);    }    nextChar();    while (ch == LINE_FEED || ch == CARRIAGE_RETURN || ch == SPACE || ch == TAB) {      if (ch == LINE_FEED || ch == CARRIAGE_RETURN) {        renderNewLine();      }      nextChar();    }  }}