Java解析HTML标签

痛定思痛。 2022-08-12 07:29 192阅读 0赞

\#基于状态机思想实现解析HTML TAG ，后续有时间的话尝试写一个JSON解析工具。

import java.util.HashMap;
    import java.util.Map;
    
    public class TagParser {
    	private Integer index = 0;
    	private char[] tagChar;
    	private int position = 0;
    	/* 解析符号 */
    	private char symbol = '"';
    	public static final String START_SCRIPT = "<";
    	public static final String END_SCRIPT = ">";
    	public static final String END_SCRIPT_1 = "/>";
    	public static final String EQ = "=";
    	public static final char SPACE = ' ';
    	public static final String MUST_SPACE = " ";
    	public static final String TAB = "	";
    	public static final String SYMBOL = "'";
    	private DFAStatus status;
    	private Map<Integer, Entity> map = new HashMap<Integer, Entity>();
    	private Map<String, String> result = new HashMap<String, String>();
    	private String tagName;
    
    	public String getTagName() {
    		return this.tagName;
    	}
    
    	public static void main(String[] args) throws SymbolError {
    		String tag = "<script  filter=\"a\'\" type=\"text/javascript\" id='node' src=\"http://www.test.com/abc.js\" async=\"true\" />";
    		int i = 0;
    		long start = System.currentTimeMillis();
    		while (i < 2) {
    			TagParser token = new TagParser(tag);
    			token.parser();
    			System.out.println(token.getAttr("src") + "|" + token.getTagName());
    			i++;
    		}
    		System.out.println("use time:" + (System.currentTimeMillis() - start));
    	}
    
    	private boolean startsWith(String str) {
    		char[] chat = str.toCharArray();
    		if (position + chat.length > tagChar.length) {
    			return false;
    		}
    		for (int i = 0; i < chat.length; i++) {
    			if (tagChar[position + i] != chat[i]) {
    				if (is_az(chat[i])) {
    					if (tagChar[position + i] == chat[i] - 32) {
    						continue;
    					}
    				}
    				return false;
    			}
    		}
    		return true;
    	}
    
    	public void parser() throws SymbolError {
    		if (status == null) {
    			status = DFAStatus.UNSTART;
    			skipSpace();
    		}
    		if (status == DFAStatus.UNSTART) {
    			if (startsWith(START_SCRIPT)) {
    				position += START_SCRIPT.length();
    				status = DFAStatus.TAG_NAME;
    				parser();
    			} else {
    				throw new SymbolError("语法错误:" + tagChar[position]);
    			}
    		} else if (status == DFAStatus.TAG_NAME) {
    			parserTagName();
    			status = DFAStatus.START;
    			parser();
    		} else if (status == DFAStatus.START) {
    			nextSpace();
    			parser();
    		} else if (status == DFAStatus.NULL) {
    			skipSpace();
    			if (startsWith(END_SCRIPT_1)) {
    				status = DFAStatus.DONE;
    				done();
    				return;
    			} else if (startsWith(END_SCRIPT)) {
    				status = DFAStatus.DONE;
    				done();
    				return;
    			}
    			parserName();
    			parser();
    		} else if (status == DFAStatus.EQ) {
    			parserVal();
    			parser();
    		} else if (status == DFAStatus.SYMBOL_END) {
    			status = DFAStatus.NULL;
    			parser();
    		}
    	}
    
    	private void parserTagName() throws SymbolError {
    		StringBuilder builder = new StringBuilder(20);
    		for (int i = position; i < tagChar.length; i++) {
    			if (is_az(tagChar[i]) || is_AZ(tagChar[i])) {
    				builder.append(tagChar[i]);
    				position++;
    			} else if (builder.length() > 0 && tagChar[i] == ' ') {
    				this.tagName = builder.toString();
    				return;
    			} else {
    				break;
    			}
    		}
    		throw new SymbolError("语法错误:" + tagChar[position]);
    	}
    
    	private void done() {
    		for (Entity entity : map.values()) {
    			result.put(entity.name, entity.value);
    		}
    	}
    
    	private void parserVal() throws SymbolError {
    		skipSpace();
    		StringBuilder builder = new StringBuilder();
    		int startIndex = position;
    		for (int i = position; i < tagChar.length; i++) {
    			if (i == startIndex) {
    				if (tagChar[i] == '\'' || tagChar[i] == '"') {
    					symbol = tagChar[i];
    					status = DFAStatus.SYMBOL_START;
    					position++;
    				} else {
    					throw new SymbolError("语法错误:" + tagChar[position]);
    				}
    			} else {
    				if (tagChar[i] == symbol) {
    					status = DFAStatus.SYMBOL_END;
    					position++;
    					break;
    				} else {
    					builder.append(tagChar[i]);
    					position++;
    				}
    			}
    		}
    		map.get(index).value = builder.toString();
    		index++;
    	}
    
    	private boolean is_AZ(char chat) {
    		return chat >= 65 && chat <= 90;
    	}
    
    	private boolean is_az(char chat) {
    		return chat >= 97 && chat <= 122;
    	}
    
    	private void parserName() throws SymbolError {
    		StringBuilder builder = new StringBuilder();
    		for (int i = position; i < tagChar.length; i++) {
    			if (is_az(tagChar[i]) || is_AZ(tagChar[i])) {
    				builder.append(tagChar[i]);
    				position++;
    			} else {
    				if (builder.length() > 0) {
    					skipSpace();
    					nextEQ();
    					break;
    				}
    			}
    		}
    		if (builder.toString().length() == 0) {
    			throw new SymbolError("语法错误:" + tagChar[position]);
    		}
    		map.put(index, new Entity(builder.toString()));
    	}
    
    	private void nextEQ() throws SymbolError {
    		if (startsWith(EQ)) {
    			position++;
    			status = DFAStatus.EQ;
    		} else {
    			throw new SymbolError("语法错误:" + tagChar[position]);
    		}
    	}
    
    	private void skipSpace() {
    		for (int i = position; i < tagChar.length; i++) {
    			if (tagChar[i] == SPACE || tagChar[i] == '\t') {
    				position++;
    			} else {
    				return;
    			}
    		}
    	}
    
    	private void nextSpace() throws SymbolError {
    		if (startsWith(MUST_SPACE)) {
    			position += MUST_SPACE.length();
    			status = DFAStatus.NULL;
    		} else if (startsWith(TAB)) {
    			position += TAB.length();
    			status = DFAStatus.NULL;
    		} else {
    			throw new SymbolError("语法错误:" + tagChar[position]);
    		}
    	}
    
    	public String getAttr(String name) {
    		return result.get(name);
    	}
    
    	public TagParser(String str) {
    		this.tagChar = str.toCharArray();
    	}
    
    	@Override
    	public String toString() {
    		return result.toString();
    	}
    
    	public static class SymbolError extends Exception {
    		private static final long serialVersionUID = 2441411373778495898L;
    
    		public SymbolError(String msg) {
    			super(msg);
    		}
    	}
    
    	public static class Entity {
    		public Entity(String name) {
    			this.name = name;
    		}
    
    		public String name;
    		public String value;
    
    		@Override
    		public String toString() {
    			return "[" + name + ":" + value + "]";
    		}
    	}
    
    	public enum DFAStatus {
    		UNSTART, START, TAG_NAME, SYMBOL_START, SYMBOL_END, DONE, NULL, EQ
    	}
    
    	public static TagParser parser(String htmlTag) throws SymbolError {
    		TagParser tag = new TagParser(htmlTag);
    		tag.parser();
    		return tag;
    	}
    }