package com.mahuan.json;import java.util.LinkedList;import java.util.List;/** * 词法分析 */public class Tokenizer { ???// 待分析的字符串 ???private String json; ???// 读取字符时的索引位置 ???private int index = 0; ???// 词法分析结果列表 ???private List<Token> tokens = new LinkedList<Token>(); ???// 获取词法分析结果时的索引位置 ???private int tokenIndex = 0; ???/** ????* 构造函数，触发词法分析 ????* @param json ????* @throws Exception ????*/ ???public Tokenizer(String json) throws Exception { ???????this.json = json; ???????this.init(); ???} ???/** ????* 读取字符串中的字符，索引位置加1 ????* @return ????*/ ???private Character read() { ???????if (index < json.length()) ???????????return json.charAt(index++); ???????else ???????????return null; ???} ???/** ????* 读取字符串中的字符，索引位置减1 ????*/ ???private void unread() { ???????index--; ???} ???/** ????* 进行词法分析 ????* @throws Exception ????*/ ???private void init() throws Exception { ???????Token token = null; ???????while ((token = token()) != null) { ???????????tokens.add(token); ???????} ???} ???/** ????* 按顺序读取字符串，获取词法分析结果 ????* @return ????* @throws Exception ????*/ ???private Token token() throws Exception { ???????Character c = read(); ???????if (c == null) ???????????return null; ???????// 忽略空白字符、换行符等 ???????while (isSpace(c)) { ???????????c = read(); ???????} ???????if (isNull(c)) ???????????return new Token(TokenType.Null, null); ???????if (c == ‘{‘) ???????????return new Token(TokenType.ObjectStart, "{"); ???????if (c == ‘}‘) ???????????return new Token(TokenType.ObjectEnd, "}"); ???????if (c == ‘[‘) ???????????return new Token(TokenType.ArrayStart, "["); ???????if (c == ‘]‘) ???????????return new Token(TokenType.ArrayEnd, "]"); ???????if (c == ‘,‘) ???????????return new Token(TokenType.Comma, ","); ???????if (c == ‘:‘) ???????????return new Token(TokenType.Colon, ":"); ???????if (isTrue(c)) ???????????return new Token(TokenType.Boolean, "true"); ???????if (isFalse(c)) ???????????return new Token(TokenType.Boolean, "false"); ???????if (c == ‘"‘) ???????????return new Token(TokenType.String, readString()); ???????if (isNum(c)) { ???????????unread(); ???????????return new Token(TokenType.Number, readNum()); ???????} ???????throw new Exception(""); ???} ???/** ????* 读取字符串 ????* @return ????*/ ???private String readString() { ???????char c = read(); ???????StringBuffer sb = new StringBuffer(); ???????while (c != ‘"‘) { ???????????sb.append(c); ???????????if (isEscape(c)) { ???????????????c = read(); ???????????????sb.append(c); ???????????} ???????????c = read(); ???????} ???????return sb.toString(); ???} ???/** ????* 读取数字，还未考虑所有数字表达形式 ????* @return ????*/ ???private String readNum() { ???????char c = read(); ???????StringBuffer sb = new StringBuffer(); ???????while (c != ‘"‘ && c != ‘:‘ && c != ‘,‘ && c != ‘]‘ && c != ‘}‘) { ???????????sb.append(c); ???????????c = read(); ???????} ???????unread(); ???????return sb.toString(); ???} ???/** ????* 判断是否为数字开头的特征 ????* @param c ????* @return ????*/ ???private boolean isNum(char c) { ???????if (c == ‘-‘ || (‘0‘ <= c && c <= ‘9‘)) ???????????return true; ???????return false; ???} ???/** ????* 判断是否为转义字符 ????* @param c ????* @return ????*/ ???private boolean isEscape(char c) { ???????if (c == ‘\\‘) ???????????return true; ???????return false; ???} ???/** ????* 是否为true字符串 ????* @param c ????* @return ????* @throws Exception ????*/ ???private boolean isTrue(char c) throws Exception { ???????if (c == ‘t‘) { ???????????c = read(); ???????????if (c == ‘r‘) { ???????????????c = read(); ???????????????if (c == ‘u‘) { ???????????????????c = read(); ???????????????????if (c == ‘e‘) { ???????????????????????return true; ???????????????????} else { ???????????????????????throw new Exception("Invalid JSON input."); ???????????????????} ???????????????} else { ???????????????????throw new Exception("Invalid JSON input."); ???????????????} ???????????} else { ???????????????throw new Exception("Invalid JSON input."); ???????????} ???????} else { ???????????return false; ???????} ???} ???/** ????* 是否为false字符串 ????* @param c ????* @return ????* @throws Exception ????*/ ???private boolean isFalse(char c) throws Exception { ???????if (c == ‘f‘) { ???????????c = read(); ???????????if (c == ‘a‘) { ???????????????c = read(); ???????????????if (c == ‘l‘) { ???????????????????c = read(); ???????????????????if (c == ‘s‘) { ???????????????????????c = read(); ???????????????????????if (c == ‘e‘) { ???????????????????????????return true; ???????????????????????} else { ???????????????????????????throw new Exception("Invalid JSON input."); ???????????????????????} ???????????????????} else { ???????????????????????throw new Exception("Invalid JSON input."); ???????????????????} ???????????????} else { ???????????????????throw new Exception("Invalid JSON input."); ???????????????} ???????????} else { ???????????????throw new Exception("Invalid JSON input."); ???????????} ???????} else { ???????????return false; ???????} ???} ???/** ????* 是否为null字符串 ????* @param c ????* @return ????* @throws Exception ????*/ ???private boolean isNull(char c) throws Exception { ???????if (c == ‘n‘) { ???????????c = read(); ???????????if (c == ‘u‘) { ???????????????c = read(); ???????????????if (c == ‘l‘) { ???????????????????c = read(); ???????????????????if (c == ‘l‘) { ???????????????????????return true; ???????????????????} else { ???????????????????????throw new Exception("Invalid JSON input."); ???????????????????} ???????????????} else { ???????????????????throw new Exception("Invalid JSON input."); ???????????????} ???????????} else { ???????????????throw new Exception("Invalid JSON input."); ???????????} ???????} else { ???????????return false; ???????} ???} ???/** ????* 是否为空字符 ????* @param c ????* @return ????*/ ???private boolean isSpace(char c) { ???????if (c == ‘\t‘) ???????????return true; ???????if (c == ‘\n‘) ???????????return true; ???????if (c == ‘\r‘) ???????????return true; ???????if (c == ‘\0‘) ???????????return true; ???????if (c == ‘ ‘) ???????????return true; ???????return false; ???} ???/** ????* 获取词法分析的下一个结果 ????* @return ????*/ ???public Token next() { ???????if (tokenIndex + 1 < tokens.size()) ???????????return tokens.get(++tokenIndex); ???????return null; ???} ???/** ????* 获取当前位置的词法分析结果 ????* @return ????*/ ???public Token get() { ???????if (tokenIndex < tokens.size()) ???????????return tokens.get(tokenIndex); ???????return null; ???}}/** * 词法分析类型 */enum TokenType { ???// object开始 ???ObjectStart, ???// object结束 ???ObjectEnd, ???// 数组开始 ???ArrayStart, ???// 数组结束 ???ArrayEnd, ???// 字符串 ???String, ???// 数字 ???Number, ???// boolean ???Boolean, ???// 空 ???Null, ???// , ???Comma, ???// : ???Colon}/** * 词法分析单元 * @author mahuan * @version 2017年12月13日 */class Token { ???public TokenType type; ???public String value; ???public Token(TokenType type, String value) { ???????this.type = type; ???????this.value = value; ???}}

package com.mahuan.json;import java.util.HashMap;import java.util.LinkedList;import java.util.List;import java.util.Map;/** * 语法分析 */public class Parser { ???/** ????* 分析Object，使用map数据结构标识 ????* @param tokenizer ????* @return ????* @throws Exception ????*/ ???public static Map<String, Object> parserObject(Tokenizer tokenizer) throws Exception { ???????Map<String, Object> map = new HashMap<>(); ???????Token token = null; ???????while (true) { ???????????token = tokenizer.get(); ???????????if (token.type == TokenType.ObjectEnd) ???????????????break; ???????????if (token.type == TokenType.ObjectStart) { ???????????????tokenizer.next(); ???????????????continue; ???????????} ???????????if (token.type == TokenType.Comma) { ???????????????tokenizer.next(); ???????????????continue;// 跳过, ???????????} ???????????String key = token.value; ???????????token = tokenizer.next(); ???????????if (token.type != TokenType.Colon) ???????????????throw new Exception(); ???????????tokenizer.next(); ???????????map.put(key, parserValue(tokenizer)); ???????} ???????return map; ???} ???/** ????* 分析Array，使用list数据结构标识 ????* @param tokenizer ????* @return ????* @throws Exception ????*/ ???public static List<Object> parserArray(Tokenizer tokenizer) throws Exception { ???????List<Object> list = new LinkedList<>(); ???????Token token = null; ???????while (true) { ???????????token = tokenizer.get(); ???????????if (token.type == TokenType.ArrayEnd) ???????????????break; ???????????if (token.type == TokenType.ArrayStart) { ???????????????tokenizer.next(); ???????????????continue; ???????????} ???????????if (token.type == TokenType.Comma) { ???????????????tokenizer.next(); ???????????????continue; ???????????} ???????????list.add(parserValue(tokenizer)); ???????} ???????return list; ???} ???/** ????* 分析值，根据token再判断值的具体类型 ????* @param tokenizer ????* @return ????* @throws Exception ????*/ ???public static Object parserValue(Tokenizer tokenizer) throws Exception { ???????Token token = tokenizer.get(); ???????try { ???????????if (token.type == TokenType.ObjectStart) ???????????????return parserObject(tokenizer); ???????????else if (token.type == TokenType.ArrayStart) ???????????????return parserArray(tokenizer); ???????????else if (token.type == TokenType.Boolean) ???????????????return Boolean.valueOf(token.value); ???????????else if (token.type == TokenType.String) ???????????????return token.value; ???????????else if (token.type == TokenType.Number) ???????????????return token.value; ???????????else if (token.type == TokenType.Null) ???????????????return null; ???????????throw new Exception(""); ???????} finally { ???????????// object和array分析完后，要跳过其end的token ???????????// 其他类型分析完后，要跳过自身 ???????????tokenizer.next(); ???????} ???}}

package com.mahuan.json;public class Test { ???public static void main(String[] args) throws Exception { ???????String json = "{ ?\"success\": true, ?\"message\": \"123\", ?\"result\": [ ???-2146464718]}"; ???????Tokenizer tokenizer = new Tokenizer(json); ???????Object map = Parser.parserValue(tokenizer); ???????System.out.println(map); ???}}