用java手写了个JSON解析&生成器
同步：https://zhufn.fun/archives/handwritejson/
主要实现思路是递归。我们把单个值也当作合法的json，先判断当前json类型，如果是单个值就直接return对应类型（解析时）或toString（编码时），如果是Object就遍历它的key值，然后取冒号后面的部分递归解析/编码，Array也差不多。
经解码再编码测试非常完美。
知识点：java泛型类如HashMap<String, Object>无法用instanceof检测。
但是，可以新写一个空类去继承他，这样就不是泛型了。
（Java快加个rust那种枚举吧）
Warning有点多，将就看
package fun.zhufn.oldcomm; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; class BadJsonException extends RuntimeException { } class JsonMap extends HashMap<String, Object> { } class JsonList extends ArrayList<Object> { } public class MyJsonParser { static void print(String s) { System.out.println(s); } public static Object parse(String json) throws BadJsonException { json = json.trim(); if (json.startsWith([) && json.endsWith(])) { JsonList ret = new JsonList(); json = json.substring(1, json.length() - 1); while(true) { int p1 = 0, p2 = findNextComma(json), len = json.length(); String curLine = json.substring(p1, p2).trim(); ret.add(parse(curLine)); if (p2 < len) json = json.substring(p2 + 1); else break; } return ret; } else if (json.startsWith({) && json.endsWith(})) { return nextObject(json); } else if (json.startsWith(\) && json.endsWith(\)) { int cnt = 0; for (int i = 0; i < json.length(); ++i) { if (json.charAt(i) == '' && (i > 0 && json.charAt(i - 1) != '\\')) { ++cnt; } } if (cnt > 2) throw new BadJsonException(); return json.substring(1, json.length() - 1); } else if (json.equals(true)) { return true; } else if (json.equals(false)) { return false; } else { try { return Double.parseDouble(json); } catch (Exception e) { throw new BadJsonException(); } } } private static JsonMap nextObject(String json) throws BadJsonException { JsonMap ret = new JsonMap(); if (!json.startsWith({) || !json.endsWith(})) { throw new BadJsonException(); } json = json.substring(1, json.length() - 1); if (json.isEmpty()) return ret; while(true) { int p1 = 0, p2 = findNextComma(json), len = json.length(); String curLine = json.substring(p1, p2).trim(); if (curLine.startsWith(\)) { int j = stringPos(curLine); String key = curLine.substring(1, j); curLine = curLine.substring(j + 1).trim(); if (!curLine.startsWith(:)) throw new BadJsonException(); ret.put(key, parse(curLine.substring(1).trim())); } else { throw new BadJsonException(); } if (p2 < len) json = json.substring(p2 + 1); else break; } return ret; } private static int intPos(String str) throws BadJsonException { int i = -1; while (i + 1 < str.length() &&str.charAt(i + 1) >= '0' && str.charAt(i + 1) <= '9') { ++i; } if (i == -1) { throw new BadJsonException(); } return i; } private static int stringPos(String str) throws BadJsonException { if (!str.startsWith(\)) { throw new BadJsonException(); } int i = 1; while (i < str.length()) { if (str.charAt(i) == '') { break; } ++i; } if (i == str.length()) throw new BadJsonException(); return i; } private static int findNextComma(String json) throws BadJsonException { int quoteCnt = 0, squareBracketsCnt = 0, bracesCnt = 0; int len = json.length(); int i = 0; while (i < len) { if (json.charAt(i) == ',' && quoteCnt % 2 == 0 && squareBracketsCnt == 0 && bracesCnt == 0) { break; } if (json.charAt(i) == '') { ++quoteCnt; } if (json.charAt(i) == '[') { ++squareBracketsCnt; } if (json.charAt(i) == '{') { ++bracesCnt; } if (json.charAt(i) == ']') { --squareBracketsCnt; } if (json.charAt(i) == '}') { --bracesCnt; } ++i; } return i; } public static String gen(Object data) { if (data instanceof JsonMap) { StringBuilder ret = new StringBuilder({); JsonMap mp = (JsonMap)data; for (String key: mp.keySet()) { ret.append(\).append(key).append(\:); ret.append(gen(mp.get(key))); ret.append(,); } ret.delete(ret.length() - 1, ret.length()); ret.append(}); return ret.toString(); } else if (data instanceof JsonList) { StringBuilder ret = new StringBuilder([); for (Object v: (JsonList)data) { ret.append(gen(v)); ret.append(,); } ret.delete(ret.length() - 1, ret.length()); ret.append(]); return ret.toString(); } else if (data instanceof String) { return \ + data + \; } else { return data.toString(); } } public static void main(String []args) { //这是一组测试数据，应该没人来开我盒 print(gen(parse( {code:0,message:0,ttl:1,data:{isLogin:true,email_verified:1,face:http://i1.hdslb.com/bfs/face/97c86ea7c397f91b1a858737d06e73859d2d86f5.jpg,face_nft:0,level_info:{current_level:6,current_min:28800,current_exp:31365,next_exp:--},mid:39100231,mobile_verified:1,money:85,moral:70,official:{role:0,title:,desc:,type:-1},officialVerify:{type:-1,desc:},pendant:{pid:6053,name:星尘,image:http://i1.hdslb.com/bfs/garb/item/92d63a9014d4f0b2cefaef64f757162f750c7ad0.png,expire:0,image_enhance:http://i1.hdslb.com/bfs/garb/item/92d63a9014d4f0b2cefaef64f757162f750c7ad0.png,image_enhance_frame:},scores:0,uname:BuringStraw,vipDueDate:1668355200000,vipStatus:1,vipType:2,vip_pay_type:0,vip_theme_type:0,vip_label:{path:,text:年度大会员,label_theme:annual_vip,text_color:#FFFFFF,bg_style:1,bg_color:#FB7299,border_color:},vip_avatar_subscript:1,vip_nickname_color:#FB7299,vip:{type:2,status:1,due_date:1668355200000,vip_pay_type:0,theme_type:0,label:{path:,text:年度大会员,label_theme:annual_vip,text_color:#FFFFFF,bg_style:1,bg_color:#FB7299,border_color:},avatar_subscript:1,nickname_color:#FB7299,role:3,avatar_subscript_url:http://i0.hdslb.com/bfs/vip/icon_Certification_big_member_22_3x.png},wallet:{mid:39100231,bcoin_balance:1,coupon_balance:0,coupon_due_time:0},has_shop:false,shop_url:,allowance_count:0,answer_status:0,is_senior_member:1}}))); } }