json转换成java对象示例

json字符串转Java对象有很多工具可以使用，下面的小例子只是我练手的

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.jfinal.kit.JsonKit;

public class JsonToJavaObject {
 public static void main(String[] args) {
  Object o1 = parse("{\"aa\":123,cc:[1,2,3,4,{cd:f,bb:234}]}");
  System.out.println(JsonKit.toJson(o1));
 }
 public static Object parse(String json){
  if(json == null){
   return null;
  }
  json = json.trim();
  if("string".equals(typeof(json))){
   return json;
  }

  if("map".equals(typeof(json))){
   return parseMap(json);
  }

  if("list".equals(typeof(json))){
   return parseList(json);
  }

  return null;
 }

 public static Map parseMap(String json){
  if(!"map".equals(typeof(json))){
   throw new RuntimeException("json 不是Map类型");
  }
  Map r = new HashMap();
  parseToken(r,json,null);
  return r;
 }

 public static List parseList(String json){
  if(!"list".equals(typeof(json))){
   throw new RuntimeException("json 不是list类型");
  }
  List r = new ArrayList();
  parseToken(null, json, r);
  return r;
 }

 public static String typeof(String json){
  if(json.length() == 0)return "string";
  if('{'==json.charAt(0)){
   if('}' == json.charAt(json.length()-1)){
    return "map";
   }
  }

  if('['==json.charAt(0)){
   if(']'==json.charAt(json.length()-1)){
    return "list";
   }
  }

  return "string";
 }
 private static void parseToken(Map r, String json,List r2) {
  boolean syh = true; //双引号
  boolean dyh = true;//单引号
  boolean dkh = true;//大括号
  boolean zkh = true;//中括号
  boolean isKey = true;
  StringBuffer key = new StringBuffer();
  StringBuffer value = new StringBuffer();
  for(int i=1;i<json.length()-1;i++){
   char item = json.charAt(i);
   if(dyh&&syh&&zkh)if(&#39;{&#39; == item || &#39;}&#39; == item){
    dkh = !dkh;
   }
   if(dyh&&syh&&dkh)if(&#39;[&#39; == item || &#39;]&#39; == item){
    zkh = !zkh;
   }
   if(dyh&&dkh&&zkh)if(&#39;"&#39; == item){
    syh = !syh;
    continue;
   }
   if(syh&&dkh&&zkh)if(syh)if(&#39;\&#39;&#39; == item){
    dyh = !dyh;
    continue;
   }
   if(dyh&&syh&&dkh&&zkh)if(r2==null)if(dyh)if(&#39;:&#39;==item){
    isKey = false;
    continue;
   }
   if(dyh&&syh&&dkh&&zkh)if(&#39;,&#39;==item){
    isKey = true;
    if(r != null){
     r.put(key.toString(), parse(value.toString()));
    }
    if(r2 != null){
     r2.add(parse(key.toString()));
    }
    key = new StringBuffer();
    value = new StringBuffer();
    continue;
   }
   if(isKey){
    key.append(item);
   }else{
    value.append(item);
   }
  }
  if(!key.toString().trim().equals("")){
   if(r != null){
    if(value.toString().trim().equals(""))throw new RuntimeException("json 格式错误");
    r.put(key.toString(), parse(value.toString()));
   }
   if(r2 != null){
    r2.add(parse(key.toString()));
   }
  }

 }
}

控制台输出

{"aa":"123","cc":["1","2","3","4",{"bb":"234","cd":"f"}]}

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