java对象转json格式-白红宇

java对象转json格式

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发布时间：2019-06-22

本文共 3938 字，大约阅读时间需要 13 分钟。

1 package com;  2   3 import java.util.ArrayList;  4 import java.util.HashMap;  5 import java.util.List;  6 import java.util.Map;  7 import java.util.Set;  8   9 import org.junit.Test; 10  11 public class TestJson { 12      13     static String string2Json(String s) { 14         StringBuilder sb = new StringBuilder(s.length() + 20); 15         sb.append('\"'); 16         for (int i = 0; i < s.length(); i++) { 17             char c = s.charAt(i); 18             switch (c) { 19             case '\"': 20                 sb.append("\\\""); 21                 break; 22             case '\\': 23                 sb.append("\\\\"); 24                 break; 25             case '/': 26                 sb.append("\\/"); 27                 break; 28             case '\b': 29                 sb.append("\\b"); 30                 break; 31             case '\f': 32                 sb.append("\\f"); 33                 break; 34             case '\n': 35                 sb.append("\\n"); 36                 break; 37             case '\r': 38                 sb.append("\\r"); 39                 break; 40             case '\t': 41                 sb.append("\\t"); 42                 break; 43             default: 44                 sb.append(c); 45             } 46         } 47         sb.append('\"'); 48         return sb.toString(); 49     } 50  51     static String number2Json(Number number) { 52         return number.toString(); 53     } 54  55     static String boolean2Json(Boolean bool) { 56         return bool.toString(); 57     } 58  59     static String array2Json(Object[] array) { 60         if (array.length == 0) 61             return "[]"; 62         StringBuilder sb = new StringBuilder(array.length << 4); 63         sb.append('['); 64         for (Object o : array) { 65             sb.append(toJson(o)); 66             sb.append(','); 67         } 68         // 将最后添加的 ',' 变为 ']': 69         sb.setCharAt(sb.length() - 1, ']'); 70         return sb.toString(); 71     } 72  73     static String map2Json(Map
     
       map) { 74         if (map.isEmpty()) 75             return "{}"; 76         StringBuilder sb = new StringBuilder(map.size() << 4); 77         sb.append('{'); 78         Set
      
        keys = map.keySet(); 79         for (String key : keys) { 80             Object value = map.get(key); 81             sb.append('\"'); 82             sb.append(key); 83             sb.append('\"'); 84             sb.append(':'); 85             sb.append(toJson(value)); 86             sb.append(','); 87         } 88         // 将最后的 ',' 变为 '}': 89         sb.setCharAt(sb.length() - 1, '}'); 90         return sb.toString(); 91     } 92  93     public static String toJson(Object o) { 94         if (o == null) 95             return "null"; 96         if (o instanceof String) 97             return string2Json((String) o); 98         if (o instanceof Boolean) 99             return boolean2Json((Boolean) o);100         if (o instanceof Number)101             return number2Json((Number) o);102         if (o instanceof Map)103             return map2Json((Map
       
        ) o);104         if (o instanceof Object[])105             return array2Json((Object[]) o);106         throw new RuntimeException("Unsupported type: "107                 + o.getClass().getName());108     }109 110     @Test(expected = StackOverflowError.class)111     public void testRecurrsiveMap2Json() {112         Map
        
          map = new HashMap
         
          ();113         map.put("key", "value");114         map.put("key2", 2);115         List
          
            array = new ArrayList
           
            ();116 array.add(1); 117 array.add(2);118 map.put("array", array);119 String json = TestJson.toJson(map);120 System.out.println(json);121 }122 }