判断一个字符串是否是合法的JSON字符串

谁借莪１个温暖的怀抱￠ 2022-05-23 06:51 330阅读 0赞

## 判断一个字符串是否是合法的JSON字符串 ##

`pom.xml`

<dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>1.2.31</version>
            </dependency>
            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-databind</artifactId>
                <version>2.7.0</version>
            </dependency>
            <dependency>
                <groupId>com.google.code.gson</groupId>
                <artifactId>gson</artifactId>
                <version>2.5</version>
            </dependency>

### `java`代码 ###

/**
         * 暴力解析:Alibaba fastjson
         * @param test
         * @return
         */
        public final static boolean isJSONValid(String test) {
            try {
                JSONObject.parseObject(test);
            } catch (JSONException ex) {
                try {
                    JSONObject.parseArray(test);
                } catch (JSONException ex1) {
                    return false;
                }
            }
            return true;
        }
    
        /**
         *  Jackson library
         * @param jsonInString
         * @return
         */
        public final static boolean isJSONValid2(String jsonInString ) {
            try {
                final ObjectMapper mapper = new ObjectMapper();
                mapper.readTree(jsonInString);
                return true;
            } catch (IOException e) {
                return false;
            }
        }
    
        /**
         * Google Gson
         * @param jsonInString
         * @return
         */
        public final static boolean isJSONValid3(String jsonInString) {
            try {
                gson.fromJson(jsonInString, Object.class);
                return true;
            } catch(JsonSyntaxException ex) {
                return false;
            }
        }

### 测试结果 ###

<table style="border-spacing:0px;width:852px;text-align:center;color:rgb(51,51,51);font-family:'-apple-system', 'SF UI Text', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'WenQuanYi Micro Hei', sans-serif, SimHei, SimSun;font-size:14px;background-color:rgb(255,255,255);"> 
 <thead> 
  <tr> 
   <th style="margin:0px;vertical-align:middle;"><code style="font-size:14px;line-height:22px;padding:4px 2px 0px;">isJSONValid()</code></th> 
   <th style="margin:0px;vertical-align:middle;">16510 ms</th> 
   <th style="margin:0px;vertical-align:middle;">16161 ms</th> 
   <th style="margin:0px;vertical-align:middle;">2018 ms</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="margin:0px;vertical-align:middle;"><code style="font-size:14px;line-height:22px;padding:4px 2px 0px;">isJSONValid2()</code></td> 
   <td style="margin:0px;vertical-align:middle;">17946 ms</td> 
   <td style="margin:0px;vertical-align:middle;">17486 ms</td> 
   <td style="margin:0px;vertical-align:middle;">2698 ms</td> 
  </tr> 
  <tr> 
   <td style="margin:0px;vertical-align:middle;"><code style="font-size:14px;line-height:22px;padding:4px 2px 0px;">isJSONValid3()</code></td> 
   <td style="margin:0px;vertical-align:middle;">20648 ms</td> 
   <td style="margin:0px;vertical-align:middle;">20208 ms</td> 
   <td style="margin:0px;vertical-align:middle;">2508 ms</td> 
  </tr> 
 </tbody> 
</table>

### 区别 ###

/**
         * 是否是合法的Gson字符串
         * @param targetStr
         * @return
         */
        private static boolean isGoodGson(String targetStr,Class clazz) {
            if(StringUtils.isBlank(targetStr)){
                return false;
            }
            try {
                new Gson().fromJson(targetStr,clazz);
                return true;
            } catch(JsonSyntaxException ex) {
                LOG.error("targetStr={} is not a valid {}",targetStr,clazz.getName(),ex);
                return false;
            }
        }
    
        /**
         * 是否是合法的JsonArray (alibaba 认为前1种不是JSON串)
         * 例如：[{a:b}]  [{'a':'b'}]  [{"a":"b"}]
         * @param targetStr
         * @return
         */
        public static boolean isJsonArray(String targetStr){
          return isGoodGson(targetStr,JsonArray.class);
        }
    
        /**
         * 是否是合法的JsonObject(alibaba 认为前1种不是JSON串)
         * 例如：{a:b} {'a':'b'} {"a":"b"}
         * @param targetStr
         * @return
         */
        public static boolean isJsonObject(String targetStr){
            return isGoodGson(targetStr,JsonObject.class);
        }

### 结论 ###

性能相差不太多，推荐方式二`isJSONValid2()`

### 参考 ###

[stackoverflow][]

[stackoverflow]: https://stackoverflow.com/questions/10174898/how-to-check-whether-a-given-string-is-valid-json-in-java