判断一个字符串是否是合法的JSON字符串

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

isJSONValid()	16510 ms	16161 ms	2018 ms
isJSONValid2()	17946 ms	17486 ms	2698 ms
isJSONValid3()	20648 ms	20208 ms	2508 ms

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