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  • json字符串转java对象

      今天遇到一个问题,前端ajax获取到一个javaBean对象,好多方法发ajax请求需要把这个对象再传到后端,后端再根据这个对象进行操作(之前计划传递id,但发现传递id的话,后端多个方法都需要根据id查询数据库获取这个javaBean,因此就修改为直接传递javaBean),这就涉及到了json字符串与java对象转化,特此记录一下。大概有两种方式比较方便:

      一、Gson的方式

      二、json-lib的方式

    1.前端jquery把对象转为json字符串

    "dclLine":JSON.stringify(selectedDclLine);

     2.后端Gson转java对象

    /**
         * 
         * @return
         */
        @RequestMapping("/getDayCharge")
        @ResponseBody
        public List<Object> getDayCharge(HttpServletRequest request){
            Map<String, Object> params = new HashMap<String, Object>(16);
            //前端左侧树回路信息
            String dclLineStr = request.getParameter("dclLine");
            Gson gson = new Gson();
            //Gson转换json字符串到java对象
            DclLine dclLine = gson.fromJson(dclLineStr, DclLine.class);
            params.put("dclLine", dclLine);
            List<Object> result = runningReportsService.getDayCharge(params);
            return result;
        }

    转换过程报错:

    threw exception [Request processing failed; nested exception is

    com.google.gson.JsonSyntaxException: java.lang.NumberFormatException: empty String] with root cause

    比较了下json数据与javaBean的类型发现javaBean定义的类型是Double,json数据是"",类型转换报错了

    把javaBean中的Double类型改为String类型后,转换成功

    但是改javaBean类型涉及改动太大,

    在不改变javaBean类型的情况下,试着用json-lib转换了下,发现json-lib转换不报错

    3.后端使用json-lib把json字符串转为java对象

    /**
         * 日用电负荷
         * @return
         */
        @RequestMapping("/getDayCharge")
        @ResponseBody
        public List<Object> getDayCharge(HttpServletRequest request){
            Map<String, Object> params = new HashMap<String, Object>(16);
            //前端左侧树回路信息
            String dclLineStr = request.getParameter("dclLine");
            JSONObject json = JSONObject.fromObject(dclLineStr);
            DclLine dclLine = (DclLine) JSONObject.toBean(json, DclLine.class);
            params.put("dclLine", dclLine);
            List<Object> result = runningReportsService.getDayCharge(params);
            return result;
        }

    4.pom配置:

    <dependency>
                <groupId>org.apache.commons</groupId>
                <artifactId>commons-lang3</artifactId>
                <version>3.7</version>
            </dependency>
            <dependency>
                <groupId>com.google.code.gson</groupId>
                <artifactId>gson</artifactId>
            </dependency>
            <dependency>
                <groupId>net.sf.json-lib</groupId>
                <artifactId>json-lib</artifactId>
                <version>2.2.3</version>
                <classifier>jdk15</classifier>
            </dependency>

    5.总结:

      Gson:

    String dclLineStr = request.getParameter("dclLine");//获取到json字符串
    Gson gson = new Gson();//com.google.gson.Gson
    //Gson转换json字符串到java对象
    DclLine dclLine = gson.fromJson(dclLineStr, DclLine.class);

      json-lib:

    String dclLineStr = request.getParameter("dclLine");//获取到json字符串
    JSONObject json = JSONObject.fromObject(dclLineStr);//net.sf.json.JSONObject
    DclLine dclLine = (DclLine) JSONObject.toBean(json, DclLine.class);
    
    

    6.参考博客:

    https://blog.csdn.net/chenbin520/article/details/8776915

    https://www.cnblogs.com/echo-ling/p/8097698.html

    https://blog.csdn.net/a77979744/article/details/53695621

    https://blog.csdn.net/tanga842428/article/details/54864485

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  • 原文地址:https://www.cnblogs.com/ph7seven/p/9264219.html
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