使用Java解析JSON数据并提取特定字段的实现步骤(以提取mailNo为例)_Java

1. 背景介绍

1.1 json简介

json（javascript object notation）是一种轻量级的数据交换格式，易于人阅读和编写，同时也易于机器解析和生成。它基于javascript的一个子集，但独立于语言，几乎所有的编程语言都支持json格式的数据处理。

1.2 实际案例

假设我们有一个json数据，其中包含多个订单信息，每个订单都有一个唯一的mailno字段。我们的目标是从这个json数据中提取出所有的mailno字段，并将其存储在一个列表中。

2. 准备工作

2.1 环境搭建

为了解析json数据，我们需要使用一个java库。在本文中，我们将使用jackson库，这是一个非常流行的json处理库，功能强大且易于使用。

2.1.1 添加依赖

如果你使用maven构建项目，可以在pom.xml中添加以下依赖：

<dependency>
    <groupid>com.fasterxml.jackson.core</groupid>
    <artifactid>jackson-databind</artifactid>
    <version>2.13.3</version>
</dependency>

如果你使用gradle构建项目，可以在build.gradle中添加以下依赖：

implementation 'com.fasterxml.jackson.core:jackson-databind:2.13.3'

2.2 json数据结构

以下是我们将要处理的json数据的示例：

{
  "msg": "操作成功!",
  "code": "ok",
  "result": {
    "records": [
      {
        "merchantid": 0,
        "organid": 0,
        "creatorid": 0,
        "creatortruename": "",
        "creatorusername": "",
        "organname": "",
        "merchanttruename": "",
        "merchantusername": "",
        "consigneename": "突然的自我",
        "consigneephone": "153****7763",
        "consigneetelphone": "*******7763",
        "consigneecompany": "",
        "consigneeprovinceid": 0,
        "consigneeprovince": "四川省",
        "consigneecityid": 0,
        "consigneecity": "绵阳市",
        "consigneedistrictid": 0,
        "consigneedistrict": "涪城区",
        "consigneeaddress": "四川省****靓妍美妆",
        "sendprovinceid": 0,
        "sendprovince": "贵州省",
        "sendcityid": 0,
        "sendcity": "遵义市",
        "senddistrictid": 0,
        "senddistrict": "红花岗区",
        "sendername": "夜郎酒业",
        "sendercompany": "",
        "senderphone": "155****7773",
        "sendertelphone": "*******7773",
        "senderdetailaddress": "贵州省****中转仓库",
        "mailno": "sf3150804745040",
        "subwaybillnolist": [],
        "waybillstatus": 50,
        "printserialnumber": "",
        "printstatus": 0,
        "printnumber": 0,
        "ordervalueaddedvo": null,
        "addedservicecodes": [],
        "callflag": "",
        "consignment": "夜郎酱宏图纯粮食大曲坤沙酒酱香型白酒礼盒装53度500ml",
        "consignmentnumber": 2,
        "parcelweight": "2.0",
        "parcelweightunit": "2.0",
        "parcelquantity": 1,
        "meterageweightqty": "2.0",
        "realweightqty": "2.0",
        "orderno": "6938567762089547327|2kbwwcmnuwx2sz",
        "originalorderno": "",
        "signbackno": "",
        "remark": "",
        "ordercreatetime": "2025-01-10 15:29:41",
        "waybillcreatetime": "2025-01-10 15:29:41",
        "printtime": null,
        "isshowexcludefile": 0,
        "freight": "1000.0",
        "referencecost": "",
        "waybillnums": 1,
        "status": "",
        "exceptionflag": 0,
        "promisetime": "",
        "receivetime": "2025-01-10 16:16:55",
        "signtime": "2025-01-11 14:13:40",
        "latestrouteinfo": "您的快件已由本人签收，如有疑问请电联快递员【杨发斌，电话：13330891935】。您的体验对于我们至关重要，如果您对我们的服务有任何的想法和建议，请随时联系我们，我们一定用心倾听，全力改进，不辜负您的信任与支持。",
        "latestopcode": "80",
        "expressproductid": 0,
        "expressproductcode": "b1",
        "expressproductname": "电商标快",
        "expresspaymethod": 1,
        "expresspaymethodname": "寄付月结",
        "monthlycard": "052***6969",
        "ordertype": 1,
        "customfield1": "",
        "customfield2": "",
        "customfield3": "",
        "amount": "",
        "collectionamount": "",
        "collectingnumber": "",
        "oldcollectingmoney": "",
        "exceptioncode": "",
        "orderid": 0,
        "waybillid": 0,
        "isupdatewaybill": 0,
        "mergeordertype": 2,
        "isdraft": null,
        "failcause": "",
        "ordercrossbordergoodsvolist": [
          {
            "productcode": "",
            "productname": "夜郎酱宏图纯粮食大曲坤沙酒酱香型白酒礼盒装53度500ml",
            "price": 0.0,
            "currencycode": "",
            "currencyname": "",
            "unit": "",
            "productnumber": 2.0,
            "ordertype": 0,
            "countryoforigin": ""
          }
        ],
        "gangaotaiextvo": null,
        "swflag": 0,
        "sendstatus": 1,
        "sendstatusname": "获取成功",
        "expresscompanymerchantid": 0,
        "totallength": 41.0,
        "totalheight": 1.0,
        "totalwidth": 1.0,
        "addedvalueserviceinfo": {
          "insuredtype": 0,
          "insuredprice": null,
          "collectingmoney": null,
          "collectingmonthlycard": "",
          "signbackname": [],
          "signbackno": "",
          "signbackwaybillstatus": 0,
          "signbackordertype": [],
          "signbackroutelist": [],
          "issignback": 0,
          "signbackremark": "",
          "signbacknum": 0,
          "thirdsignback": 0,
          "thirdconsigneename": "",
          "thirdconsigneephone": "",
          "thirdconsigneetel": "",
          "thirdconsigneeprovince": "",
          "thirdconsigneecity": "",
          "thirdconsigneearea": "",
          "thirdconsigneeaddress": "",
          "thirdconsigneecompany": "",
          "takephotoback": [],
          "takephotonum": 0,
          "takephotobackremark": "",
          "timingsendinformtype": 0,
          "timingsendinformdate": "",
          "timingsendinformtime": "",
          "electronicback": 0,
          "secretkeyauthentication": "",
          "secretkeyauthenticationvalue": "",
          "woodenpackage": 0,
          "woodenpackageinfo": "",
          "readysend": 0,
          "woodenremovalnum": 0,
          "packagingservice": "",
          "packagingmaterialvos": [],
          "overweightservice": 0,
          "timinginsured": 0,
          "freshservice": 0,
          "homedeliveryext": [],
          "installationtype": 0,
          "installationcontent": [],
          "selfpickup": 0,
          "exhibitionservice": 0,
          "exhibitionexitservice": 0,
          "addedservicecodes": [],
          "customdeliverytime": ""
        },
        "signbackinfo": "",
        "signbacknum": "",
        "pickupappointtime": "",
        "consvaluecurrencycode": "",
        "exportdeclarationmethod": "",
        "customsbatchs": "",
        "taxaccount": "",
        "taxpaymenttype": "",
        "custreferenceno": "",
        "issignback": 0,
        "signbackremark": "",
        "canceltime": null
      },
      {
        "merchantid": 0,
        "organid": 0,
        "creatorid": 0,
        "creatortruename": "",
        "creatorusername": "",
        "organname": "",
        "merchanttruename": "",
        "merchantusername": "",
        "consigneename": "**",
        "consigneephone": "157*********2541",
        "consigneetelphone": "************2541",
        "consigneecompany": "",
        "consigneeprovinceid": 0,
        "consigneeprovince": "贵州省",
        "consigneecityid": 0,
        "consigneecity": "贵阳市",
        "consigneedistrictid": 0,
        "consigneedistrict": "修文县",
        "consigneeaddress": "贵州省****兽霸鞋店",
        "sendprovinceid": 0,
        "sendprovince": "贵州省",
        "sendcityid": 0,
        "sendcity": "遵义市",
        "senddistrictid": 0,
        "senddistrict": "红花岗区",
        "sendername": "小包",
        "sendercompany": "",
        "senderphone": "155****1949",
        "sendertelphone": "*******1949",
        "senderdetailaddress": "贵州省****菜鸟驿站",
        "mailno": "sf3150809345059",
        "subwaybillnolist": [],
        "waybillstatus": 50,
        "printserialnumber": "",
        "printstatus": 0,
        "printnumber": 0,
        "ordervalueaddedvo": null,
        "addedservicecodes": [],
        "callflag": "",
        "consignment": "2024男鞋男士舒适时尚百搭黑色41",
        "consignmentnumber": 1,
        "parcelweight": "2.5",
        "parcelweightunit": "2.5",
        "parcelquantity": 1,
        "meterageweightqty": "2.5",
        "realweightqty": "2.5",
        "orderno": "6938535195456968508|6780cc24dd560100",
        "originalorderno": "",
        "signbackno": "",
        "remark": "驴孤品42码",
        "ordercreatetime": "2025-01-10 15:28:59",
        "waybillcreatetime": "2025-01-10 15:28:59",
        "printtime": null,
        "isshowexcludefile": 0,
        "freight": "1000.0",
        "referencecost": "",
        "waybillnums": 1,
        "status": "",
        "exceptionflag": 0,
        "promisetime": "",
        "receivetime": "2025-01-10 18:42:03",
        "signtime": "2025-01-11 09:40:32",
        "latestrouteinfo": "您的快件已由本人签收，如有疑问请电联快递员【王昭发，电话：18143512989】。您的体验对于我们至关重要，如果您对我们的服务有任何的想法和建议，请随时联系我们，我们一定用心倾听，全力改进，不辜负您的信任与支持。",
        "latestopcode": "80",
        "expressproductid": 0,
        "expressproductcode": "b1",
        "expressproductname": "电商标快",
        "expresspaymethod": 1,
        "expresspaymethodname": "寄付月结",
        "monthlycard": "052***6969",
        "ordertype": 1,
        "customfield1": "",
        "customfield2": "",
        "customfield3": "",
        "amount": "",
        "collectionamount": "",
        "collectingnumber": "",
        "oldcollectingmoney": "",
        "exceptioncode": "",
        "orderid": 0,
        "waybillid": 0,
        "isupdatewaybill": 0,
        "mergeordertype": 2,
        "isdraft": null,
        "failcause": "",
        "ordercrossbordergoodsvolist": [
          {
            "productcode": "",
            "productname": "2024男鞋男士舒适时尚百搭黑色41",
            "price": 0.0,
            "currencycode": "",
            "currencyname": "",
            "unit": "",
            "productnumber": 1.0,
            "ordertype": 0,
            "countryoforigin": ""
          }
        ],
        "gangaotaiextvo": null,
        "swflag": 0,
        "sendstatus": 1,
        "sendstatusname": "获取成功",
        "expresscompanymerchantid": 0,
        "totallength": 0.0,
        "totalheight": 0.0,
        "totalwidth": 0.0,
        "addedvalueserviceinfo": {
          "insuredtype": 0,
          "insuredprice": null,
          "collectingmoney": null,
          "collectingmonthlycard": "",
          "signbackname": [],
          "signbackno": "",
          "signbackwaybillstatus": 0,
          "signbackordertype": [],
          "signbackroutelist": [],
          "issignback": 0,
          "signbackremark": "",
          "signbacknum": 0,
          "thirdsignback": 0,
          "thirdconsigneename": "",
          "thirdconsigneephone": "",
          "thirdconsigneetel": "",
          "thirdconsigneeprovince": "",
          "thirdconsigneecity": "",
          "thirdconsigneearea": "",
          "thirdconsigneeaddress": "",
          "thirdconsigneecompany": "",
          "takephotoback": [],
          "takephotonum": 0,
          "takephotobackremark": "",
          "timingsendinformtype": 0,
          "timingsendinformdate": "",
          "timingsendinformtime": "",
          "electronicback": 0,
          "secretkeyauthentication": "",
          "secretkeyauthenticationvalue": "",
          "woodenpackage": 0,
          "woodenpackageinfo": "",
          "readysend": 0,
          "woodenremovalnum": 0,
          "packagingservice": "",
          "packagingmaterialvos": [],
          "overweightservice": 0,
          "timinginsured": 0,
          "freshservice": 0,
          "homedeliveryext": [],
          "installationtype": 0,
          "installationcontent": [],
          "selfpickup": 0,
          "exhibitionservice": 0,
          "exhibitionexitservice": 0,
          "addedservicecodes": [],
          "customdeliverytime": ""
        },
        "signbackinfo": "",
        "signbacknum": "",
        "pickupappointtime": "",
        "consvaluecurrencycode": "",
        "exportdeclarationmethod": "",
        "customsbatchs": "",
        "taxaccount": "",
        "taxpaymenttype": "",
        "custreferenceno": "",
        "issignback": 0,
        "signbackremark": "",
        "canceltime": null
      }
    ],
    "total": 5167,
    "size": 1000,
    "current": 1,
    "orders": [],
    "searchcount": true,
    "pages": 6
  }
}

3. 实现步骤

3.1 创建java类

我们将创建一个名为mailnoextractor的java类，用于解析json数据并提取mailno字段。

import com.fasterxml.jackson.databind.jsonnode;
import com.fasterxml.jackson.databind.objectmapper;

import java.io.ioexception;
import java.util.arraylist;
import java.util.list;

public class mailnoextractor {

    public static list<string> extractmailnos(string json) throws ioexception {
        objectmapper objectmapper = new objectmapper();
        jsonnode rootnode = objectmapper.readtree(json);
        jsonnode recordsnode = rootnode.path("result").path("records");

        list<string> mailnos = new arraylist<>();

        for (jsonnode record : recordsnode) {
            string mailno = record.path("mailno").astext();
            mailnos.add(mailno);
        }

        return mailnos;
    }

    public static void main(string[] args) {
        string json = "{\"msg\":\"操作成功!\",\"code\":\"ok\",\"result\":{\"records\":[{\"merchantid\":0,\"organid\":0,\"creatorid\":0,\"creatortruename\":\"\",\"creatorusername\":\"\",\"organname\":\"\",\"merchanttruename\":\"\",\"merchantusername\":\"\",\"consigneename\":\"突然的自我\",\"consigneephone\":\"153****7763\",\"consigneetelphone\":\"*******7763\",\"consigneecompany\":\"\",\"consigneeprovinceid\":0,\"consigneeprovince\":\"四川省\",\"consigneecityid\":0,\"consigneecity\":\"绵阳市\",\"consigneedistrictid\":0,\"consigneedistrict\":\"涪城区\",\"consigneeaddress\":\"四川省****靓妍美妆\",\"sendprovinceid\":0,\"sendprovince\":\"贵州省\",\"sendcityid\":0,\"sendcity\":\"遵义市\",\"senddistrictid\":0,\"senddistrict\":\"红花岗区\",\"sendername\":\"夜郎酒业\",\"sendercompany\":\"\",\"senderphone\":\"155****7773\",\"sendertelphone\":\"*******7773\",\"senderdetailaddress\":\"贵州省****中转仓库\",\"mailno\":\"sf3150804745040\",\"subwaybillnolist\":[],\"waybillstatus\":50,\"printserialnumber\":\"\",\"printstatus\":0,\"printnumber\":0,\"ordervalueaddedvo\":null,\"addedservicecodes\":[],\"callflag\":\"\",\"consignment\":\"夜郎酱宏图纯粮食大曲坤沙酒酱香型白酒礼盒装53度500ml\",\"consignmentnumber\":2,\"parcelweight\":\"2.0\",\"parcelweightunit\":\"2.0\",\"parcelquantity\":1,\"meterageweightqty\":\"2.0\",\"realweightqty\":\"2.0\",\"orderno\":\"6938567762089547327|2kbwwcmnuwx2sz\",\"originalorderno\":\"\",\"signbackno\":\"\",\"remark\":\"\",\"ordercreatetime\":\"2025-01-10 15:29:41\",\"waybillcreatetime\":\"2025-01-10 15:29:41\",\"printtime\":null,\"isshowexcludefile\":0,\"freight\":\"1000.0\",\"referencecost\":\"\",\"waybillnums\":1,\"status\":\"\",\"exceptionflag\":0,\"promisetime\":\"\",\"receivetime\":\"2025-01-10 16:16:55\",\"signtime\":\"2025-01-11 14:13:40\",\"latestrouteinfo\":\"您的快件已由本人签收，如有疑问请电联快递员【杨发斌，电话：13330891935】。您的体验对于我们至关重要，如果您对我们的服务有任何的想法和建议，请随时联系我们，我们一定用心倾听，全力改进，不辜负您的信任与支持。\",\"latestopcode\":\"80\",\"expressproductid\":0,\"expressproductcode\":\"b1\",\"expressproductname\":\"电商标快\",\"expresspaymethod\":1,\"expresspaymethodname\":\"寄付月结\",\"monthlycard\":\"052***6969\",\"ordertype\":1,\"customfield1\":\"\",\"customfield2\":\"\",\"customfield3\":\"\",\"amount\":\"\",\"collectionamount\":\"\",\"collectingnumber\":\"\",\"oldcollectingmoney\":\"\",\"exceptioncode\":\"\",\"orderid\":0,\"waybillid\":0,\"isupdatewaybill\":0,\"mergeordertype\":2,\"isdraft\":null,\"failcause\":\"\",\"ordercrossbordergoodsvolist\":[{\"productcode\":\"\",\"productname\":\"夜郎酱宏图纯粮食大曲坤沙酒酱香型白酒礼盒装53度500ml\",\"price\":0.0,\"currencycode\":\"\",\"currencyname\":\"\",\"unit\":\"\",\"productnumber\":2.0,\"ordertype\":0,\"countryoforigin\":\"\"}],\"gangaotaiextvo\":null,\"swflag\":0,\"sendstatus\":1,\"sendstatusname\":\"获取成功\",\"expresscompanymerchantid\":0,\"totallength\":41.0,\"totalheight\":1.0,\"totalwidth\":1.0,\"addedvalueserviceinfo\":{\"insuredtype\":0,\"insuredprice\":null,\"collectingmoney\":null,\"collectingmonthlycard\":\"\",\"signbackname\":[],\"signbackno\":\"\",\"signbackwaybillstatus\":0,\"signbackordertype\":[],\"signbackroutelist\":[],\"issignback\":0,\"signbackremark\":\"\",\"signbacknum\":0,\"thirdsignback\":0,\"thirdconsigneename\":\"\",\"thirdconsigneephone\":\"\",\"thirdconsigneetel\":\"\",\"thirdconsigneeprovince\":\"\",\"thirdconsigneecity\":\"\",\"thirdconsigneearea\":\"\",\"thirdconsigneeaddress\":\"\",\"thirdconsigneecompany\":\"\",\"takephotoback\":[],\"takephotonum\":0,\"takephotobackremark\":\"\",\"timingsendinformtype\":0,\"timingsendinformdate\":\"\",\"timingsendinformtime\":\"\",\"electronicback\":0,\"secretkeyauthentication\":\"\",\"secretkeyauthenticationvalue\":\"\",\"woodenpackage\":0,\"woodenpackageinfo\":\"\",\"readysend\":0,\"woodenremovalnum\":0,\"packagingservice\":\"\",\"packagingmaterialvos\":[],\"overweightservice\":0,\"timinginsured\":0,\"freshservice\":0,\"homedeliveryext\":[],\"installationtype\":0,\"installationcontent\":[],\"selfpickup\":0,\"exhibitionservice\":0,\"exhibitionexitservice\":0,\"addedservicecodes\":[],\"customdeliverytime\":\"\"},\"signbackinfo\":\"\",\"signbacknum\":\"\",\"pickupappointtime\":\"\",\"consvaluecurrencycode\":\"\",\"exportdeclarationmethod\":\"\",\"customsbatchs\":\"\",\"taxaccount\":\"\",\"taxpaymenttype\":\"\",\"custreferenceno\":\"\",\"issignback\":0,\"signbackremark\":\"\",\"canceltime\":null},{\"merchantid\":0,\"organid\":0,\"creatorid\":0,\"creatortruename\":\"\",\"creatorusername\":\"\",\"organname\":\"\",\"merchanttruename\":\"\",\"merchantusername\":\"\",\"consigneename\":\"**\",\"consigneephone\":\"157*********2541\",\"consigneetelphone\":\"************2541\",\"consigneecompany\":\"\",\"consigneeprovinceid\":0,\"consigneeprovince\":\"贵州省\",\"consigneecityid\":0,\"consigneecity\":\"贵阳市\",\"consigneedistrictid\":0,\"consigneedistrict\":\"修文县\",\"consigneeaddress\":\"贵州省****兽霸鞋店\",\"sendprovinceid\":0,\"sendprovince\":\"贵州省\",\"sendcityid\":0,\"sendcity\":\"遵义市\",\"senddistrictid\":0,\"senddistrict\":\"红花岗区\",\"sendername\":\"小包\",\"sendercompany\":\"\",\"senderphone\":\"155****1949\",\"sendertelphone\":\"*******1949\",\"senderdetailaddress\":\"贵州省****菜鸟驿站\",\"mailno\":\"sf3150809345059\",\"subwaybillnolist\":[],\"waybillstatus\":50,\"printserialnumber\":\"\",\"printstatus\":0,\"printnumber\":0,\"ordervalueaddedvo\":null,\"addedservicecodes\":[],\"callflag\":\"\",\"consignment\":\"2024男鞋男士舒适时尚百搭黑色41\",\"consignmentnumber\":1,\"parcelweight\":\"2.5\",\"parcelweightunit\":\"2.5\",\"parcelquantity\":1,\"meterageweightqty\":\"2.5\",\"realweightqty\":\"2.5\",\"orderno\":\"6938535195456968508|6780cc24dd560100\",\"originalorderno\":\"\",\"signbackno\":\"\",\"remark\":\"驴孤品42码\",\"ordercreatetime\":\"2025-01-10 15:28:59\",\"waybillcreatetime\":\"2025-01-10 15:28:59\",\"printtime\":null,\"isshowexcludefile\":0,\"freight\":\"1000.0\",\"referencecost\":\"\",\"waybillnums\":1,\"status\":\"\",\"exceptionflag\":0,\"promisetime\":\"\",\"receivetime\":\"2025-01-10 18:42:03\",\"signtime\":\"2025-01-11 09:40:32\",\"latestrouteinfo\":\"您的快件已由本人签收，如有疑问请电联快递员【王昭发，电话：18143512989】。您的体验对于我们至关重要，如果您对我们的服务有任何的想法和建议，请随时联系我们，我们一定用心倾听，全力改进，不辜负您的信任与支持。\",\"latestopcode\":\"80\",\"expressproductid\":0,\"expressproductcode\":\"b1\",\"expressproductname\":\"电商标快\",\"expresspaymethod\":1,\"expresspaymethodname\":\"寄付月结\",\"monthlycard\":\"052***6969\",\"ordertype\":1,\"customfield1\":\"\",\"customfield2\":\"\",\"customfield3\":\"\",\"amount\":\"\",\"collectionamount\":\"\",\"collectingnumber\":\"\",\"oldcollectingmoney\":\"\",\"exceptioncode\":\"\",\"orderid\":0,\"waybillid\":0,\"isupdatewaybill\":0,\"mergeordertype\":2,\"isdraft\":null,\"failcause\":\"\",\"ordercrossbordergoodsvolist\":[{\"productcode\":\"\",\"productname\":\"2024男鞋男士舒适时尚百搭黑色41\",\"price\":0.0,\"currencycode\":\"\",\"currencyname\":\"\",\"unit\":\"\",\"productnumber\":1.0,\"ordertype\":0,\"countryoforigin\":\"\"}],\"gangaotaiextvo\":null,\"swflag\":0,\"sendstatus\":1,\"sendstatusname\":\"获取成功\",\"expresscompanymerchantid\":0,\"totallength\":0.0,\"totalheight\":0.0,\"totalwidth\":0.0,\"addedvalueserviceinfo\":{\"insuredtype\":0,\"insuredprice\":null,\"collectingmoney\":null,\"collectingmonthlycard\":\"\",\"signbackname\":[],\"signbackno\":\"\",\"signbackwaybillstatus\":0,\"signbackordertype\":[],\"signbackroutelist\":[],\"issignback\":0,\"signbackremark\":\"\",\"signbacknum\":0,\"thirdsignback\":0,\"thirdconsigneename\":\"\",\"thirdconsigneephone\":\"\",\"thirdconsigneetel\":\"\",\"thirdconsigneeprovince\":\"\",\"thirdconsigneecity\":\"\",\"thirdconsigneearea\":\"\",\"thirdconsigneeaddress\":\"\",\"thirdconsigneecompany\":\"\",\"takephotoback\":[],\"takephotonum\":0,\"takephotobackremark\":\"\",\"timingsendinformtype\":0,\"timingsendinformdate\":\"\",\"timingsendinformtime\":\"\",\"electronicback\":0,\"secretkeyauthentication\":\"\",\"secretkeyauthenticationvalue\":\"\",\"woodenpackage\":0,\"woodenpackageinfo\":\"\",\"readysend\":0,\"woodenremovalnum\":0,\"packagingservice\":\"\",\"packagingmaterialvos\":[],\"overweightservice\":0,\"timinginsured\":0,\"freshservice\":0,\"homedeliveryext\":[],\"installationtype\":0,\"installationcontent\":[],\"selfpickup\":0,\"exhibitionservice\":0,\"exhibitionexitservice\":0,\"addedservicecodes\":[],\"customdeliverytime\":\"\"},\"signbackinfo\":\"\",\"signbacknum\":\"\",\"pickupappointtime\":\"\",\"consvaluecurrencycode\":\"\",\"exportdeclarationmethod\":\"\",\"customsbatchs\":\"\",\"taxaccount\":\"\",\"taxpaymenttype\":\"\",\"custreferenceno\":\"\",\"issignback\":0,\"signbackremark\":\"\",\"canceltime\":null}],\"total\":5167,\"size\":1000,\"current\":1,\"orders\":[],\"searchcount\":true,\"pages\":6}}";

        try {
            list<string> mailnos = extractmailnos(json);
            for (string mailno : mailnos) {
                system.out.println(mailno);
            }
        } catch (ioexception e) {
            e.printstacktrace();
        }
    }
}

3.2 代码解析

3.2.1 extractmailnos 方法

功能：该方法接收一个json字符串作为输入，使用jackson库解析json，并提取出所有mailno字段的值，返回一个包含所有mailno的列表。
步骤：
1. 使用objectmapper将json字符串解析为jsonnode对象。
2. 通过path方法获取result节点下的records数组。
3. 遍历records数组，提取每个记录中的mailno字段，并将其添加到列表中。