从嵌套的 java 对象中获取字段的所有值

Question

我有一个 Java 对象，如下所示。我需要遍历这个嵌套对象并获取一个字段的所有值。下面的java对象的前'时间'。

如果是列表，我可以使用 java 8 过滤器。但是如何在对象上执行此操作？

另外，我需要以通用的方式来做。

    {

  "dataType": "Node",

  "totalCount": 1,

  "count": 1,

  "startIndex": 0,

  "data": [

    {

      "id": "a4b7a825f67930965747445709011120-Node-6f638b5e71debd5807ec7fb73b9dc20b",

      "refObjects": {},

      "tid": "a4b7a825f67930965747445709011120",

      "creationDate": "2018-09-20T06:55:36.742+0000",

      "lmd": "2018-09-20T06:55:36.799+0000",

      "exceptions": [

        {

          "name": "projectedInventory",

          "status": "Stockout",

          "severity": "High",

          "time": "2018-09-20T00:00:00.000+0000"

        }

      ],

      "criticalities": [

        "HotItem"

      ],

      "customerName": "Best Buys",

      "supplierName": "Samsung",

      "customerItemName": "Ship to item name",

      "nodeType": "inventory",

      "supplierItemName": "Ship from item name",

      "shipToSiteName": "IT06",

      "shipFromSiteName": "IT07",

      "status": "Active",

      "lob": "HC",

      "processType": "demandSupply",

      "measures": {

        "maxInventory": [

          {

            "refObjects": {},

            "time": "2018-09-26T00:00:00.000+0000",

            "quantity": 0

          },

          {

            "refObjects": {},

            "time": "2018-09-27T00:00:00.000+0000",

            "quantity": 0

          }

        ],

        "maxDistribution": [

          {

            "refObjects": {},

            "time": "2018-09-28T00:00:00.000+0000",

            "quantity": 0

          },

          {

            "refObjects": {},

            "time": "2018-09-29T00:00:00.000+0000",

            "quantity": 0

          },

现在我想检索“时间”字段的所有值并将其保存在列表中。这样做的最佳方法是什么？

输出应该是这样的：

{

  "time": [

    "2018-12-30T00:00:00.000+0000",

    "2018-08-24T12:00:00.000+0000"

  ]

}

Answer 1

您也可以使用反射，但 apache-commons 使它更容易。我在下面编写的方法有两个参数，一个是您的 POJO 对象，另一个是空列表。"time"即使存在嵌套对象，它也会通过填充输入对象中的所有属性值来返回相同的列表。在else if我添加了一个条件，我正在检查 className 是否包含“com.your.packageName”，这是因为在这里我假设您的所有 POJO（可以嵌套在您的输入对象中）都存储在一个包中“ com.your.packageName”，因此如果您将所有 POJO 存储在一个位置，那么您可以将其替换为您的包名称。为 common-beanutils 添加以下依赖项。&nbsp;<groupId>commons-beanutils</groupId>&nbsp;<artifactId>commons-beanutils</artifactId>&nbsp;<version>1.9.2</version>&nbsp; &nbsp; import org.apache.commons.beanutils.BeanMap;&nbsp; &nbsp; import org.apache.commons.beanutils.PropertyUtilsBean;&nbsp; &nbsp; &nbsp;private static List<String> getPropertyValue(Object myObj, List<String> timeList) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; final BeanMap beanMap = new BeanMap(myObj);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; PropertyUtilsBean pp = new PropertyUtilsBean();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; beanMap.keySet().stream().forEach(x -> {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; try {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;String propertyName= ""+x;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;//GET THE CLASS TYPE OF PROPERTY&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;String proprtyTypeClassName=""+pp.getPropertyType((Object)myObj,propertyName);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println(propertyName+"&nbsp; "+proprtyTypeClassName);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;if(propertyName.equals("time")) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;//GET THE VALUE OF A propertyName FROM object myObj&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;timeList.add((String)pp.getProperty(myObj, propertyName));&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;else if(proprtyTypeClassName.contains("com.your.packageName")) {//recursively call same method if value is another POJO object nested inside&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;getPropertyValue(pp.getProperty(myObj, propertyName),timeList);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } catch (IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; e.printStackTrace();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; });&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return timeList;&nbsp; &nbsp; &nbsp; &nbsp; }如果您有任何疑问，请告诉我。

Answer 2

非常感谢。我正在尝试一些解决方案，并在下面找到了一个。如果这看起来也正确，请告诉我：package com.company.dct.exec.lib.relationships.util;import com.fasterxml.jackson.annotation.JsonInclude;import com.fasterxml.jackson.databind.ObjectMapper;import com.jayway.jsonpath.JsonPath;import java.util.Map;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.stereotype.Component;@Component("objectPathValuesExtractor")public class ObjectPathValuesExtractor {&nbsp; &nbsp; private static final Logger LOGGER = LoggerFactory.getLogger(ObjectPathValuesExtractor.class);&nbsp; &nbsp; /**&nbsp; &nbsp; &nbsp;* Extract values for a given path from current object.&nbsp; &nbsp; &nbsp;*&nbsp; &nbsp; &nbsp;* @param object the object&nbsp; &nbsp; &nbsp;*/&nbsp; &nbsp; public <T extends Object> T extractValues(Object object, String pathExpression) {&nbsp; &nbsp; &nbsp; &nbsp; T values = null;&nbsp; &nbsp; &nbsp; &nbsp; if (object == null) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return values;&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; try {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ObjectMapper mapper = new ObjectMapper();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; mapper.setDefaultPropertyInclusion(JsonInclude.Value.construct(JsonInclude.Include.ALWAYS, JsonInclude.Include.NON_NULL));&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Map<String, Object> mappedObject = mapper.convertValue(object, Map.class);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; values = JsonPath.read(mappedObject, pathExpression);&nbsp; &nbsp; &nbsp; &nbsp; } catch (Exception e) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; LOGGER.error("Failed to load alert referenced object.", e);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; return values;&nbsp; &nbsp; }}在这里我使用compile group: 'com.jayway.jsonpath', name: 'json-path', version: '2.4.0' 来自 apache然后我调用这个函数List<Map<String, Extensible>> refObjects = objectPathValuesExtractor.extractValues(object, "$..time");