java如何遍历嵌套json数组

Java如何遍历嵌套JSON数组：全面指南与代码示例

在Java开发中，处理JSON数据是非常常见的任务，尤其是当遇到嵌套的JSON数组时，如何高效遍历这些结构成为许多开发者面临的挑战，本文将详细介绍在Java中遍历嵌套JSON数组的多种方法，包括使用原生库、第三方库以及最佳实践。

JSON与嵌套JSON数组概述

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,嵌套JSON数组指的是数组中包含其他数组或对象的结构，

{
  "name": "公司部门",
  "departments": [
    {
      "name": "技术部",
      "employees": [
        {"id": 1, "name": "张三"},
        {"id": 2, "name": "李四"}
      ]
    },
    {
      "name": "市场部",
      "employees": [
        {"id": 3, "name": "王五"},
        {"id": 4, "name": "赵六"}
      ]
    }
  ]
}

使用原生库遍历嵌套JSON数组

使用org.json库

我们需要添加org.json库的依赖（Maven）：

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20231013</version>
</dependency>

遍历嵌套JSON数组的示例代码：

import org.json.JSONArray;
import org.json.JSONObject;
public class NestedJsonTraversal {
    public static void main(String[] args) {
        String jsonString = "{\"name\":\"公司部门\",\"departments\":[{\"name\":\"技术部\",\"employees\":[{\"id\":1,\"name\":\"张三\"},{\"id\":2,\"name\":\"李四\"}]},{\"name\":\"市场部\",\"employees\":[{\"id\":3,\"name\":\"王五\"},{\"id\":4,\"name\":\"赵六\"}]}]}";
        JSONObject jsonObject = new JSONObject(jsonString);
        JSONArray departments = jsonObject.getJSONArray("departments");
        for (int i = 0; i < departments.length(); i++) {
            JSONObject department = departments.getJSONObject(i);
            System.out.println("部门: " + department.getString("name"));
            JSONArray employees = department.getJSONArray("employees");
            for (int j = 0; j < employees.length(); j++) {
                JSONObject employee = employees.getJSONObject(j);
                System.out.println("  员工ID: " + employee.getInt("id") + 
                                 ", 姓名: " + employee.getString("name"));
            }
        }
    }
}

使用javax.json（JSON-P）Java API for JSON Processing

添加依赖：

<dependency>
    <groupId>org.glassfish</groupId>
    <artifactId>javax.json</artifactId>
    <version>1.1.4</version>
</dependency>

示例代码：

import javax.json.Json;
import javax.json.JsonArray;
import javax.json.JsonObject;
import javax.json.JsonReader;
import java.io.StringReader;
public class JsonpNestedTraversal {
    public static void main(String[] args) {
        String jsonString = "{\"name\":\"公司部门\",\"departments\":[{\"name\":\"技术部\",\"employees\":[{\"id\":1,\"name\":\"张三\"},{\"id\":2,\"name\":\"李四\"}]},{\"name\":\"市场部\",\"employees\":[{\"id\":3,\"name\":\"王五\"},{\"id\":4,\"name\":\"赵六\"}]}]}";
        JsonReader reader = Json.createReader(new StringReader(jsonString));
        JsonObject jsonObject = reader.readObject();
        JsonArray departments = jsonObject.getJsonArray("departments");
        for (int i = 0; i < departments.size(); i++) {
            JsonObject department = departments.getJsonObject(i);
            System.out.println("部门: " + department.getString("name"));
            JsonArray employees = department.getJsonArray("employees");
            for (int j = 0; j < employees.size(); j++) {
                JsonObject employee = employees.getJsonObject(j);
                System.out.println("  员工ID: " + employee.getInt("id") + 
                                 ", 姓名: " + employee.getString("name"));
            }
        }
        reader.close();
    }
}

使用第三方库遍历嵌套JSON数组

使用Gson库

添加依赖：

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.10.1</version>
</dependency>

示例代码：

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
public class GsonNestedTraversal {
    public static void main(String[] args) {
        String jsonString = "{\"name\":\"公司部门\",\"departments\":[{\"name\":\"技术部\",\"employees\":[{\"id\":1,\"name\":\"张三\"},{\"id\":2,\"name\":\"李四\"}]},{\"name\":\"市场部\",\"employees\":[{\"id\":3,\"name\":\"王五\"},{\"id\":4,\"name\":\"赵六\"}]}]}";
        JsonElement jsonElement = JsonParser.parseString(jsonString);
        JsonObject jsonObject = jsonElement.getAsJsonObject();
        JsonArray departments = jsonObject.getAsJsonArray("departments");
        for (JsonElement departmentElement : departments) {
            JsonObject department = departmentElement.getAsJsonObject();
            System.out.println("部门: " + department.get("name").getAsString());
            JsonArray employees = department.getAsJsonArray("employees");
            for (JsonElement employeeElement : employees) {
                JsonObject employee = employeeElement.getAsJsonObject();
                System.out.println("  员工ID: " + employee.get("id").getAsInt() + 
                                 ", 姓名: " + employee.get("name").getAsString());
            }
        }
    }
}

使用Jackson库

添加依赖：

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.2</version>
</dependency>

示例代码：

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
public class JacksonNestedTraversal {
    public static void main(String[] args) throws IOException {
        String jsonString = "{\"name\":\"公司部门\",\"departments\":[{\"name\":\"技术部\",\"employees\":[{\"id\":1,\"name\":\"张三\"},{\"id\":2,\"name\":\"李四\"}]},{\"name\":\"市场部\",\"employees\":[{\"id\":3,\"name\":\"王五\"},{\"id\":4,\"name\":\"赵六\"}]}]}";
        ObjectMapper objectMapper = new ObjectMapper();
        JsonNode rootNode = objectMapper.readTree(jsonString);
        JsonNode departmentsNode = rootNode.get("departments");
        for (JsonNode departmentNode : departmentsNode) {
            System.out.println("部门: " + departmentNode.get("name").asText());
            JsonNode employeesNode = departmentNode.get("employees");
            for (JsonNode employeeNode : employeesNode) {
                System.out.println("  员工ID: " + employeeNode.get("id").asInt() + 
                                 ", 姓名: " + employeeNode.get("name").asText());
            }
        }
    }
}

递归方法处理深度嵌套JSON

对于深度嵌套的JSON结构，递归方法更为适用,以下是一个使用Gson的递归示例：

import com.google.gson.JsonElement;
import com.google.gson.JsonParser;
public class RecursiveJsonTraversal {
    public static void main(String[] args) {
        String jsonString = "{\"name\":\"公司部门\",\"departments\":[{\"name\":\"技术部\",\"employees\":[{\"id\":1,\"name\":\"张三\",\"projects\":[{\"name\":\"项目A\"},{\"name\":\"项目B\"}]},{\"id\":2,\"name\":\"李四\"}]},{\"name\":\"市场部\",\"employees\":[{\"id\":3,\"name\":\"王五\"},{\"id\":4,\"name\":\"赵六\"}]}]}";
        JsonElement jsonElement = JsonParser.parseString(jsonString);
        traverseJson(jsonElement, 0);
    }
    public static void traverseJson(JsonElement element, int level) {
        if (element.isJsonArray()) {
            JsonArray array = element.getAsJsonArray();
            for (JsonElement child : array) {
                traverseJson(child, level + 1);
            }
        } else if (element.isJsonObject()) {
            JsonObject obj = element.getAsJsonObject();
            for (String key : obj.keySet()) {
                JsonElement value = obj.get(key);
                if (!value.isJsonArray() && !value.isJsonObject()) {
                    System.out.println("  ".repeat(level) + key + ": " + value.getAsString());
                } else {
                    System.out.println("  ".repeat(level) + key + ":");
                    traverseJson(value, level + 1);
                }
            }
        }
    }
}