如何通过Spring Boot API调用提取嵌套JSON值并按类别过滤

问题背景 #

从Controller接口拿到的JSON数据如下：

[
    {
        "id": 1,
        "footwearList": [
            {
                "id": 1,
                "name": "sandals",
                "category": "men"
            },
            {
                "id": 3,
                "name": "sandals",
                "category": "women"
            }
        ],
        "clothingList": [
            {
                "id": 1,
                "name": "t-shirt",
                "category": "men"
            },
            {
                "id": 3,
                "name": "tshirt",
                "category": "women"
            }
        ]
    },
    {
        "id": 2,
        "footwearList": [
            {
                "id": 2,
                "name": "shoes",
                "category": "men"
            },
            {
                "id": 4,
                "name": "shoes",
                "category": "women"
            }
        ],
        "clothingList": [
            {
                "id": 2,
                "name": "shirt",
                "category": "men"
            },
            {
                "id": 4,
                "name": "shirt",
                "category": "women"
            }
        ]
    }
]

已添加JsonPath依赖：

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.7.0</version>
</dependency>

但使用以下代码提取数据失败：

public List<Store> getCategory(){
    List<Store> footwear = JsonPath.read(json, "$..footwear");
}

问题原因 #

代码里的JsonPath表达式写错了——JSON中的列表字段是footwearList，但表达式用了$..footwear，路径不匹配导致提取不到数据。

解决方案 #

1. 正确提取嵌套列表数据

要获取所有footwearList或clothingList，修改JsonPath表达式为对应字段名：

• 提取所有鞋类列表：$..footwearList
• 提取所有服装列表：$..clothingList

如果要映射到自定义实体类，先定义对应类：

// 鞋类实体
public class Footwear {
    private Integer id;
    private String name;
    private String category;
    // 构造方法、getter/setter省略
}

// 服装实体
public class Clothing {
    private Integer id;
    private String name;
    private String category;
    // 构造方法、getter/setter省略
}

然后用泛型读取数据：

// 提取所有鞋类数据，合并为一个List
List<Footwear> allFootwear = JsonPath.read(json, "$..footwearList[*]", new TypeRef<List<Footwear>>() {});

// 提取所有服装数据
List<Clothing> allClothing = JsonPath.read(json, "$..clothingList[*]", new TypeRef<List<Clothing>>() {});

2. 按Category过滤数据

有两种过滤方式：

方式一：用JsonPath表达式直接过滤

直接在表达式中指定category条件，返回符合要求的数据：

// 提取所有男性鞋类
List<Footwear> menFootwear = JsonPath.read(json, "$..footwearList[?(@.category == 'men')]", new TypeRef<List<Footwear>>() {});

// 提取所有女性服装
List<Clothing> womenClothing = JsonPath.read(json, "$..clothingList[?(@.category == 'women')]", new TypeRef<List<Clothing>>() {});

方式二：提取后在Java代码中过滤

如果需要更复杂的过滤逻辑，先提取所有数据再用Stream过滤：

List<Footwear> allFootwear = JsonPath.read(json, "$..footwearList[*]", new TypeRef<List<Footwear>>() {});
// 过滤男性鞋类
List<Footwear> menFootwear = allFootwear.stream()
    .filter(item -> "men".equals(item.getCategory()))
    .collect(Collectors.toList());

完整示例代码 #

import com.jayway.jsonpath.JsonPath;
import com.jayway.jsonpath.TypeRef;
import java.util.List;
import java.util.stream.Collectors;

public class JsonPathDemo {
    public static void main(String[] args) {
        String json = "你的JSON字符串";

        // 提取并过滤男性鞋类
        List<Footwear> menFootwear = JsonPath.read(json, "$..footwearList[?(@.category == 'men')]", new TypeRef<List<Footwear>>() {});
        
        // 提取所有服装后过滤女性款
        List<Clothing> allClothing = JsonPath.read(json, "$..clothingList[*]", new TypeRef<List<Clothing>>() {});
        List<Clothing> womenClothing = allClothing.stream()
                .filter(c -> "women".equals(c.getCategory()))
                .collect(Collectors.toList());
    }
}

class Footwear {
    private Integer id;
    private String name;
    private String category;

    // getter和setter
    public Integer getId() { return id; }
    public void setId(Integer id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getCategory() { return category; }
    public void setCategory(String category) { this.category = category; }
}

class Clothing {
    private Integer id;
    private String name;
    private String category;

    // getter和setter
    public Integer getId() { return id; }
    public void setId(Integer id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getCategory() { return category; }
    public void setCategory(String category) { this.category = category; }
}

内容的提问来源于stack exchange，提问作者NJ42