Spring Boot中使用Jackson将天气API响应JSON映射为多POJO类问题咨询

1. 前置依赖引入 #

Maven项目直接在pom.xml中添加Jackson核心依赖即可：

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

Gradle项目对应添加implementation 'com.fasterxml.jackson.core:jackson-databind:2.15.2'即可。 #

2. 定义对应层级的POJO类 #

JSON响应是三层嵌套结构：外层对象包含location、current两个子对象，current内部又嵌套condition子对象，POJO需要和这个结构对应：

2.1 位置信息类（Location） #

对应JSON中location节点的字段：

import com.fasterxml.jackson.annotation.JsonProperty;

public class Location {
    private String name;
    private String region;
    private String country;
    private Double lat;
    private Double lon;
    @JsonProperty("tz_id") // 字段名和JSON键名不一致时用该注解绑定
    private String tzId;
    @JsonProperty("localtime_epoch")
    private Long localtimeEpoch;
    private String localtime;

    // 补充所有属性的getter、setter方法，也可直接用Lombok的@Data注解省略手写
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    // 其余getter、setter省略
}

2.2 天气状况类（Condition） #

对应JSON中current.condition节点的字段：

public class Condition {
    private String text;
    private String icon;
    private Integer code;

    // getter、setter省略
}

2.3 当前天气类（Current） #

对应JSON中current节点的字段，内部嵌套Condition类：

import com.fasterxml.jackson.annotation.JsonProperty;

public class Current {
    @JsonProperty("last_updated_epoch")
    private Long lastUpdatedEpoch;
    @JsonProperty("last_updated")
    private String lastUpdated;
    @JsonProperty("temp_c")
    private Double tempC;
    @JsonProperty("temp_f")
    private Double tempF;
    @JsonProperty("is_day")
    private Integer isDay;
    private Condition condition; // 嵌套天气状况类
    @JsonProperty("wind_mph")
    private Double windMph;
    @JsonProperty("wind_kph")
    private Double windKph;
    @JsonProperty("wind_degree")
    private Integer windDegree;
    @JsonProperty("wind_dir")
    private String windDir;
    @JsonProperty("pressure_mb")
    private Double pressureMb;
    @JsonProperty("pressure_in")
    private Double pressureIn;
    @JsonProperty("precip_mm")
    private Double precipMm;
    @JsonProperty("precip_in")
    private Double precipIn;
    private Integer humidity;
    private Integer cloud;
    @JsonProperty("feelslike_c")
    private Double feelslikeC;
    @JsonProperty("feelslike_f")
    private Double feelslikeF;
    @JsonProperty("vis_km")
    private Double visKm;
    @JsonProperty("vis_miles")
    private Double visMiles;
    private Double uv;
    @JsonProperty("gust_mph")
    private Double gustMph;
    @JsonProperty("gust_kph")
    private Double gustKph;

    // getter、setter省略
}

2.4 外层响应包装类（可选） #

如果需要一次性解析整个JSON，可以新增外层包装类：

public class WeatherResponse {
    private Location location;
    private Current current;

    public Location getLocation() { return location; }
    public void setLocation(Location location) { this.location = location; }
    public Current getCurrent() { return current; }
    public void setCurrent(Current current) { this.current = current; }
}

3. 执行反序列化操作 #

方案1：通过外层包装类一次性解析 #

拿到API返回的JSON字符串后直接转成外层包装类对象，即可提取所有对应POJO实例：

import com.fasterxml.jackson.databind.ObjectMapper;

public class WeatherParseTest {
    public static void main(String[] args) {
        // 替换为实际调用天气API拿到的响应字符串
        String jsonResponse = "API返回的JSON字符串";
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            WeatherResponse resp = objectMapper.readValue(jsonResponse, WeatherResponse.class);
            // 直接获取各POJO实例
            Location location = resp.getLocation();
            Current current = resp.getCurrent();
            Condition condition = current.getCondition();
            // 后续业务逻辑
            System.out.println("当前城市：" + location.getName());
            System.out.println("当前温度：" + current.getTempC() + "℃");
            System.out.println("天气状况：" + condition.getText());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

方案2：单独解析指定节点（无需定义外层包装类） #

如果只需要部分节点的POJO，也可以先解析为JsonNode再单独转对应类型：

JsonNode rootNode = objectMapper.readTree(jsonResponse);
// 单独解析location节点为Location对象
Location location = objectMapper.treeToValue(rootNode.get("location"), Location.class);
// 单独解析current节点为Current对象
Current current = objectMapper.treeToValue(rootNode.get("current"), Current.class);

4. 常用配置说明 #

• 忽略JSON中存在但POJO没有定义的字段，避免反序列化报错：

  objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
  

• 空字符串转空对象不报错：

  objectMapper.configure(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true);
  

内容的提问来源于stack exchange，提问作者SkepticalTiger