Java?Record類介紹及使用方法詳解

更新時間：2025年08月06日 09:59:26 作者：冉成未來

Record是Java新增的庫類,在Java 14和Java 15中以預(yù)覽（preview）形式公布,這篇文章主要介紹了Java?Record類介紹及使用方法的相關(guān)資料,需要的朋友可以參考下

簡介

Java Record類是Java 14引入的預(yù)覽特性，并在Java 16中正式成為標(biāo)準(zhǔn)功能，主要用于簡化不可變數(shù)據(jù)載體的創(chuàng)建，自動生成構(gòu)造方法、字段訪問器、equals()、hashCode()和toString()等方法。

Java Record類的核心特性‌

不可變性‌：所有字段默認(rèn)是final的，實例化后不可修改，適合表示純數(shù)據(jù)模型如DTO或值對象。‌‌
自動生成方法‌：編譯器自動生成全參數(shù)構(gòu)造器、字段訪問器（如name()而非getName()）、equals()、hashCode()和toString()方法，顯著減少樣板代碼。‌‌‌‌
簡潔語法‌：與傳統(tǒng)類相比，Record類的聲明更簡潔。

例如：

public record Point(int x, int y) {}

等效于包含多個手動編寫方法的普通類。‌‌

與普通類的區(qū)別‌

繼承限制‌：Record類隱式繼承java.lang.Record，不能顯式繼承其他類，但可以實現(xiàn)接口。‌‌
字段限制‌：僅能定義頭部聲明的字段，不支持額外實例變量（靜態(tài)字段除外）。‌‌
默認(rèn)方法‌：自動生成規(guī)范方法，且不可重寫父類方法（因父類為Record）。‌‌

使用場景與最佳實踐‌

‌數(shù)據(jù)傳輸對象（DTO）‌：簡化API請求/響應(yīng)的數(shù)據(jù)封裝。‌‌

‌不可變數(shù)據(jù)快照‌：如領(lǐng)域事件或配置參數(shù)，確保數(shù)據(jù)一致性。‌‌

‌擴展功能‌：

通過緊湊構(gòu)造器實現(xiàn)參數(shù)校驗：

public record User(String name) {
public User { Objects.requireNonNull(name); }
}

添加自定義方法（如計算衍生屬性）。‌‌

jackson中的注解解釋

@JsonProperty :此注解用于屬性上，作用是把該屬性的名稱序列化為另外一個名稱，如把trueName屬性序列化為name，@JsonProperty(“name”)。對屬性名稱重命名，比如在很多場景下Java對象的屬性是按照規(guī)范的駝峰書寫，但在數(shù)據(jù)庫設(shè)計時使用的是下劃線連接方式，此處在進行映射的時候就可以使用該注解。
@JsonIgnore此注解用于屬性或者方法上（最好是屬性上），用來完全忽略被注解的字段和方法對應(yīng)的屬性，即便這個字段或方法可以被自動檢測到或者還有其他的注解，一般標(biāo)記在屬性或者方法上，返回的json數(shù)據(jù)即不包含該屬性。
@JsonIgnoreProperties此注解是類注解，作用是json序列化時將java bean中的一些屬性忽略掉，序列化和反序列化都受影響。
@JsonFormat此注解用于屬性或者方法上（最好是屬性上），可以方便的把Date類型直接轉(zhuǎn)化為我們想要的模式。例子：@JsonFormat(pattern=“yyyy-MM-dd hh:mm:ss”) @JsonFormat(pattern=“yyyy-MM-dd HH:mm:ss”) private Date updateTime;
@JsonSerialize此注解用于屬性或者getter方法上，用于在序列化時嵌入我們自定義的代碼，比如序列化一個double時在其后面限制兩位小數(shù)點。
@JsonDeserialize此注解用于屬性或者setter方法上，用于在反序列化時可以嵌入我們自定義的代碼，類似于上面的@JsonSerialize。
@JsonInclude 屬性值為null的不參與序列化。例子：@JsonInclude(Include.NON_NULL)

代碼示例

@Service
public class WeatherService {

    private static final String BASE_URL = "https://api.weather.gov";

    private final RestClient restClient;

    public WeatherService() {
        this.restClient = RestClient.builder()
                .baseUrl(BASE_URL)
                .defaultHeader("Accept", "application/geo+json")
                .defaultHeader("User-Agent", "WeatherApiClient/1.0 (your@email.com)")
                .build();
    }

    @JsonIgnoreProperties(ignoreUnknown = true)
    public record Points(@JsonProperty("properties") Props properties) {
        @JsonIgnoreProperties(ignoreUnknown = true)
        public record Props(@JsonProperty("forecast") String forecast) {
        }
    }

    @JsonIgnoreProperties(ignoreUnknown = true)
    public record Forecast(@JsonProperty("properties") Props properties) {
        @JsonIgnoreProperties(ignoreUnknown = true)
        public record Props(@JsonProperty("periods") List<Period> periods) {
        }

        @JsonIgnoreProperties(ignoreUnknown = true)
        public record Period(@JsonProperty("number") Integer number, @JsonProperty("name") String name,
                             @JsonProperty("startTime") String startTime, @JsonProperty("endTime") String endTime,
                             @JsonProperty("isDaytime") Boolean isDayTime, @JsonProperty("temperature") Integer temperature,
                             @JsonProperty("temperatureUnit") String temperatureUnit,
                             @JsonProperty("temperatureTrend") String temperatureTrend,
                             @JsonProperty("probabilityOfPrecipitation") Map probabilityOfPrecipitation,
                             @JsonProperty("windSpeed") String windSpeed, @JsonProperty("windDirection") String windDirection,
                             @JsonProperty("icon") String icon, @JsonProperty("shortForecast") String shortForecast,
                             @JsonProperty("detailedForecast") String detailedForecast) {
        }
    }

    @JsonIgnoreProperties(ignoreUnknown = true)
    public record Alert(@JsonProperty("features") List<Feature> features) {

        @JsonIgnoreProperties(ignoreUnknown = true)
        public record Feature(@JsonProperty("properties") Properties properties) {
        }

        @JsonIgnoreProperties(ignoreUnknown = true)
        public record Properties(@JsonProperty("event") String event, @JsonProperty("areaDesc") String areaDesc,
                                 @JsonProperty("severity") String severity, @JsonProperty("description") String description,
                                 @JsonProperty("instruction") String instruction) {
        }
    }

    /**
     * Get forecast for a specific latitude/longitude
     * @param latitude Latitude
     * @param longitude Longitude
     * @return The forecast for the given location
     * @throws RestClientException if the request fails
     */
    @Tool(description = "Get weather forecast for a specific latitude/longitude")
    public String getWeatherForecastByLocation(double latitude, double longitude) {

        var points = restClient.get()
                .uri("/points/{latitude},{longitude}", latitude, longitude)
                .retrieve()
                .body(Points.class);

        var forecast = restClient.get().uri(points.properties().forecast()).retrieve().body(Forecast.class);

        String forecastText = forecast.properties().periods().stream().map(p -> {
            return String.format("""
					%s:
					Temperature: %s %s
					Wind: %s %s
					Forecast: %s
					""", p.name(), p.temperature(), p.temperatureUnit(), p.windSpeed(), p.windDirection(),
                    p.detailedForecast());
        }).collect(Collectors.joining());

        return forecastText;
    }

    /**
     * Get alerts for a specific area
     * @param state Area code. Two-letter US state code (e.g. CA, NY)
     * @return Human readable alert information
     * @throws RestClientException if the request fails
     */
    @Tool(description = "Get weather alerts for a US state. Input is Two-letter US state code (e.g. CA, NY)")
    public String getAlerts(@ToolParam( description =  "Two-letter US state code (e.g. CA, NY") String state) {
        Alert alert = restClient.get().uri("/alerts/active/area/{state}", state).retrieve().body(Alert.class);

        return alert.features()
                .stream()
                .map(f -> String.format("""
					Event: %s
					Area: %s
					Severity: %s
					Description: %s
					Instructions: %s
					""", f.properties().event(), f.properties.areaDesc(), f.properties.severity(),
                        f.properties.description(), f.properties.instruction()))
                .collect(Collectors.joining("\n"));
    }

    public static void main(String[] args) {
        WeatherService client = new WeatherService();
        System.out.println(client.getWeatherForecastByLocation(47.6062, -122.3321));
        System.out.println(client.getAlerts("NY"));
    }

}

@JsonIgnoreProperties(ignoreUnknown = true)
public record Points(@JsonProperty("properties") Props properties) {
    @JsonIgnoreProperties(ignoreUnknown = true)
    public record Props(@JsonProperty("forecast") String forecast) {
    }
}
相當(dāng)于下面結(jié)構(gòu)
Points:{
  "properties": {
    "forecast": "晴天",
    "extraField": "會被忽略的值"
  },
  "anotherExtra": "也會被忽略"
}


@JsonIgnoreProperties(ignoreUnknown = true)
public record Forecast(@JsonProperty("properties") Props properties) {
    @JsonIgnoreProperties(ignoreUnknown = true)
    public record Props(@JsonProperty("periods") List<Period> periods) {
    }

    @JsonIgnoreProperties(ignoreUnknown = true)
    public record Period(@JsonProperty("number") Integer number, @JsonProperty("name") String name,
                         @JsonProperty("startTime") String startTime, @JsonProperty("endTime") String endTime,
                         @JsonProperty("isDaytime") Boolean isDayTime, @JsonProperty("temperature") Integer temperature,
                         @JsonProperty("temperatureUnit") String temperatureUnit,
                         @JsonProperty("temperatureTrend") String temperatureTrend,
                         @JsonProperty("probabilityOfPrecipitation") Map probabilityOfPrecipitation,
                         @JsonProperty("windSpeed") String windSpeed, @JsonProperty("windDirection") String windDirection,
                         @JsonProperty("icon") String icon, @JsonProperty("shortForecast") String shortForecast,
                         @JsonProperty("detailedForecast") String detailedForecast) {
    }
}

相當(dāng)于下面的結(jié)構(gòu)：
{
  "properties": {
    "periods": [
      {
        "number": 1,
        "name": "Tonight",
        "startTime": "2023-11-01T18:00:00-05:00",
        "endTime": "2023-11-02T06:00:00-05:00",
        "isDaytime": false,
        "temperature": 45,
        "temperatureUnit": "F",
        "temperatureTrend": "rising",
        "probabilityOfPrecipitation": {
          "value": 20,
          "unit": "percent"
        },
        "windSpeed": "5 to 10 mph",
        "windDirection": "SW",
        "icon": "https://api.weather.gov/icons/land/night/few?size=medium",
        "shortForecast": "Partly Cloudy",
        "detailedForecast": "Partly cloudy, with a low around 45. Southwest wind 5 to 10 mph."
      },
      {
        "number": 2,
        "name": "Wednesday",
        "startTime": "2023-11-02T06:00:00-05:00",
        "endTime": "2023-11-02T18:00:00-05:00",
        "isDaytime": true,
        "temperature": 72,
        "temperatureUnit": "F",
        "temperatureTrend": null,
        "probabilityOfPrecipitation": {
          "value": 0,
          "unit": "percent"
        },
        "windSpeed": "10 mph",
        "windDirection": "W",
        "icon": "https://api.weather.gov/icons/land/day/skc?size=medium",
        "shortForecast": "Sunny",
        "detailedForecast": "Sunny, with a high near 72. West wind around 10 mph."
      }
    ]
  }
}