<!-- Maven -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.2</version> <!-- 用最新穩(wěn)定版，避免舊版本漏洞 -->
</dependency>

<!-- Gradle -->
implementation 'com.fasterxml.jackson.core:jackson-databind:2.15.2'

{
  "userId": 10086,
  "username": "老碼農(nóng)",
  "roles": ["admin", "developer"],
  "createTime": "2024-08-01 12:00:00",
  "address": {
    "province": "北京",
    "city": "北京"
  }
}

import lombok.Data;
import com.fasterxml.jackson.annotation.JsonFormat;
import java.util.Date;
import java.util.List;

@Data // 自動(dòng)生成getter/setter，減少模板代碼
public class UserConfig {
    private Long userId;
    private String username;
    private List<String> roles;
    
    // 解決日期格式化問(wèn)題：指定JSON中的日期格式
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
    private Date createTime;
    
    private Address address; // 嵌套對(duì)象
    
    @Data
    public static class Address { // 內(nèi)部類定義嵌套對(duì)象
        private String province;
        private String city;
    }
}

import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;
import java.io.IOException;

public class JsonFileUtils {
    // 單例ObjectMapper：避免重復(fù)創(chuàng)建，提升性能
    private static final ObjectMapper objectMapper = new ObjectMapper();
    
    /**
     * 解析JSON文件為Java對(duì)象
     * @param filePath 文件路徑
     * @param clazz 目標(biāo)類
     * @return 解析后的對(duì)象
     */
    public static <T> T parseJsonFile(String filePath, Class<T> clazz) {
        try {
            // 核心API：readValue(File, Class)
            return objectMapper.readValue(new File(filePath), clazz);
        } catch (IOException e) {
            // 八年踩坑：日志必須打印詳細(xì)信息（文件路徑、異常棧），否則排查死人
            log.error("解析JSON文件失敗，路徑：{}", filePath, e);
            throw new RuntimeException("JSON解析異常", e); // 轉(zhuǎn)運(yùn)行時(shí)異常，由上層處理
        }
    }
}

// 調(diào)用示例
public class Main {
    public static void main(String[] args) {
        UserConfig config = JsonFileUtils.parseJsonFile("src/main/resources/user-config.json", UserConfig.class);
        System.out.println("用戶名：" + config.getUsername());
        System.out.println("省份：" + config.getAddress().getProvince());
    }
}

[  {"userId": 1, "username": "張三"},  {"userId": 2, "username": "李四"}]

import com.fasterxml.jackson.core.type.TypeReference;
import java.util.List;

// 工具類新增泛型解析方法
public static <T> T parseJsonFileGeneric(String filePath, TypeReference<T> typeReference) {
    try {
        return objectMapper.readValue(new File(filePath), typeReference);
    } catch (IOException e) {
        log.error("解析泛型JSON文件失敗，路徑：{}", filePath, e);
        throw new RuntimeException("JSON泛型解析異常", e);
    }
}

// 調(diào)用示例：解析為L(zhǎng)ist<UserConfig>
List<UserConfig> userList = JsonFileUtils.parseJsonFileGeneric(
    "src/main/resources/user-list.json", 
    new TypeReference<List<UserConfig>>() {} // 匿名內(nèi)部類指定泛型
);

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.JsonNode;
import java.io.File;
import java.io.IOException;

/**
 * 流式解析大JSON文件（逐行讀?。?
 * 適用場(chǎng)景：日志文件、批量數(shù)據(jù)文件
 */
public static void parseLargeJsonFile(String filePath) {
    try (JsonParser parser = objectMapper.getFactory().createParser(new File(filePath))) {
        parser.setCodec(objectMapper);
        // 開(kāi)始解析數(shù)組
        if (parser.nextToken() == JsonToken.START_ARRAY) {
            while (parser.nextToken() != JsonToken.END_ARRAY) {
                // 逐個(gè)解析對(duì)象，避免一次性加載到內(nèi)存
                JsonNode node = parser.readValueAsTree();
                Long userId = node.get("userId").asLong();
                String username = node.get("username").asText();
                // 處理單條數(shù)據(jù)（如寫(xiě)入數(shù)據(jù)庫(kù)、統(tǒng)計(jì)分析）
                processUser(userId, username);
            }
        }
    } catch (IOException e) {
        log.error("解析大JSON文件失敗，路徑：{}", filePath, e);
        throw new RuntimeException("大文件解析異常", e);
    }
}

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

@Data
public class User {
    // 字段名映射：JSON的user_id → Java的userId
    @JsonProperty("user_id") 
    private Long userId;
    
    // 自定義反序列化：比如解密JSON中的加密用戶名
    @JsonDeserialize(using = DecryptDeserializer.class)
    private String username;
    
    // 自定義序列化：日期轉(zhuǎn)時(shí)間戳（如果前端需要）
    @JsonSerialize(using = TimestampSerializer.class)
    private Date createTime;
}

// 自定義解密反序列化器示例
public class DecryptDeserializer extends StdDeserializer<String> {
    public DecryptDeserializer() {
        super(String.class);
    }
    
    @Override
    public String deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        String encrypted = p.getValueAsString();
        return decrypt(encrypted); // 調(diào)用解密方法
    }
}