使用Jackson自定义反序列化器处理美团API中不规范JSON字段的兼容方案

使用Jackson自定义反序列化器处理美团API中不规范JSON字段的兼容方案

在对接美团开放平台API时，开发者常遇到返回JSON结构不规范的问题：例如字段类型不一致（字符串与数字混用）、布尔值以"1"/"0"表示、时间格式非ISO8601、甚至同一字段在不同接口下含义不同。若直接使用标准Jackson反序列化，极易抛出JsonMappingException。本文将基于baodanbao.com.cn.*包结构，展示如何通过自定义JsonDeserializer实现健壮的兼容解析。

1. 问题场景示例

美团某订单接口返回如下片段：

{
  "order_id": "123456",
  "is_valid": "1",
  "amount": "89.50",
  "create_time": "2024-03-05 14:30:00"
}

理想Java类应为：

public class MeituanOrder {
    private Long orderId;
    private Boolean isValid;
    private BigDecimal amount;
    private LocalDateTime createTime;
}

但默认反序列化会因类型不匹配失败。需定制逻辑。

2. 自定义Boolean反序列化器

处理 "1"/"0" 或 "true"/"false" 混合情况：

package baodanbao.com.cn.deserializer;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

import java.io.IOException;

public class FlexibleBooleanDeserializer extends JsonDeserializer<Boolean> {

    @Override
    public Boolean deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        String value = p.getText().trim();
        if (value.isEmpty()) return null;
        if ("1".equals(value) || "true".equalsIgnoreCase(value)) {
            return true;
        }
        if ("0".equals(value) || "false".equalsIgnoreCase(value)) {
            return false;
        }
        throw new IllegalArgumentException("无法解析布尔值: " + value);
    }
}

3. 自定义数值反序列化器（支持字符串转BigDecimal）

package baodanbao.com.cn.deserializer;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

import java.io.IOException;
import java.math.BigDecimal;

public class StringToBigDecimalDeserializer extends JsonDeserializer<BigDecimal> {

    @Override
    public BigDecimal deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        String value = p.getText().trim();
        if (value.isEmpty()) return null;
        try {
            return new BigDecimal(value);
        } catch (NumberFormatException e) {
            throw new IllegalArgumentException("无法解析金额: " + value, e);
        }
    }
}

4. 自定义LocalDateTime反序列化器（兼容空格分隔时间）

package baodanbao.com.cn.deserializer;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;

public class FlexibleLocalDateTimeDeserializer extends JsonDeserializer<LocalDateTime> {

    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

    @Override
    public LocalDateTime deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        String value = p.getText().trim();
        if (value.isEmpty()) return null;
        try {
            return LocalDateTime.parse(value, FORMATTER);
        } catch (DateTimeParseException e) {
            throw new IllegalArgumentException("无法解析时间: " + value, e);
        }
    }
}

5. 在实体类中应用自定义反序列化器

package baodanbao.com.cn.model.meituan;

import baodanbao.com.cn.deserializer.*;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;

import java.math.BigDecimal;
import java.time.LocalDateTime;

public class MeituanOrder {

    @JsonDeserialize(using = StringToLongDeserializer.class)
    private Long orderId;

    @JsonDeserialize(using = FlexibleBooleanDeserializer.class)
    private Boolean isValid;

    @JsonDeserialize(using = StringToBigDecimalDeserializer.class)
    private BigDecimal amount;

    @JsonDeserialize(using = FlexibleLocalDateTimeDeserializer.class)
    private LocalDateTime createTime;

    // getters and setters
}

其中StringToLongDeserializer实现类似：

package baodanbao.com.cn.deserializer;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

import java.io.IOException;

public class StringToLongDeserializer extends JsonDeserializer<Long> {
    @Override
    public Long deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        String text = p.getText().trim();
        return text.isEmpty() ? null : Long.parseLong(text);
    }
}

6. 全局注册（可选）

若多个类需复用，可在ObjectMapper中全局注册：

package baodanbao.com.cn.config;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class JacksonConfig {

    @Bean
    public ObjectMapper objectMapper() {
        ObjectMapper mapper = new ObjectMapper();
        SimpleModule module = new SimpleModule();
        module.addDeserializer(Boolean.class, new FlexibleBooleanDeserializer());
        module.addDeserializer(BigDecimal.class, new StringToBigDecimalDeserializer());
        mapper.registerModule(module);
        return mapper;
    }
}

但注意：全局注册可能影响其他接口，建议优先使用字段级@JsonDeserialize。

7. 异常容错增强：忽略非法字段

在配置中开启宽容模式，避免因个别字段异常导致整个响应解析失败：

@Bean
public ObjectMapper objectMapper() {
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(com.fasterxml.jackson.core.JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
    mapper.configure(com.fasterxml.jackson.databind.DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    mapper.configure(com.fasterxml.jackson.databind.DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL, true);
    // 注册模块...
    return mapper;
}

8. 单元测试验证

package baodanbao.com.cn.test;

import baodanbao.com.cn.model.meituan.MeituanOrder;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.*;

public class MeituanOrderDeserializationTest {

    @Test
    void testDeserializeFromMeituanJson() throws Exception {
        String json = """
            {
              "order_id": "789012",
              "is_valid": "1",
              "amount": "123.45",
              "create_time": "2024-03-05 14:30:00"
            }
            """;

        ObjectMapper mapper = new ObjectMapper();
        MeituanOrder order = mapper.readValue(json, MeituanOrder.class);

        assertEquals(789012L, order.getOrderId());
        assertTrue(order.getIsValid());
        assertEquals(new BigDecimal("123.45"), order.getAmount());
        assertEquals(LocalDateTime.of(2024, 3, 5, 14, 30, 0), order.getCreateTime());
    }
}

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