springboot2优雅个性化定制Jackson配置

前言

通过实现Jackson2ObjectMapperBuilderCustomizer接口并注册到容器，进行个性化定制，Spring Boot不会覆盖默认ObjectMapper的配置，而是进行了合并增强，具体还会根据Jackson2ObjectMapperBuilderCustomizer实现类的Order优先级进行排序，因此上面的JacksonConfig配置类还实现了Ordered接口。

默认的Jackson2ObjectMapperBuilderCustomizerConfiguration优先级是0，因此如果我们想要覆盖配置，设置优先级大于0即可。

**注意：**在SpringBoot2环境下，不要将自定义的ObjectMapper对象注入容器，这样会将原有的ObjectMapper配置覆盖！

优雅个性化定制Jackson实现示例

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.std.StdScalarDeserializer;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalTimeDeserializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalTimeSerializer;
import org.moyu.common.Constants;
import org.moyu.common.serializer.JacksonLocalDateTimeDeserializer;
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

import java.io.IOException;
import java.math.BigInteger;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;

/**
 * 自定义Jackson配置
 */
@Configuration
public class JacksonConfig implements Jackson2ObjectMapperBuilderCustomizer, Ordered {
    
    
    @Override
    public void customize(Jackson2ObjectMapperBuilder builder) {
    
    
        // 将入参中的空字符串""转为null
        builder.deserializerByType(String.class, new StdScalarDeserializer<String>(String.class) {
    
    
            @Override
            public String deserialize(JsonParser jsonParser, DeserializationContext ctx)
                    throws IOException {
    
    
                // 重点在这儿:如果为空白则返回null
                String value = jsonParser.getValueAsString();
                if (value == null || "".equals(value.trim())) {
    
    
                    return null;
                }
                return value;
            }
        });

        // 设置java.util.Date时间类的序列化以及反序列化的格式
        builder.simpleDateFormat(Constants.YYYY_MM_DD_HH_MM_SS);

        // JSR 310日期时间处理
        JavaTimeModule javaTimeModule = new JavaTimeModule();
        javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(Constants.YYYY_MM_DD_HH_MM_SS)));
        javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(DateTimeFormatter.ofPattern(Constants.YYYY_MM_DD)));
        javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(DateTimeFormatter.ofPattern(Constants.HH_MM_SS)));
        javaTimeModule.addDeserializer(LocalDateTime.class, new JacksonLocalDateTimeDeserializer());
        javaTimeModule.addDeserializer(LocalDate.class, new LocalDateDeserializer(DateTimeFormatter.ofPattern(Constants.YYYY_MM_DD)));
        javaTimeModule.addDeserializer(LocalTime.class, new LocalTimeDeserializer(DateTimeFormatter.ofPattern(Constants.HH_MM_SS)));
        builder.modules(javaTimeModule);

        // 全局转化Long类型为String，解决序列化后传入前端Long类型精度丢失问题
        builder.serializerByType(BigInteger.class, ToStringSerializer.instance);
        builder.serializerByType(Long.class, ToStringSerializer.instance);
    }

    @Override
    public int getOrder() {
    
    
        return 1;
    }
}

JacksonLocalDateTimeDeserializer

public class JacksonLocalDateTimeDeserializer extends StdDeserializer<LocalDateTime> {
    
    
    public JacksonLocalDateTimeDeserializer() {
    
    
        super(LocalDateTime.class);
    }

    protected JacksonLocalDateTimeDeserializer(Class<?> vc) {
    
    
        super(vc);
    }

    public LocalDateTime deserialize(JsonParser jp, DeserializationContext deserializationContext) throws IOException {
    
    
        String dateText = jp.getValueAsString();
        DateTime parse = DateUtil.parse(dateText);
        Instant instant = parse.toInstant();
        ZoneId zoneId = ZoneId.systemDefault();
        return instant.atZone(zoneId).toLocalDateTime();
    }
}