[QUESTION] ObjectReader 怎么实现？

[yangcanlin]

你好，请问能不能提供一个 实现 ObjectReader 的例子，FastJson2 网上教程太难找了，全是 FastJson1 的教程，然后 com.alibaba.fastjson2.writer 包下的类是不是现在还不能使用，如 ObjectWriterImplLocalDateTime.class

我想解决的问题是，后端接收 LocalDateTime 属性，前端传值：“2022-05-26”，正常，但是传值：“2022-05-26 16:42:11” 就会报错，下面是我写的 配置类 , 学习的路上，能不能提供一个解决方案，琢磨一整天了。

import com.alibaba.fastjson2.JSON;
import com.alibaba.fastjson2.JSONException;
import com.alibaba.fastjson2.JSONReader;
import com.alibaba.fastjson2.JSONWriter;
import com.alibaba.fastjson2.reader.ObjectReader;
import com.alibaba.fastjson2.support.config.FastJsonConfig;
import com.alibaba.fastjson2.support.spring.http.converter.FastJsonHttpMessageConverter;
import com.alibaba.fastjson2.writer.ObjectWriter;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import java.lang.reflect.Type;
import java.nio.charset.StandardCharsets;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Collections;
import java.util.List;

@Configuration
@EnableWebMvc
public class MyWebMvcConfigurer implements WebMvcConfigurer {

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonConfig config = new FastJsonConfig();
        
        config.setDateFormat("yyyy-MM-dd HH:mm:ss");
        
        config.setReaderFeatures(JSONReader.Feature.FieldBased, JSONReader.Feature.SupportArrayToBean, JSONReader.Feature.SupportAutoType);
        config.setWriterFeatures(JSONWriter.Feature.WriteMapNullValue, JSONWriter.Feature.WriteNulls);
        
        JSON.register(LocalDateTime.class, MyLocalDateTimeWriter.instance);
        JSON.register(LocalDate.class, MyLocalDateWriter.instance);
    
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        converter.setFastJsonConfig(config);
        converter.setDefaultCharset(StandardCharsets.UTF_8);
        converter.setSupportedMediaTypes(Collections.singletonList(MediaType.APPLICATION_JSON));
        converters.add(0, converter);
    }
}

class MyLocalDateTimeWriter implements ObjectWriter {
    static MyLocalDateTimeWriter instance = new MyLocalDateTimeWriter();
    
    @Override
    public void write(JSONWriter jsonWriter, Object object, Object fieldName, Type fieldType, long features) {
        if (object == null) {
            jsonWriter.writeNull();
            return;
        }
        LocalDateTime dateTime = (LocalDateTime) object;
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String format = formatter.format(dateTime);
        // 优先使用name
        jsonWriter.writeString(format);
    }
}

class MyLocalDateWriter implements ObjectWriter {
    static MyLocalDateWriter instance = new MyLocalDateWriter();
    
    @Override
    public void write(JSONWriter jsonWriter, Object object, Object fieldName, Type fieldType, long features) {
        if (object == null) {
            jsonWriter.writeNull();
            return;
        }
        LocalDateTime dateTime = (LocalDateTime) object;
        LocalDate date = dateTime.toLocalDate();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        String format = formatter.format(date);
        // 优先使用name
        jsonWriter.writeString(format);
    }
}

[wenshao]

收到，我周六看你的例子，并且补一个文档

[wenshao]

https://github.com/alibaba/fastjson2/releases/tag/2.0.5
2.0.5支持自动识别了，不用自己写ObjectReader/ObjectWriter，你升级试试看

[yangcanlin]

https://github.com/alibaba/fastjson2/releases/tag/2.0.5 2.0.5支持自动识别了，不用自己写ObjectReader/ObjectWriter，你升级试试看

好的 我明天试一下 感谢大佬

[yangcanlin]

你好，我刚刚试了，LocalDate 确实没问题了，但是 LocalTime 好像没有修复哦，你看看是我操作错误还是没有修复。

// 全局注册
JSON.register(LocalTime.class, JdbcSupport.createTimeReader("yyyy-MM-dd HH:mm:ss", Locale.CHINESE));

// 前端输入
{ "localTime": "2022-05-30 11:36:11" }

虽说很少用上 LocalTime 吧，但难免还是有用上的，期待，谢谢！

[yangcanlin]

注意！！！ 2.0.5 修复了 LocalDate 的问题，2.0.6 又出现了 LocalDate 报错问题！！！

异常：Could not write JSON: FASTJSON-2.0.6 write JSON errorUnsupported field: HourOfDay; nested exception is com.alibaba.fastjson2.JSONException: FASTJSON-2.0.6 write JSON errorUnsupported field: HourOfDay

[wenshao]

bug已经修复，请用2.0.7-SNAPSHOT版本验证
https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson2/fastjson2/2.0.7-SNAPSHOT/

[wenshao]

https://github.com/alibaba/fastjson2/releases/tag/2.0.7
问题已经修复，请用新版本