Jackson Object Mapper in spring MVC not working

问题:

Every object with Date format is being serialized as a long.

I've read around that I need to create a custom object mapper

and so I did:

public class CustomObjectMapper extends ObjectMapper {

    public CustomObjectMapper() {
        super();
        configure(Feature.WRITE_DATES_AS_TIMESTAMPS, false);
        setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));

    }

}

I've also registered that custom mapper as a converter

@Override
protected void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    converters.add(converter());
    addDefaultHttpMessageConverters(converters);
}

@Bean
MappingJacksonHttpMessageConverter converter() {
    MappingJacksonHttpMessageConverter converter = new MappingJacksonHttpMessageConverter();
    converter.setObjectMapper(new CustomObjectMapper());

    return converter;
}

but still, it doesn't work, and I recieve a long as a date.

Any idea what am I doing wrong?

回答1:

You'll need to implement your own Dateserializer, just like the following (got it from this tutorial, so props to Loiane, not me ;-) ):

package ....util.json;

import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.map.JsonSerializer;
import org.codehaus.jackson.map.SerializerProvider;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

@Component
public class JsonDateSerializer extends JsonSerializer<Date>{

private static final SimpleDateFormat dateFormat = new SimpleDateFormat("dd.MM.yyyy HH:mm "); // change according to your needs 

@Override
public void serialize(Date date, JsonGenerator gen, SerializerProvider provider)
        throws IOException {

    String formattedDate = dateFormat.format(date);

    gen.writeString(formattedDate);
}

}

then you could just add the following annotation to your Date-Objects and it will persist fine:

@JsonSerialize(using = JsonDateSerializer.class)
public Date getCreated() {
    return created;
}

At least it works with spring 3.2.4 and jackson 1.9.13 here.

edit: Think about using FastDateFormat instead of SimpleDateFormat, for it's the threadsafe-alternative (as mentioned in the comments of Loianes article)

回答2:

Try adding 0 as index in #add()

@Configuration
@ComponentScan()
@EnableWebMvc
@PropertySource("classpath:/web.properties")
public class WebConfig extends WebMvcConfigurerAdapter
{

    @Override
    public void configureMessageConverters(final List<HttpMessageConverter<?>> converters)
    {
        converters.add(0, jsonConverter());
    }

    @Bean
    public MappingJacksonHttpMessageConverter jsonConverter()
    {
        final MappingJacksonHttpMessageConverter converter = new MappingJacksonHttpMessageConverter();
        converter.setObjectMapper(new CustomObjectMapper());

        return converter;
    }
}

It worked for me.