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Using @ JsonFormat annotations does not take effect

Baidu has a lot of solutions, including using @ JsonField, getting rid of fastjson, and adding a lot of configurations, but they are all useless.

The version number used this time

1 、 springboot2.2.2

2 、 fastjson 1.1.26

3 、 1.9.10

2.10.3

The third point and related dependencies may not be needed, and it doesn't matter if you add them.

Dependencies in the pom file:

Com.alibaba fastjson ${fastjson.version} org.codehaus.jackson jackson-mapper-asl ${jackson-mapper-asl.version} com.fasterxml.jackson.core jackson-core ${jackson-core.version} com.fasterxml. Jackson.core jackson-databind ${jackson-core.version} com.fasterxml.jackson.core jackson-annotations ${jackson-core.version} solution

The first step is to create a new conversion class to customize the type converter applied when Jackson deserializes the date type, which is generally used when @ RequestBody accepts parameters.

Import com.fasterxml.jackson.core.JsonParser;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.DeserializationContext;import com.fasterxml.jackson.databind.JsonDeserializer;import org.apache.commons.lang3.StringUtils;import org.apache.commons.lang3.time.DateUtils; import java.io.IOException;import java.text.ParseException;import java.util.Date / * * Custom Jackson type converter used when deserializing date types is generally used when @ RequestBody accepts parameters * subclasses are borrowed from others on the Internet, and a date formatting type is added * / public class DateJacksonConverter extends JsonDeserializer {/ / is particularly important here Please find out what the date format type of error reported in your console is / / mine is 2020-04-29T16:23:44.999Z, so I added the format "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'" to the following array. If the format type you want is not found in the following array Others can be added according to their own circumstances private static String [] pattern = new String [] {"yyyy-MM-dd", "yyyy-MM-dd HH:mm", "yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd HH:mm:ss.S", "yyyy.MM.dd", "yyyy.MM.dd HH:mm", "yyyy.MM.dd HH:mm:ss" "yyyy.MM.dd HH:mm:ss.S", "yyyy/MM/dd", "yyyy/MM/dd HH:mm", "yyyy/MM/dd HH:mm:ss", "yyyy/MM/dd HH:mm:ss.S", "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"} @ Override public Date deserialize (JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {Date targetDate = null; String originDate = p.getText (); if (StringUtils.isNotEmpty (originDate)) {try {long longDate = Long.valueOf (originDate.trim ()); targetDate = new Date (longDate) } catch (NumberFormatException e) {try {targetDate = DateUtils.parseDate (originDate, DateJacksonConverter.pattern) } catch (ParseException pe) {throw new IOException (String.format ("% s' can not convert to type 'java.util.Date',just support timestamp (type of long) and following date format (% s)", originDate, StringUtils.join (pattern, ") } return targetDate;} @ Override public Class handledType () {return Date.class;}}

After creating the above class, if you don't want to continue, you can annotate the entity object properties.

The imported package path is:

Import com.fasterxml.jackson.databind.annotation.JsonDeserialize;@JsonDeserialize (using=DateJacksonConverter.class) private Date startDate

If you don't want to add this annotation to the entity class, you can write a public configuration as follows:

Import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean;import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter; import com.fasterxml.jackson.databind.ObjectMapper;import com.fx.base.serializer.DateJacksonConverter; @ Configurationpublic class ConverterConfig {@ Bean public DateJacksonConverter dateJacksonConverter () {return new DateJacksonConverter () } @ Bean public Jackson2ObjectMapperFactoryBean jackson2ObjectMapperFactoryBean (@ Autowired DateJacksonConverter dateJacksonConverter) {Jackson2ObjectMapperFactoryBean jackson2ObjectMapperFactoryBean = new Jackson2ObjectMapperFactoryBean (); jackson2ObjectMapperFactoryBean.setDeserializers (dateJacksonConverter); return jackson2ObjectMapperFactoryBean;} @ Bean public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter (@ Autowired ObjectMapper objectMapper) {MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter = new MappingJackson2HttpMessageConverter (); mappingJackson2HttpMessageConverter.setObjectMapper (objectMapper) Return mappingJackson2HttpMessageConverter;}}

There is no need to annotate each entity class attribute at this point.

The role of @ JsonFormat and @ DateTimeFormat

@ DatetimeFormat is used to convert String to Date, which is usually used when passing values from the foreground to the background

When import org.springframework.format.annotation.DateTimeFormat; / * is sent to the background in the foreground, the string is automatically encapsulated into a date * / @ DateTimeFormat (pattern = "yyyy-MM-dd HH:mm:ss") private Date birth

@ JsonFormat (pattern= "yyyy-MM-dd") converts Date to String when passing values to the foreground in the background

When the import com.fasterxml.jackson.annotation.JsonFormat; / * background returns to the foreground, the date is automatically formatted * / @ JsonFormat (pattern = "yyyy-MM-dd HH:mm:ss") private Date birth

Note:

@ JsonFormat can not only complete the type conversion of background-to-foreground parameter passing, but also achieve foreground-to-background type conversion.

When content-type is application/json, the pattern of @ JsonFormat is preferred for type conversion. Instead of using @ DateTimeFormat for type conversion.

The purpose of the @ JsonFormat annotation is to convert json strings to java objects, regardless of the direction in which the parameters are passed.

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