java 日期类型的转换

• 封装的工具类，主要用于LocalDateTime、Date、String 三者之间的相互转换。其中String与Date的转换还可以使用SimpleDateFormat，这里主要以DateTimeFormatter为主。

• import java.text.SimpleDateFormat;
  import java.time.LocalDateTime;
  import java.time.OffsetDateTime;
  import java.time.ZoneId;
  import java.time.ZoneOffset;
  import java.time.format.DateTimeFormatter;
  import java.time.temporal.TemporalAccessor;
  import java.util.Date;
  
  
  public class DateUtil {
      public static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
  
  
      /**
       * String 转 LocalDateTime
       * @param date
       * @return
       */
      public static LocalDateTime stringToLocalDateTime(String date) {
  
          //也可以自己定义格式
          //DateTimeFormatter formatter = DateTimeFormatter.ISO_OFFSET_DATE_TIME;
          DateTimeFormatter formatter = DateTimeFormatter.ISO_LOCAL_DATE_TIME;
          LocalDateTime dateTime = LocalDateTime.parse(date, formatter);
  
          return dateTime;
  
      }
  
      /**
       * localDateTime 转 时间戳
       * @param localDateTime
       * @return
       */
  
      public static Long localDateTimeToTimeStamp(LocalDateTime localDateTime) {
          return localDateTime.toInstant(ZoneOffset.of("+8")).toEpochMilli();
      }
  
      /**
       * String 转 Date
       * @param happenTime
       * @param dateFormat
       * @return
       */
      public static Date stringToDate(String happenTime, String dateFormat) {
  
          DateTimeFormatter formatter = DateTimeFormatter.ofPattern(dateFormat);
          OffsetDateTime offsetDateTime = OffsetDateTime.parse(happenTime, formatter);
  
          // 转换为java.util.Date对象
          Date date = Date.from(offsetDateTime.toInstant());
  
          return date;
      }
  
  
  
      /**
       * Date 转字符串 用SimpleDateFormat
       *
       * @param time
       * @return
       */
      public static String format(Date time) {
          return format(time, DATE_FORMAT);
      }
  
      public static String format(Date time, String pattern) {
          SimpleDateFormat formatter = new SimpleDateFormat(pattern);
          return formatter.format(time);
      }
  
  
      /**
       * Date 转字符串  用DateTimeFormatter
       */
  
      public static String format2(Date time, String pattern) {
          DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
          return formatter.format(date2LocalDateTime(time));
      }
  
  
      /**
       * LocalDateTime 转字符串
       */
      public static String format3(LocalDateTime time, String pattern) {
          DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
          return formatter.format(time);
  
      }
  
      /**
       * Date 转 LocalDateTime
       */
      public static LocalDateTime date2LocalDateTime(Date date) {
          return date.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
      }
  
      /**
       * LocalDateTime 转Date
       */
      public static Date localDateTime2Date(LocalDateTime time) {
          return Date.from(time.atZone(ZoneId.systemDefault()).toInstant());
      }
  }

• 两个实体类，主要涉及对象与json串之间的转换（涉及日期类型），当对象含有LocalDateTime、LocalDate、LocalTime类型的属性时，在利用ObjectMapper转换成Json字符串时，需要给objectMapper添加一些格式类型。

package com.example.restservice.pojo;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.format.annotation.DateTimeFormat;

import java.util.Date;

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class Animal {
    private String name;
    private Integer age;
   @JsonFormat(pattern = "yyyy-MM-dd'T'HH:mm:ss", timezone = "GMT+8")
    private Date birthday;
}

package com.example.restservice.pojo;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateSerializer;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.util.Date;
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class AnimalCC {
    private String name;
    private Integer age;

    @JsonFormat(pattern = "yyyy-MM-dd'T'HH:mm:ss", timezone = "GMT+8")
    private LocalDateTime birthday;

    private LocalDate localDate;
    @JsonFormat(pattern = "HH:mm:ss:SSS", timezone = "GMT+8")
    private LocalTime localTime;
}

• 一些测试例子

• package com.example.restservice.util;
  
  import com.example.restservice.pojo.Animal;
  import com.example.restservice.pojo.AnimalCC;
  import com.fasterxml.jackson.core.JsonProcessingException;
  import com.fasterxml.jackson.databind.ObjectMapper;
  import com.fasterxml.jackson.datatype.jsr310.*;
  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 java.text.DateFormat;
  import java.text.ParseException;
  import java.text.SimpleDateFormat;
  import java.time.LocalDate;
  import java.time.LocalDateTime;
  import java.time.LocalTime;
  import java.time.ZoneId;
  import java.time.format.DateTimeFormatter;
  import java.util.Date;
  import java.util.HashMap;
  import java.util.Map;
  
  public class Test {
      public static void main(String[] args) throws JsonProcessingException, ParseException {
  
  
          ObjectMapper objectMapper = new ObjectMapper();
          JavaTimeModule javaTimeModule = new JavaTimeModule();
          javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
          javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
          javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(DateTimeFormatter.ofPattern("HH:mm:ss")));
          objectMapper.registerModule(javaTimeModule);
  
          Animal animal = new Animal();
          animal.setAge(3);
          animal.setName("小狗");
          animal.setBirthday(new Date());
          System.out.println(animal);
          String s = objectMapper.writeValueAsString(animal);
          System.out.println(s);
          System.out.println("=====================================");
          System.out.println(animal.getBirthday());
          DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy/MM/dd-HH:mm:ss.SSS");
          System.out.println(dateTimeFormatter.format(LocalDateTime.now()));
  
  
          String dateTime1 = "2021-01-01T12:12:12.123+08:00";
          SimpleDateFormat simpleDateFormat2 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS+08:00");
          Animal animal1 = new Animal();
          animal1.setAge(3);
          animal1.setName("小狗");
          animal1.setBirthday(simpleDateFormat2.parse(dateTime1));
          System.out.println(simpleDateFormat2.format(new Date()));
          System.out.println(animal);
          String s8 = objectMapper.writeValueAsString(animal);
          System.out.println(s8);
  
  
          System.out.println("=====================================");
  
  
          AnimalCC animalCC = new AnimalCC();
          animalCC.setAge(3);
          animalCC.setName("小狗");
          animalCC.setBirthday(DateUtil.date2LocalDateTime(new Date()));
          animalCC.setLocalDate(LocalDateTime.now().toLocalDate());
          animalCC.setLocalTime(LocalDateTime.now().toLocalTime());
          System.out.println(animalCC);
          String s2 = objectMapper.writeValueAsString(animalCC);
          System.out.println(s2);
  
  
          System.out.println("=====================================");
          String dateTime = "2021-01-01T12:12:12";
          SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
          Date date = simpleDateFormat.parse(dateTime);
          String s3 = simpleDateFormat.format(date);
          System.out.println(date);
          System.out.println(s3);
          String s1 = objectMapper.writeValueAsString(date);
          System.out.println(s1);
  
  
          Date from = Date.from(DateUtil.stringToLocalDateTime(dateTime).atZone(ZoneId.systemDefault()).toInstant());
          System.out.println(from);
          LocalDateTime localDateTime = DateUtil.stringToLocalDateTime(dateTime);
          System.out.println(localDateTime);
  
  
          System.out.println("**********************************************");
          System.out.println(DateUtil.format3(LocalDateTime.now(), "yyyy-MM-dd HH:mm:ss"));
          System.out.println(DateUtil.format2(new Date(), "yyyy-MM-dd HH:mm:ss.SSS+08:00"));
  
  
          System.out.println("**********************************************");
          String animalStr = "{\"name\":\"小狗\",\"age\":3,\"birthday\":\"2021-01-01T12:12:12\"}";
          String animalStr2 = "{\"name\":\"小狗\",\"age\":3,\"birthday\":\"2021-01-01T12:12:12\",\"localDate\":\"2021-01-01\",\"localTime\":\"12:12:12.333\"}";
          Animal animal2 = objectMapper.readValue(animalStr, Animal.class);
          AnimalCC animalCC2 = objectMapper.readValue(animalStr2, AnimalCC.class);
          System.out.println(animal2);
          System.out.println(animalCC2);
  
  
      }
  }