在本教程中，我们将为LocalDate和LocalDateTime类编写自定义序列化程序和反序列化程序。

LocalDateSerializer
LocalDateTimeSerializer
LocalDateDeserializer
LocalDateTimeDeserializer

Order POJO Class-要序列化和反序列化的对象

让我们首先定义一个要序列化和反序列化的对象-Order.java

class Order {
    private int id;
    private String orderName;
    private String orderDesc;
    private LocalDate orderCreatedDate;
    private LocalDateTime orderCreatedDateTime;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getOrderName() {
        return orderName;
    }

    public void setOrderName(String orderName) {
        this.orderName = orderName;
    }

    public String getOrderDesc() {
        return orderDesc;
    }

    public void setOrderDesc(String orderDesc) {
        this.orderDesc = orderDesc;
    }

    public LocalDate getOrderCreatedDate() {
        return orderCreatedDate;
    }

    public void setOrderCreatedDate(LocalDate orderCreatedDate) {
        this.orderCreatedDate = orderCreatedDate;
    }

    public LocalDateTime getOrderCreatedDateTime() {
        return orderCreatedDateTime;
    }

    public void setOrderCreatedDateTime(LocalDateTime orderCreatedDateTime) {
        this.orderCreatedDateTime = orderCreatedDateTime;
    }

    @Override
    public String toString() {
        return "Order [id=" + id + ", orderName=" + orderName + ", orderDesc=" + orderDesc + ", orderCreatedDate=" +
            orderCreatedDate + ", orderCreatedDateTime=" + orderCreatedDateTime + "]";
    }
}

1.自定义GSON LocalDateSerializer

class LocalDateSerializer implements JsonSerializer < LocalDate > {
    private static final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d-MMM-yyyy");

    @Override
    public JsonElement serialize(LocalDate localDate, Type srcType, JsonSerializationContext context) {
        return new JsonPrimitive(formatter.format(localDate));
    }
}

请注意，我们将默认本地日期“2018-10-26”格式化为“2018年10月27日”。

2.自定义GSON LocalDateTimeSerializer

class LocalDateTimeSerializer implements JsonSerializer < LocalDateTime > {
    private static final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss");

    @Override
    public JsonElement serialize(LocalDateTime localDateTime, Type srcType, JsonSerializationContext context) {
        return new JsonPrimitive(formatter.format(localDateTime));
    }
}

请注意，我们将默认本地日期“2018-10-26T11:09:05”格式化为“27:：Oct:：2018 14:：35:：13”。

3.自定义GSON LocalDateDeserializer

class LocalDateDeserializer implements JsonDeserializer < LocalDate > {
    @Override
    public LocalDate deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
    throws JsonParseException {
        return LocalDate.parse(json.getAsString(),
            DateTimeFormatter.ofPattern("d-MMM-yyyy").withLocale(Locale.ENGLISH));
    }
}

4.自定义GSON LocalDateTimeDeserializer

class LocalDateTimeDeserializer implements JsonDeserializer < LocalDateTime > {
    @Override
    public LocalDateTime deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
    throws JsonParseException {
        return LocalDateTime.parse(json.getAsString(),
            DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss").withLocale(Locale.ENGLISH));
    }
}

注册自定义序列化程序和反序列化程序

GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateSerializer());

gsonBuilder.registerTypeAdapter(LocalDateTime.class, new LocalDateTimeSerializer());

gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateDeserializer());

gsonBuilder.registerTypeAdapter(LocalDateTime.class, new LocalDateTimeDeserializer());

Gson gson = gsonBuilder.setPrettyPrinting().create();

GSON自定义序列化和反序列化示例

让我们编写一个完整的示例来演示GSON自定义序列化器和反序列化器的用法。

package net.javaguides.gson;

import java.lang.reflect.Type;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

public class GSONCustomSerDerExample {
    public static void main(String[] args) {
        Order order = new Order();
        order.setId(100);
        order.setOrderName("Book purchase");
        order.setOrderDesc("Java Head First");
        order.setOrderCreatedDate(LocalDate.now());
        order.setOrderCreatedDateTime(LocalDateTime.now());

        GsonBuilder gsonBuilder = new GsonBuilder();
        gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateSerializer());

        gsonBuilder.registerTypeAdapter(LocalDateTime.class, new LocalDateTimeSerializer());

        gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateDeserializer());

        gsonBuilder.registerTypeAdapter(LocalDateTime.class, new LocalDateTimeDeserializer());

        Gson gson = gsonBuilder.setPrettyPrinting().create();

        // Convert to JSON
        System.out.println(gson.toJson(order));

        String orderJson = "{\r\n" + "  \"id\": 100,\r\n" + "  \"orderName\": \"Book purchase\",\r\n" +
            "  \"orderDesc\": \"Java Head First\",\r\n" + "  \"orderCreatedDate\": \"26-Oct-2018\",\r\n" +
            "  \"orderCreatedDateTime\": \"26::Oct::2018 11::09::05\",\r\n" +
            "  \"orderCreatedZonedDateTime\": \"Oct 26 2018  11:09 AM\"\r\n" + "}";
        // Convert to java objects
        System.out.println(gson.fromJson(orderJson, Order.class));

    }

}

class Order {
    private int id;
    private String orderName;
    private String orderDesc;
    private LocalDate orderCreatedDate;
    private LocalDateTime orderCreatedDateTime;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getOrderName() {
        return orderName;
    }

    public void setOrderName(String orderName) {
        this.orderName = orderName;
    }

    public String getOrderDesc() {
        return orderDesc;
    }

    public void setOrderDesc(String orderDesc) {
        this.orderDesc = orderDesc;
    }

    public LocalDate getOrderCreatedDate() {
        return orderCreatedDate;
    }

    public void setOrderCreatedDate(LocalDate orderCreatedDate) {
        this.orderCreatedDate = orderCreatedDate;
    }

    public LocalDateTime getOrderCreatedDateTime() {
        return orderCreatedDateTime;
    }

    public void setOrderCreatedDateTime(LocalDateTime orderCreatedDateTime) {
        this.orderCreatedDateTime = orderCreatedDateTime;
    }

    @Override
    public String toString() {
        return "Order [id=" + id + ", orderName=" + orderName + ", orderDesc=" + orderDesc + ", orderCreatedDate=" +
            orderCreatedDate + ", orderCreatedDateTime=" + orderCreatedDateTime + "]";
    }
}

class LocalDateSerializer implements JsonSerializer < LocalDate > {
    private static final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d-MMM-yyyy");

    @Override
    public JsonElement serialize(LocalDate localDate, Type srcType, JsonSerializationContext context) {
        return new JsonPrimitive(formatter.format(localDate));
    }
}

class LocalDateTimeSerializer implements JsonSerializer < LocalDateTime > {
    private static final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss");

    @Override
    public JsonElement serialize(LocalDateTime localDateTime, Type srcType, JsonSerializationContext context) {
        return new JsonPrimitive(formatter.format(localDateTime));
    }
}

class LocalDateDeserializer implements JsonDeserializer < LocalDate > {
    @Override
    public LocalDate deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
    throws JsonParseException {
        return LocalDate.parse(json.getAsString(),
            DateTimeFormatter.ofPattern("d-MMM-yyyy").withLocale(Locale.ENGLISH));
    }
}

class LocalDateTimeDeserializer implements JsonDeserializer < LocalDateTime > {
    @Override
    public LocalDateTime deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
    throws JsonParseException {
        return LocalDateTime.parse(json.getAsString(),
            DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss").withLocale(Locale.ENGLISH));
    }
}

输出：

{
  "id": 100,
  "orderName": "Book purchase",
  "orderDesc": "Java Head First",
  "orderCreatedDate": "27-Oct-2018",
  "orderCreatedDateTime": "27::Oct::2018 14::35::13"
}
Order [id=100, orderName=Book purchase, orderDesc=Java Head First, orderCreatedDate=2018-10-26, orderCreatedDateTime=2018-10-26T11:09:05]