Moshi java.time.LocalDate requires explicit JsonAdapter to be registered
Moshi does not have built-in adapters to process types like Java 8 date time APIs java.time.* or JSR-310; we need to manually provide a custom adapter to handle the Java 8 date time type.
This article shows how to use Moshi to convert the Java 8 Localdate type to JSON data.
Table of contents:
- 1. Download Moshi
- 2. LocalDate requires explicit JsonAdapter
- 3. Make Moshi supports Java 8 Date Time APIs
- 4. Download Source Code
- 5. References
P.S Tested with Moshi 1.15.1
1. Download Moshi
Declare moshi in the pom.xml.
<dependency>
<groupId>com.squareup.moshi</groupId>
<artifactId>moshi</artifactId>
<version>1.15.1</version>
</dependency>
2. LocalDate requires explicit JsonAdapter
The following Book object contains the type Java 8 date API java.time.LocalDate.
package com.mkyong.json.model;
import java.time.LocalDate;
public class Book {
private Long id;
private String title;
private LocalDate publishDate; // java 8
// getters, setters, constructors and etc.
}
If we use Moshi to serialize the object into JSON, Moshi will throw the error java.time.LocalDate requires explicit JsonAdapter to be registered.
Moshi moshi = new Moshi.Builder().build();
JsonAdapter<Book> jsonAdapter = moshi.adapter(Book.class);
Book book = createBook();
String json = jsonAdapter.toJson(book); // throws error
Caused by: java.lang.IllegalArgumentException:
Platform class java.time.LocalDate requires explicit JsonAdapter to be registered
at com.squareup.moshi.ClassJsonAdapter$1.create(ClassJsonAdapter.java:76)
at com.squareup.moshi.Moshi.adapter(Moshi.java:146)
... 6 more
3. Make Moshi supports Java 8 Date Time APIs
We need to create and register a custom JsonAdapter to handle the serialization and deserialization of LocalDate objects.
3.1 Define LocalDate Adapter
Create logic to handle the LocalDate. The ISO-8601 format (uuuu-MM-dd) is commonly used and is the default format for LocalDate.toString().
package com.mkyong.json.moshi.adapter;
import com.squareup.moshi.FromJson;
import com.squareup.moshi.ToJson;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
public class LocalDateJsonAdapter {
private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ISO_LOCAL_DATE;
// Serialize the LocalDate to String
@ToJson
String toJson(LocalDate date) {
return date.format(FORMATTER);
}
// Parse the String back to a LocalDate
@FromJson
LocalDate fromJson(String date) {
return LocalDate.parse(date, FORMATTER);
}
}
3.2 Register the Adapter with Moshi
The following example will register a LocalDateJsonAdapter and convert the type LocalDate to JSON.
package com.mkyong.json.moshi;
import com.mkyong.json.model.Book;
import com.mkyong.json.moshi.adapter.BigDecimalJsonAdapter;
import com.mkyong.json.moshi.adapter.LocalDateJsonAdapter;
import com.squareup.moshi.JsonAdapter;
import com.squareup.moshi.Moshi;
import java.math.BigDecimal;
import java.time.LocalDate;
public class MoshiJava8DateTimeExample {
public static void main(String[] args) {
Moshi moshi = new Moshi.Builder()
.add(new LocalDateJsonAdapter()) // Register the LocalDate adapter
.build();
JsonAdapter<Book> jsonAdapter = moshi.adapter(Book.class);
Book book =
new Book(1L, "Book A", LocalDate.of(2023, 10, 1));
try {
String json = jsonAdapter.toJson(book);
System.out.println(json);
} catch (Exception e) {
System.err.println("Error parsing JSON: " + e.getMessage());
}
}
}
Output
{"id":1,"publishDate":"2023-10-01","title":"Book A"}
4. Download Source Code
$ git clone https://github.com/mkyong/java-json
$ cd moshi
5. References
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