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Spring - Creating a Custom Converter

[Last Updated: Oct 17, 2022]

This tutorial shows how to create a custom converter and register with ConversionService.

Example

In this example we are going to create a custom converter to convert String to java.time.LocalDateTime.

Implementing Converter interface

package com.logicbig.example;

import org.springframework.core.convert.converter.Converter;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class StringToLocalDateConverter
      implements Converter<String, LocalDate> {
  DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy/MM/dd");

  @Override
  public LocalDate convert(String dateTimeString) {
      return LocalDate.parse(dateTimeString, formatter);
  }
}

Registering our converter

Besides implementing ConversionService, DefaultConversionService also implements ConverterRegistry interface which is an abstraction of converters registration with the underlying conversion service. In following configuration we are registering our custom converter with DefaultConversionService

package com.logicbig.example;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;

@Configuration
public class Config {
  @Bean
  public ConversionService conversionService() {
      DefaultConversionService service = new DefaultConversionService();
      service.addConverter(new StringToLocalDateConverter());
      return service;
  }

  @Bean
  public ClientBean clientBean() {
      return new ClientBean("2010/10/05");
  }
}

Client code using ConversionService

public class ClientBean {
  private final String date;
  @Autowired
  private ConversionService conversionService;

  ClientBean(String date) {
      this.date = date;
  }

  public void showLocalDateTime() {
      LocalDate localDate = conversionService.convert(date, LocalDate.class);
      System.out.println(localDate);
  }
}

Main class

package com.logicbig.example;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class CustomConverterExample {
  public static void main(String[] args) {
      AnnotationConfigApplicationContext context = new
              AnnotationConfigApplicationContext(
              Config.class);

      ClientBean clientBean = context.getBean(ClientBean.class);
      clientBean.showLocalDateTime();
  }
}

Output

2010-10-05

Example Project

Dependencies and Technologies Used:

  • spring-context 5.3.23 (Spring Context)
     Version Compatibility: 3.2.3.RELEASE - 5.3.23 Version List
    ×

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    Versions in green have been tested.

  • JDK 8
  • Maven 3.8.1

Spring - Creating and registering a custom converter Select All Download
  • spring-conversion-service-custom-converter
    • src
      • main
        • java
          • com
            • logicbig
              • example
                • StringToLocalDateConverter.java

    See Also