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Spring - Creating Custom ConverterFactory

[Last Updated: Oct 17, 2022]

Let's say we have a hierarchy of multiple of classes extending a same base class: Shape.
In this example we are going to create a converter factory, IdToEntityConverterFactory which will tie all subclass of Entity to a single converter StringToShapeConverterFactory. This converter will convert provided string to a shape object.

Example

package com.logicbig.example;

public interface Shape {
}
package com.logicbig.example;

public class Circle implements Shape {
  private int radius;
    .............
}
package com.logicbig.example;

public class Square implements Shape{
private int side;
    .............
}

The converter factory implementation:

public class StringToShapeConverterFactory implements ConverterFactory<String, Shape> {

  @Override
  public <T extends Shape> Converter<String, T> getConverter(Class<T> targetType) {
      return new ShapeConverter<>(targetType);
  }
}
package com.logicbig.example;

import org.springframework.core.convert.converter.Converter;

public class ShapeConverter<T extends Shape> implements Converter<String, T> {

  private Class<T> targetType;

  public ShapeConverter(Class<T> targetType) {
      this.targetType = targetType;
  }

  @Override
  public T convert(String source) {
     if(targetType==Square.class){
         int side = Integer.parseInt(source);
         return (T) new Square(side);
     }else if(targetType==Circle.class){
         int radius = Integer.parseInt(source);
         return (T) new Circle(radius);
     }
      return null;
  }
}

Configuring beans and using Conversion service:

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();
      //registering our custom ConverterFactory
      service.addConverterFactory(new StringToShapeConverterFactory());
      return service;
  }

  @Bean
  public ClientBean clientBean() {
      return new ClientBean();
  }
}
package com.logicbig.example;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.convert.ConversionService;

public class ClientBean {
  @Autowired
  private ConversionService service;

  public Shape getShape(String shapeString, Class<? extends Shape> type) {
      return service.convert(shapeString, type);
  }
}
package com.logicbig.example;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class CustomConverterFactoryExample {

  public static void main(String[] args) {

      AnnotationConfigApplicationContext context = new
              AnnotationConfigApplicationContext(Config.class);

      ClientBean clientBean = context.getBean(ClientBean.class);
      Shape shape = clientBean.getShape("10", Circle.class);
      System.out.println(shape);

      shape = clientBean.getShape("4", Square.class);
      System.out.println(shape);
  }
}

Output

Circle{radius=10}
Square{side=4}


Example Project

Dependencies and Technologies Used:

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

    Version compatibilities of spring-context with this example:

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    Versions in green have been tested.

  • JDK 8
  • Maven 3.8.1

Sporing - Custom ConverterFactory example Select All Download
  • spring-custom-converter-factory-example
    • src
      • main
        • java
          • com
            • logicbig
              • example
                • StringToShapeConverterFactory.java

    See Also