EntityUtil.java code snippet

I usually do ‘select’ query before ‘update’ or ‘insert’ query using Jpa, Java.

For example, I must create new entity if the entity is null by ‘select’ query, or I do just setAge(); if the entity exists.

So I code as below by most commonly.

public void putSomeEntity(String name, int age) {
    SomeEntity someEntity = someEntityRepository.findByName(name);

    if (someEntity == null) {
        someEntity = new SomeEntity();
        someEntity.setName(name);
    }

    someEntity.setAge(age);

    someEntityRepository.save(someEntity);
}

I don’t want to do it, checking null, always. It is very pesky pattern.

So I create a utility class as below.

package kr.co.freeism.util;

import com.google.common.base.Preconditions;
import lombok.AccessLevel;
import lombok.NoArgsConstructor;

import javax.persistence.Entity;

/**
 * @author freeism
 * @since 2018. 6. 2.
 */
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class EntityUtil {
  /**
   * return new Entity by default constructor, if null
   * return bypassing the Entity, given method parameter
   *
   * @param obj the target for checking null. need to declare @Entity annotation
   * @param clazz default entity type for returning, if the object is null
   * @return obj != null ? obj : new obj()
   * @throws NullPointerException If clazz is null.
   * @throws IllegalArgumentException If @Entity annotaion is missing.
   * @throws IllegalArgumentException If clazz.newInstance() throws Exception.
   */
  public static <T> T defaultEntity(T obj, Class<T> clazz) {
    Preconditions.checkNotNull(clazz, "clazz must be defined.");
    Preconditions.checkArgument(clazz.isAnnotationPresent(Entity.class), "clazz must be Entity annotated class.");

    try {
      return obj == null ? clazz.newInstance() : obj;
    } catch (IllegalAccessException | InstantiationException e) {
      throw new IllegalArgumentException("clazz must have default constructor.");
    }
  }
}
public void putSomeEntity(String name, int age) {
    SomeEntity someEntity = EntityUtil.defaultEntity(someEntityRepository.findByName(name), SomeEntity.class);

    someEntity.setAge(age);

    someEntityRepository.save(someEntity);
}

Originally published at ThinkCUBES.