[CQ Engine] I want to handle collections like Stream or .Net LINQ even in Java 7.

background

• In legacy environment, Java8 cannot be used due to middleware and Stream cannot be used.
• When formatting the collection, the for statement is used.

So I searched for Java7 that can perform smart collection operations like Stream and LinQ. (If you know any other way to avoid turning the for statement, please let me know)

About CQ Engine

Awesome Java: Great Java Framework Library Software It was introduced in the above article.

CQEngine Official repository Github: CQengin

• CQEngine seems to be a library that provides ultra-fast Collection operations by setting an Index for a model.
• This time we will verify whether it can be used with Java 7 instead of Stream
• Index is not verified because it deviates from the subject

License The license of "CQ Engine" is "Apache License 2.0".

How to describe collection operations in CQEngine

Use of Query

• merit
• Can be type-safe
• Higher readability than turning with a for statement
• It seems to be faster than Java 8 Stream by setting Index * [question] Performance difference in Query vs standard collection lambda
• Demerit
• POJO cannot be used as it is
• Learning how to set Attribute seems to cost money
• Requires description method for CQ Engine

// already defined Attribute in Car Class
// search brand-new AAACar
uery<Car> query1 =	and(
						endsWith(Car.NAME, "AAACar"),
						equal(Car.DISCREPRION, "brandNew")
					);
ResultSet<car> resultSet = cars.retrieve(query1));

Using CQN dialects

• merit
• Applicable to POJO
• Higher readability than turning with a for statement ...?
• Demerit
• Not type safe
• Requires description method for CQ Engine *

import static com.googlecode.cqengine.codegen.AttributeBytecodeGenerator.*;

// generate Attribute
CQNParser<Car> parser = CQNParser.forPojoWithAttributes(Car.class, createAttributes(Car.class));
// search brand-new AAACar
ResultSet<Car> results = parser.retrieve(cars,
								"and("
									+ "equal(\"name\",\"AAACar\"),"
									+ "equal(\"discription\", \"brandNew\")"
								+ " )");

Using SQL dialects

• merit
• Applicable to POJO
• Can be used by anyone who understands SQL (there may be slightly different rules)
• Demerit
• Not type safe

// generate Attribute
SQLParser<Car> parser = SQLParser.forPojoWithAttributes(Car.class, createAttributes(Car.class));

// search brand-new AAACar
ResultSet<Car> results = parser.retrieve(cars,
								"SELECT * FROM cars " +
								"WHERE (" +
									" name = 'AAACar' " +
									" AND discription = 'brandNew')"
								);

for (Car car : results ) {
	System.out.println(car.toString());
}

Verification

Maven ~~ The latest version at the moment is included ~~ Insert "2.12.4" that can be used with Java 7.

<dependency>
  <groupId>com.googlecode.cqengine</groupId>
  <artifactId>cqengine</artifactId>
  <version>2.12.4</version>
</dependency>

Looking at the release notes, it seems that Ver3 to Java7 and below are excluded. CQEngine Release Notes

Preparing data for comparison

Preparing a model for the collection

I made a Car. * @Data is described because lombok is used.

@Data
public class Car {
	private int carId;
	private String name;
	private String discription;
	private List<String> features;
}

Comparison

Java for statement

// create car collection
Set<Car> cars = new HashSet<>();
cars.add( Car.builder().carId(0).name("AAACar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );
cars.add( Car.builder().carId(1).name("BBBCar").discription("used").features( Arrays.asList("spare tyre", "radio")).build() );
cars.add( Car.builder().carId(2).name("CCCCar").discription("used").features( Arrays.asList("radio", "sunroof")).build() );
cars.add( Car.builder().carId(3).name("DDDCar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );
cars.add( Car.builder().carId(4).name("AAACar").discription("used").features( Arrays.asList("radio", "sunroof")).build() );
cars.add( Car.builder().carId(5).name("BBBCar").discription("brandNew").features( Arrays.asList("spare tyre", "radio")).build() );
cars.add( Car.builder().carId(6).name("CCCCar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );
cars.add( Car.builder().carId(7).name("DDDCar").discription("used").features( Arrays.asList("radio", "sunroof")).build() );
cars.add( Car.builder().carId(8).name("AAACar").discription("used").features( Arrays.asList("spare tyre", "sunroof")).build() );
cars.add( Car.builder().carId(9).name("BBBCar").discription("used").features( Arrays.asList("spare tyre", "radio")).build() );
cars.add( Car.builder().carId(10).name("CCCCar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );

// search brand-new AAACar
Set<Car> results = new HashSet<>();
for (Car car : cars) {
	if ( Objects.equals(car.getName(), "AAACar")
			&& Objects.equals(car.getDiscription(), "brandNew") ) {
		results.add(car);
	}
}

for (Car car : results ) {
	System.out.println(car.toString()); // => Car(carId=0, name=AAACar, discription=brandNew, features=[spare tyre, sunroof])
}

Use CQN (CQ Engine Native)

Since it is intended to be used as a substitute for Stream, we will verify it with a policy of not adding Attribute to POJO. Try using CQN notation without Attribute. Generate attributes from private class fields It seems difficult to get private fields of POJO, so I set the setting to use getter in createAttributes.

// generate Attribute
CQNParser<Car> parser = CQNParser.forPojoWithAttributes(Car.class, createAttributes(Car.class, MemberFilters.GETTER_METHODS_ONLY));

// create car collection
IndexedCollection<Car> cars = new ConcurrentIndexedCollection<>();
cars.add( Car.builder().carId(0).name("AAACar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );
//(abridgement)
cars.add( Car.builder().carId(10).name("CCCCar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );

// search brand-new AAACar
ResultSet<Car> results = parser.retrieve(cars,
								"and("
									+ "equal(\"getName\",\"AAACar\"),"
									+ "equal(\"getDiscription\", \"brandNew\")"
								+ " )");

for (Car car : results ) {
	System.out.println(car.toString());   // => Car(carId=0, name=AAACar, discription=brandNew, features=[spare tyre, sunroof])
}

Java 8 Stream

// create car collection
Set<Car> cars = new HashSet<>();
cars.add( Car.builder().carId(0).name("AAACar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );
//(abridgement)
cars.add( Car.builder().carId(10).name("CCCCar").discription("brandNew").features( Arrays.asList("spare tyre", "sunroof")).build() );

// search brand-new AAACar
Set<Car> results =  cars.stream()
						.filter(car -> Objects.equals(car.getName(), "AAACar")
								&& Objects.equals(car.getDiscription(), "brandNew") )
						.collect(Collectors.toSet());

for (Car car : results ) {
	System.out.println(car.toString());
}

How to use CQ Engine with Java 7 or lower

Since Java7 is not supported for CQEngine Ver3 and above, the following error will occur.

 Unsupported major.minor version 52.0

Conclusion

• If you don't care about type safety, readability can be improved.
• It is necessary to add some effort to use it as type-safe (set Attribute in POJO)
• The latest version cannot be used with Java 7
• I didn't find it so attractive in terms of using it as a substitute for Stream in Java7 (it wasn't originally such a library). Remember as a candidate when you want to process a large amount of data at high speed

Use Stream more straightforwardly with Java7-

Lightweight-Stream-API-I want to use Stream API with Java 6 and 7 This seems to be a library that can be used like Stream as it is When migrating to Java8, this library is used before migration, and the code after migration is Java8 Stream. I thought I had to be careful not to get into a chaotic situation This time, I decided to investigate from the viewpoint of whether CQ Engine can exceed the standard library even for Java 8 or later. So, in the future, I would like to evaluate the performance of CQ Engine in mass data processing.

Use with large amounts of data

(I will write in another article) It is difficult to prepare the data, so look for an API that can get a lot of data. Can be used by individuals! Recommended API list