Java 8 in action.Jinq

Sergey Morenets, morenets@mail.ru

March, 12 2015

About author• Works in IT since 2000

• 11 year of Java SE/EE experience

• Regular speaker on Java User Group conferences

• Java evangelist

Agenda

• Java 8 overview

• Libraries support

• Jinq

• Q&A

Java 8 overview

Java 8 overview

• Lambda expressions

• Streams API

• Java time

• Default & static methods

• Method references

• Repeating & type annotations

• Hashorn

• Metaspace

Native support

• Lambda expressions

• Default methods

• Method references

• Nashorn

• Metaspace

Type annotations

• @Nullable

• @NonNull

• @ReadOnly

Repeatable annotations

• Spring Framework

Java time

• Joda replacement

• Supported in Spring 4

• Ignored by Hibernate, partially supported by JPA

Hibernate

JPA

JPA

Streams API

Streams API

File storage

Data access

Data access

• JDBC

• Spring JDBC

• ORM (Hibernate)

• JPA

• Functional programming

Recently

• SQL

• HQL/JPQL

• Hibernate/JPA criteria

• Custom API

Jinq

• Initially developed by Dr. Ming-Yee

• Open-source project

• Functional database queries in Java and Scala

• Inspired by LINQ

• Required JPA & Java 8

Jinq flow

• Translated Java code and Run it as database query

statements

• Run as ordinary Java code

Configuration

• Map entities

• JPA provider

• JPA configuration

Configuration

Configuration

Count

select count(city.id) from City city

Filtering

Jinq

select city.id, city.name, city.population from City city

limit ?

Where

select count(city.id) from City city where

city.population>100

Variables

select count(city.id) from City city where

city.population > ?

Select

select city.name from City city limit ?

Comparison

select count(city.id) from City city where

city.name='Odessa'

Comparison

select count(city.id) from City city where city.name is

not null

Concatenation

select concat('City:', city.name) from City city limit ?

Concatenation

Aggregate

select max(city.population) from City city

Methods

Sorting

select city.id, city.name, city.population as from City

city order by city.population ASC, city.name ASC limit

?

Country

Associations

select count(city.id) from City city cross join Country

country where city.countryId=country.id and

country.name='Ukraine'

Pairs

select city.id, country.id, city.countryId, city.name,

city.population, country.name from City city inner join

Country country on city.countryId=country.id limit ?

Join

• join()

• joinList()

• selectAll()

Grouping

• select city.countryId, sum(city.population),

count(city.id), country.id, country.name from City

city inner join Country country on city.countryId=

country.id group by city.countryId limit ?

Limitations

• Your code cannot contain any loops

• Your code can call other methods but only those

from a restricted list with known side-effects

• Your code can read and modify local variables

(since these changes will be discarded once the

function exits)

• Your code can read but not modify non-local

variables

• Your code cannot contain casting between

different data types

Data types

Java type Supported operations

String equals()

BigDecimal, BigInteger, Integer, int, Double, double, Long, long

==, <, <=, >, >=, !=, +, -, *, /

Boolean, boolean !, &&, ||, ==

java.util.Date, java.sql.Date, java.sql.Time, java.sql.Timestamp, java.util.Calendar

equals(), before(), after()

enums ==, !=

entities ==, !=

java.util.Collection contains(), JPQL.isIn()

Functions

Java JPQL alternative

Math.abs() / BigDecimal.abs() / BigInteger.abs()

ABS()

Math.sqrt() SQRT()

% MOD()

String.toUpperCase() / String.toLowerCase()

UPPER() / LOWER()

String.trim() TRIM()

String.length() LENGTH()

String.indexOf() LOCATE()

Pro

• Brings up functional style

• Database & provider independent

• SQL-92 - compatible

Cons

• Requires JPA

• Limited to JPA functionality

• No stored procedures

• Lacks NoSQL support

• Hard to debug

To be continued?

• XML

• JSON

• JDBC

Jooq

• Java object oriented querying

• Lightweight alternative

• JDBC wrapper

• SQL building, code generation & SQL execution

• Jinq provides basic support for Jooq

• Open-source & paid version

References

Q&A

Sergey Morenets, morenets@mail.ru