requery


Source link: https://github.com/requery/requery

A light but powerful object mapping and SQL generator for Java/Kotlin/Android with RxJava and Java 8 support. Easily map to or create databases, perform queries and updates from any platform that uses Java.

Examples

Define entities from an abstract class:

@Entity abstract class AbstractPerson {

@Key @Generated
  int id;

@Index("name_index")

// table specification
  String name;

@OneToMany

 // relationships 1:1, 1:many, many to many
  Set<Phone> phoneNumbers;

@Converter(EmailToStringConverter.class) // custom type conversion
  Email email;

@PostLoad

  // lifecycle callbacks
  void afterLoad() {

updatePeopleList();

  
}

  // getter, setters, equals & hashCode automatically generated into Person.java 
}
 

or from an interface:

@Entity public interface Person {

@Key @Generated
  int getId();

String getName();

@OneToMany
  Set<Phone> getPhoneNumbers();

String getEmail();
 
}

or use immutable types such as those generated by @AutoValue:

@AutoValue @Entity abstract class Person {

@AutoValue.Builder
  static abstract class Builder {

abstract Builder setId(int id);

abstract Builder setName(String name);

abstract Builder setEmail(String email);

abstract Person build();

  
}

static Builder builder() {

return new AutoValue_Person.Builder();

  
}

@Key
  abstract int getId();

abstract String getName();

  abstract String getEmail();
 
}

(Note some features will not be available when using immutable types, see here)

Queries: dsl based query that maps to SQL

Result<Person> query = data
  .select(Person.class)
  .where(Person.NAME.lower().like("b%")).and(Person.AGE.gt(20))
  .orderBy(Person.AGE.desc())
  .limit(5)
  .get();

Relationships: represent relations more efficiently with Java 8 Streams, RxJava Observables or plain iterables. (sets and lists are supported to)

@Entity abstract class AbstractPerson {

@Key @Generated
  int id;

@ManyToMany
  Result<Group> groups;
  // equivalent to:
  // data.select(Group.class)
  // .join(Group_Person.class).on(Group_ID.equal(Group_Person.GROUP_ID))
  // .join(Person.class).on(Group_Person.PERSON_ID.equal(Person.ID))
  // .where(Person.ID.equal(id)) 
}

Kotlin specific support using property references and infix functions:

data {

  val result = select(Person::class) where (Person::age gt 21) and (Person::name eq "Bob") limit 10 
}

Java 8 streams:

data.select(Person.class)
  .orderBy(Person.AGE.desc())
  .get()
  .stream().forEach(System.out::println);

Java 8 optional and time support:

public interface Person {

@Key @Generated
  int getId();

String getName();

  Optional<String> getEmail();

  ZonedDateTime getBirthday();
 
}

RxJava Observables:

Supports both RxJava 1.0 and 2.0. (RxJava 2.0 examples shown)

Observable<Person> observable = data
  .select(Person.class)
  .orderBy(Person.AGE.desc())
  .get()
  .observable();

RxJava observe query on table changes:

Observable<Person> observable = data
  .select(Person.class)
  .orderBy(Person.AGE.desc())
  .get()
  .observableResult().subscribe(::updateFromResult);

Read/write separation Along with immutable types optionally separate queries (reading) and updates (writing):

int rows = data.update(Person.class)
  .set(Person.ABOUT, "student")
  .where(Person.AGE.lt(21)).get().value();

Features

  • No Reflection
  • Fast startup & performance
  • No dependencies (RxJava is optional)
  • Typed query language
  • Table generation
  • Supports JDBC and most popular databases (MySQL, Oracle, SQL Server, Postgres and more)
  • Supports Android (SQLite, RecyclerView, Databinding, SQLCipher)
  • Blocking and non-blocking API
  • Partial objects/refresh
  • Upsert support
  • Caching
  • Lifecycle callbacks
  • Custom type converters
  • Compile time entity validation
  • JPA annotations (however requery is not a JPA provider)

Reflection free

requery uses compile time annotation processing to generate entity model classes and mapping attributes. On Android this means you get about the same performance reading objects from a query as if it was populated using the standard Cursor and ContentValues API.

Query with Java

The compiled classes work with the query API to take advantage of compile time generated attributes. Create type safe queries and avoid hard to maintain, error prone string concatenated queries.

Relationships

You can define One-to-One, One-to-Many, Many-to-One, and Many-to-Many relations in your models using annotations. Relationships can be navigated in both directions. Of many type relations can be loaded into standard java collection objects or into a more efficient Result type. From a Result easily create a Stream, RxJava Observable, Iterator, List or Map.

Many-to-Many junction tables can be generated automatically. Additionally the relation model is validated at compile time eliminating runtime errors.

vs JPA

requery provides a modern set of interfaces for persisting and performing queries. Some key differences between requery and JPA providers like Hibernate or EclipseLink:

  • Queries maps directly to SQL as opposed to JPQL.
  • Dynamic Queries easily done through a DSL as opposed to the verbose CriteriaQuery API.
  • Uses easily understandable extended/generated code instead of reflection/bytecode weaving for state tracking and member access

Android

Designed specifically with Android support in mind. See requery-android/example for an example Android project using databinding and interface based entities. For more information see the Android page.

Supported Databases

Tested on some of the most popular databases:

  • PostgresSQL (9.1+)
  • MySQL 5.x
  • Oracle 12c+
  • Microsoft SQL Server 2012 or later
  • SQLite (Android or with the xerial JDBC driver)
  • Apache Derby 10.11+
  • H2 1.4+
  • HSQLDB 2.3+

JPA Annotations

A subset of the JPA annotations that map onto the requery annotations are supported. See here for more information.

Upserts

Upserts are generated with the appropriate database specific query statements:

  • Oracle/SQL Server/HSQL: merge into when matched/not matched
  • PostgresSQL: on conflict do update (requires 9.5 or later)
  • MySQL: on duplicate key update

Using it

Versions are available on bintray jcenter / maven central.

repositories {

  jcenter() 
}
  dependencies {

  compile 'io.requery:requery:1.4.1'
  compile 'io.requery:requery-android:1.4.1' // for android
  annotationProcessor 'io.requery:requery-processor:1.4.1' 
}

For information on gradle and annotation processing & gradle see the wiki.

License

Copyright (C) 2017 requery.io  Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License. You may obtain a copy of the License at  http://www.apache.org/licenses/LICENSE-2.0  Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. 

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