JavaOne2016 - How to Generate Customized Java 8 Code from Your Database [TUT4489]

Tutorial: How to Generate Customized Java 8 Code from Your Database Per Minborg CTO, Speedment, Inc Emil Forslund Developer, Speedment, Inc.

Every Decision a Developer Makes is a Trade-off The best code is no code at all

Using Code Generation • Makes the code efficient and short • Modifications are done once and applied everywhere • Minimizes errors • “DRY” (Don’t Repeat Yourself) vs. ”WET” (We Enjoy Typing) • “Code your code” But how can we control the generated code?

About Us Per Minborg • Founder of several IT companies • Lives in Palo Alto • 20 years of Java experience • 15+ US patents • Speaker at Java events • Blog: Minborg’s Java Pot Emil Forslund • Java Developer • Lives in Palo Alto • 8 years of Java experience • Speaker at Java events • Blog: Age of Java Spire • Speedment Open Source mascot • Lives on GitHub • 1.5 years of mascot experience

Agenda • Problem Description • Code Generation in Database Applications • How Does it Work? • Hands on Demo • Controlling the Code Generation • Generate Custom Classes • Add new Method to Existing Classes • Hands on Demo • Additional Features • Real World Examples • Questions & Answers

Do You Recognize This Code? Class.forName("org.postgresql.Driver"); try (final Connection conn = DriverManager.getConnection( "jdbc:postgresql://hostname:port/dbname", "username", "password")) { // Database Logic Here... }

Why Creating DB-Apps is So Time Consuming • Even trivial database operations require a lot of boilerplate code • Mixing SQL and Java is error-prone • ORMs require you to write annotated POJOs for every table • Creating even a simple DB app can take hours

Open-Source Project Speedment • Stream ORM Java toolkit and runtime • Generate domain-model from the database • No need for complicated configurations or setup • All operations are type-safe • Data is accessed using Java 8 Streams • Business friendly Apache 2- license

Speedment Workflow customers.stream() .filter(…) .filter(…) .map(…) .collect(toList()); Step 1: Generate Code Step 2: Write Logic Step 3: Run Application Step 4: Iterate

Artifacts • com.speedment: • runtime • generator • tool • speedment-maven-plugin

So How Do the Generated Code Work? • Code is organized based on database structure • Hash-sums make sure user changes are not overwritten If the DB structure changes, the code is updated with the press of a button

Entities, Managers and Applications • An Entity represents a row in a table • Is a POJO • Customer • CustomerImpl • A Manager represents a table • Responsible for the CRUD operations • CustomerManager • CustomerManagerImpl • An Application represents the entire project • Responsible for configuration and settings • SalesApplication • SalesApplicationBuilder

Querying the Database using Streams • Queries are expressed using Java 8 streams • Streams are analyzed to produce high-performance queries

Expressing Queries as Streams customers.stream() .filter(Customer.REGION.equal(Region.NORTH_AMERICA)) .filter(Customer.REGISTERED.greaterOrEqual(startOfYear)) .count(); Standard Stream API Generated Enum Constants Only 1 value is loaded from DB Full Type-Safety SELECT COUNT('id') FROM 'customer' WHERE 'customer'.'region' = ‘North America’ AND 'customer'.'registered' >= ‘2016-01-01’;

Querying the Database using Streams SELECT * FROM 'customer' REGION.equal(NORTH_AMERICA) REGISTERED.greaterOrEqual(2016-01-01) count() Sourc e Filter Filter Term. Pipeline

Querying the Database using Streams SELECT * FROM 'customer' WHERE 'customer'.'region' = ‘North America’ REGION.equal(NORTH_AMERICA) REGISTERED.greaterOrEqual(2016-01-01) count() Sourc e Filter Filter Term. Pipeline

Querying the Database using Streams SELECT * FROM 'customer' WHERE 'customer'.'region' = ‘North America’ AND 'customer'.'registered' >= ‘2016-01-01’; REGISTERED.greaterOrEqual(2016-01-01) count() Sourc e Filter Term. Pipeline

Querying the Database using Streams SELECT COUNT('id') FROM 'customer' WHERE 'customer'.'region' = ‘North America’ AND 'customer'.'registered' >= ‘2016-01-01’; count() Sourc e Term. Pipeline

Querying the Database using Streams SELECT COUNT('id') FROM 'customer' WHERE 'customer'.'region' = ‘North America’ AND 'customer'.'registered' >= ‘2016-01-01’; Sourc e Pipeline

Expressing Queries as Streams // Gets the second page of customers in North America // sorted by name in the form of a JSON array “[“+ customers.stream() .filter(REGION.equal(Region.NORTH_AMERICA)) .sorted(NAME.comparator()) .skip(10) .limit(10) // JVM from here… .map(JsonEncoder.allOf(customers)::apply) .collect(joining(“, ”)) +”]”;

Expressing Queries as Streams // Supports parallelism on custom executors // with full control of thread work item layout customers.stream() .parallel() .filter(REGION.equal(Region.NORTH_AMERICA)) .forEach(expensiveOperatation());

Application Example • Total Count of Customers • Located in North America • Registered This Year

Step 1: Getting Speedment using Maven <plugin> <groupId>com.speedment</groupId> <artifactId>speedment-maven-plugin</artifactId> <version>3.0.0-EA</version> <dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.39</version> </dependency> </dependencies> </plugin> Generate source files based on database The JDBC connector to use

Step 2: Initializing Speedment SalesApplication app = new SalesApplicationBuilder() .withPassword("qwerty") .build(); CustomerManager customers = app.getOrThrow(CustomerManager.class); These classes are generated automatically Instance is configured using Builder- pattern A manager class is generated for every database table

Step 3: Querying Region fromWhere = Region.NORTH_AMERICA; Instant fromWhen = Instant.parse("2016-01-01"); long count = customers.stream() .filter(Customer.REGION.equal(fromWhere)) .filter(Customer.REGISTERED.greaterOrEqual(fromWhen)) .count();

Step 4: Output System.out.println( "A total of %d customers from %s " + "have registered this year.", count, fromWhere.name() );

Full Application public static void main(String… args) { SalesApplication app = new SalesApplicationBuilder() .withPassword("qwerty") .build(); CustomerManager customers = app.getOrThrow(CustomerManager.class); Region fromWhere = Region.NORTH_AMERICA; Instant fromWhen = Instant.parse("2016-01-01"); long count = customers.stream() .filter(Customer.REGION.equal(fromWhere)) .filter(Customer.REGISTERED.greaterOrEqual(fromWhen)) .count(); System.out.println( "A total of %d customers from %s " + "have registered this year.", count, fromWhere.name() ); }

Output Pers-MacBook-Pro:~ pemi$ java –jar salesapplication.jar A total of 354 customers from NORTH_AMERICA have registered this year.

Live Demo: Speedment • Generate Domain Model • Write Java Stream that: • Determine the ID of a certain city • Alphabetical list of last names of salespersons in that city • Execute

Controlling the Code Generation • So far we have queried a database with streams • We have used code generation to create entities and managers • Can it be used for more?

What is Available out of the Box? • MVC oriented code generation • Modular design • Database domain model • JSON configuration (DSL) • Java language namer • Translator and TranslatorDecorator • Maven goals • Type mappers

MVC Oriented Code Generation • Model • File, Class, Interface, Enum, Field, Method, Constructor, Type, Generic, Annotation, … • View • Renders a model to Java (or another language) • Set code style using custom views • Control • AutoImport, AutoEquals, AutoJavadoc, SetGetAdd, FinalParameters • Write custom controllers to automate recurring tasks

MVC Oriented Code Generation • Separation of concerns • Code generation is type safe • Catch errors compile time • Discover methods directly in the IDE • Reuse code segments and controllers

Database Domain Model • Project • Dbms • Schema • Table • Column • PrimaryKey • ForeignKey • Index List<Table> tables = project.dbmses() .flatMap(Dbms::schemas) .flatMap(Schema::tables) .collect(toList());

JSON Configuration (DSL) { "config" : { "name" : "sales", "dbmses" : [{ "name" : "db0", "typeName" : "MySQL", "ipAddress" : "127.0.0.1", "username" : "root", "schemas" : [{ "name" : "sales", "tables" : [ { "name" : "city" }, { "name" : "salesperson" } ] }] }] } }

Java Language Namer • Camel caser: converts from “some_db_name” to “someDbName” • Java naming conventions: user, User and USER • Detects keywords like “final”,”static” and escapes them • Detects collisions • Pluralizer: bag → bags, entity → entities, fish → fish

Translator and TranslatorDecorator • Translator • Renders a DB entity like a Table to a new Class or an Interface • TranslatorDecorator • Modifies an existing Class or Interface

Maven Goals • speedment:tool • Launches the graphical tool • Allows customization of configuration model • Code generation • speedment:generate • Code generation without launching the tool • speedment:reload • Reloads database metadata without launching the tool • speedment:clear • Removes all the generated classes (except manual changes) without launching the tool

Type Mappers • Controls how columns are implemented • Runtime conversion between Database and Java types java.sql.Timestamp long

Generation vs. Templates • Separation of concerns • Easily change code style • Minimize maintenance • Maximize reusability

Generate a New Custom Class 1. Create a new Translator 2. Model how the new class should look 3. Define a Plugin Class 4. Include it in project pom.xml Example: Generate a Point class

Step 1: Create a New Translator Class public class PointTranslator extends AbstractJavaClassTranslator<Project, Class> { public final static TranslatorKey<Project, Class> POINT_KEY = new TranslatorKey.of(“generated_point", Class.class); public PointTranslator(Project document) { super(document, Class::of); } @Override protected Class makeCodeGenModel(File file) { return newBuilder(file, getClassOrInterfaceName()) .forEveryProject((clazz, project) -> { // Generate Content Here }).build(); } @Override protected String getClassOrInterfaceName() { return ”Point"; } @Override protected String getJavadocRepresentText() { return "A 2-dimensional coordinate."; } } Every translator is identified by a TranslatorKey Name of generated class Javadoc Called every time the translator is invoked forEvery(Project|Dbms|Schema|Table|Column| …)

Step 2: The makeCodeGenModel - methodclazz.public_() .add(Field.of(“x”, int.class) .private_().final_() ) .add(Field.of(“y”, int.class) .private_().final_() ) .add(Constructor.of().public_() .add(Field.of(“x”, int.class)) .add(Field.of(“y”, int.class)) .add(“this.x = x;”, “this.y = y;” ) ) .add(Method.of(“getX”, int.class).public_() .add(“return x;”) ) .add(Method.of(“getY”, int.class).public_() .add(“return y;”) ) .call(new AutoEquals<>()) .call(new AutoToString<>());

Step 3: Define a Plugin Class public class PointPlugin { @ExecuteBefore(RESOLVED) protected void install(CodeGenerationComponent codeGen) { codeGen.put( Project.class, PointTranslator.POINT_KEY, PointTranslator::new ); } } The key defined earlier Will execute when Speedment is being initialized How the translator is constructed

Step 4: Include it in Project pom.xml <plugin> <groupId>com.speedment</groupId> <artifactId>speedment-maven-plugin</artifactId> <version>3.0.0-EA</version> <dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.39</version> </dependency> <dependency> <groupId>com.example</groupId> <artifactId>point-plugin</artifactId> <version>1.0.0-SNAPSHOT</version> </dependency> </dependencies> <configuration> <components> <component>com.example.pointplugin.PointPlugin</component> </components> </configuration> </plugin> This tells Speedment to load the plugin Make sure our plugin project is on the classpath

Execute /** * A 2-dimensional coordinate. * <p> * This file is safe to edit. It will not be overwritten by the code generator. * * @author company */ public class Point { private final int x; private final int y; public Point(int x, int y) { this.x = x; this.y = y; } public int getX() { return x; } public int getY() { return y; } The following file is generated: public int hashCode() { int hashCode = 31; hashCode += 41 * x; hashCode += 41 * y; return hashCode; } public Boolean equals(Object other) { if (this == other) return true; else if (other == null) return false; else if (!(other instanceof Point)) { return false; } final Point point = (Point) other; return x == point.x && y == point.y; } public String toString() { return new StringBuilder(“Point{”) .append(“x: “).append(x).append(“, “) .append(“y: “).append(y).append(“}”); } }

A More Concrete Example 1. Create a new Translator 2. Model how the new class should look 3. Define a Plugin Class 4. Include it in project pom.xml Example: Generate an Enum of tables in the database

Step 1: Create a New Translator Class public class TableEnumTranslator extends AbstractJavaClassTranslator<Project, Enum> { public final static TranslatorKey<Project, Enum> TABLES_ENUM_KEY = new TranslatorKey.of(“tables_enum", Enum.class); public TableEnumTranslator(Project document) { super(document, Enum::of); } @Override protected Enum makeCodeGenModel(File file) { return newBuilder(file, getClassOrInterfaceName()) .forEveryProject((clazz, project) -> { // Generate Content Here }).build(); } @Override protected String getClassOrInterfaceName() { return ”Tables"; } @Override protected String getJavadocRepresentText() { return "An enumeration of tables in the database."; } } Every translator is identified by a TranslatorKey Name of generated class Javadoc Called every time the translator is invoked forEvery(Project|Dbms|Schema|Table|Column| …)

Step 2: The makeCodeGenModel - method DocumentDbUtil.traverseOver(project, Table.class) .map(Table::getJavaName) .map(getSupport().namer()::javaStaticFieldName) .sorted() .map(EnumConstant::of) .forEachOrdered(clazz::add);

Step 3: Define a Plugin Class public class TableEnumPlugin { @ExecuteBefore(RESOLVED) protected void install(CodeGenerationComponent codeGen) { codeGen.put( Project.class, TableEnumTranslator.TABLES_ENUM_KEY, TableEnumTranslator::new ); } }

Step 4: Include it in Project pom.xml <plugin> <groupId>com.speedment</groupId> <artifactId>speedment-maven-plugin</artifactId> <version>3.0.0-EA</version> <dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.39</version> </dependency> <dependency> <groupId>com.example</groupId> <artifactId>table-enum-plugin</artifactId> <version>1.0.0-SNAPSHOT</version> </dependency> </dependencies> <configuration> <components> <component>com.example.tableenumplugin.TableEnumPlugin</component> </components> </configuration> </plugin> This tells Speedment to load the plugin Make sure our plugin project is on the classpath

Execute /** * An enumeration of tables in the database. * <p> * This file is safe to edit. It will not be overwritten by the code generator. * * @author company */ enum Tables { CITY, SALESPERSON; } The following file is generated:

Generate all the Things • Gson Adapters • Spring Configuration Files • REST Controllers • and much more…

Add New Method to Existing Classes • So far we have • Queried a database with generated classes • Generated a custom class • How do we modify the existing generation of classes?

Add New Method to Existing Classes • Fit Into Existing Class Hierarchy • Change Naming Conventions • Optimize Internal Implementations • Add Custom Methods

Add New Method to Existing Classes Example: Add a getColumnCount method to generated managers 1. Create a new TranslatorDecorator class 2. Write code generation logic 3. Add it to Speedment

Step 1: Creating a New Decorator Class public class ColumnCountDecorator implements TranslatorDecorator<Table, Interface> { @Override public void apply(JavaClassTranslator<Table, Interface> translator) { translator.onMake(builder -> { builder.forEveryTable((intrf, table) -> { // Code generation logic goes here }); }); } }

Step 2: Write Code Generation Logic int columnCount = table.columns().count(); intrf.add(Method.of("getColumnCount", int.class) .default_() .set(Javadoc.of("Returns the number of columns in this table.") .add(RETURN.setValue("the column count")) ) .add("return " + columnCount + ";") );

Step 3: Add it to Speedment public final class TableEnumPlugin { @ExecuteBefore(RESOLVED) protected void install(CodeGenerationComponent codeGen) { codeGen.put( Project.class, TableEnumTranslator.TABLES_ENUM_KEY, TableEnumTranslator::new ); codeGen.add( Table.class, StandardTranslatorKey.GENERATED_MANAGER, new ColumnCountDecorator() ); } } Modify an existing translator key Our new decorator The same plugin class as we created earlier

Execute When the project is regenerated, a new method is added to each manager

Demo: Advanced Plugin • Use the Speedment Spring Plugin to generate a working REST API

Additional Features • Add GUI Tool components for custom configuration • Extend the JSON DSL dynamically with plugins • Automate your build environment with Maven • Add custom data type mappers

Additional Features • Plugin a custom namer • Generate classes that are related to other domain models • Generate classes for other languages • Style the GUI Tool

Database Connectors Open Source • MySQL • PostgreSQL • MariaDB Enterprise • Oracle • Microsoft SQL server • dB2

In-JVM-Memory Data Store • Alternative stream source • Uses code generation • Optimized serializers for offheap storage • No changes to user-written code • 10-100x faster queries

Q&A www.speedment.org github.com/speedment @speedment www.speedment.com Linkedin: Per Minborg Emil Forslund

JavaOne2016 - How to Generate Customized Java 8 Code from Your Database [TUT4489]

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