The best code is the one you never need to write. Using code generation and automated builds you can minimize the risk of human error when developing software, but how do you maintain control over code when large parts of it is handed over to a machine? In this tutorial, you will learn how to use open-source software to create and control code automation. You will see how you can generate a completely object-oriented domain model by automatically analyzing your database schemas. Every aspect of the process is transparent and configurable, giving you as a developer 100% control of the generated code. This will not only increase your productivity, but also help you build safer and more maintainable Java applications.
Silicon Valley JUG - How to generate customized java 8 code from your database
1. How to Generate Customized Java 8 Code
From Your Database
Per Minborg
CTO, Speedment, Inc
Emil Forslund
Developer, Speedment, Inc.
2. Every Decision a Developer Makes is a
Trade-off
The best code is
no code at all
3. 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?
4. 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
• 2 years of mascot experience
5. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
6. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
7. 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...
}
8. 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
9. 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
14. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
15. 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
16. 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
17. Querying the Database using Streams
• Queries are expressed using
the standard Java 8 Stream
API
• Streams are analyzed to
produce high-performance
queries
18. 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’;
19. Querying the Database using Streams
SELECT * FROM 'customer'
REGION.equal(NORTH_AMERICA)
REGISTERED.greaterOrEqual(2016-01-01)
count()
Sourc
e
Filter
Filter
Term.
Pipeline
20. 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
21. 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
22. 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
23. Querying the Database using Streams
SELECT COUNT('id') FROM 'customer'
WHERE 'customer'.'region' = ‘North America’
AND 'customer'.'registered' >= ‘2016-01-01’;
Sourc
e
Pipeline
24. 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…
.collect(toJson(encode.allOf(customers)))
[
{”id”:11, ”name”: …},
{…},
…
]
25. 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());
27. Step 1: Getting Speedment using Maven
<plugin>
<groupId>com.speedment</groupId>
<artifactId>speedment-maven-plugin</artifactId>
<version>3.0.3</version>
</plugin>
Generate source files based on database
28. 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
29. 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();
33. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
34. 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?
35. 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
36. 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
37. 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
41. 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
42. 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
43. 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
44. Type Mappers
• Controls how columns are implemented
• Runtime conversion between Database and Java types
java.sql.Timestamp long
45. Generation vs. Templates
• Separation of concerns
• Easily change code style
• Minimize maintenance
• Maximize reusability
46. 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
47. 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|
…)
49. Step 3: Define a Plugin Class
public class PointPlugin {
@ExecuteBefore(RESOLVED)
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
50. Step 4: Include it in Project pom.xml
<plugin>
<groupId>com.speedment</groupId>
<artifactId>speedment-maven-plugin</artifactId>
<version>3.0.3</version>
<dependencies>
<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
51. 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(“}”);
}
}
52. 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
53. 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|
…)
55. 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
);
}
}
56. Step 4: Include it in Project pom.xml
<plugin>
<groupId>com.speedment</groupId>
<artifactId>speedment-maven-plugin</artifactId>
<version>3.0.3</version>
<dependencies>
<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
57. 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:
58. Generate all the Things
• Gson Adapters
• Spring Configuration Files
• REST Controllers
• and much more…
60. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
61. 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?
62. Add New Method to Existing Classes
• Fit Into Existing Class Hierarchy
• Change Naming Conventions
• Optimize Internal Implementations
• Add Custom Methods
63. 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
64. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
65. 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
});
});
}
}
66. 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 + ";")
);
67. 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
69. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
70. 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
71. Additional Features
• Plugin a custom namer
• Generate classes that are related to other domain models
• Generate classes for other languages
• Style the GUI Tool
73. Agenda
• Problem Description
• Code Generation in Database Applications
• How Does it Work?
• Code Example
• Controlling the Code Generation
• Generate Custom Classes
• Add new Method to Existing Classes
• Code Example
• Additional Features
• Beyond Open Source
• Questions & Answers
74. Beyond Open-Source
• Speedment Enterprise
• Run your database queries orders of magnitude faster!
• 10x, 100x, 1 000x, 10 000x, …
• Use the same Stream API
75. How is This Possible?
• No changes to user-written code
• Alternative stream source
• Data is stored in-memory
• Generates optimized serializers
for offheap storage