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annotation-generation.mdbuilders.mdextensions.mdindex.mdmemoization.mdpretty-strings.mdserialization.mdstandalone-builders.mdtagged-unions.mdvalue-classes.md
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tessl/maven-com-google-auto-value--auto-value

Generated immutable value classes for Java 8+ using annotation processing

Workspace
tessl
Visibility
Public
Created
Last updated
Describes
mavenpkg:maven/com.google.auto.value/auto-value@1.11.x

To install, run

npx @tessl/cli install tessl/maven-com-google-auto-value--auto-value@1.11.0

index.mddocs/

AutoValue

AutoValue is a Java annotation processor that automatically generates immutable value classes, eliminating the need to manually write repetitive equals(), hashCode(), and toString() methods. It provides a clean, declarative way to create value objects using annotations, supporting advanced features like builders, extensions for serialization and memoization, and integration with popular Java frameworks.

Package Information

  • Package Name: auto-value
  • Package Type: maven
  • Language: Java
  • Group ID: com.google.auto.value
  • Installation: 
    <dependency>
  <groupId>com.google.auto.value</groupId>
  <artifactId>auto-value-annotations</artifactId>
  <version>1.11.0</version>
</dependency>
<dependency>
  <groupId>com.google.auto.value</groupId>
  <artifactId>auto-value</artifactId>
  <version>1.11.0</version>
  <scope>provided</scope>
</dependency>

Core Imports

import com.google.auto.value.AutoValue;
import com.google.auto.value.AutoBuilder;
import com.google.auto.value.AutoAnnotation;
import com.google.auto.value.AutoOneOf;

Basic Usage

import com.google.auto.value.AutoValue;

@AutoValue
public abstract class Person {
  public static Person create(String name, int age) {
    return new AutoValue_Person(name, age);
  }

  public abstract String name();
  public abstract int age();
}

// Usage
Person person = Person.create("Alice", 30);
System.out.println(person); // Person{name=Alice, age=30}
System.out.println(person.equals(Person.create("Alice", 30))); // true

Architecture

AutoValue uses annotation processing to generate implementation classes at compile time. The key components are:

  • Annotations: Declarative markers for code generation (@AutoValue, @AutoBuilder, etc.)
  • Annotation Processor: Compile-time code generator that creates implementations
  • Extension Framework: Pluggable system for customizing generated code
  • Built-in Extensions: Common functionality like memoization, serialization, and pretty printing

Capabilities

Value Class Generation

Generate immutable value classes with proper equals, hashCode, and toString implementations.

@AutoValue
public abstract class YourClass {
  // Abstract getters define properties
  public abstract PropertyType propertyName();
  
  // Static factory method
  public static YourClass create(PropertyType propertyName) {
    return new AutoValue_YourClass(propertyName);
  }
}

Value Classes

Builder Pattern Support

Generate builder classes for complex object construction with optional properties.

@AutoValue
public abstract class YourClass {
  public abstract PropertyType property();
  
  public static Builder builder() {
    return new AutoValue_YourClass.Builder();
  }
  
  @AutoValue.Builder
  public abstract static class Builder {
    public abstract Builder property(PropertyType value);
    public abstract YourClass build();
  }
}

Builder Pattern

Standalone Builder Generation

Generate builders for existing classes or constructors.

@AutoBuilder(ofClass = TargetClass.class)
public abstract class TargetClassBuilder {
  public abstract TargetClassBuilder property(PropertyType value);
  public abstract TargetClass build();
  
  public static TargetClassBuilder builder() {
    return new AutoBuilder_TargetClassBuilder();
  }
}

Standalone Builders

Annotation Implementation Generation

Generate proper annotation implementations with correct equals and hashCode.

@AutoAnnotation
public static AnnotationType createAnnotation(ParamType param) {
  return new AutoAnnotation_ClassName_createAnnotation(param);
}

Annotation Generation

Tagged Union Types

Generate tagged union (one-of) types for representing values that can be one of several types.

@AutoOneOf(Kind.class)
public abstract class StringOrInteger {
  public enum Kind { STRING, INTEGER }
  
  public abstract Kind getKind();
  public abstract String string();
  public abstract int integer();
  
  public static StringOrInteger ofString(String s) {
    return AutoOneOf_StringOrInteger.string(s);
  }
  
  public static StringOrInteger ofInteger(int i) {
    return AutoOneOf_StringOrInteger.integer(i);
  }
}

Tagged Unions

Method Memoization

Cache method results for expensive computations with thread-safe lazy initialization.

@Memoized
public abstract ComputedType expensiveComputation() {
  return performExpensiveCalculation();
}

Memoization

Serialization Support

Generate serializable implementations for classes with non-serializable fields.

@SerializableAutoValue
@AutoValue
public abstract class SerializableClass implements Serializable {
  public abstract Optional<String> optionalField();
  public abstract ImmutableList<Integer> listField();
}

Serialization

Pretty String Generation

Generate human-readable string representations with structured formatting.

@ToPrettyString
public abstract String toPrettyString();

Pretty String Generation

Extension Framework

Create custom extensions to modify or enhance generated code.

public abstract class AutoValueExtension {
  public abstract boolean applicable(Context context);
  public abstract String generateClass(Context context, String className, String classToExtend, boolean isFinal);
}

Extension Framework

Core Types

// Core annotation
@Retention(RetentionPolicy.CLASS)
@Target(ElementType.TYPE)
public @interface AutoValue {
  
  @Retention(RetentionPolicy.CLASS)
  @Target(ElementType.TYPE)
  public @interface Builder {}
  
  @Retention(RetentionPolicy.CLASS)
  @Target({ElementType.TYPE, ElementType.METHOD})
  public @interface CopyAnnotations {
    Class<? extends Annotation>[] exclude() default {};
  }
}

// Builder annotation
@Retention(RetentionPolicy.CLASS)
@Target(ElementType.TYPE)
public @interface AutoBuilder {
  String callMethod() default "";
  Class<?> ofClass() default Void.class;
}

// Annotation generation
@Retention(RetentionPolicy.CLASS)
@Target(ElementType.METHOD)
public @interface AutoAnnotation {}

// Tagged unions
@Retention(RetentionPolicy.CLASS)
@Target(ElementType.TYPE)
public @interface AutoOneOf {
  Class<? extends Enum<?>> value();
}