Share the technical principles and best practice of the "AutoValue Processor" framework in the Java library
AutoValue Processor is a framework for automatically generating the Java class. It can reduce the workload of developers to write model code and improve the readability and maintenance of code.This article will introduce the technical principles and best practices of AutoValue Processor, and provide relevant Java code examples.
1. Technical principles
AutoValue Processor is based on the expansion of the Google AutoValue library. It uses the Java annotation processor function to generate Java classes with specific templates.AutoValue Processor mainly completes the automatic production work through the following steps:
1. Definition annotation: Use the annotations provided by AutoValue, such as@AutoValue` and@AutoValue.property to define the structure and attributes of the Java class that need to be generated.
2. Create a template class: Writing a template class that uses the attributes defined by annotation to generate the corresponding Getter and Equals methods, as well as other custom operations.
3. Create an annotation processor: Write a annotation processor that scans the annotation in the code and generate the corresponding Java class based on the defined template class.
4. Register an annotation processor: Register the written annotation processor into the construction tool to automatically trigger it during the project construction process.
5. Construction project: By constructing a project, the annotation processor will scan the annotations in the code during the compilation period and generate the corresponding Java class according to the template class.
2. Best practice
Below is the best practice to use AutoValue Processor, which can help developers better use the framework:
1. Follow the naming specifications: According to the agreement, the AutoValue Processor will generate the corresponding AutoValue implementation class according to the class name of the `@AutoValue`.Therefore, it is best to name `` xxxautovalue` `xxxautovalue` with the category of`@AutoValue` to clearly distinguish.
2. Define attribute list: When using@AutoValue.property`, you should specify the attribute name and type.This will be used to generate the corresponding Getter and Equals methods.For example:
@AutoValue.Property
String name();
3. Custom template class: AutoValue Processor can generate the Java class according to the template class.When writing a template class, you can customize the generation logic of Getter and Equals methods according to actual needs.For example:
@AutoValue.Generate
class XxxAutoValueTemplate {
String name() {
return "Xxx";
}
boolean equals(Object o) {
if (o == this) {
return true;
}
if (o instanceof Xxx) {
Xxx that = (Xxx) o;
return this.name().equals(that.name());
}
return false;
}
}
4. Registration annotation processor: According to the different construction tools used, the method of registering the annotation processor will be different.In Maven, you need to configure the `Auto-Value` plug-in in the pom.xml file, and add the corresponding annotation processor.For example:
<build>
<plugins>
<plugin>
<groupId>com.google.auto.value</groupId>
<artifactId>auto-value</artifactId>
<version>1.7</version>
<executions>
<execution>
<phase>generate-sources</phase>
<goals>
<goal>extensions</goal>
</goals>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>com.google.auto.value</groupId>
<artifactId>auto-value</artifactId>
<version>1.7</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
5. Generate Java class: By constructing a project, AutoValue Processor will automatically trigger during the compilation and generate the corresponding Java class according to the defined template class.
Third, sample code
Below is an example code using AutoValue Processor:
@AutoValue
abstract class Person {
@AutoValue.Property
abstract String name();
@AutoValue.Property
abstract int age();
static Person create(String name, int age) {
return new AutoValue_Person(name, age);
}
}
class Main {
public static void main(String[] args) {
Person person = Person.create("Alice", 25);
System.out.println(person.name());
System.out.println(person.age());
}
}
Through `@autoValue` and`@AutoValue.property's annotation, define a `Person` class and define the attributes of` name` and `age`.Then, a `Person` object was created in the` main` class, and its attribute value was output.
Summarize:
AutoValue Processor is a framework for automatically generating the Java class.This article introduces the technical principles and best practices of AutoValue Processor, and provides related example code to help developers better understand and use the framework.By using AutoValue Processor, developers can reduce the writing of model code and improve the readability and maintenance of code.
