"Learn the JannoCessor framework: Implement the custom code generator in the Java class library"

JannoCessor is a powerful Java code generation framework that allows developers to implement custom code generators in the Java class library.This article will introduce how to learn the JannoCessor framework and how to use it to generate code from the Java class library. 1. What is the JannoCessor framework? JannoCessor is a Java code generating framework based on annotations.It uses annotations to identify the template for generating code, and then automatically generates the corresponding Java code by processing these annotations during compilation.The JannoCessor framework provides a rich API, so that developers can easily define the templates and logic required for generating code. 2. Why do you learn the JannoCessor framework? Code generation is a common demand in software development, such as generating data access layer code such as POJO, DTO, DAO.Manually writing these duplicated code is both time -consuming and easy to make errors, and the JannoCessor framework can help developers automatically generate these code and improve development efficiency.In addition, the JannoCessor framework also provides many expansion and customized options, enabling developers to generate specific code according to their needs. Third, the steps to learn JannoCessor framework: 1. Import the JannoCessor framework: import the relevant library files of the JannoCessor framework into your project. 2. Define the template that generates code: Use the annotations provided by JannoCessor to add corresponding annotations to the classes, interfaces or methods that need to generate code.These annotations define the templates and their execution logic for generating code.For example, you can use @GenerateClass annotation to define a generating template, and use @GENTEMETHOD annotation to define a template for generating methods. 3. Realize the annotation processor: Create an annotation processor class, which realizes the abstract class of javax.annotation.processing.abstractProcessor.In this class, you need to implement the corresponding method, such as the process () method to process the annotation and generate code. 4. Configure annotation processor: Configure the annotation processor in your project configuration file (such as Pom.xml or Build.gradle) to tell the compiler which processor you need. 5. Compilation and operation: Use the compiler to compile your project, and the compiler will automatically call the annotation processor to generate code.After the compilation is completed, you can find the generated code file in the target directory. Fourth, the example code of the JannoCessor framework: The following is a simple example that demonstrates how to generate the Getter and Setter method in the Java class library to generate the Getter and Setter method: 1. Define a note for GenerateGettersetter: import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Target(ElementType.TYPE) @Retention(RetentionPolicy.SOURCE) public @interface GenerateGetterSetter { } 2. Create an annotation processor GenerateGettersetterProcessor: import javax.annotation.processing.AbstractProcessor; import javax.annotation.processing.Processor; import javax.annotation.processing.RoundEnvironment; import javax.lang.model.element.Element; import javax.lang.model.element.ElementKind; import javax.lang.model.element.TypeElement; import javax.tools.Diagnostic; import java.util.Set; @SupportedAnnotationTypes("com.example.GenerateGetterSetter") @SupportedSourceVersion(SourceVersion.RELEASE_8) public class GenerateGetterSetterProcessor extends AbstractProcessor { @Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { for (TypeElement annotation : annotations) { Set<? extends Element> annotatedElements = roundEnv.getElementsAnnotatedWith(annotation); for (Element element : annotatedElements) { if (element.getKind() == ElementKind.CLASS) { String className = element.getSimpleName().toString(); processingEnv.getMessager().printMessage(Diagnostic.Kind.NOTE, "Generating getter/setter for class: " + className); // The code logic of generating the getter/setter method } } } return true; } } 3. Configure the annotation processor: In the construction file of the project (such as pom.xml), configure the annotation processor: <build> <plugins> <plugin> <groupId>org.bsc.maven</groupId> <artifactId>maven-processor-plugin</artifactId> <version>2.2.4</version> <executions> <execution> <id>process</id> <phase>generate-sources</phase> <goals> <goal>process</goal> </goals> <configuration> <processors> <processor>com.example.GenerateGetterSetterProcessor</processor> </processors> </configuration> </execution> </executions> <dependencies> <dependency> <groupId>com.example</groupId> <artifactId>your-annotation-processor</artifactId> <version>1.0-SNAPSHOT</version> </dependency> </dependencies> </plugin> </plugins> </build> Through the above steps, compile your Java class library, the JannoCessor framework will automatically generate the corresponding Getter and Setter method according to the @GENTEGETERSETER annotation. Summarize: By learning the JannoCessor framework, you can implement a custom code generator in your own Java class library to improve development efficiency.The above is a simple example, which demonstrates how to generate the Getter and Setter method with the JannoCessor framework.You can expand and customize the JannoCessor framework according to your needs to achieve richer code generation functions.