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daniel 3 years ago
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5
.gitignore vendored
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/annotation-processor/target/
/annotation-user/target/
/annotation_processing.iml
/annotation-processor/annotationprocessor.iml
/.idea/

13
README.md
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refer to: https://www.baeldung.com/java-annotation-processing-builder
# 1 主要演示效果
在编译期，将
annotation-user/target/classes/com/roadl/annouser/Person.class
setter上的注解生成辅助类：
annotation-user/target/classes/com/roadl/annouser/PersonBuilder.class
# 2 module化
annotation_processing 父project
annotation_processing/annotation-user 子module A，依赖module B
annotation_processing/annotation-processor 子module B

29
annotation-processor/pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>annotation_processing</artifactId>
<groupId>com.roadl</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>annotation-processor</artifactId>
<properties>
<auto-service.version>1.0-rc2</auto-service.version>
</properties>
<dependencies>
<dependency>
<groupId>com.google.auto.service</groupId>
<artifactId>auto-service</artifactId>
<version>${auto-service.version}</version>
<scope>provided</scope>
</dependency>
</dependencies>
</project>

136
annotation-processor/src/main/java/com/roadl/annoprocessor/BuilderProcessor.java
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package com.roadl.annoprocessor;
import com.google.auto.service.AutoService;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.Processor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.ExecutableType;
import javax.tools.Diagnostic;
import javax.tools.JavaFileObject;
@SupportedAnnotationTypes("com.roadl.annoprocessor.BuilderProperty")
@SupportedSourceVersion(SourceVersion.RELEASE_8)
@AutoService(Processor.class)
public class BuilderProcessor extends AbstractProcessor {
@Override
public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
for (TypeElement annotation : annotations) {
Set<? extends Element> annotatedElements = roundEnv.getElementsAnnotatedWith(annotation);
Map<Boolean, List<Element>> annotatedMethods = annotatedElements.stream().collect(
Collectors.partitioningBy(element ->
((ExecutableType) element.asType()).getParameterTypes().size() == 1
&& element.getSimpleName().toString().startsWith("set")));
List<Element> setters = annotatedMethods.get(true);
List<Element> otherMethods = annotatedMethods.get(false);
otherMethods.forEach(element ->
processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR,
"@com.roadl.annoprocessor.BuilderProperty must be applied to a setXxx method "
+ "with a single argument", element));
if (setters.isEmpty()) {
continue;
}
String className = ((TypeElement) setters.get(0)
.getEnclosingElement()).getQualifiedName().toString();
Map<String, String> setterMap = setters.stream().collect(Collectors.toMap(
setter -> setter.getSimpleName().toString(),
setter -> ((ExecutableType) setter.asType())
.getParameterTypes().get(0).toString()
));
try {
writeBuilderFile(className, setterMap);
} catch (IOException e) {
e.printStackTrace();
}
}
return true;
}
private void writeBuilderFile(
String className, Map<String, String> setterMap)
throws IOException {
String packageName = null;
int lastDot = className.lastIndexOf('.');
if (lastDot > 0) {
packageName = className.substring(0, lastDot);
}
String simpleClassName = className.substring(lastDot + 1);
String builderClassName = className + "Builder";
String builderSimpleClassName = builderClassName
.substring(lastDot + 1);
JavaFileObject builderFile = processingEnv.getFiler()
.createSourceFile(builderClassName);
try (PrintWriter out = new PrintWriter(builderFile.openWriter())) {
if (packageName != null) {
out.print("package ");
out.print(packageName);
out.println(";");
out.println();
}
out.print("public class ");
out.print(builderSimpleClassName);
out.println(" {");
out.println();
out.print(" private ");
out.print(simpleClassName);
out.print(" object = new ");
out.print(simpleClassName);
out.println("();");
out.println();
out.print(" public ");
out.print(simpleClassName);
out.println(" build() {");
out.println(" return object;");
out.println(" }");
out.println();
setterMap.entrySet().forEach(setter -> {
String methodName = setter.getKey();
String argumentType = setter.getValue();
out.print(" public ");
out.print(builderSimpleClassName);
out.print(" ");
out.print(methodName);
out.print("(");
out.print(argumentType);
out.println(" value) {");
out.print(" object.");
out.print(methodName);
out.println("(value);");
out.println(" return this;");
out.println(" }");
out.println();
});
out.println("}");
}
}
}

12
annotation-processor/src/main/java/com/roadl/annoprocessor/BuilderProperty.java
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package com.roadl.annoprocessor;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.SOURCE)
public @interface BuilderProperty {
}

21
annotation-user/pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>annotation_processing</artifactId>
<groupId>com.roadl</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>annotation-user</artifactId>
<dependencies>
<dependency>
<groupId>com.roadl</groupId>
<artifactId>annotation-processor</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
</dependencies>
</project>

26
annotation-user/src/main/java/com/roadl/annouser/Person.java
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package com.roadl.annouser;
import com.roadl.annoprocessor.BuilderProperty;
public class Person {
private int age;
private String name;
public int getAge() {
return age;
}
@BuilderProperty
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
@BuilderProperty
public void setName(String name) {
this.name = name;
}
}

15
annotation-user/src/test/java/com/roadl/annouser/PersonBuilderUnitTest.java
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package com.roadl.annouser;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class PersonBuilderUnitTest {
@Test
public void whenBuildPersonWithBuilder_thenObjectHasPropertyValues() {
Person person = new PersonBuilder().setAge(25).setName("John").build();
assertEquals(25, person.getAge());
assertEquals("John", person.getName());
}
}

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pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.roadl</groupId>
<artifactId>annotation_processing</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<modules>
<module>annotation-processor</module>
<module>annotation-user</module>
</modules>
<dependencies>
<!-- https://mvnrepository.com/artifact/junit/junit -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
</dependencies>
<!--
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project annotation-processor: Compilation failure: Compilation failure:
[ERROR] Source option 5 is no longer supported. Use 6 or later.
-->
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
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