利用Java手写一个简易的lombok的示例代码

<?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>lombok</groupId>
    <artifactId>com.compass.lombok</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>com.sun</groupId>
            <artifactId>tools</artifactId>
            <version>1.8</version>
            <scope>system</scope>
            <systemPath>C:/Program Files/Java/jdk1.8.0_251/lib/tools.jar</systemPath>
        </dependency>
        <dependency>
            <groupId>com.Google.auto.service</groupId>
            <artifactId>auto-service</artifactId>
            <version>1.0-rc5</version>
        </dependency>
    </dependencies>
    <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>

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.RUNTIME)
public @interface Data {
}

import com.compass.lombok.annotation.Data;
import com.google.auto.service.AutoService;
import com.sun.source.tree.Tree;
import com.sun.tools.javac.api.JavacTrees;
import com.sun.tools.javac.code.Flags;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.processing.JavacProcessingEnvironment;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.TreeMaker;
import com.sun.tools.javac.tree.TreeTranslator;
import com.sun.tools.javac.util.*;

import javax.annotation.processing.*;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import java.util.Set;


@AutoService(Processor.class)
@SupportedAnnotationTypes("com.compass.lombok.annotation.Data")
@SupportedSourceVersion(SourceVersion.RELEASE_8)
public class DataAnnotationProcessor extends AbstractProcessor {
    private JavacTrees javacTrees;
    private TreeMaker treeMaker;
    private Names names;

    @Override
    public synchronized void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
        Context context = ((JavacProcessingEnvironment) processingEnv).getContext();
         javacTrees = JavacTrees.instance(context);
         treeMaker = TreeMaker.instance(context);
         names = Names.instance(context);
    }

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        Set<? extends Element> set = roundEnv.getElementsAnnotatedWith(Data.class);
        for (Element element : set) {
            javacTrees.getTree(element).accept(new TreeTranslator(){
                @Override
                public void visitClassDef(JCTree.JCClassDecl jcClassDecl) {
                    jcClassDecl.defs.stream()
                            .filter(it->it.getKind().equals(Tree.Kind.VARIABLE))
                            .map(it->(JCTree.JCVariableDecl) it).forEach(it->{
                                jcClassDecl.defs = jcClassDecl.defs.prepend(genGetterMethod(it));
                                jcClassDecl.defs = jcClassDecl.defs.prepend(genSetterMethod(it));

                    });
                    super.visitClassDef(jcClassDecl);
                }
            });
        }
        return true;
    }

    private JCTree.JCMethodDecl genGetterMethod(JCTree.JCVariableDecl jcVariableDecl){
        JCTree.JCIdent _this = treeMaker.Ident(names.fromString("this"));
        Name name = jcVariableDecl.getName();
        JCTree.JCFieldAccess select = treeMaker.Select(_this, name);
        JCTree.JCReturn returnStatement = treeMaker.Return(select);

        ListBuffer<JCTree.JCStatement> statements = new ListBuffer<>();
        statements.append(returnStatement);

        JCTree.JCModifiers modifiers = treeMaker.Modifiers(Flags.PUBLIC);

        Name getMethodName = getGetMethodName(jcVariableDecl.getName());

        JCTree.JCExpression returnMethodType = jcVariableDecl.vartype;

        JCTree.JCBlock body = treeMaker.Block(0, statements.toList());

        List<JCTree.JCTypeParameter> methodGenericParamList = List.nil();

        List<JCTree.JCVariableDecl> parameterList = List.nil();

        List<JCTree.JCExpression> throwList = List.nil();

        return treeMaker.MethodDef(modifiers, getMethodName, returnMethodType, methodGenericParamList, parameterList, throwList, body, null);

    }
    public  JCTree.JCMethodDecl genSetterMethod(JCTree.JCVariableDecl jcVariableDecl){

        JCTree.JCIdent _this = treeMaker.Ident(names.fromString("this"));
        Name name = jcVariableDecl.getName();
        JCTree.JCFieldAccess select = treeMaker.Select(_this, name);
        JCTree.JCAssign statementAssign = treeMaker.Assign(select, treeMaker.Ident(jcVariableDecl.getName()));
        JCTree.JCExpressionStatement statement = treeMaker.Exec(statementAssign);
        ListBuffer<JCTree.JCStatement> statements = new ListBuffer<>();
        statements.append(statement);

        JCTree.JCVariableDecl params = treeMaker.VarDef(
                treeMaker.Modifiers(Flags.PARAMETER, List.nil()),
                jcVariableDecl.name,
                jcVariableDecl.vartype,
                null
        );

        JCTree.JCModifiers modifiers = treeMaker.Modifiers(Flags.PUBLIC);

        Name setMethodName = getSetMethodName(jcVariableDecl.getName());

        JCTree.JCExpression returnMethodType = treeMaker.Type(new Type.JCVoidType());

        JCTree.JCBlock body = treeMaker.Block(0, statements.toList());

        List<JCTree.JCTypeParameter> methodGenericParamList = List.nil();

        List<JCTree.JCVariableDecl> parameterList = List.of(params);

        List<JCTree.JCExpression> throwList = List.nil();

        return treeMaker.MethodDef(modifiers, setMethodName, returnMethodType, methodGenericParamList, parameterList, throwList, body, null);
    }

    private Name getGetMethodName(Name name){
        String filedName = name.toString();
        return names.fromString("get"+filedName.substring(0,1).toUpperCase()+filedName.substring(1));
    }

    private Name getSetMethodName(Name name){
        String filedName = name.toString();
        return names.fromString("set"+filedName.substring(0,1).toUpperCase()+filedName.substring(1));
    }

}