Previous article introduced Java annotations relevant content (see Java Annotations Annotation processing time), this article will introduce and compile Lombok behind.
Generating POJO setter / getter by annotating
First define an annotation @Data:
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.SOURCE)
public @interface Data {
}
复制代码The annotation processor to achieve @Data
public class DataProcessor extends AbstractProcessor {
private Messager messager;
private JavacTrees trees;
// 创建AST节点工具
private TreeMaker treeMaker;
private Names names;
/** 获取处理器框架组件 */
@Override
public synchronized void init(ProcessingEnvironment processingEnv) {
super.init(processingEnv);
messager = processingEnv.getMessager();
trees = JavacTrees.instance(processingEnv);
Context context = ((JavacProcessingEnvironment) processingEnv).getContext();
treeMaker = TreeMaker.instance(context);
names = Names.instance(context);
}
/** 注解处理逻辑，在这里修改AST */
@Override
public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
messager.printMessage(Kind.NOTE, "starting process");
/** 获取Data注解的元素 */
Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(Data.class);
for (Element element : elements) {
JCTree jcTree = trees.getTree(element);
// 遍历类定义的元素
jcTree.accept(new TreeTranslator() {
@Override
public void visitClassDef(JCClassDecl jcClassDecl) {
super.visitClassDef(jcClassDecl);
try {
java.util.List<JCVariableDecl> jcVariableDeclList = new ArrayList<>();
for (JCTree tree : jcClassDecl.defs) {
// 收集所有field
if (tree.getKind() == Tree.Kind.VARIABLE) {
jcVariableDeclList.add((JCVariableDecl) tree);
}
}
for (JCVariableDecl jcVariableDecl : jcVariableDeclList) {
// 生成相应的geeter，setter
generateElement(jcClassDecl, jcVariableDecl);
}
} catch (Throwable e) {
try {
e.printStackTrace(new PrintStream(new FileOutputStream("error.txt")));
} catch (FileNotFoundException e1) {
messager.printMessage(Kind.ERROR, "Error create log file");
}
}
}
});
}
return true;
}
/** 处理的注解类型 */
@Override
public Set<String> getSupportedAnnotationTypes() {
LinkedHashSet<String> supportedAnnotations = new LinkedHashSet<>();
supportedAnnotations.add("*");
return supportedAnnotations;
}
/** 支持的JDK版本 */
@Override
public SourceVersion getSupportedSourceVersion() {
return SourceVersion.latestSupported();
}
}
复制代码Specific method of generating logic:
private void generateElement(JCClassDecl jcClassDecl, JCVariableDecl jcVariableDecl) throws Exception {
// 将生成的getter方法插入类语法树中
JCMethodDecl getter = generateGetterMethodElement(jcVariableDecl);
jcClassDecl.defs = jcClassDecl.defs.append(getter);
// 将生成的setter方法插入类语法树中
JCMethodDecl setter = generateSetterMethodElement(jcVariableDecl);
jcClassDecl.defs = jcClassDecl.defs.append(setter);
}
/** 生成getter方法 */
private JCMethodDecl generateGetterMethodElement(JCVariableDecl jcVariableDecl) {
String field = jcVariableDecl.getName().toString();
Name name = names.fromString("get" + field.substring(0, 1).toUpperCase() + field.substring(1, field.length()));
ListBuffer<JCStatement> statements = new ListBuffer<>();
statements.append(
treeMaker.Return(treeMaker.Select(treeMaker.Ident(names.fromString("this")), jcVariableDecl.getName())));
JCTree.JCBlock body = treeMaker.Block(0, statements.toList());
return treeMaker.MethodDef(treeMaker.Modifiers(Flags.PUBLIC), name, jcVariableDecl.vartype,
List.nil(), List.nil(), List.nil(), body, null);
}
/** 生成setter方法 */
private JCMethodDecl generateSetterMethodElement(JCVariableDecl jcVariableDecl) throws Exception {
String field = jcVariableDecl.getName().toString();
Name name = names.fromString("set" + field.substring(0, 1).toUpperCase() + field.substring(1, field.length()));
JCTree.JCExpression returnMethodType = treeMaker
.Type((Type) (Class.forName("com.sun.tools.javac.code.Type$JCVoidType").newInstance()));
ListBuffer<JCStatement> statements = new ListBuffer<>();
statements.append(treeMaker.Exec(treeMaker
.Assign(treeMaker.Select(treeMaker.Ident(names.fromString("this")), jcVariableDecl.getName()),
treeMaker.Ident(jcVariableDecl.getName()))));
JCTree.JCBlock body = treeMaker.Block(0, statements.toList());
JCTree.JCVariableDecl param = treeMaker
.VarDef(treeMaker.Modifiers(Flags.PARAMETER, List.nil()), jcVariableDecl.name, jcVariableDecl.vartype,
jcVariableDecl.nameexpr);
List<JCTree.JCVariableDecl> parameters = List.of(param);
return treeMaker.MethodDef(treeMaker.Modifiers(Flags.PUBLIC), name, returnMethodType,
List.nil(), parameters, List.nil(), body, null);
}
复制代码With @Data annotation to modify a class:
@Data
public class Member {
private Long id;
private String name;
private Date joinDate;
}
复制代码Get! Verify:
javac DataProcessor.java && javac -g -processor DataProcessor Member.java && javap -p Member
复制代码SPI packaged into kits by
maven build configuration:
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<excludes>
<!-- 构建时排除Service声明，此时Processor还不可用 -->
<exclude>META-INF/**/*</exclude>
</excludes>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>8</source>
<target>8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
<executions>
<execution>
<!-- prepare-package阶段再把services拷贝到生成类目标目录 -->
<id>process-META</id>
<phase>prepare-package</phase>
<goals>
<goal>copy-resources</goal>
</goals>
<configuration>
<outputDirectory>target/classes</outputDirectory>
<resources>
<resource>
<directory>${basedir}/src/main/resources/</directory>
<includes>
<include>**/*</include>
</includes>
</resource>
</resources>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
复制代码New projects, introduction of dependence:
<dependency>
<groupId>org.yannis</groupId>
<artifactId>srctool</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
复制代码Copy Member.java to the new items:
mvn clean packageObserved target generated class Member.class decompile Results:
So far, it has achieved a simple function of lombok!
chilli
Lombok is what I prefer in the individual events with a tool that can enable us to generate a series of class boilerplate code at compile time by simply notes, source code can be kept very simple. Following is a brief introduction of several commonly used notes, you can view more Quguan network usage.
Dependency:
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.20</version>
<scope>provided</scope>
</dependency>
复制代码Note: the mounting plug Lombok idea, eclipse ide and the like, you can see the method of generating a direct
@Getter/@Setter
Generating an instance field getter / setter method, the default is public, access control level may be changed by AccessLevel. Properties can be identified by the prefix @Accessors (prefix = "m").
@ToString
Generating object toString () method, by exclude field is set to be excluded.
@EqualsAndHashCode
Generating object hashCode () and equals () method, exclude provided to exclude field
@NoArgsConstructor, @RequiredArgsConstructor and @AllArgsConstructor
No parameters generated with the parameter (final modified attributes or @NotNull) constructor, the whole argument constructor.
@Data
Corresponds @ ToString, collection @ EqualsAndHashCode, @ Getter / @Setter @RequiredArgsConstructor and the effect is as follows:
@Builder
Constructor for the class to generate a static class XxxBuilder, commonly
@Log
The introduction of the log, very convenient
Finish!
Past articles:
All articles micro-channel public number of first time update