Javapoet用于生成Java文件的API，常用于注解处理过程,该API简单易懂，可以辅助自动化生成一些重复的Java文件，提高工作效率
/*
* TypeSpec:生成类/接口/枚举对象
* MethodSpec：生成方法对象
* ParameterSpec：生成参数对象
* AnnotationSpec：生成注解对象
* FieldSpec：生成变量对象
* CLassName：通过包名+类名生成的对象
* ParameterizedTypeName：泛型类型
* JavaFile：生成类文件的输出类
* */
/*
* $L:Literial,拼接,常用于MethodSpec的addStatement()方法
* $S:Strings,字符串
* $T:Type,可以映射并自动import，常用于java.lang.*的自动导入等
* $N:Nmae，可以引用另外一个MethodSpec的名称作为方法
* */
private static void generate(){
/*--------------------------- Field --------------------------------*/
//基本类型变量
FieldSpec mInt = FieldSpec.builder(int.class,"mInt",Modifier.PUBLIC).initializer("100").build();
//基本类型包装类型
FieldSpec mInteger = FieldSpec.builder(Integer.class,"mInteger",Modifier.PUBLIC).initializer("101").build();
//String类型
FieldSpec mString = FieldSpec.builder(String.class,"mString",Modifier.PRIVATE).initializer("$S","StringFiled").build();
//其它类型
FieldSpec mFile = FieldSpec.builder(File.class,"mFile",Modifier.FINAL).initializer("new File($S)","/data/test.txt").build();
//构造方法
MethodSpec mConstructor = MethodSpec.constructorBuilder().addParameter(int.class,"i").addParameter(String.class,"s")
.addStatement("this.$N = i ;\nthis.$N=s",mInt,mString).build();
//main方法
MethodSpec mainMethod = MethodSpec.methodBuilder("main")
.addParameter(String[].class,"args")
.returns(Void.TYPE)
.addModifiers(Modifier.PUBLIC,Modifier.STATIC)
.addStatement("System.out.println($S)","hello poet !").build();
//注解方法,重写run方法
//若只addSuperinterface(Runnable.class) ，不会默认生成重写接口
ClassName SystemClazz = ClassName.get(System.class);
MethodSpec overrideMethod = MethodSpec.methodBuilder("run")
.returns(void.class)
.addAnnotation(Override.class)
.addModifiers(Modifier.PUBLIC)
.addStatement("$T.out.println($S)",SystemClazz,"Runnable Task Start").build();
//生成接口
// 注意：1.接口方法必须用Modifier.PUBLIC和Modifier.ABSTRACT修饰;2.接口变量必须用Modifier.PUBLIC，Modifier.STATIC,Modifier.FINAL修饰
FieldSpec mInterfaceField = FieldSpec.builder(String.class,"mStatus")
.addModifiers(Modifier.STATIC,Modifier.FINAL, Modifier.PUBLIC)
.initializer("$S","initStatus")
.build();
MethodSpec mInterfaceMethod = MethodSpec.methodBuilder("onStatus")
.returns(void.class)
.addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT)
.addParameter(int.class,"status")
.build();
TypeSpec mInterface = TypeSpec.interfaceBuilder("Callback")
.addField(mInterfaceField)
.addMethod(mInterfaceMethod)
.build();
//枚举类
TypeSpec mEnum = TypeSpec.enumBuilder("Season")
.addEnumConstant("Spring")
.addEnumConstant("Summer")
.addEnumConstant("Autumn")
.addEnumConstant("Winter")
.build();
//方法内匿名内部类
//Runnable内部类
TypeSpec anonymousInnerClass = TypeSpec.anonymousClassBuilder("")
.addSuperinterface(Runnable.class)
.addMethod(
MethodSpec.methodBuilder("run")
.addModifiers(Modifier.PUBLIC)
.addAnnotation(Override.class)
.returns(void.class)
.addStatement("System.out.println($S)"," anonymousInnerClass task start...")
.build()
).build();
//带泛型的匿名内部类
TypeSpec anonymousInnerComparator = TypeSpec.anonymousClassBuilder("")
.addSuperinterface(ParameterizedTypeName.get(Comparator.class,String.class))
.addMethod(
MethodSpec.methodBuilder("compare")
.addModifiers(Modifier.PUBLIC)
.returns(int.class)
.addParameter(String.class,"a")
.addParameter(String.class,"b")
.addAnnotation(Override.class)
.addStatement("return $N.length()-$N.length()","a","b")
.build()
).build();
MethodSpec m1 = MethodSpec.methodBuilder("testInner")
.returns(void.class)
.addParameter(ParameterizedTypeName.get(List.class,String.class),"lists")
.addModifiers(Modifier.PUBLIC)
.addStatement("new $T($L).start()",Thread.class,anonymousInnerClass)
.addStatement("$T.sort($N,$L)",Collections.class,"lists",anonymousInnerComparator)
.build();
//方法注解
MethodSpec annotationMethod = MethodSpec.methodBuilder("download")
.addModifiers(Modifier.PUBLIC)
.returns(void.class)
.addAnnotation(
AnnotationSpec.builder(GET.class)
.addMember("value","$S","/download")
.build()
).build();
/*
* 父类+接口
* 1.若superclass是Object，生成代码不会写extends Object
* */
TypeSpec test = TypeSpec.classBuilder("TestPoet")
.addModifiers(Modifier.PUBLIC,Modifier.FINAL)
.addField(mInt)
.addField(mInteger)
.addField(mFile)
.addField(mString)
.addMethod(mConstructor)
.addMethod(mainMethod)
.addMethod(overrideMethod)
.addMethod(m1)
.addMethod(annotationMethod)
.addSuperinterface(Runnable.class)
.superclass(Object.class)
.addType(mInterface)
.addType(mEnum)
.build();
JavaFile javaFile = JavaFile.builder("com.lbt.buk.poet",test).build();
try {
File file = new File("F:\pj0803\src\com\lbt\buk\poet\TestPoet.java");
if (file.exists()){
file.delete();
}
javaFile.writeTo(new File("F:\pj0803\src"));
} catch (IOException e) {
e.printStackTrace();
}
}
生成的Java文件如下：
public final class TestPoet implements Runnable {
public int mInt = 100;
public Integer mInteger = 101;
final File mFile = new File("/data/test.txt");
private String mString = "StringFiled";
TestPoet(int i, String s) {
this.mInt = i;
this.mString = s;
}
public static void main(String[] args) {
System.out.println("hello poet !");
}
@Override
public void run() {
System.out.println("Runnable Task Start");
}
public void testInner(List<String> lists) {
new Thread(new Runnable() {
@Override
public void run() {
System.out.println(" anonymousInnerClass task start...");
}
}).start();
Collections.sort(lists, new Comparator<String>() {
@Override
public int compare(String a, String b) {
return a.length() - b.length();
}
});
}
@GET("/download")
public void download() {
}
interface Callback {
String mStatus = "initStatus";
void onStatus(int status);
}
enum Season {
Spring,
Summer,
Autumn,
Winter
}
}
