在java中，我想過用註釋處理。 在將源文件解析爲javac命令之前，apt工具會掃描源文件。
在源文件的彙編，輸出將被打印出來：
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
public @interface MyInterface {
int offset() default 0;
int last() default 100;
}
處理器工廠：
3210
實際註釋處理器：
public class MyInterfaceAnnotationProcessor implements AnnotationProcessor {
private AnnotationProcessorEnvironment ape;
private AnnotationTypeDeclaration atd;
public MyInterfaceAnnotationProcessor(AnnotationProcessorEnvironment ape) {
this.ape = ape;
atd = (AnnotationTypeDeclaration) ape.getTypeDeclaration("practiceproject.MyInterface");
}
public void process() {
Collection<Declaration> decls = ape.getDeclarationsAnnotatedWith(atd);
for (Declaration dec : decls) {
processDeclaration(dec);
}
}
private void processDeclaration(Declaration d) {
Collection<AnnotationMirror> ams = d.getAnnotationMirrors();
for (AnnotationMirror am : ams) {
if (am.getAnnotationType().getDeclaration().equals(atd)) {
Map<AnnotationTypeElementDeclaration, AnnotationValue> values = am.getElementValues();
int offset = 0;
int last = 100;
for (Map.Entry<AnnotationTypeElementDeclaration, AnnotationValue> entry : values.entrySet()) {
AnnotationTypeElementDeclaration ated = entry.getKey();
AnnotationValue v = entry.getValue();
String name = ated.getSimpleName();
if (name.equals("offset")) {
offset = ((Integer) v.getValue()).intValue();
} else if (name.equals("last")) {
last = ((Integer) v.getValue()).intValue();
}
}
//find the sum
System.err.println("Sum: " + ((last + 1 - offset)/2) * (2 * offset + (last - offset)));
}
}
}
}
然後我們創建一個源文件。
@MyInterface(offset = 1, last = 1000)
public class Main {
@MyInterface
void doNothing() {
System.out.println("Doing nothing");
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
Main m = new Main();
m.doNothing();
MyInterface my = (MyInterface) m.getClass().getAnnotation(MyInterface.class);
System.out.println("offset: " + my.offset());
System.out.println("Last: " + my.last());
}
}
註釋處理器被編譯成一個jar文件，則易於工具用於編譯源文件爲：：使用MyInterface的註釋簡單的類
apt -cp "D:\Variance project\PracticeProject\dist\practiceproject.jar" -factory practiceproject.annotprocess.MyInterfaceAnnotationProcessorFactory "D:\Variance project\PracticeProject2\src\practiceproject2\Main.java"
該項目的輸出：
Called supportedAnnotationTypes...........................
Called getProcessorFor................
Sum: 5000
Sum: 500500
#error「500500」編譯錯誤是否計爲「完成」？ – Mysticial 2012-01-06 19:43:27
提示本質上意味着您使用C++模板。顯然不一樣，但這一個是打印1到1000，我相信你可以修改它以增加到一千... http://stackoverflow.com/questions/4568645/printing-1-to-1000-無環或條件 – Joe 2012-01-06 19:43:29
'const int value = 1 + 2 + 3 .... + 1000;安慰。WriteLine（value）;'; P – 2012-01-06 19:44:15