我遇到了以下javac编译失败,其中javac无法识别具有公共枚举的静态嵌套类上的注释。一旦我将枚举移出静态嵌套类,就解决了编译错误。有谁知道为什么javac失败了?这是一个java编译器错误吗?或者是否有我不知道的java细微差别?
以下是一个独立的测试用例。
无法编译:
package test;
import test.AnnotationBug.NestedClassWithEnum.ParticipantType;
import lombok.Data;
import lombok.NoArgsConstructor;
import com.googlecode.objectify.annotation.Embed;
public class AnnotationBug {
ParticipantType type;
@Embed
@Data
@NoArgsConstructor
public static final class NestedClassNoEnum {
}
@Embed
@Data
@NoArgsConstructor
public static final class NestedClassWithEnum {
ParticipantType type;
public enum ParticipantType {
ORGANIZER,
REGISTERED,
WAIT_LISTED
}
}
}
编译输出:
$ javac -classpath /home/avaliani/projects/jars/objectify-4.0b2.jar:/home/avaliani/projects/jars/lombok.jar test/AnnotationBug.java
test/AnnotationBug.java:20: error: cannot find symbol
@Embed
^
symbol: class Embed
location: class AnnotationBug
test/AnnotationBug.java:21: error: cannot find symbol
@Data
^
symbol: class Data
location: class AnnotationBug
test/AnnotationBug.java:22: error: cannot find symbol
@NoArgsConstructor
^
symbol: class NoArgsConstructor
location: class AnnotationBug
编译:
package test;
// import test.AnnotationBug.NestedClassWithEnum.ParticipantType;
import lombok.Data;
import lombok.NoArgsConstructor;
import com.googlecode.objectify.annotation.Embed;
public class AnnotationBug {
ParticipantType type;
@Embed
@Data
@NoArgsConstructor
public static final class NestedClassNoEnum {
}
@Embed
@Data
@NoArgsConstructor
public static final class NestedClassWithEnum {
ParticipantType type;
}
public enum ParticipantType {
ORGANIZER,
REGISTERED,
WAIT_LISTED
}
}
编译没有错误:
$ javac -classpath /home/avaliani/projects/jars/objectify-4.0b2.jar:/home/avaliani/projects/jars/lombok.jar test/AnnotationBug.java
要指出的事情:
1)注意编译失败的行号。解析NestedClassNoEnum的注释没有问题。
2)Java版本:
$ java -version
java version "1.7.0_21"
OpenJDK Runtime Environment (IcedTea 2.3.9) (7u21-2.3.9-0ubuntu0.12.10.1)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)
答案 0 :(得分:11)
如果你删除静态类的导入,代码编译得很好,请看下面的代码[注意:我没有使用@Embed注释,因为我没有jar,但它不会有任何区别]:
//import NestedClassWithEnum.ParticipantType;
import lombok.Data;
import lombok.NoArgsConstructor;
public class AnnotationBug {
NestedClassWithEnum.ParticipantType type;
@Data
@NoArgsConstructor
public static final class NestedClassNoEnum {
}
@Data
@NoArgsConstructor
public static final class NestedClassWithEnum {
ParticipantType type;
public enum ParticipantType {
ORGANIZER,
REGISTERED,
WAIT_LISTED
}
}
}
原因似乎与列和静态类的类加载有关。 Enums are eagerly loaded懒惰地加载静态类。因此,java可能会尝试在编译时自行停止,但这是猜测。
编辑: 根据与保罗的讨论,上面的猜测是不正确的。