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JDK8 Access to Parameter Names at Runtime

JDK 8的新特性之一, 运行时获取方法参数的名称

JDK8之前, Eclipse自带的ECJ编译器,同本地变量表,把方法参数的名字,放在最前面,使其编译出来的class的名字看推测.

而 JDK8把这种行为规范化(终于…) http://openjdk.java.net/jeps/118

参考文章 Java 8 parameter name at runtime

演示代码

package nutz_jdk8; import java.lang.reflect.Constructor; import java.lang.reflect.Parameter; public class Bot {  private final String name;  private final String author;  private final int rating;  private final int score;  public Bot(String name, String author, int rating, int score) {   this.rating = rating; // 注意这里的顺序,并非按参数顺序逐一调用   this.score = score;   this.name = name;   this.author = author;  }  public static void main(String[] args) throws NoSuchMethodException, SecurityException {   Class<Bot> clazz = Bot.class;   Constructor ctor = clazz.getConstructor(String.class, String.class, int.class, int.class);   Parameter[] ctorParameters =ctor.getParameters();   for (Parameter param: ctorParameters) {    System.out.println(param.isNamePresent() + ":" + param.getName());   }  } }

输出的结果是:

true:name true:author true:rating true:score

然后, 这个特性并未默认启用,javac需要额外的参数”-parameters”

javac -parameters nutz_jdk8/Bot.java java -cp nutz_jdk8.Bot

如果是Eclipse 4.4 (正式支持JDK8的初始版本), 则需要手动在”Java Compiler”中启用之

JDK8 Access to Parameter Names at Runtime

如果是maven,则需要这段

<plugin>  <groupId>org.apache.maven.plugins</groupId>  <artifactId>maven-compiler-plugin</artifactId>  <version>3.1</version>  <configuration>   <source>1.8</source>   <target>1.8</target>   <compilerArgument>-parameters</compilerArgument>  </configuration> </plugin>