【Javac编译异常】javac编译提示jdk中的包找不到的问题error: package jdk.internal.org.objectweb.asm does not exist 和 error: cannot find symbol

一、复现步骤

1）编写待编译的java类

package f_asm_and_javassist;

import jdk.internal.org.objectweb.asm.*;

import java.io.*;

import static jdk.internal.org.objectweb.asm.Opcodes.ASM5;

/**
 * @Author zhangboqing
 * @Date 2020/3/26
 */
public class AsmDemo {

    //访问类的方法和字段
    public static void main(String[] args) {
        byte[] bytes  = getBytes(); // MyMain.class 文件的字节数组
        ClassReader cr = new ClassReader(bytes);
        ClassWriter cw = new ClassWriter(0);
        ClassVisitor cv = new ClassVisitor(ASM5, cw) {
            @Override
            public FieldVisitor visitField(int access, String name, String desc, String signature, Object value) {
                System.out.println("field: " + name);
                return super.visitField(access, name, desc, signature, value);
            }

            @Override
            public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
                System.out.println("method: " + name);
                return super.visitMethod(access, name, desc, signature, exceptions);
            }
        };
        cr.accept(cv, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG);
    }

    private static byte[] getBytes() {

        StringBuilder sb = new StringBuilder();
        try(FileInputStream fileInputStream = new FileInputStream(new File("MyMain.class"));
            BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream)) {

            byte[] buffer = new byte[1024*8];
            while (bufferedInputStream.available() > 0) {

                int length = bufferedInputStream.read(buffer);
                sb.append(new String(buffer,0,length) );
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return sb.toString().getBytes();
    }
}

2）在当前目录使用javac编译

 javac -d . AsmDemo.java

提示如下错误：

➜  f_asm_and_javassist git:(master) ✗ javac -d . AsmDemo.java
AsmDemo.java:3: error: package jdk.internal.org.objectweb.asm does not exist
import jdk.internal.org.objectweb.asm.*;
^
AsmDemo.java:7: error: package jdk.internal.org.objectweb.asm does not exist
import static jdk.internal.org.objectweb.asm.Opcodes.ASM5;
                                            ^
AsmDemo.java:7: error: static import only from classes and interfaces
import static jdk.internal.org.objectweb.asm.Opcodes.ASM5;
^
AsmDemo.java:18: error: cannot find symbol
        ClassReader cr = new ClassReader(bytes);
        ^
  symbol:   class ClassReader
  location: class AsmDemo
AsmDemo.java:18: error: cannot find symbol
        ClassReader cr = new ClassReader(bytes);
                             ^
  symbol:   class ClassReader
  location: class AsmDemo
AsmDemo.java:19: error: cannot find symbol
        ClassWriter cw = new ClassWriter(0);
        ^
  symbol:   class ClassWriter
  location: class AsmDemo
AsmDemo.java:19: error: cannot find symbol
        ClassWriter cw = new ClassWriter(0);
                             ^
  symbol:   class ClassWriter
  location: class AsmDemo
AsmDemo.java:20: error: cannot find symbol
        ClassVisitor cv = new ClassVisitor(ASM5, cw) {
        ^
  symbol:   class ClassVisitor
  location: class AsmDemo
AsmDemo.java:20: error: cannot find symbol
        ClassVisitor cv = new ClassVisitor(ASM5, cw) {
                              ^
  symbol:   class ClassVisitor
  location: class AsmDemo
AsmDemo.java:20: error: cannot find symbol
        ClassVisitor cv = new ClassVisitor(ASM5, cw) {
                                           ^
  symbol:   variable ASM5
  location: class AsmDemo
AsmDemo.java:33: error: cannot find symbol
        cr.accept(cv, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG);
                      ^
  symbol:   variable ClassReader
  location: class AsmDemo
AsmDemo.java:33: error: cannot find symbol
        cr.accept(cv, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG);
                                              ^
  symbol:   variable ClassReader
  location: class AsmDemo
12 errors

二、解决办法

这就是javac的限制。默认情况下，javac不会从rt.jar中读取类。它从一个符号文件中读取，该文件只包含标准API和一些内部API(例如com.sun.,com.oracle.和sun . *)。

要禁用此机制，可以使用 javac -XDignore.symbol.file=true

使用maven可以用：

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <configuration>
    <compilerArgument>-XDignore.symbol.file</compilerArgument>
  </configuration>
</plugin>

上述问题采用下面命令执行就可以成功了：

 javac -XDignore.symbol.file=true -d . AsmDemo.java

待包名的类，需要使用 -d .，表示在当前目录自动生成包路径