使用java-9 build 9-ea + 149 和jol 0.6.
运行这个简单的代码:
ArrayList<Integer> list = new ArrayList<>();
list.add(12);
System.out.println(ClassLayout.parseInstance(list).toPrintable());
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输出:
OFFSET SIZE TYPE DESCRIPTION VALUE
0 4 (object header) 01 00 00 00 (00000001 00000000 00000000 00000000) (1)
4 4 (object header) 00 00 00 00 (00000000 00000000 00000000 00000000) (0)
8 4 (object header) 0e 8d 00 f8 (00001110 10001101 00000000 11111000) (-134181618)
12 4 int AbstractList.modCount (access denied)
16 4 int ArrayList.size (access denied)
20 4 Object[] ArrayList.elementData (access denied)
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此访问被拒绝的部分来自方法中的FieldData.java:
public String safeValue(Object object) {
if (refField != null) {
try {
return ObjectUtils.safeToString(refField.get(object));
} catch (IllegalAccessException iae) {
// exception, try again
}
try {
refField.setAccessible(true);
return ObjectUtils.safeToString(refField.get(object));
} catch (Exception e) {
return "(access denied)";
}
} else {
return "N/A";
}
}
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实际的例外是:
无法使字段保护的瞬态int java.util.AbstractList.modCount accessible:module java.base不会"打开java.util"到未命名的模块@ 479d31f3.
我认为这与被锁定的不安全功能有关.问题是如何让它运行?
我看过以下属性:
-XaddExports:java.base/sun.security.provider=ALL-UNNAMED
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但无法真正说明应该是什么样子.
解决方案确实是提出正确的论点。
--add-opens java.base/java.util=ALL-UNNAMED
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正如这里所建议的