KNI接口 "KNI_GetFieldID" 调用失败问题的解决

KNI接口 "KNI_GetFieldID" 调用失败问题的解决

每次调用KNI_GetFieldID总是返回0，也就是在函数_KNI_field_lookup_helper()中执行到如下代码片段：

if (!field.is_valid() || (field.is_static() != is_static) ||

// We do not support field IDs in super classes:

(field.is_static() && !holder().equals(&ic))) {

return (jfieldID)0;

然而在 kni.h 中有这么一段注释：

/**

* Instance field access.

*

* Note specific to this VM: KNI_GetFieldID() must not be applied

* on a class whose

* fields have been renamed by the romizer. You need to use

* the DontRenameNonPublicFields flag in your romizer configuration

* file. See src/vm/cldc_rom.cfg in this VM source distribution

* for an example.

*/

KNIEXPORT jfieldID KNI_GetFieldID(jclass classHandle, const char* name,

const char* signature);

也就是说 class 的 fields 会被 romizer 改名，而KNI_GetFieldID对改名后的 fields 会获取失败；

为避免 fields 被改名，需要在cldc/src/vm/cldc_rom.cfg 中使用DontRenameNonPublicFields，如下：

# Do not rename the non-public fields/methods of the following classes,

# because these fields are accessed by name in KNI code.

DontRenameNonPublicFields = com.eastcom.eui.entity.Contact

DontRenameNonPublicFields = com.sun.cldc.io.ResourceInputStream

If CLDC_11

DontRenameNonPublicFields = java.lang.ref.WeakReference

EndIf

#Some symbols are referenced during bootstrap to verify the class

If ISOLATES

DontRenameNonPublicFields = com.sun.cldc.isolate.Isolate

DontRenameNonPublicMethods = com.sun.cldc.isolate.Isolate

EndIf

修改后验证，KNI_GetFieldID 获取成功。

结论就是KNI对应的JAVA上层实体类的成员一般最好定义成public的，如果是private，

需要修改cldc/src/vm/cldc_rom.cfg文件。

PS: 从字面上理解DontRenameNonPublicFields，private域会被修改，而public域是否不会被改名呢？

KNI_GetFieldID 对 public域是否能总是获取成功？此猜想待验证(不会改名)