Framework定制-在JAVA核心库中移植Android Log

在java核心库中，由于无法导入android的包，要想使用Log，最粗暴的方式就是用反射调用，还有一种方式就是移植Android的Log到java核心库中。

具体实现如下：

创建JLog.java

复制代码

aosp/libcore/ojluni/src/main/java/java/lang

package java.lang;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.json.JSONObject;
 
public class JLog {
    public static final String mTag = "Yooha-log";
    public static final int INFO = 4;
    public static final int ERROR = 6;
 
    public static native int println_native(int bufID, int priority, String tag, String msg);
    public static native int getpid();

 
    public static void print_info(String tag, String info) {
        try{
            JSONObject jsinfo = new JSONObject();
            jsinfo.put("Type", tag);
            jsinfo.put("PID", getProcessID());
            jsinfo.put("Info", info);
            i(mTag, jsinfo.toString());
        } catch (Exception e){
            showException(e);
        }
    }
 
    public static void print_stack(String type, String clz, String method, String ret, String...param) {
        try{
            JSONObject jsinfo = new JSONObject();
            jsinfo.put("Type", type);
            jsinfo.put("PID", getProcessID());
            jsinfo.put("Class", clz);
            jsinfo.put("Method", method);
             
            if (param != null){
                jsinfo.put("Param", param.toString());
            }else{
                jsinfo.put("Param", "NULL");
            }
 
            if (ret == null){
                jsinfo.put("Return", "NULL");
            }else{
                jsinfo.put("Return", ret);
            }
            jsinfo.put("stackTrace", getStackTrace());
            i(mTag, jsinfo.toString());
        } catch (Exception e){
            showException(e);
        }
    }
 
    public static String getStackTrace() {
        StringBuffer sb = new StringBuffer();
        try{
            Throwable ex = new Throwable();
            StackTraceElement[] stackElements = ex.getStackTrace();
            for (int i = 0; i < stackElements.length; i++) {
                StackTraceElement element = stackElements[i];
                sb.append("at " +
                        element.getClassName() +
                        "." +
                        element.getMethodName() +
                        "(" +
                        element.getFileName() +
                        ":" +
                        element.getLineNumber() +
                        ")\n");
            }
        } catch(Exception e){
 
        }
        return sb.toString();
    }
 
    public static void showException(Exception e){
        e(mTag, "Type:Exception, ExceptionLine:" + getExceptionLine() + ", Exception:" + e.toString());
    }
 
    public static String getExceptionLine(){
        StackTraceElement element = new Throwable().getStackTrace()[1];
        return element.getFileName() + "-->" + element.getLineNumber() + " : " + element.getClassName();
    }
 
    public static int getProcessID(){
        try{
            return getpid();
        } catch (Exception e){
        }
        return -1;
    }
 
    public static int i(String tag, String msg){
        return println_native(0, INFO, tag, msg);
    }
    public static int e(String tag, String msg){
        return println_native(0, ERROR, tag, msg);
    }
}

将JLog.java文件添加到编译文件链
- 路径：/home/yooha/aosp/libcore/penjdk_java_files.bp
filegroup {
name: "openjdk_javadoc_files",
srcs: [
...省略
"ojluni/src/main/java/java/lang/System.java",
///ADD START
"ojluni/src/main/java/java/lang/JLog.java",
///ADD END
"ojluni/src/main/java/java/lang/ThreadDeath.java",
...省略
复制代码
```
  ],
```
}
在libcore native层添加JLog.c

/aosp/libcore/ojluni/src/main/native

#include <log/log.h>
#include <utils/Log.h>
#include <jni.h>
#include <nativehelper/JNIHelp.h>
//#include <process.h>
#include <unistd.h>

static jint java_lang_JLog_println_native(JNIEnv* env, jclass clazz,
jint bufID, jint priority, jstring tagObj, jstring msgObj)
{
const char* tag = NULL;
const char* msg = NULL;
复制代码
```
  if (msgObj == NULL) {
      //JNU_ThrowNullPointerException(env, "println needs a message");
      return -1;
  }

  if (bufID < 0 || bufID >= LOG_ID_MAX) {
      //JNU_ThrowNullPointerException(env, "bad bufID");
      return -1;
  }

  if (tagObj != NULL)
      tag = (*env)->GetStringUTFChars(env,tagObj, NULL);
  msg = (*env)->GetStringUTFChars(env,msgObj, NULL);

  int res = __android_log_buf_write(bufID, (android_LogPriority)priority, tag, msg);

  if (tag != NULL)
      (*env)->ReleaseStringUTFChars(env,tagObj, tag);
  (*env)->ReleaseStringUTFChars(env,msgObj, msg);

  return res;
```
}

static jint java_lang_JLog_getpid(JNIEnv* env, jclass clazz){
return getpid();
}

static const JNINativeMethod gMethods[] = {
/* name, signature, funcPtr /
{ "println_native", "(IILjava/lang/String;Ljava/lang/String;)I", (void) java_lang_JLog_println_native },
{ "getpid", "()I", (void*) java_lang_JLog_getpid }
};

void register_java_lang_JLog(JNIEnv* env) {
jniRegisterNativeMethods(env, "java/lang/JLog", gMethods, NELEM(gMethods));
}
OnLoad.cpp中声明和调用 register_java_lang_JLog
- 路径：libcore/ojluni/src/main/native/OnLoad.cpp
...省略
///ADD START
extern "C" void register_java_lang_JLog(JNIEnv* env);
///ADD END
...省略
extern "C" JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void*) {
...省略
///ADD START
register_java_lang_JLog(env);
///ADD END
...省略
}
...省略
Android.bp中添加XLog.c文件到编译文件中
- 路径：/home/yooha/aosp/libcore/ojluni/src/main/native/Android.bp
filegroup {
name: "libopenjdk_native_srcs",
srcs: [
...省略
///ADD START
"JLog.c",
///ADD END
...省略
],
}

最后编译刷机，就可以正常使用了