[Android] Print log in Java libcore

Reference:
在Java核心库中打印log
android 在Java核心库libcore中打印log


Follow below steps to add log utility function in libcore/luni/src/main/java/java/text/SimpleDateFormat.java

Android version: 4.0.4
Affected files:

1. libcore\luni\src\main\java\java\text\SimpleDateFormat.java
2. libcore\luni\src\main\native\Register.cpp
3. libcore\luni\src\main\native\sub.mk

Added file:

1. libcore\luni\src\main\native\java_text_SimpleDateFormat.cpp

[Step 1]

Create libcore\luni\src\main\native\java_text_SimpleDateFormat.cpp 

 #define LOG_TAG "SimpleDateFormat"  
 #include "JNIHelp.h"  
 #include "JniConstants.h"  
 #include "JniException.h"  
 #include "ScopedPrimitiveArray.h"  
 #include "UniquePtr.h"  
 #include <stdlib.h>  
 #include <string.h>  
 static jint SimpleDateFormat_println_native(JNIEnv* env, jclass,  
     jint bufID, jint priority, jstring tagObj, jstring msgObj)  
 {  
   const char* tag = NULL;  
   const char* msg = NULL;  
   if (msgObj == NULL) {  
     jniThrowNullPointerException(env, "println needs a message");  
     return -1;  
   }  
   if (bufID < 0 || bufID >= LOG_ID_MAX) {  
     jniThrowNullPointerException(env, "bad bufID");  
     return -1;  
   }  
   if (tagObj != NULL)  
     tag = env->GetStringUTFChars(tagObj, NULL);  
   msg = env->GetStringUTFChars(msgObj, NULL);  
   int res = __android_log_buf_write(bufID, (android_LogPriority)priority, tag, msg);  
   if (tag != NULL)  
     env->ReleaseStringUTFChars(tagObj, tag);  
   env->ReleaseStringUTFChars(msgObj, msg);  
   return res;  
 }  
 static JNINativeMethod gMethods[] = {  
   NATIVE_METHOD(SimpleDateFormat, println_native, "(IILjava/lang/String;Ljava/lang/String;)I"),  
 };  
 int register_java_text_SimpleDateFormat(JNIEnv* env) {  
   return jniRegisterNativeMethods(env, "java/text/SimpleDateFormat", gMethods, NELEM(gMethods));  
 }  

[Step 2]

Add java_text_SimpleDateFormat.cpp into make file libcore\luni\src\main\native\sub.mk

 LOCAL_SRC_FILES := \  
      AsynchronousSocketCloseMonitor.cpp \  
      JniConstants.cpp \  
      JniException.cpp \  
      NetworkUtilities.cpp \  
      Register.cpp \  
      cbigint.cpp \  
      java_io_Console.cpp \  
      java_io_File.cpp \  
      java_io_ObjectStreamClass.cpp \  
      java_lang_Character.cpp \  
      java_lang_Math.cpp \  
      java_lang_ProcessManager.cpp \  
      java_lang_RealToString.cpp \  
      java_lang_StrictMath.cpp \  
      java_lang_StringToReal.cpp \  
      java_lang_System.cpp \  
      java_math_NativeBN.cpp \  
      java_nio_ByteOrder.cpp \  
      java_nio_charset_Charsets.cpp \  
      java_text_Bidi.cpp \  
      java_text_SimpleDateFormat.cpp \  
      java_util_regex_Matcher.cpp \  
      java_util_regex_Pattern.cpp \  
      java_util_zip_Adler32.cpp \  
      java_util_zip_CRC32.cpp \  
      java_util_zip_Deflater.cpp \  
      java_util_zip_Inflater.cpp \  
      libcore_icu_ICU.cpp \  
      libcore_icu_NativeBreakIterator.cpp \  
      libcore_icu_NativeCollation.cpp \  
      libcore_icu_NativeConverter.cpp \  
      libcore_icu_NativeDecimalFormat.cpp \  
      libcore_icu_NativeIDN.cpp \  
      libcore_icu_NativeNormalizer.cpp \  
      libcore_icu_NativePluralRules.cpp \  
      libcore_icu_TimeZones.cpp \  
      libcore_io_AsynchronousCloseMonitor.cpp \  
      libcore_io_Memory.cpp \  
      libcore_io_OsConstants.cpp \  
      libcore_io_Posix.cpp \  
      libcore_net_RawSocket.cpp \  
      org_apache_harmony_xml_ExpatParser.cpp \  
      org_apache_harmony_xnet_provider_jsse_NativeCrypto.cpp \  
      readlink.cpp \  
      realpath.cpp \  
      toStringArray.cpp \  
      valueOf.cpp  

[Step 3]

Register java_text_SimpleDateFormat(env) in libcore\luni\src\main\native\Register.cpp

 extern int register_java_nio_ByteOrder(JNIEnv* env);  
 extern int register_java_nio_charset_Charsets(JNIEnv* env);  
 extern int register_java_text_Bidi(JNIEnv* env);  
 extern int register_java_text_SimpleDateFormat(JNIEnv* env);  
 extern int register_java_util_regex_Matcher(JNIEnv* env);  
 extern int register_java_util_regex_Pattern(JNIEnv* env);  
 extern int register_java_util_zip_Adler32(JNIEnv* env);  

       register_java_nio_ByteOrder(env) != -1 &&  
       register_java_nio_charset_Charsets(env) != -1 &&  
       register_java_text_Bidi(env) != -1 &&  
       register_java_text_SimpleDateFormat(env) != -1 &&  
       register_java_util_regex_Matcher(env) != -1 &&  
       register_java_util_regex_Pattern(env) != -1 &&  
       register_java_util_zip_Adler32(env) != -1 &&  

[Step 4]

Declare native function in libcore\luni\src\main\java\java\text\SimpleDateFormat.java

   private static native int println_native(int bufID, int priority, String tag, String msg);   
   private static final String TAG = "SimpleDateFormat";  
   private static final int LOG_ID_MAIN = 0;   
   private static final int DEBUG = 3;   
   private static int Log(String tag, String msg) {   
     return println_native(LOG_ID_MAIN, DEBUG, tag, msg);   
   }  

[Step 5]

Finally, we can use Log(TAG, msg) in SimpleDataFormat.java!

 Log("SimpleDateFormat", "This is debug message");