値は、実行時にネイティブ コードを使用して設定されます。System.c内に設定され、Java_java_lang_System_initPropertiesと呼ばれる関数
スニペット
JNIEXPORT jobject JNICALL
Java_java_lang_System_initProperties(JNIEnv *env, jclass cla, jobject props)
{
char buf[128];
java_props_t *sprops = GetJavaProperties(env);
jmethodID putID = (*env)->GetMethodID(env,
(*env)->GetObjectClass(env, props),
"put",
"(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;");
jmethodID removeID = (*env)->GetMethodID(env,
(*env)->GetObjectClass(env, props),
"remove",
"(Ljava/lang/Object;)Ljava/lang/Object;");
jmethodID getPropID = (*env)->GetMethodID(env,
(*env)->GetObjectClass(env, props),
"getProperty",
"(Ljava/lang/String;)Ljava/lang/String;");
jobject ret = NULL;
jstring jVMVal = NULL;
if (sprops == NULL || putID == NULL ) return NULL;
PUTPROP(props, "java.specification.version",
JDK_MAJOR_VERSION "." JDK_MINOR_VERSION);
PUTPROP(props, "java.specification.name",
"Java Platform API Specification");
PUTPROP(props, "java.specification.vendor",
JAVA_SPECIFICATION_VENDOR);
PUTPROP(props, "java.version", RELEASE);
PUTPROP(props, "java.vendor", VENDOR);
PUTPROP(props, "java.vendor.url", VENDOR_URL);
PUTPROP(props, "java.vendor.url.bug", VENDOR_URL_BUG);
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