利用JNI调用C/C++方法实现从控制台输入密码
最近看到一个问题,如何用Java实现从控制台输入密码?
本来以为是很简单的问题,查了一下发现Java居然没提供这样一个方法。目前实现的方式有2个,一个是利用JNI来调用C/C++方法,另一个是使用多线程。
下面是使用JNI的方法:
首先,写出我们的Java类:
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这一段使用System.loadLiberary("..");来加载本地类库,PasswordDLL是文件名,不需要加dll后缀,系统会自动辨认。
编译成JNIPasswordReader.class以后,使用
javah -jni JNIPasswordReader
命令,生成一个JNIPasswordReader.h文件,文件内容如下:
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然后,我们需要写一个cpp文件来实现
JNIEXPORT jstring JNICALL Java_JNIPasswordReader_readPassword (JNIEnv *, jobject);
接口。
于是,我写了一个PasswordDLL.cpp文件,内容如下:
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我使用VS2005来生成对应的dll文件,在生成之前,需要把$JDK_HOME/include/jni.h和$JDK_HOME/include/win32/jni_md.h这两个文件copy到Microsoft Visio Studio 8/VC/include目录下,我就在这里卡了大概1个小时,一直说找不到jni.h文件
然后就可以使用VS2005来生成dll了,生成好对应的PasswordDLL.dll以后,把该dll文件放到系统变量PATH能找到的地方,比如windows/system32/或者jdk/bin目录,我是放到JDK_HOME/bin下面了
放好以后,
执行java JNIPasswordReader
就可以输入密码了。
关于JNI的更详细内容,可以参考:
《在Windows中实现Java本地方法》http://www.ibm.com/developerworks/cn/java/jnimthds/index.html
我的Password.dll文件
http://www.blogjava.net/Files/richardeee/PasswordDLL.zip
评论
Console console = System.console();
if (console != null) {
String user = new String(console.readLine("Enter username:"));
String pwd = new String(console.readPassword("Enter passowrd:"));
console.printf("User is :" + user + "\n");
console.printf("Password is: " + pwd + "\n");
} else {
System.out.println("Console is unavailable");
}
但是在某些情况下System.console()返回一个null。比如输入被重定向。具体的看JDK6的API Doc
http://java.sun.com/javase/6/docs/api/java/io/Console.html
是不是这种方法有不符合你的要求的地方?
呵呵,你的意思是我用JNI么?首先我的JDK版本是5.0的,其次我在写这个之前还真没见到您的那篇JNI文章……其实解决密码输入的最好方法我觉得还是利用JDK6.0的特性,毕竟把Java跟本地代码绑在一块还是不太好
同意你的观点, 本地代码是最后一个选择,实在没法才用.