Windows上的RxTx安装java.lang.NoClassDefFoundError：gnu / io / CommPort [英] RxTx installation on windows java.lang.NoClassDefFoundError: gnu/io/CommPort
问题描述
我把 rxtxcomm.jar 放到 jre / lib / ext 文件夹中，但我仍然得到 NoClassDefFoundError 这个文件夹不会自动进入全局类路径吗？
I put rxtxcomm.jar into jre/lib/ext folder, but I still get NoClassDefFoundError Isn't this folder automatically taken into the global classpath?
谢谢
推荐答案
是的，它会被自动带到类路径，但RXTXcomm使用JNI /本机外部库（.so和.dll文件），在运行程序时必须提供它们的路径命令行：
yes it is taken automatically to classpath, but RXTXcomm uses JNI /native external libraries (.so and .dll files), you must provide the path to them when running your program in command line:
java -jar yourprogram.jar -Djava.library.path="PATH_TO_EXTERNAL_LIBRARIES"
for linux：
for linux:
假设您解压缩 rxtx.zip 到
/ home / user /
suppose you unpacked the rxtx.zip to /home/user/
如果你有32位x86 platofrm：
if you have 32bit x86 platofrm:
PATH_TO_EXTERNAL_LIBRARIES = / home / user / Linux / i686-unknown-linux-gnu /
PATH_TO_EXTERNAL_LIBRARIES = /home/user/Linux/i686-unknown-linux-gnu/
如果你有64位x86平台那么它就行了d be：
if you have 64bit x86 platform the it would be:
PATH_TO_EXTERNAL_LIBRARIES = / home / user / Linux / x86_64-unknown-linux-gnu /
PATH_TO_EXTERNAL_LIBRARIES = /home/user/Linux/x86_64-unknown-linux-gnu/
for windows：
for windows:
假设你下载并解压缩到C：\ rxtxt
suppose you downloaded and unpacked it to C:\rxtxt
PATH_TO_EXTERNAL_LIBRARIES = C：\ rxtxt \ Windows\i368-mingw32 \
PATH_TO_EXTERNAL_LIBRARIES = C:\rxtxt\Windows\i368-mingw32\
如果你发现从命令行执行它很麻烦，你可以从你的代码（之前通过RXTXcomm打开端口）这样做：
If you find it cumbersome to do it from command line you can do it from yout code (before opening port via RXTXcomm):
System.setProperty("java.library.path","PATH_TO_EXTERNAL_LIBRARIES");
编辑：
当然，你除了以上所有内容之外，还必须将RXTXcomm.jar放在类路径中。如果从命令行运行jar包装程序 - yourprogram.jar - 在jar中你必须有一个包含MANIFEST.MF的META-INF文件夹，其中包含以下条目：
of course, you must put RXTXcomm.jar in your classpath in addition to all of the above. If running from command line as jar packaged program - yourprogram.jar - inside the jar you must have a META-INF folder that contains MANIFEST.MF with the following entries:
Class-Path: lib/RXTXcomm.jar
Main-Class: pkg.Main
和yourprogram.jar必须位于文件夹中，其中包含文件夹lib，其中包含RXTXcomm.jar，同时
该类包含
and yourprogram.jar must be in folder which has folder lib in which is RXTXcomm.jar, also the class with
public static void main(String[] args)
方法必须称为Main并驻留在名为pkg的包中（只需将pkg.Main替换为您拥有的任何内容）。
method must be called Main and reside in package named pkg (just replace pkg.Main with whatever you have).
然后，您可以成功运行程序并打开串行端口有一个。这种方法也消除了在jre / lib / ext文件夹中复制任何内容的需要
Then you can run your program succesfully and open a serial port if you have one. This approach also eliminates the need to copy anything in jre/lib/ext folder
编辑^ 2：
或者，如果您不想将程序包装在jar中，请将自己放在包含文件夹pkg的文件夹中并写入：
or, if you don't want to pack your program in jar, position yourself in folder which contains the folder pkg and write:
java -cp PATH_TO_RXTX/RXTXcomm.jar -Djava.library.path="PATH_TO_EXTERNAL_LIBRARIES" pkg.Main
（所有路径可以是相对的或绝对的）
(all paths can be relative or absolute)
编辑^ 3：
但我建议 Java简单串行连接器而不是RXTXcomm：
but I would recommend Java Simple Serial Connector instead of RXTXcomm:
- 它处理来自多个线程的重负载而不是RXTXcomm（在生产中测试）
- 外部库在jar中打包所以有无需设置java.library.path
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