java调用Oracle EXP备忘
一眼看过去相信大家都知道用Runtime.getRuntime().exec来调用，我的需求就是：调用Oracle EXP命令完成备份，并返回生成的备份文件名，这个备份文件会很快在其他的地方被使用。
采用Runtime.getRuntime().exec我们都知道，需要处理它的InputStream，以避免出现执行的命令输出的信息过多使得进程被堵死，OK，按照这样的方法，开写：
http://www.blogjava.net/Images/OutliningIndicators/None.gif String[] cmds= newString[ 3 ];
http://www.blogjava.net/Images/OutliningIndicators/None.gifcmds[ 0 ]= " cmd " ;
http://www.blogjava.net/Images/OutliningIndicators/None.gifcmds[ 1 ]= " /C " ;
http://www.blogjava.net/Images/OutliningIndicators/None.gifcmds[ 2 ] = "exp username/password@sid file=xxx.dmp log=xxx.log";http://www.blogjava.net/Images/OutliningIndicators/None.gif
Process process = Runtime.getRuntime().exec(cmds);
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockStart.gif try {
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif InputStreamReader isr= newInputStreamReader(process.getInputStream());
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif BufferedReader br= newBufferedReader(isr);
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif String line= null ;
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockStart.gif while((line=br.readLine())!= null ) {
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gif System.out.println(line);
}
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gif }
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockStart.gif catch(IOException ioe){
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif ioe.printStackTrace();
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gif }
写完收工，执行，傻了，进程被挂S了，到底什么原因呢，开始瞎尝试，把读取process的InputStream的部分全部去掉，执行，竟然OK，更晕，但这个时候出现了一个问题，那就是没法知道什么时候备份文件完全生成了，如果在Runtime.getRuntime后去获取备份文件，那个时候甚至连备份文件都没生成，之后甚至尝试过轮询直到备份文件生成，再往下走，那样还是有问题，就是生成的那个备份文件永远都只有正常的一半的大小，只有在整个进程退出的时候它才正常的全部生成。
竟然碰到这样的问题，彻底晕，开始google，竟然只查到一篇和我这同样的问题，更郁闷的是那个帖子最后楼主写了一句“问题解决了”，但没写是怎么解决的，郁闷S。
只好自己开始尝试各种办法，上网抓人到处问，最后在自己不断的尝试下终于是出现了转机，在我的N+1次尝试的时候我改为只读取process的ErrorStream，然后执行，晕，OK了，在导出成功的情况下没有问题，但在导出有错误的时候(像sid不对，用户名错误，数据库没启动等)进程还是被挂S，但只要导出成功没问题，导出有错误的问题是很好处理的，OK，最后试验的代码改为这样：
http://www.blogjava.net/Images/OutliningIndicators/None.gifString[] cmds = new String;
http://www.blogjava.net/Images/OutliningIndicators/None.gif cmds = "cmd";
http://www.blogjava.net/Images/OutliningIndicators/None.gif cmds = "/C";
http://www.blogjava.net/Images/OutliningIndicators/None.gif cmds=commandBuf.toString();
http://www.blogjava.net/Images/OutliningIndicators/None.gif Process process=Runtime.getRuntime().exec(cmds);
http://www.blogjava.net/Images/OutliningIndicators/None.gif boolean shouldClose=false;
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockStart.gif try {
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif InputStreamReader isr = new InputStreamReader(process.getErrorStream());
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif BufferedReader br = new BufferedReader(isr);
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif String line = null;
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockStart.gif while ((line = br.readLine()) != null){
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockStart.gif if(line.indexOf("错误")!=-1){
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif shouldClose=true;
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif break;
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gif }
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockStart.gif catch (IOException ioe) {
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif shouldClose=true;
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gif }
http://www.blogjava.net/Images/OutliningIndicators/None.gif if(shouldClose)
http://www.blogjava.net/Images/OutliningIndicators/None.gif process.destroy();
http://www.blogjava.net/Images/OutliningIndicators/None.gif int exitVal = process.waitFor();
当然，实际的代码中不能像这里写的一样，直接去判断是否含错误这个字符串，而且这段代码是只适合在winnt版本以上的windows操作系统上执行的。
这样反而可以了，说明什么呢，说明在执行oracle的exp时，出现了一个很怪的现象，就是exp在console输出的信息没有被放入InputStream，反而是放到了ErrorStream中(即使正确的情况也是)，这就导致了按照正常的情况去写这段代码的话反而会出问题。
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