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java 监听文件或文件夹变化

2019年09月25日  | 移动技术网IT编程  | 我要评论

    今天遇到一个新需求，当从服务器下载文件后用指定的本地程序打开，不知道何时文件下载完成，只能考虑监听文件夹，当有新文件创建的时候打开指定程序。

在此给出一个完整的下载和打开过程：

1、下载文件

jsp页面

1 <body>
2     <div>
3         <a href="<%=basepath%>/user/downloadfile?filename=proplan.dwg" >点击下载</a>
4     </div>
5 </body>

java代码

 1  public static void downloadtfile(httpservletresponse response, file file) throws ioexception
 2     {
 3         response.reset();
 4         response.setcontenttype("application/vnd.ms-excel;charset=utf-8");
 5         response.setheader("content-disposition",
 6                 "attachment; filename=" + new string(file.getname().getbytes(), "iso-8859-1"));
 7         outputstream outputstream = response.getoutputstream();
 8         inputstream in = new fileinputstream(file);
 9         byte[] b = new byte[1024];
10         int len = 0;
11         while ((len = in.read(b)) > 0)
12         {
13             outputstream.write(b, 0, len);
14         }
15         outputstream.write(b);
16         outputstream.flush();
17         in.close();
18     }

2、监听文件夹，执行打开程序

 1 package demo;
 2 
 3 import java.io.ioexception;
 4 import java.nio.file.filesystems;
 5 import java.nio.file.path;
 6 import java.nio.file.paths;
 7 import java.nio.file.standardwatcheventkinds;
 8 import java.nio.file.watchevent;
 9 import java.nio.file.watchkey;
10 import java.nio.file.watchservice;
11 import java.util.list;
12 import java.util.concurrent.executorservice;
13 import java.util.concurrent.executors;
14 
15 public class folderlistener {
16     private static executorservice fixedthreadpool = executors.newcachedthreadpool();
17     private watchservice ws;
18     private string listenerpath;
19     private folderlistener(string path) {
20         try {
21             ws = filesystems.getdefault().newwatchservice();
22             this.listenerpath = path;
23             start();
24         } catch (ioexception e) {
25             e.printstacktrace();
26         }
27     }
28 
29     private void start() {
30         fixedthreadpool.execute(new listner(ws,this.listenerpath));
31     }
32 
33     public static void addlistener(string path) throws ioexception {
34         folderlistener resourcelistener = new folderlistener(path);
35         path p = paths.get(path);
36         //注册监听事件，文件的修改、删除和创建
37         p.register(resourcelistener.ws,
38             standardwatcheventkinds.entry_modify,
39             standardwatcheventkinds.entry_delete,
40             standardwatcheventkinds.entry_create);
41     }
42     
43 
44     public static void main(string[] args) throws ioexception {
45         //监听下载目录的变化
46         folderlistener.addlistener("c:\\users\\administrator\\downloads\\");
47     }
48 }
49 
50 class listner implements runnable {
51     private watchservice service;
52     private string rootpath;
53     
54     public listner(watchservice service,string rootpath) {
55         this.service = service;
56         this.rootpath = rootpath;
57     }
58 
59     public void run() {
60         try {
61             while(true){
62                 watchkey watchkey = service.take();
63                 list<watchevent<?>> watchevents = watchkey.pollevents();
64                 for(watchevent<?> event : watchevents){
65                     if(event.context().tostring().endswith(".dwg"))
66                     // 根据事件类型采取不同的操作。。。。。。。
67                     try {
68                         system.out.println("["+rootpath+event.context()+"]文件发生了["+event.kind()+"]事件"+    event.count());  
69                         string[] cmd = { "d:\\cad\\autocad\\acad.exe", "c:\\users\\administrator\\downloads\\" + event.context().tostring() };
70                         runtime.getruntime().exec(cmd);
71                     } catch (ioexception e) {
72                         e.printstacktrace();
73                     }
74                 }
75                 watchkey.reset();
76             }
77         } catch (interruptedexception e) {
78             e.printstacktrace();
79         }finally{
80             system.out.println("fdsfsdf");
81             try {
82                 service.close();
83             } catch (ioexception e) {
84                 e.printstacktrace();
85             }
86         }
87         
88     }
89 }

 

补充，除了执行指定exe，打开软件外还可以执行命令行

 1 package demo;
 2 
 3 import java.io.bufferedreader;
 4 import java.io.inputstream;
 5 import java.io.inputstreamreader;  
 6   
 7 public class command {  
 8     
 9     public static void main(string[] args) {
10         string s = execmd("ipconfig");
11         system.out.println(s);
12     }
13     
14     public static string execmd(string commandstr) {  
15         bufferedreader br = null;  
16         stringbuilder sb = new stringbuilder(); 
17         try {  
18             process p = runtime.getruntime().exec(commandstr);  
19             br = new bufferedreader(new inputstreamreader(p.getinputstream(), "gb2312"));
20 //            inputstream in = p.getinputstream();
21 //            byte[] b = new byte[1024];
22 //            int len = 0;
23 //            while((len = in.read(b)) > 0){
24 //                sb.append(new string(b,"gb2312")).append("\n");
25 //            }
26             string line = null;  
27             while ((line = br.readline()) != null) {  
28                 sb.append(line).append("\n");  
29             }  
30         } catch (exception e) {  
31             e.printstacktrace();  
32         }   
33         finally  
34         {  
35             if (br != null)  
36             {  
37                 try {  
38                     br.close();  
39                 } catch (exception e) {  
40                     e.printstacktrace();  
41                 }  
42             }  
43         }  
44         return sb.tostring();
45     }  
46 }

 

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