JAVA文件锁

谁践踏了优雅 2022-04-15 07:25 203阅读 0赞

项目使用到集群环境，流程发送时如果确保一个流程不会被两个流程同时调用？

有一种办法是用文件锁的方式来实现。

代码如下：

锁接口：

Java代码 ![收藏代码][icon_star.png]

1.  **package**lock;
2.  
3.  **import**java.io.FileNotFoundException;
4.  **import**java.io.IOException;
5.  
6.  **public****interface**Lock\{ 
7.  
8.  /\*\*
9.  \*检测是否被锁定
10. \*@returntrue被锁定,false空闲
11. \*\*/
12. **public****abstract****boolean**isLocked()**throws**FileNotFoundException;
13. 
14. /\*\*
15. \*获取锁资源
16. \*@returntrue成功锁定目标资源,false锁定操作失败
17. \*\*/
18. **public****abstract****boolean**obtain()**throws**IOException;
19. 
20. /\*\*
21. \*释放锁
22. \*\*/
23. **public****abstract****void**unlock();
24. 
25. \}

文件锁的实现：

Java代码 ![收藏代码][icon_star.png]

1.  **package**lock;
2.  
3.  **import**java.io.File;
4.  **import**java.io.FileNotFoundException;
5.  **import**java.io.IOException;
6.  **import**java.io.RandomAccessFile;
7.  **import**java.nio.channels.FileChannel;
8.  **import**java.nio.channels.FileLock;
9.  **import**java.nio.channels.OverlappingFileLockException;
10. 
11. **public****class**FileProgrameLock**implements**Lock\{ 
12. **private**StringcallerThreadID=**null**;
13. **private**StringlockFileName=**null**;
14. FileChannelchannel=**null**;
15. **private**FileLocklock=**null**;
16. 
17. **public****static**Lockget(StringfileName,StringcallerThreadID)\{ 
18. FileProgrameLockd=**new**FileProgrameLock(fileName);
19. d.callerThreadID=callerThreadID;
20. **return**(Lock)d;
21. \}
22. 
23. **public**FileProgrameLock(StringlockFileName)\{ 
24. **this**.lockFileName=lockFileName;
25. \}
26. 
27. /\*\*
28. \*检测是否被锁定-不建议使用
29. \*@returntrue被锁定,false空闲
30. \*@deprecated
31. \*\*/
32. **public****boolean**isLocked()**throws**FileNotFoundException\{ 
33. Filetf=**new**File(lockFileName);
34. **if**(!tf.exists())\{ 
35. **return****false**;
36. \}
37. FileChannel\_\_channel=**new**RandomAccessFile(tf,"rw").getChannel();
38. FileLocktl=**null**;
39. **try**\{ 
40. tl=\_\_channel.tryLock();
41. **if**(tl==**null**)\{ 
42. **return****true**;
43. \}**else**\{ 
44. 
45. **return****false**;
46. \}
47. \}**catch**(OverlappingFileLockExceptione)\{ 
48. **return****true**;
49. \}**catch**(IOExceptione)\{ 
50. **return****true**;
51. \}**catch**(Exceptione)\{ 
52. **return****true**;
53. \}**finally**\{ 
54. **try**\{ 
55. **if**(tl!=**null**)\{ 
56. tl.release();
57. \}
58. tl=**null**;
59. **if**(\_\_channel.isOpen())\{ 
60. \_\_channel.close();
61. \}
62. \_\_channel=**null**;
63. tf=**null**;
64. \}**catch**(IOExceptione)\{ 
65. e.printStackTrace();
66. \}
67. 
68. \}
69. \}
70. 
71. /\*\*
72. \*获取锁资源
73. \*@returntrue成功锁定目标资源,false锁定操作失败
74. \*\*/
75. **public****boolean**obtain()**throws**IOException\{ 
76. Filetf=**new**File(lockFileName);
77. createFile();
78. channel=**new**RandomAccessFile(tf,"rw").getChannel();
79. **try**\{ 
80. //System.out.println("getlock000>>>>>>>>>>>>>>>");
81. lock=channel.lock();
82. //System.out.println("getlock>>>>>>>>>>>>>>>");
83. **return****true**;
84. \}**catch**(OverlappingFileLockExceptione)\{ 
85. **return****false**;
86. \}**catch**(Exceptione)\{ 
87. **return****false**;
88. \}
89. \}
90. 
91. /\*\*
92. \*释放锁
93. \*\*/
94. **public****void**unlock()\{ 
95. **try**\{ 
96. **if**(lock!=**null**)\{ 
97. lock.release();
98. \}
99. System.out.println(callerThreadID+"unlockXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX");
100. **if**(channel!=**null**&&channel.isOpen())\{ 
101. channel.close();
102. \}
103. lock=**null**;
104. channel=**null**;
105. **this**.deleteFile();
106. \}**catch**(IOExceptione)\{ 
107. \}
108. \}
109. 
110. **protected****void**finalize()**throws**Throwable\{ 
111. System.out.println(callerThreadID+**this**.getClass()+".finalize()");
112. **super**.finalize();
113. \}
114. 
115. **private****void**createFile()**throws**IOException\{ 
116. **try**\{ 
117. Filetf=**new**File(lockFileName);
118. **if**(!tf.exists())\{ 
119. tf.createNewFile();
120. \}
121. tf=**null**;
122. \}**catch**(IOExceptione)\{ 
123. System.out.println(e+lockFileName);
124. **throw**e;
125. \}
126. \}
127. 
128. **private****void**deleteFile()\{ 
129. Filetf=**new**File(lockFileName);
130. **if**(tf.exists())\{ 
131. tf.delete();
132. \}
133. tf=**null**;
134. \}
135. \}

工厂类:

Java代码 ![收藏代码][icon_star.png]

1.  **package**lock;
2.  
3.  **import**java.io.File;
4.  **import**java.io.FileNotFoundException;
5.  **import**java.io.IOException;
6.  
7.  **public****class**MakeLock**implements**Runnable\{ 
8.  **private**StringthreadID="";
9.  **public****void**run()\{ 
10. **try**\{ 
11. **while**(**true**)\{ 
12. test2(threadID);
13. Thread.sleep(200);
14. \}
15. \}**catch**(IOExceptione)\{ 
16. System.out.println(e);
17. e.printStackTrace();
18. \}**catch**(InterruptedExceptione)\{ 
19. System.out.println(e);
20. \}
21. \}
22. 
23. **public****void**test2(StringthreadID)**throws**FileNotFoundException,IOException,InterruptedException\{ 
24. Locklock=**new**MakeLock(threadID).getLock("c:/001/lockfile001.lock",threadID);
25. System.out.println(threadID+":obtain...");
26. **boolean**b=lock.obtain();
27. //当有重叠时会发生等待，所以外侧先执行isLocked()判断
28. System.out.println(threadID+":obtained"\+b);
29. **if**(b)\{ //执行业务逻辑
30. Thread.sleep(390);
31. **for**(**int**i=0;i<Integer.MAX\_VALUE;i++)\{ 
32. ;
33. \}
34. lock.unlock();
35. \}
36. lock=**null**;
37. 
38. \}
39. 
40. **public**MakeLock(StringthreadID)\{ 
41. **this**.threadID=threadID;
42. \}
43. 
44. **public**LockgetLock(Stringname,StringthreadID)\{ 
45. **final**StringBufferbuf=**new**StringBuffer();
46. **return**FileProgrameLock.get(name,threadID);
47. \}
48. 
49. \}

使用方法：

Java代码 ![收藏代码][icon_star.png]

1.  **public****void**test2(StringthreadID)**throws**FileNotFoundException,IOException,InterruptedException\{ 
2.  Locklock=**new**MakeLock(threadID).getLock("c:/001/lockfile001.lock",threadID);
3.  **if**(!lock.isLocked())\{ 
4.  System.out.println(threadID+":obtain...");
5.  **boolean**b=lock.obtain();
6.  System.out.println(threadID+":obtained"\+b);
7.  **if**(b)\{ //执行业务逻辑
8.  Thread.sleep(390);
9.  **for**(**int**i=0;i<Integer.MAX\_VALUE;i++)\{ 
10. ;
11. \}
12. lock.unlock();
13. \}
14. \}**else**\{ 
15. System.out.println(threadID+":can'tgetalock:"\+lock);
16. \}
17. lock=**null**;
18. 
19. \}

多线程调用测试：

Java代码 ![收藏代码][icon_star.png]

1.  **public****static****void**main(String\[\]args)\{ 
2.  //newAAA().test();
3.  System.out.println("=========================================");
4.  Threadth1=**new**Thread(**new**MakeLock("====================thread1===================="));
5.  Threadth2=**new**Thread(**new**MakeLock("\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#thread2\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#"));
6.  Threadth3=**new**Thread(**new**MakeLock("@@@@@@@@@@@@@@@@@@@@thread3@@@@@@@@@@@@@@@@@@@@"));
7.  Threadth4=**new**Thread(**new**MakeLock("$$$$$$$$$$$$$$$$$$$$thread4$$$$$$$$$$$$$$$$$$$$"));
8.  Threadth5=**new**Thread(**new**MakeLock("&&&&&&&&&&&&&&&&&&&&thread5&&&&&&&&&&&&&&&&&&&&"));
9.  th1.start();
10. th2.start();
11. th3.start();
12. th4.start();
13. th5.start();
14. \}

=================

经测试可以在共享文件系统下工作。

附件中AAA.java多线程测试代码可以直接运行。

项目使用到集群环境，流程发送时如果确保一个流程不会被两个流程同时调用？

有一种办法是用文件锁的方式来实现。

代码如下：

锁接口：

Java代码 ![收藏代码][icon_star.png]

文件锁的实现：

Java代码 ![收藏代码][icon_star.png]

工厂类:

Java代码 ![收藏代码][icon_star.png]