SimpleDateFormat的线程安全问题

今天数据库保存的时间有错乱了,以前我以为是服务器的时间有问题,今天才发现原来是SimpleDateFormat这个类的format方法不是线程安全的,里面使用的calendar是个类变量,所以导致多线程静态对象出现了数据错乱或以下的一些异常:

Exception in thread "pool-1-thread-123" java.lang.NumberFormatException: For input string: ""
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.lang.Long.parseLong(Long.java:601)
	at java.lang.Long.parseLong(Long.java:631)
	at java.text.DigitList.getLong(DigitList.java:195)
	at java.text.DecimalFormat.parse(DecimalFormat.java:2051)
	at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:2160)
	at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
	at java.text.DateFormat.parse(DateFormat.java:364)
	at com.demo.time.Format$1.run(Format.java:25)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Exception in thread "pool-1-thread-314" java.lang.NumberFormatException: multiple points
	at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1890)
	at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
	at java.lang.Double.parseDouble(Double.java:538)
	at java.text.DigitList.getDouble(DigitList.java:169)
	at java.text.DecimalFormat.parse(DecimalFormat.java:2056)
	at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1867)
	at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
	at java.text.DateFormat.parse(DateFormat.java:364)
	at com.demo.time.Format$1.run(Format.java:25)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

解决办法:

  1. 使用局部变量SimpleDateFormat
  2. 使用ThreadLocal
  3. 使用synchronized
  4. 改用其他转换工具类org.apache.commons.lang.time.DateUtils.parseDate

验证代码:https://svn.acgist.com/open/study/src/main/java/com/acgist/date/Format.java

参考文章:http://www.cnblogs.com/peida/archive/2013/05/31/3070790.html